    // street_ways.bin (string remap + offset fixup for node_offset)
    {
        auto old_w = read_file(old_dir + "/street_ways.bin");
        remap_field(old_w, way_stride, way_stride == 12 ? 8 : 5, str_remap);
        auto new_w = read_file(new_dir + "/street_ways.bin");
        auto old_n = read_file(old_dir + "/street_nodes.bin");
        auto new_n = read_file(new_dir + "/street_nodes.bin");
        // Record fixups: (record_index, new_node_offset)
        auto& fixups = file_fixups[static_cast<uint32_t>(PatchFileId::STREET_WAYS)];
        // Save old offsets, apply fixups, then record changes
        size_t wn = old_w.size() / way_stride;
        std::vector<uint32_t> old_offsets(wn);
        for (size_t i = 0; i < wn; i++) memcpy(&old_offsets[i], old_w.data() + i * way_stride, 4);
        fixup_way_offsets(old_w, old_n, new_w, new_n, way_stride);
        for (size_t i = 0; i < wn; i++) {
            uint32_t new_off; memcpy(&new_off, old_w.data() + i * way_stride, 4);
            if (new_off != old_offsets[i]) fixups.push_back({static_cast<uint32_t>(i), new_off});
        }
        write_merge(PatchFileId::STREET_WAYS, "street_ways.bin", old_w, new_w, way_stride);
    }

// geocoder-diff v3: Fully custom patch format using merge-sequence encoding.
//
// For each data file: walk old (string-remapped) and new in parallel,
// match records by content, emit MATCH/INSERT/DELETE operations.
// For entry/cell files: include changed cell entry data directly.
// geo_cells rebuilt by patch tool from entries (not delta-patched).
//
// Patch format: custom binary, zstd-compressed as a whole for transport.
//
// Usage: geocoder-diff <old-dir> <new-dir> -o <patch-file>

#include <algorithm>
#include <cstdint>
#include <cstdlib>
#include <cstring>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <string>
#include <unistd.h>
#include <unordered_map>
#include <unordered_set>
#include <vector>

#include "patch_format.h"

// --- Merge sequence encoding ---
// Walk two sorted arrays (old remapped, new), matching by record bytes.
// Emit: MATCH(n) = copy n records from old, INSERT(n,data) = add n new records,
//       DELETE(n) = skip n old records.

enum MergeOp : uint8_t { OP_MATCH_RUN = 0, OP_INSERT_RUN = 1, OP_DELETE_RUN = 2 };

struct MergeSequence {
    std::vector<char> data; // serialized ops

    void add_match(uint32_t count) {
        uint8_t op = OP_MATCH_RUN;
        data.insert(data.end(), (char*)&op, (char*)&op + 1);
        data.insert(data.end(), (char*)&count, (char*)&count + 4);
    }
    void add_delete(uint32_t count) {
        uint8_t op = OP_DELETE_RUN;
        data.insert(data.end(), (char*)&op, (char*)&op + 1);
        data.insert(data.end(), (char*)&count, (char*)&count + 4);
    }
    void add_insert(const char* records, uint32_t count, size_t stride) {
        uint8_t op = OP_INSERT_RUN;
        data.insert(data.end(), (char*)&op, (char*)&op + 1);
        data.insert(data.end(), (char*)&count, (char*)&count + 4);
        data.insert(data.end(), records, records + count * stride);
    }
};

// Build merge sequence for a data file.
// old_data has string remap already applied.
// Records are compared by byte equality (stride bytes).
static MergeSequence build_merge_seq(
    const std::vector<char>& old_data, const std::vector<char>& new_data,
    size_t stride)
{
    size_t old_n = old_data.size() / stride;
    size_t new_n = new_data.size() / stride;
    size_t oi = 0, ni = 0;
    MergeSequence seq;
    uint32_t match_run = 0, del_run = 0;

    auto flush_match = [&]() { if (match_run > 0) { seq.add_match(match_run); match_run = 0; } };
    auto flush_del = [&]() { if (del_run > 0) { seq.add_delete(del_run); del_run = 0; } };

    while (oi < old_n && ni < new_n) {
        const char* op = old_data.data() + oi * stride;
        const char* np = new_data.data() + ni * stride;

        if (memcmp(op, np, stride) == 0) {
            flush_del();
            match_run++;
            oi++; ni++;
        } else {
            // Mismatch: look ahead to determine if it's a deletion in old or insertion in new.
            // Check: does the OLD record appear later in new? If so, there are inserts before it.
            // Check: does the NEW record appear later in old? If so, there are deletes before it.
            // Simple heuristic: look ahead up to 100 records in each direction.
            bool found_old_in_new = false, found_new_in_old = false;
            size_t lookahead = std::min((size_t)200, std::min(old_n - oi, new_n - ni));
            for (size_t k = 1; k <= lookahead; k++) {
                if (ni + k < new_n && memcmp(op, new_data.data() + (ni + k) * stride, stride) == 0) {
                    found_old_in_new = true;
                    // Insert k records from new before continuing
                    flush_match(); flush_del();
                    seq.add_insert(new_data.data() + ni * stride, k, stride);
                    ni += k;
                    break;
                }
                if (oi + k < old_n && memcmp(np, old_data.data() + (oi + k) * stride, stride) == 0) {
                    found_new_in_old = true;
                    // Delete k records from old
                    flush_match();
                    del_run += k;
                    oi += k;
                    break;
                }
            }
            if (!found_old_in_new && !found_new_in_old) {
                // Both records are different and neither appears nearby.
                // Treat as delete old + insert new.
                flush_match();
                del_run++;
                oi++;
                flush_del();
                seq.add_insert(np, 1, stride);
                ni++;
            }
        }
    }

    flush_match(); flush_del();
    // Remaining old records: deletions
    if (oi < old_n) seq.add_delete(old_n - oi);
    // Remaining new records: insertions
    if (ni < new_n) seq.add_insert(new_data.data() + ni * stride, new_n - ni, stride);

    return seq;
}

// --- String remap ---

static std::unordered_map<uint32_t, uint32_t> build_string_remap(
    const std::vector<char>& old_pool, const std::vector<char>& new_pool)
{
    std::unordered_map<std::string, uint32_t> new_idx;
    size_t pos = 0;
    while (pos < new_pool.size()) {
        const char* s = new_pool.data() + pos;
        size_t len = strlen(s);
        new_idx[std::string(s, len)] = static_cast<uint32_t>(pos);
        pos += len + 1;
    }
    std::unordered_map<uint32_t, uint32_t> remap;
    pos = 0;
    while (pos < old_pool.size()) {
        const char* s = old_pool.data() + pos;
        size_t len = strlen(s);
        auto it = new_idx.find(std::string(s, len));
        if (it != new_idx.end())
            remap[static_cast<uint32_t>(pos)] = it->second;
        pos += len + 1;
    }
    return remap;
}

// --- Remap + fixup helpers ---

static void remap_addr_points(std::vector<char>& data, const std::unordered_map<uint32_t,uint32_t>& rm) {
    for (size_t i = 0; i + 16 <= data.size(); i += 16)
        for (size_t off : {8, 12}) {
            uint32_t v; memcpy(&v, data.data() + i + off, 4);
            auto it = rm.find(v); if (it != rm.end()) memcpy(data.data() + i + off, &it->second, 4);
        }
}
static void remap_field(std::vector<char>& data, size_t stride, size_t field_off,
                         const std::unordered_map<uint32_t,uint32_t>& rm) {
    for (size_t i = 0; i + stride <= data.size(); i += stride) {
        uint32_t v; memcpy(&v, data.data() + i + field_off, 4);
        auto it = rm.find(v); if (it != rm.end()) memcpy(data.data() + i + field_off, &it->second, 4);
    }
}

// Content matching for ways (by name + nodes, ignoring node_offset)
static uint64_t fnv_mix(uint64_t h, uint64_t v) { h ^= v; h *= 1099511628211ULL; return h; }

static void fixup_way_offsets(std::vector<char>& old_ways, const std::vector<char>& old_nodes,
                                const std::vector<char>& new_ways, const std::vector<char>& new_nodes,
                                size_t stride) {
    size_t name_off = (stride == 12) ? 8 : 5;
    size_t old_n = old_ways.size() / stride, new_n = new_ways.size() / stride;
    size_t old_nc = old_nodes.size() / 8, new_nc = new_nodes.size() / 8;

    auto way_hash = [&](const char* w, const char* nodes, size_t max_n) -> uint64_t {
        uint32_t node_offset, name_id; uint8_t node_count;
        memcpy(&node_offset, w, 4); node_count = (uint8_t)w[4]; memcpy(&name_id, w + name_off, 4);
        uint64_t h = 14695981039346656037ULL;
        h = fnv_mix(h, name_id); h = fnv_mix(h, node_count);
        for (uint8_t j = 0; j < node_count && (node_offset + j) < max_n; j++) {
            float lat, lng;
            memcpy(&lat, nodes + (node_offset + j) * 8, 4);
            memcpy(&lng, nodes + (node_offset + j) * 8 + 4, 4);
            h = fnv_mix(h, to_grid(lat)); h = fnv_mix(h, to_grid(lng));
        }
        return h;
    };

    std::unordered_multimap<uint64_t, uint32_t> new_map;
    new_map.reserve(new_n);
    for (uint32_t i = 0; i < new_n; i++)
        new_map.emplace(way_hash(new_ways.data() + i * stride, new_nodes.data(), new_nc), i);

    for (uint32_t i = 0; i < old_n; i++) {
        uint64_t h = way_hash(old_ways.data() + i * stride, old_nodes.data(), old_nc);
        auto it = new_map.find(h);
        if (it != new_map.end()) {
            // Fix node_offset to match new way
            uint32_t new_node_off;
            memcpy(&new_node_off, new_ways.data() + it->second * stride, 4);
            memcpy(old_ways.data() + i * stride, &new_node_off, 4);
            new_map.erase(it);
        }
    }
}

// Same for admin polygons (vertex_offset)
static void fixup_admin_offsets(std::vector<char>& old_polys, const std::vector<char>& old_verts,
                                  const std::vector<char>& new_polys, const std::vector<char>& new_verts,
                                  size_t stride) {
    size_t old_n = old_polys.size() / stride, new_n = new_polys.size() / stride;
    size_t old_vc = old_verts.size() / 8, new_vc = new_verts.size() / 8;

    auto poly_hash = [&](const char* p, const char* verts, size_t max_v) -> uint64_t {
        uint32_t vert_offset, vert_count, name_id;
        memcpy(&vert_offset, p, 4); memcpy(&vert_count, p + 4, 4); memcpy(&name_id, p + 8, 4);
        uint8_t level = (uint8_t)p[12]; uint16_t cc; memcpy(&cc, p + stride - 2, 2);
        uint64_t h = 14695981039346656037ULL;
        h = fnv_mix(h, name_id); h = fnv_mix(h, level); h = fnv_mix(h, cc); h = fnv_mix(h, vert_count);
        for (uint32_t j = 0; j < std::min(vert_count, 10u) && (vert_offset + j) < max_v; j++) {
            float lat, lng;
            memcpy(&lat, verts + (vert_offset + j) * 8, 4); memcpy(&lng, verts + (vert_offset + j) * 8 + 4, 4);
            h = fnv_mix(h, to_grid(lat)); h = fnv_mix(h, to_grid(lng));
        }
        return h;
    };

    std::unordered_multimap<uint64_t, uint32_t> new_map;
    new_map.reserve(new_n);
    for (uint32_t i = 0; i < new_n; i++)
        new_map.emplace(poly_hash(new_polys.data() + i * stride, new_verts.data(), new_vc), i);

    for (uint32_t i = 0; i < old_n; i++) {
        uint64_t h = poly_hash(old_polys.data() + i * stride, old_verts.data(), old_vc);
        auto it = new_map.find(h);
        if (it != new_map.end()) {
            uint32_t new_vert_off;
            memcpy(&new_vert_off, new_polys.data() + it->second * stride, 4);
            memcpy(old_polys.data() + i * stride, &new_vert_off, 4);
            new_map.erase(it);
        }
    }
}

// Same for interp ways
static void fixup_interp_offsets(std::vector<char>& old_data, const std::vector<char>& old_nodes,
                                   const std::vector<char>& new_data, const std::vector<char>& new_nodes,
                                   size_t stride) {
    size_t street_off = (stride >= 20) ? 8 : 5;
    size_t old_n = old_data.size() / stride, new_n = new_data.size() / stride;
    size_t old_nc = old_nodes.size() / 8, new_nc = new_nodes.size() / 8;

    auto ihash = [&](const char* p, const char* nodes, size_t max_n) -> uint64_t {
        uint32_t node_offset, street_id, start, end; uint8_t count, itype;
        memcpy(&node_offset, p, 4); count = (uint8_t)p[4];
        memcpy(&street_id, p + street_off, 4); memcpy(&start, p + street_off + 4, 4);
        memcpy(&end, p + street_off + 8, 4);
        itype = (street_off + 12 < stride) ? (uint8_t)p[street_off + 12] : 0;
        uint64_t h = 14695981039346656037ULL;
        h = fnv_mix(h, street_id); h = fnv_mix(h, start); h = fnv_mix(h, end);
        h = fnv_mix(h, itype); h = fnv_mix(h, count);
        for (uint8_t j = 0; j < count && (node_offset + j) < max_n; j++) {
            float lat, lng;
            memcpy(&lat, nodes + (node_offset + j) * 8, 4); memcpy(&lng, nodes + (node_offset + j) * 8 + 4, 4);
            h = fnv_mix(h, to_grid(lat)); h = fnv_mix(h, to_grid(lng));
        }
        return h;
    };

    std::unordered_multimap<uint64_t, uint32_t> new_map;
    new_map.reserve(new_n);
    for (uint32_t i = 0; i < new_n; i++)
        new_map.emplace(ihash(new_data.data() + i * stride, new_nodes.data(), new_nc), i);
    for (uint32_t i = 0; i < old_n; i++) {
        uint64_t h = ihash(old_data.data() + i * stride, old_nodes.data(), old_nc);
        auto it = new_map.find(h);
        if (it != new_map.end()) {
            uint32_t new_off; memcpy(&new_off, new_data.data() + it->second * stride, 4);
            memcpy(old_data.data() + i * stride, &new_off, 4);
            new_map.erase(it);
        }
    }
}

// --- Write helpers ---
static void wval(std::vector<char>& buf, const void* data, size_t size) {
    buf.insert(buf.end(), (const char*)data, (const char*)data + size);
}

int main(int argc, char* argv[]) {
    if (argc < 5 || std::string(argv[3]) != "-o") {
        std::cerr << "Usage: geocoder-diff <old-dir> <new-dir> -o <patch-file>" << std::endl;
        return 1;
    }
    std::string old_dir = argv[1], new_dir = argv[2], patch_path = argv[4];
    std::string tmpdir = "/tmp/geocoder-diff-" + std::to_string(getpid());
    ensure_dir(tmpdir);

    // Build string remap
    std::cerr << "Building string remap..." << std::endl;
    auto old_strings = read_file(old_dir + "/strings.bin");
    auto new_strings = read_file(new_dir + "/strings.bin");
    auto str_remap = build_string_remap(old_strings, new_strings);

    // Detect strides
    auto detect = [](const std::string& path, std::vector<size_t> cs) -> size_t {
        auto d = read_file(path);
        for (size_t s : cs) if (d.size() % s == 0 && d.size() > 0) return s;
        return cs[0];
    };
    size_t way_stride = detect(old_dir + "/street_ways.bin", {12, 9});
    size_t interp_stride = detect(old_dir + "/interp_ways.bin", {24, 20, 18});
    size_t admin_stride = detect(old_dir + "/admin_polygons.bin", {24, 20, 19});

    // Build patch data (uncompressed, will be zstd-compressed at the end)
    std::vector<char> patch;
    patch.insert(patch.end(), GCPATCH_MAGIC, GCPATCH_MAGIC + 8);
    uint32_t ver = 2, flags = 0; // version 2 = custom format
    wval(patch, &ver, 4); wval(patch, &flags, 4);

    // --- Section: String remap ---
    {
        std::vector<std::pair<uint32_t,uint32_t>> entries;
        size_t pos = 0;
        while (pos < old_strings.size()) {
            uint32_t old_off = static_cast<uint32_t>(pos);
            auto it = str_remap.find(old_off);
            entries.push_back({old_off, (it != str_remap.end()) ? it->second : old_off});
            pos += strlen(old_strings.data() + pos) + 1;
        }
        uint32_t marker = 0xFFFFFFFE, count = static_cast<uint32_t>(entries.size());
        wval(patch, &marker, 4); wval(patch, &count, 4);
        for (auto& [o, n] : entries) { wval(patch, &o, 4); wval(patch, &n, 4); }
        std::cerr << "  String remap: " << count << " entries (" << count * 8 << " bytes)" << std::endl;
    }

    // --- Section: Per-file merge sequences ---
    // Track fixups per file (applied before merge, included in patch for patch tool)
    std::unordered_map<uint32_t, std::vector<std::pair<uint32_t,uint32_t>>> file_fixups;

    auto write_merge = [&](PatchFileId id, const std::string& name,
                             const std::vector<char>& old_data, const std::vector<char>& new_data,
                             size_t stride) {
        auto seq = build_merge_seq(old_data, new_data, stride);
        uint32_t fid = static_cast<uint32_t>(id);
        uint64_t os = old_data.size(), ns = new_data.size(), ss = seq.data.size();

        // Check for fixups
        auto fit = file_fixups.find(fid);
        uint32_t n_fixups = fit != file_fixups.end() ? static_cast<uint32_t>(fit->second.size()) : 0;

        wval(patch, &fid, 4);
        uint32_t st = static_cast<uint32_t>(stride);
        wval(patch, &st, 4);
        wval(patch, &os, 8); wval(patch, &ns, 8);
        // Fixup count + data before merge sequence
        wval(patch, &n_fixups, 4);
        if (n_fixups > 0) {
            for (auto& [idx, val] : fit->second) { wval(patch, &idx, 4); wval(patch, &val, 4); }
        }
        wval(patch, &ss, 8);
        patch.insert(patch.end(), seq.data.begin(), seq.data.end());
        std::cerr << "  " << name << ": seq=" << ss << " fixups=" << n_fixups
                  << " (" << std::fixed << std::setprecision(2)
                  << (ns > 0 ? ss * 100.0 / ns : 0) << "%)" << std::endl;
    };

    // strings.bin: full new (small file)
    {
        uint32_t fid = static_cast<uint32_t>(PatchFileId::STRINGS);
        uint32_t st = 1; // byte stride
        uint64_t os = old_strings.size(), ns = new_strings.size();
        auto seq = build_merge_seq(old_strings, new_strings, 1);
        uint64_t ss = seq.data.size();
        wval(patch, &fid, 4); wval(patch, &st, 4);
        wval(patch, &os, 8); wval(patch, &ns, 8); wval(patch, &ss, 8);
        patch.insert(patch.end(), seq.data.begin(), seq.data.end());
        std::cerr << "  strings.bin: seq=" << ss << " bytes" << std::endl;
    }

    // addr_points.bin
    {
        auto old_data = read_file(old_dir + "/addr_points.bin");
        remap_addr_points(old_data, str_remap);
        auto new_data = read_file(new_dir + "/addr_points.bin");
        write_merge(PatchFileId::ADDR_POINTS, "addr_points.bin", old_data, new_data, 16);
    }

    // street_ways.bin (string remap + offset fixup for node_offset)
    {
        auto old_w = read_file(old_dir + "/street_ways.bin");
        remap_field(old_w, way_stride, way_stride == 12 ? 8 : 5, str_remap);
        auto new_w = read_file(new_dir + "/street_ways.bin");
        auto old_n = read_file(old_dir + "/street_nodes.bin");
        auto new_n = read_file(new_dir + "/street_nodes.bin");
        // Build fixup table and apply to old_w before merge
        fixup_way_offsets(old_w, old_n, new_w, new_n, way_stride);
        write_merge(PatchFileId::STREET_WAYS, "street_ways.bin", old_w, new_w, way_stride);
    }

    // street_nodes.bin (no remap)
    {
        auto old_data = read_file(old_dir + "/street_nodes.bin");
        auto new_data = read_file(new_dir + "/street_nodes.bin");
        write_merge(PatchFileId::STREET_NODES, "street_nodes.bin", old_data, new_data, 8);
    }

    // interp_ways.bin (string remap + offset fixup)
    {
        auto old_data = read_file(old_dir + "/interp_ways.bin");
        remap_field(old_data, interp_stride, interp_stride >= 20 ? 8 : 5, str_remap);
        auto old_n = read_file(old_dir + "/interp_nodes.bin");
        auto new_data = read_file(new_dir + "/interp_ways.bin");
        auto new_n = read_file(new_dir + "/interp_nodes.bin");
        fixup_interp_offsets(old_data, old_n, new_data, new_n, interp_stride);
        write_merge(PatchFileId::INTERP_WAYS, "interp_ways.bin", old_data, new_data, interp_stride);
    }

    // interp_nodes.bin
    {
        auto old_data = read_file(old_dir + "/interp_nodes.bin");
        auto new_data = read_file(new_dir + "/interp_nodes.bin");
        write_merge(PatchFileId::INTERP_NODES, "interp_nodes.bin", old_data, new_data, 8);
    }

    // admin_polygons.bin (string remap + offset fixup)
    {
        auto old_data = read_file(old_dir + "/admin_polygons.bin");
        remap_field(old_data, admin_stride, 8, str_remap);
        auto old_v = read_file(old_dir + "/admin_vertices.bin");
        auto new_data = read_file(new_dir + "/admin_polygons.bin");
        auto new_v = read_file(new_dir + "/admin_vertices.bin");
        fixup_admin_offsets(old_data, old_v, new_data, new_v, admin_stride);
        write_merge(PatchFileId::ADMIN_POLYGONS, "admin_polygons.bin", old_data, new_data, admin_stride);
    }

    // admin_vertices.bin
    {
        auto old_data = read_file(old_dir + "/admin_vertices.bin");
        auto new_data = read_file(new_dir + "/admin_vertices.bin");
        write_merge(PatchFileId::ADMIN_VERTICES, "admin_vertices.bin", old_data, new_data, 8);
    }

    // --- Section: Entry/cell files as full new data ---
    // These are small relative to data files and rebuilt by patch tool isn't reliable.
    // Include them as full replacement. zstd transport compression handles the rest.
    for (auto& [id, name] : std::vector<std::pair<PatchFileId, std::string>>{
        {PatchFileId::GEO_CELLS, "geo_cells.bin"},
        {PatchFileId::STREET_ENTRIES, "street_entries.bin"},
        {PatchFileId::ADDR_ENTRIES, "addr_entries.bin"},
        {PatchFileId::INTERP_ENTRIES, "interp_entries.bin"},
        {PatchFileId::ADMIN_CELLS, "admin_cells.bin"},
        {PatchFileId::ADMIN_ENTRIES, "admin_entries.bin"}}) {
        auto data = read_file(new_dir + "/" + name);
        uint32_t fid = static_cast<uint32_t>(id);
        uint32_t st = 0; // stride 0 = full replacement
        uint64_t os = 0, ns = data.size(), ss = data.size();
        wval(patch, &fid, 4); wval(patch, &st, 4);
        wval(patch, &os, 8); wval(patch, &ns, 8); wval(patch, &ss, 8);
        patch.insert(patch.end(), data.begin(), data.end());
        std::cerr << "  " << name << ": full " << data.size() << " bytes" << std::endl;
    }

    // End marker
    uint32_t end_marker = 0xFFFFFFFF;
    wval(patch, &end_marker, 4);

    std::cerr << "\nUncompressed patch: " << patch.size() << " bytes ("
              << patch.size() / 1024 / 1024 << " MiB)" << std::endl;

    // Compress whole patch with zstd for transport
    {
        std::string raw_path = tmpdir + "/patch.raw";
        write_file(raw_path, patch);
        std::string cmd = "zstd -19 '" + raw_path + "' -o '" + patch_path + "' -f --quiet 2>/dev/null";
        system(cmd.c_str());
        auto compressed = read_file(patch_path);
        std::cerr << "Compressed patch: " << compressed.size() << " bytes ("
                  << compressed.size() / 1024 / 1024 << " MiB)" << std::endl;
        remove(raw_path.c_str());
    }

    std::string rm_cmd = "rm -rf '" + tmpdir + "'";
    system(rm_cmd.c_str());
    return 0;
}

-        // Build fixup table and apply to old_w before merge

+        // Record fixups: (record_index, new_node_offset)

+        auto& fixups = file_fixups[static_cast<uint32_t>(PatchFileId::STREET_WAYS)];

+        // Save old offsets, apply fixups, then record changes

+        size_t wn = old_w.size() / way_stride;

+        std::vector<uint32_t> old_offsets(wn);

+        for (size_t i = 0; i < wn; i++) memcpy(&old_offsets[i], old_w.data() + i * way_stride, 4);

+        for (size_t i = 0; i < wn; i++) {

+            uint32_t new_off; memcpy(&new_off, old_w.data() + i * way_stride, 4);

+            if (new_off != old_offsets[i]) fixups.push_back({static_cast<uint32_t>(i), new_off});


Do the same for interps and admin:


Edit

    // interp_ways.bin (string remap + offset fixup)
    {
        auto old_data = read_file(old_dir + "/interp_ways.bin");
        remap_field(old_data, interp_stride, interp_stride >= 20 ? 8 : 5, str_remap);
        auto old_n = read_file(old_dir + "/interp_nodes.bin");
        auto new_data = read_file(new_dir + "/interp_ways.bin");
        auto new_n = read_file(new_dir + "/interp_nodes.bin");
        fixup_interp_offsets(old_data, old_n, new_data, new_n, interp_stride);
        write_merge(PatchFileId::INTERP_WAYS, "interp_ways.bin", old_data, new_data, interp_stride);
    }

    // interp_ways.bin
    {
        auto old_data = read_file(old_dir + "/interp_ways.bin");
        remap_field(old_data, interp_stride, interp_stride >= 20 ? 8 : 5, str_remap);
        auto old_n = read_file(old_dir + "/interp_nodes.bin");
        auto new_data = read_file(new_dir + "/interp_ways.bin");
        auto new_n = read_file(new_dir + "/interp_nodes.bin");
        auto& fixups = file_fixups[static_cast<uint32_t>(PatchFileId::INTERP_WAYS)];
        size_t in_count = old_data.size() / interp_stride;
        std::vector<uint32_t> old_offsets(in_count);
        for (size_t i = 0; i < in_count; i++) memcpy(&old_offsets[i], old_data.data() + i * interp_stride, 4);
        fixup_interp_offsets(old_data, old_n, new_data, new_n, interp_stride);
        for (size_t i = 0; i < in_count; i++) {
            uint32_t new_off; memcpy(&new_off, old_data.data() + i * interp_stride, 4);
            if (new_off != old_offsets[i]) fixups.push_back({static_cast<uint32_t>(i), new_off});
        }
        write_merge(PatchFileId::INTERP_WAYS, "interp_ways.bin", old_data, new_data, interp_stride);
    }


The file /root/traccar-geocoder/builder/tools/geocoder_diff.cpp has been updated successfully.

    // interp_ways.bin
    {
        auto old_data = read_file(old_dir + "/interp_ways.bin");
        remap_field(old_data, interp_stride, interp_stride >= 20 ? 8 : 5, str_remap);
        auto old_n = read_file(old_dir + "/interp_nodes.bin");
        auto new_data = read_file(new_dir + "/interp_ways.bin");
        auto new_n = read_file(new_dir + "/interp_nodes.bin");
        auto& fixups = file_fixups[static_cast<uint32_t>(PatchFileId::INTERP_WAYS)];
        size_t in_count = old_data.size() / interp_stride;
        std::vector<uint32_t> old_offsets(in_count);
        for (size_t i = 0; i < in_count; i++) memcpy(&old_offsets[i], old_data.data() + i * interp_stride, 4);
        fixup_interp_offsets(old_data, old_n, new_data, new_n, interp_stride);
        for (size_t i = 0; i < in_count; i++) {
            uint32_t new_off; memcpy(&new_off, old_data.data() + i * interp_stride, 4);
            if (new_off != old_offsets[i]) fixups.push_back({static_cast<uint32_t>(i), new_off});
        }
        write_merge(PatchFileId::INTERP_WAYS, "interp_ways.bin", old_data, new_data, interp_stride);
    }

// geocoder-diff v3: Fully custom patch format using merge-sequence encoding.
//
// For each data file: walk old (string-remapped) and new in parallel,
// match records by content, emit MATCH/INSERT/DELETE operations.
// For entry/cell files: include changed cell entry data directly.
// geo_cells rebuilt by patch tool from entries (not delta-patched).
//
// Patch format: custom binary, zstd-compressed as a whole for transport.
//
// Usage: geocoder-diff <old-dir> <new-dir> -o <patch-file>

#include <algorithm>
#include <cstdint>
#include <cstdlib>
#include <cstring>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <string>
#include <unistd.h>
#include <unordered_map>
#include <unordered_set>
#include <vector>

#include "patch_format.h"

// --- Merge sequence encoding ---
// Walk two sorted arrays (old remapped, new), matching by record bytes.
// Emit: MATCH(n) = copy n records from old, INSERT(n,data) = add n new records,
//       DELETE(n) = skip n old records.

enum MergeOp : uint8_t { OP_MATCH_RUN = 0, OP_INSERT_RUN = 1, OP_DELETE_RUN = 2 };

struct MergeSequence {
    std::vector<char> data; // serialized ops

    void add_match(uint32_t count) {
        uint8_t op = OP_MATCH_RUN;
        data.insert(data.end(), (char*)&op, (char*)&op + 1);
        data.insert(data.end(), (char*)&count, (char*)&count + 4);
    }
    void add_delete(uint32_t count) {
        uint8_t op = OP_DELETE_RUN;
        data.insert(data.end(), (char*)&op, (char*)&op + 1);
        data.insert(data.end(), (char*)&count, (char*)&count + 4);
    }
    void add_insert(const char* records, uint32_t count, size_t stride) {
        uint8_t op = OP_INSERT_RUN;
        data.insert(data.end(), (char*)&op, (char*)&op + 1);
        data.insert(data.end(), (char*)&count, (char*)&count + 4);
        data.insert(data.end(), records, records + count * stride);
    }
};

// Build merge sequence for a data file.
// old_data has string remap already applied.
// Records are compared by byte equality (stride bytes).
static MergeSequence build_merge_seq(
    const std::vector<char>& old_data, const std::vector<char>& new_data,
    size_t stride)
{
    size_t old_n = old_data.size() / stride;
    size_t new_n = new_data.size() / stride;
    size_t oi = 0, ni = 0;
    MergeSequence seq;
    uint32_t match_run = 0, del_run = 0;

    auto flush_match = [&]() { if (match_run > 0) { seq.add_match(match_run); match_run = 0; } };
    auto flush_del = [&]() { if (del_run > 0) { seq.add_delete(del_run); del_run = 0; } };

    while (oi < old_n && ni < new_n) {
        const char* op = old_data.data() + oi * stride;
        const char* np = new_data.data() + ni * stride;

        if (memcmp(op, np, stride) == 0) {
            flush_del();
            match_run++;
            oi++; ni++;
        } else {
            // Mismatch: look ahead to determine if it's a deletion in old or insertion in new.
            // Check: does the OLD record appear later in new? If so, there are inserts before it.
            // Check: does the NEW record appear later in old? If so, there are deletes before it.
            // Simple heuristic: look ahead up to 100 records in each direction.
            bool found_old_in_new = false, found_new_in_old = false;
            size_t lookahead = std::min((size_t)200, std::min(old_n - oi, new_n - ni));
            for (size_t k = 1; k <= lookahead; k++) {
                if (ni + k < new_n && memcmp(op, new_data.data() + (ni + k) * stride, stride) == 0) {
                    found_old_in_new = true;
                    // Insert k records from new before continuing
                    flush_match(); flush_del();
                    seq.add_insert(new_data.data() + ni * stride, k, stride);
                    ni += k;
                    break;
                }
                if (oi + k < old_n && memcmp(np, old_data.data() + (oi + k) * stride, stride) == 0) {
                    found_new_in_old = true;
                    // Delete k records from old
                    flush_match();
                    del_run += k;
                    oi += k;
                    break;
                }
            }
            if (!found_old_in_new && !found_new_in_old) {
                // Both records are different and neither appears nearby.
                // Treat as delete old + insert new.
                flush_match();
                del_run++;
                oi++;
                flush_del();
                seq.add_insert(np, 1, stride);
                ni++;
            }
        }
    }

    flush_match(); flush_del();
    // Remaining old records: deletions
    if (oi < old_n) seq.add_delete(old_n - oi);
    // Remaining new records: insertions
    if (ni < new_n) seq.add_insert(new_data.data() + ni * stride, new_n - ni, stride);

    return seq;
}

// --- String remap ---

static std::unordered_map<uint32_t, uint32_t> build_string_remap(
    const std::vector<char>& old_pool, const std::vector<char>& new_pool)
{
    std::unordered_map<std::string, uint32_t> new_idx;
    size_t pos = 0;
    while (pos < new_pool.size()) {
        const char* s = new_pool.data() + pos;
        size_t len = strlen(s);
        new_idx[std::string(s, len)] = static_cast<uint32_t>(pos);
        pos += len + 1;
    }
    std::unordered_map<uint32_t, uint32_t> remap;
    pos = 0;
    while (pos < old_pool.size()) {
        const char* s = old_pool.data() + pos;
        size_t len = strlen(s);
        auto it = new_idx.find(std::string(s, len));
        if (it != new_idx.end())
            remap[static_cast<uint32_t>(pos)] = it->second;
        pos += len + 1;
    }
    return remap;
}

// --- Remap + fixup helpers ---

static void remap_addr_points(std::vector<char>& data, const std::unordered_map<uint32_t,uint32_t>& rm) {
    for (size_t i = 0; i + 16 <= data.size(); i += 16)
        for (size_t off : {8, 12}) {
            uint32_t v; memcpy(&v, data.data() + i + off, 4);
            auto it = rm.find(v); if (it != rm.end()) memcpy(data.data() + i + off, &it->second, 4);
        }
}
static void remap_field(std::vector<char>& data, size_t stride, size_t field_off,
                         const std::unordered_map<uint32_t,uint32_t>& rm) {
    for (size_t i = 0; i + stride <= data.size(); i += stride) {
        uint32_t v; memcpy(&v, data.data() + i + field_off, 4);
        auto it = rm.find(v); if (it != rm.end()) memcpy(data.data() + i + field_off, &it->second, 4);
    }
}

// Content matching for ways (by name + nodes, ignoring node_offset)
static uint64_t fnv_mix(uint64_t h, uint64_t v) { h ^= v; h *= 1099511628211ULL; return h; }

static void fixup_way_offsets(std::vector<char>& old_ways, const std::vector<char>& old_nodes,
                                const std::vector<char>& new_ways, const std::vector<char>& new_nodes,
                                size_t stride) {
    size_t name_off = (stride == 12) ? 8 : 5;
    size_t old_n = old_ways.size() / stride, new_n = new_ways.size() / stride;
    size_t old_nc = old_nodes.size() / 8, new_nc = new_nodes.size() / 8;

    auto way_hash = [&](const char* w, const char* nodes, size_t max_n) -> uint64_t {
        uint32_t node_offset, name_id; uint8_t node_count;
        memcpy(&node_offset, w, 4); node_count = (uint8_t)w[4]; memcpy(&name_id, w + name_off, 4);
        uint64_t h = 14695981039346656037ULL;
        h = fnv_mix(h, name_id); h = fnv_mix(h, node_count);
        for (uint8_t j = 0; j < node_count && (node_offset + j) < max_n; j++) {
            float lat, lng;
            memcpy(&lat, nodes + (node_offset + j) * 8, 4);
            memcpy(&lng, nodes + (node_offset + j) * 8 + 4, 4);
            h = fnv_mix(h, to_grid(lat)); h = fnv_mix(h, to_grid(lng));
        }
        return h;
    };

    std::unordered_multimap<uint64_t, uint32_t> new_map;
    new_map.reserve(new_n);
    for (uint32_t i = 0; i < new_n; i++)
        new_map.emplace(way_hash(new_ways.data() + i * stride, new_nodes.data(), new_nc), i);

    for (uint32_t i = 0; i < old_n; i++) {
        uint64_t h = way_hash(old_ways.data() + i * stride, old_nodes.data(), old_nc);
        auto it = new_map.find(h);
        if (it != new_map.end()) {
            // Fix node_offset to match new way
            uint32_t new_node_off;
            memcpy(&new_node_off, new_ways.data() + it->second * stride, 4);
            memcpy(old_ways.data() + i * stride, &new_node_off, 4);
            new_map.erase(it);
        }
    }
}

// Same for admin polygons (vertex_offset)
static void fixup_admin_offsets(std::vector<char>& old_polys, const std::vector<char>& old_verts,
                                  const std::vector<char>& new_polys, const std::vector<char>& new_verts,
                                  size_t stride) {
    size_t old_n = old_polys.size() / stride, new_n = new_polys.size() / stride;
    size_t old_vc = old_verts.size() / 8, new_vc = new_verts.size() / 8;

    auto poly_hash = [&](const char* p, const char* verts, size_t max_v) -> uint64_t {
        uint32_t vert_offset, vert_count, name_id;
        memcpy(&vert_offset, p, 4); memcpy(&vert_count, p + 4, 4); memcpy(&name_id, p + 8, 4);
        uint8_t level = (uint8_t)p[12]; uint16_t cc; memcpy(&cc, p + stride - 2, 2);
        uint64_t h = 14695981039346656037ULL;
        h = fnv_mix(h, name_id); h = fnv_mix(h, level); h = fnv_mix(h, cc); h = fnv_mix(h, vert_count);
        for (uint32_t j = 0; j < std::min(vert_count, 10u) && (vert_offset + j) < max_v; j++) {
            float lat, lng;
            memcpy(&lat, verts + (vert_offset + j) * 8, 4); memcpy(&lng, verts + (vert_offset + j) * 8 + 4, 4);
            h = fnv_mix(h, to_grid(lat)); h = fnv_mix(h, to_grid(lng));
        }
        return h;
    };

    std::unordered_multimap<uint64_t, uint32_t> new_map;
    new_map.reserve(new_n);
    for (uint32_t i = 0; i < new_n; i++)
        new_map.emplace(poly_hash(new_polys.data() + i * stride, new_verts.data(), new_vc), i);

    for (uint32_t i = 0; i < old_n; i++) {
        uint64_t h = poly_hash(old_polys.data() + i * stride, old_verts.data(), old_vc);
        auto it = new_map.find(h);
        if (it != new_map.end()) {
            uint32_t new_vert_off;
            memcpy(&new_vert_off, new_polys.data() + it->second * stride, 4);
            memcpy(old_polys.data() + i * stride, &new_vert_off, 4);
            new_map.erase(it);
        }
    }
}

// Same for interp ways
static void fixup_interp_offsets(std::vector<char>& old_data, const std::vector<char>& old_nodes,
                                   const std::vector<char>& new_data, const std::vector<char>& new_nodes,
                                   size_t stride) {
    size_t street_off = (stride >= 20) ? 8 : 5;
    size_t old_n = old_data.size() / stride, new_n = new_data.size() / stride;
    size_t old_nc = old_nodes.size() / 8, new_nc = new_nodes.size() / 8;

    auto ihash = [&](const char* p, const char* nodes, size_t max_n) -> uint64_t {
        uint32_t node_offset, street_id, start, end; uint8_t count, itype;
        memcpy(&node_offset, p, 4); count = (uint8_t)p[4];
        memcpy(&street_id, p + street_off, 4); memcpy(&start, p + street_off + 4, 4);
        memcpy(&end, p + street_off + 8, 4);
        itype = (street_off + 12 < stride) ? (uint8_t)p[street_off + 12] : 0;
        uint64_t h = 14695981039346656037ULL;
        h = fnv_mix(h, street_id); h = fnv_mix(h, start); h = fnv_mix(h, end);
        h = fnv_mix(h, itype); h = fnv_mix(h, count);
        for (uint8_t j = 0; j < count && (node_offset + j) < max_n; j++) {
            float lat, lng;
            memcpy(&lat, nodes + (node_offset + j) * 8, 4); memcpy(&lng, nodes + (node_offset + j) * 8 + 4, 4);
            h = fnv_mix(h, to_grid(lat)); h = fnv_mix(h, to_grid(lng));
        }
        return h;
    };

    std::unordered_multimap<uint64_t, uint32_t> new_map;
    new_map.reserve(new_n);
    for (uint32_t i = 0; i < new_n; i++)
        new_map.emplace(ihash(new_data.data() + i * stride, new_nodes.data(), new_nc), i);
    for (uint32_t i = 0; i < old_n; i++) {
        uint64_t h = ihash(old_data.data() + i * stride, old_nodes.data(), old_nc);
        auto it = new_map.find(h);
        if (it != new_map.end()) {
            uint32_t new_off; memcpy(&new_off, new_data.data() + it->second * stride, 4);
            memcpy(old_data.data() + i * stride, &new_off, 4);
            new_map.erase(it);
        }
    }
}

// --- Write helpers ---
static void wval(std::vector<char>& buf, const void* data, size_t size) {
    buf.insert(buf.end(), (const char*)data, (const char*)data + size);
}

int main(int argc, char* argv[]) {
    if (argc < 5 || std::string(argv[3]) != "-o") {
        std::cerr << "Usage: geocoder-diff <old-dir> <new-dir> -o <patch-file>" << std::endl;
        return 1;
    }
    std::string old_dir = argv[1], new_dir = argv[2], patch_path = argv[4];
    std::string tmpdir = "/tmp/geocoder-diff-" + std::to_string(getpid());
    ensure_dir(tmpdir);

    // Build string remap
    std::cerr << "Building string remap..." << std::endl;
    auto old_strings = read_file(old_dir + "/strings.bin");
    auto new_strings = read_file(new_dir + "/strings.bin");
    auto str_remap = build_string_remap(old_strings, new_strings);

    // Detect strides
    auto detect = [](const std::string& path, std::vector<size_t> cs) -> size_t {
        auto d = read_file(path);
        for (size_t s : cs) if (d.size() % s == 0 && d.size() > 0) return s;
        return cs[0];
    };
    size_t way_stride = detect(old_dir + "/street_ways.bin", {12, 9});
    size_t interp_stride = detect(old_dir + "/interp_ways.bin", {24, 20, 18});
    size_t admin_stride = detect(old_dir + "/admin_polygons.bin", {24, 20, 19});

    // Build patch data (uncompressed, will be zstd-compressed at the end)
    std::vector<char> patch;
    patch.insert(patch.end(), GCPATCH_MAGIC, GCPATCH_MAGIC + 8);
    uint32_t ver = 2, flags = 0; // version 2 = custom format
    wval(patch, &ver, 4); wval(patch, &flags, 4);

    // --- Section: String remap ---
    {
        std::vector<std::pair<uint32_t,uint32_t>> entries;
        size_t pos = 0;
        while (pos < old_strings.size()) {
            uint32_t old_off = static_cast<uint32_t>(pos);
            auto it = str_remap.find(old_off);
            entries.push_back({old_off, (it != str_remap.end()) ? it->second : old_off});
            pos += strlen(old_strings.data() + pos) + 1;
        }
        uint32_t marker = 0xFFFFFFFE, count = static_cast<uint32_t>(entries.size());
        wval(patch, &marker, 4); wval(patch, &count, 4);
        for (auto& [o, n] : entries) { wval(patch, &o, 4); wval(patch, &n, 4); }
        std::cerr << "  String remap: " << count << " entries (" << count * 8 << " bytes)" << std::endl;
    }

    // --- Section: Per-file merge sequences ---
    // Track fixups per file (applied before merge, included in patch for patch tool)
    std::unordered_map<uint32_t, std::vector<std::pair<uint32_t,uint32_t>>> file_fixups;

    auto write_merge = [&](PatchFileId id, const std::string& name,
                             const std::vector<char>& old_data, const std::vector<char>& new_data,
                             size_t stride) {
        auto seq = build_merge_seq(old_data, new_data, stride);
        uint32_t fid = static_cast<uint32_t>(id);
        uint64_t os = old_data.size(), ns = new_data.size(), ss = seq.data.size();

        // Check for fixups
        auto fit = file_fixups.find(fid);
        uint32_t n_fixups = fit != file_fixups.end() ? static_cast<uint32_t>(fit->second.size()) : 0;

        wval(patch, &fid, 4);
        uint32_t st = static_cast<uint32_t>(stride);
        wval(patch, &st, 4);
        wval(patch, &os, 8); wval(patch, &ns, 8);
        // Fixup count + data before merge sequence
        wval(patch, &n_fixups, 4);
        if (n_fixups > 0) {
            for (auto& [idx, val] : fit->second) { wval(patch, &idx, 4); wval(patch, &val, 4); }
        }
        wval(patch, &ss, 8);
        patch.insert(patch.end(), seq.data.begin(), seq.data.end());
        std::cerr << "  " << name << ": seq=" << ss << " fixups=" << n_fixups
                  << " (" << std::fixed << std::setprecision(2)
                  << (ns > 0 ? ss * 100.0 / ns : 0) << "%)" << std::endl;
    };

    // strings.bin: full new (small file)
    {
        uint32_t fid = static_cast<uint32_t>(PatchFileId::STRINGS);
        uint32_t st = 1; // byte stride
        uint64_t os = old_strings.size(), ns = new_strings.size();
        auto seq = build_merge_seq(old_strings, new_strings, 1);
        uint64_t ss = seq.data.size();
        wval(patch, &fid, 4); wval(patch, &st, 4);
        wval(patch, &os, 8); wval(patch, &ns, 8); wval(patch, &ss, 8);
        patch.insert(patch.end(), seq.data.begin(), seq.data.end());
        std::cerr << "  strings.bin: seq=" << ss << " bytes" << std::endl;
    }

    // addr_points.bin
    {
        auto old_data = read_file(old_dir + "/addr_points.bin");
        remap_addr_points(old_data, str_remap);
        auto new_data = read_file(new_dir + "/addr_points.bin");
        write_merge(PatchFileId::ADDR_POINTS, "addr_points.bin", old_data, new_data, 16);
    }

    // street_ways.bin (string remap + offset fixup for node_offset)
    {
        auto old_w = read_file(old_dir + "/street_ways.bin");
        remap_field(old_w, way_stride, way_stride == 12 ? 8 : 5, str_remap);
        auto new_w = read_file(new_dir + "/street_ways.bin");
        auto old_n = read_file(old_dir + "/street_nodes.bin");
        auto new_n = read_file(new_dir + "/street_nodes.bin");
        // Record fixups: (record_index, new_node_offset)
        auto& fixups = file_fixups[static_cast<uint32_t>(PatchFileId::STREET_WAYS)];
        // Save old offsets, apply fixups, then record changes
        size_t wn = old_w.size() / way_stride;
        std::vector<uint32_t> old_offsets(wn);
        for (size_t i = 0; i < wn; i++) memcpy(&old_offsets[i], old_w.data() + i * way_stride, 4);
        fixup_way_offsets(old_w, old_n, new_w, new_n, way_stride);
        for (size_t i = 0; i < wn; i++) {
            uint32_t new_off; memcpy(&new_off, old_w.data() + i * way_stride, 4);
            if (new_off != old_offsets[i]) fixups.push_back({static_cast<uint32_t>(i), new_off});
        }
        write_merge(PatchFileId::STREET_WAYS, "street_ways.bin", old_w, new_w, way_stride);
    }

    // street_nodes.bin (no remap)
    {
        auto old_data = read_file(old_dir + "/street_nodes.bin");
        auto new_data = read_file(new_dir + "/street_nodes.bin");
        write_merge(PatchFileId::STREET_NODES, "street_nodes.bin", old_data, new_data, 8);
    }

    // interp_ways.bin (string remap + offset fixup)
    {
        auto old_data = read_file(old_dir + "/interp_ways.bin");
        remap_field(old_data, interp_stride, interp_stride >= 20 ? 8 : 5, str_remap);
        auto old_n = read_file(old_dir + "/interp_nodes.bin");
        auto new_data = read_file(new_dir + "/interp_ways.bin");
        auto new_n = read_file(new_dir + "/interp_nodes.bin");
        fixup_interp_offsets(old_data, old_n, new_data, new_n, interp_stride);
        write_merge(PatchFileId::INTERP_WAYS, "interp_ways.bin", old_data, new_data, interp_stride);
    }

    // interp_nodes.bin
    {
        auto old_data = read_file(old_dir + "/interp_nodes.bin");
        auto new_data = read_file(new_dir + "/interp_nodes.bin");
        write_merge(PatchFileId::INTERP_NODES, "interp_nodes.bin", old_data, new_data, 8);
    }

    // admin_polygons.bin (string remap + offset fixup)
    {
        auto old_data = read_file(old_dir + "/admin_polygons.bin");
        remap_field(old_data, admin_stride, 8, str_remap);
        auto old_v = read_file(old_dir + "/admin_vertices.bin");
        auto new_data = read_file(new_dir + "/admin_polygons.bin");
        auto new_v = read_file(new_dir + "/admin_vertices.bin");
        fixup_admin_offsets(old_data, old_v, new_data, new_v, admin_stride);
        write_merge(PatchFileId::ADMIN_POLYGONS, "admin_polygons.bin", old_data, new_data, admin_stride);
    }

    // admin_vertices.bin
    {
        auto old_data = read_file(old_dir + "/admin_vertices.bin");
        auto new_data = read_file(new_dir + "/admin_vertices.bin");
        write_merge(PatchFileId::ADMIN_VERTICES, "admin_vertices.bin", old_data, new_data, 8);
    }

    // --- Section: Entry/cell files as full new data ---
    // These are small relative to data files and rebuilt by patch tool isn't reliable.
    // Include them as full replacement. zstd transport compression handles the rest.
    for (auto& [id, name] : std::vector<std::pair<PatchFileId, std::string>>{
        {PatchFileId::GEO_CELLS, "geo_cells.bin"},
        {PatchFileId::STREET_ENTRIES, "street_entries.bin"},
        {PatchFileId::ADDR_ENTRIES, "addr_entries.bin"},
        {PatchFileId::INTERP_ENTRIES, "interp_entries.bin"},
        {PatchFileId::ADMIN_CELLS, "admin_cells.bin"},
        {PatchFileId::ADMIN_ENTRIES, "admin_entries.bin"}}) {
        auto data = read_file(new_dir + "/" + name);
        uint32_t fid = static_cast<uint32_t>(id);
        uint32_t st = 0; // stride 0 = full replacement
        uint64_t os = 0, ns = data.size(), ss = data.size();
        wval(patch, &fid, 4); wval(patch, &st, 4);
        wval(patch, &os, 8); wval(patch, &ns, 8); wval(patch, &ss, 8);
        patch.insert(patch.end(), data.begin(), data.end());
        std::cerr << "  " << name << ": full " << data.size() << " bytes" << std::endl;
    }

    // End marker
    uint32_t end_marker = 0xFFFFFFFF;
    wval(patch, &end_marker, 4);

    std::cerr << "\nUncompressed patch: " << patch.size() << " bytes ("
              << patch.size() / 1024 / 1024 << " MiB)" << std::endl;

    // Compress whole patch with zstd for transport
    {
        std::string raw_path = tmpdir + "/patch.raw";
        write_file(raw_path, patch);
        std::string cmd = "zstd -19 '" + raw_path + "' -o '" + patch_path + "' -f --quiet 2>/dev/null";
        system(cmd.c_str());
        auto compressed = read_file(patch_path);
        std::cerr << "Compressed patch: " << compressed.size() << " bytes ("
                  << compressed.size() / 1024 / 1024 << " MiB)" << std::endl;
        remove(raw_path.c_str());
    }

    std::string rm_cmd = "rm -rf '" + tmpdir + "'";
    system(rm_cmd.c_str());
    return 0;
}

-    // interp_ways.bin (string remap + offset fixup)

+        auto& fixups = file_fixups[static_cast<uint32_t>(PatchFileId::INTERP_WAYS)];

+        size_t in_count = old_data.size() / interp_stride;

+        std::vector<uint32_t> old_offsets(in_count);

+        for (size_t i = 0; i < in_count; i++) memcpy(&old_offsets[i], old_data.data() + i * interp_stride, 4);

+        for (size_t i = 0; i < in_count; i++) {

+            uint32_t new_off; memcpy(&new_off, old_data.data() + i * interp_stride, 4);


    // admin_polygons.bin (string remap + offset fixup)
    {
        auto old_data = read_file(old_dir + "/admin_polygons.bin");
        remap_field(old_data, admin_stride, 8, str_remap);
        auto old_v = read_file(old_dir + "/admin_vertices.bin");
        auto new_data = read_file(new_dir + "/admin_polygons.bin");
        auto new_v = read_file(new_dir + "/admin_vertices.bin");
        fixup_admin_offsets(old_data, old_v, new_data, new_v, admin_stride);
        write_merge(PatchFileId::ADMIN_POLYGONS, "admin_polygons.bin", old_data, new_data, admin_stride);
    }

    // admin_polygons.bin
    {
        auto old_data = read_file(old_dir + "/admin_polygons.bin");
        remap_field(old_data, admin_stride, 8, str_remap);
        auto old_v = read_file(old_dir + "/admin_vertices.bin");
        auto new_data = read_file(new_dir + "/admin_polygons.bin");
        auto new_v = read_file(new_dir + "/admin_vertices.bin");
        auto& fixups = file_fixups[static_cast<uint32_t>(PatchFileId::ADMIN_POLYGONS)];
        size_t an = old_data.size() / admin_stride;
        std::vector<uint32_t> old_offsets(an);
        for (size_t i = 0; i < an; i++) memcpy(&old_offsets[i], old_data.data() + i * admin_stride, 4);
        fixup_admin_offsets(old_data, old_v, new_data, new_v, admin_stride);
        for (size_t i = 0; i < an; i++) {
            uint32_t new_off; memcpy(&new_off, old_data.data() + i * admin_stride, 4);
            if (new_off != old_offsets[i]) fixups.push_back({static_cast<uint32_t>(i), new_off});
        }
        write_merge(PatchFileId::ADMIN_POLYGONS, "admin_polygons.bin", old_data, new_data, admin_stride);
    }


    // admin_polygons.bin
    {
        auto old_data = read_file(old_dir + "/admin_polygons.bin");
        remap_field(old_data, admin_stride, 8, str_remap);
        auto old_v = read_file(old_dir + "/admin_vertices.bin");
        auto new_data = read_file(new_dir + "/admin_polygons.bin");
        auto new_v = read_file(new_dir + "/admin_vertices.bin");
        auto& fixups = file_fixups[static_cast<uint32_t>(PatchFileId::ADMIN_POLYGONS)];
        size_t an = old_data.size() / admin_stride;
        std::vector<uint32_t> old_offsets(an);
        for (size_t i = 0; i < an; i++) memcpy(&old_offsets[i], old_data.data() + i * admin_stride, 4);
        fixup_admin_offsets(old_data, old_v, new_data, new_v, admin_stride);
        for (size_t i = 0; i < an; i++) {
            uint32_t new_off; memcpy(&new_off, old_data.data() + i * admin_stride, 4);
            if (new_off != old_offsets[i]) fixups.push_back({static_cast<uint32_t>(i), new_off});
        }
        write_merge(PatchFileId::ADMIN_POLYGONS, "admin_polygons.bin", old_data, new_data, admin_stride);
    }

// geocoder-diff v3: Fully custom patch format using merge-sequence encoding.
//
// For each data file: walk old (string-remapped) and new in parallel,
// match records by content, emit MATCH/INSERT/DELETE operations.
// For entry/cell files: include changed cell entry data directly.
// geo_cells rebuilt by patch tool from entries (not delta-patched).
//
// Patch format: custom binary, zstd-compressed as a whole for transport.
//
// Usage: geocoder-diff <old-dir> <new-dir> -o <patch-file>

#include <algorithm>
#include <cstdint>
#include <cstdlib>
#include <cstring>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <string>
#include <unistd.h>
#include <unordered_map>
#include <unordered_set>
#include <vector>

#include "patch_format.h"

// --- Merge sequence encoding ---
// Walk two sorted arrays (old remapped, new), matching by record bytes.
// Emit: MATCH(n) = copy n records from old, INSERT(n,data) = add n new records,
//       DELETE(n) = skip n old records.

enum MergeOp : uint8_t { OP_MATCH_RUN = 0, OP_INSERT_RUN = 1, OP_DELETE_RUN = 2 };

struct MergeSequence {
    std::vector<char> data; // serialized ops

    void add_match(uint32_t count) {
        uint8_t op = OP_MATCH_RUN;
        data.insert(data.end(), (char*)&op, (char*)&op + 1);
        data.insert(data.end(), (char*)&count, (char*)&count + 4);
    }
    void add_delete(uint32_t count) {
        uint8_t op = OP_DELETE_RUN;
        data.insert(data.end(), (char*)&op, (char*)&op + 1);
        data.insert(data.end(), (char*)&count, (char*)&count + 4);
    }
    void add_insert(const char* records, uint32_t count, size_t stride) {
        uint8_t op = OP_INSERT_RUN;
        data.insert(data.end(), (char*)&op, (char*)&op + 1);
        data.insert(data.end(), (char*)&count, (char*)&count + 4);
        data.insert(data.end(), records, records + count * stride);
    }
};

// Build merge sequence for a data file.
// old_data has string remap already applied.
// Records are compared by byte equality (stride bytes).
static MergeSequence build_merge_seq(
    const std::vector<char>& old_data, const std::vector<char>& new_data,
    size_t stride)
{
    size_t old_n = old_data.size() / stride;
    size_t new_n = new_data.size() / stride;
    size_t oi = 0, ni = 0;
    MergeSequence seq;
    uint32_t match_run = 0, del_run = 0;

    auto flush_match = [&]() { if (match_run > 0) { seq.add_match(match_run); match_run = 0; } };
    auto flush_del = [&]() { if (del_run > 0) { seq.add_delete(del_run); del_run = 0; } };

    while (oi < old_n && ni < new_n) {
        const char* op = old_data.data() + oi * stride;
        const char* np = new_data.data() + ni * stride;

        if (memcmp(op, np, stride) == 0) {
            flush_del();
            match_run++;
            oi++; ni++;
        } else {
            // Mismatch: look ahead to determine if it's a deletion in old or insertion in new.
            // Check: does the OLD record appear later in new? If so, there are inserts before it.
            // Check: does the NEW record appear later in old? If so, there are deletes before it.
            // Simple heuristic: look ahead up to 100 records in each direction.
            bool found_old_in_new = false, found_new_in_old = false;
            size_t lookahead = std::min((size_t)200, std::min(old_n - oi, new_n - ni));
            for (size_t k = 1; k <= lookahead; k++) {
                if (ni + k < new_n && memcmp(op, new_data.data() + (ni + k) * stride, stride) == 0) {
                    found_old_in_new = true;
                    // Insert k records from new before continuing
                    flush_match(); flush_del();
                    seq.add_insert(new_data.data() + ni * stride, k, stride);
                    ni += k;
                    break;
                }
                if (oi + k < old_n && memcmp(np, old_data.data() + (oi + k) * stride, stride) == 0) {
                    found_new_in_old = true;
                    // Delete k records from old
                    flush_match();
                    del_run += k;
                    oi += k;
                    break;
                }
            }
            if (!found_old_in_new && !found_new_in_old) {
                // Both records are different and neither appears nearby.
                // Treat as delete old + insert new.
                flush_match();
                del_run++;
                oi++;
                flush_del();
                seq.add_insert(np, 1, stride);
                ni++;
            }
        }
    }

    flush_match(); flush_del();
    // Remaining old records: deletions
    if (oi < old_n) seq.add_delete(old_n - oi);
    // Remaining new records: insertions
    if (ni < new_n) seq.add_insert(new_data.data() + ni * stride, new_n - ni, stride);

    return seq;
}

// --- String remap ---

static std::unordered_map<uint32_t, uint32_t> build_string_remap(
    const std::vector<char>& old_pool, const std::vector<char>& new_pool)
{
    std::unordered_map<std::string, uint32_t> new_idx;
    size_t pos = 0;
    while (pos < new_pool.size()) {
        const char* s = new_pool.data() + pos;
        size_t len = strlen(s);
        new_idx[std::string(s, len)] = static_cast<uint32_t>(pos);
        pos += len + 1;
    }
    std::unordered_map<uint32_t, uint32_t> remap;
    pos = 0;
    while (pos < old_pool.size()) {
        const char* s = old_pool.data() + pos;
        size_t len = strlen(s);
        auto it = new_idx.find(std::string(s, len));
        if (it != new_idx.end())
            remap[static_cast<uint32_t>(pos)] = it->second;
        pos += len + 1;
    }
    return remap;
}

// --- Remap + fixup helpers ---

static void remap_addr_points(std::vector<char>& data, const std::unordered_map<uint32_t,uint32_t>& rm) {
    for (size_t i = 0; i + 16 <= data.size(); i += 16)
        for (size_t off : {8, 12}) {
            uint32_t v; memcpy(&v, data.data() + i + off, 4);
            auto it = rm.find(v); if (it != rm.end()) memcpy(data.data() + i + off, &it->second, 4);
        }
}
static void remap_field(std::vector<char>& data, size_t stride, size_t field_off,
                         const std::unordered_map<uint32_t,uint32_t>& rm) {
    for (size_t i = 0; i + stride <= data.size(); i += stride) {
        uint32_t v; memcpy(&v, data.data() + i + field_off, 4);
        auto it = rm.find(v); if (it != rm.end()) memcpy(data.data() + i + field_off, &it->second, 4);
    }
}

// Content matching for ways (by name + nodes, ignoring node_offset)
static uint64_t fnv_mix(uint64_t h, uint64_t v) { h ^= v; h *= 1099511628211ULL; return h; }

static void fixup_way_offsets(std::vector<char>& old_ways, const std::vector<char>& old_nodes,
                                const std::vector<char>& new_ways, const std::vector<char>& new_nodes,
                                size_t stride) {
    size_t name_off = (stride == 12) ? 8 : 5;
    size_t old_n = old_ways.size() / stride, new_n = new_ways.size() / stride;
    size_t old_nc = old_nodes.size() / 8, new_nc = new_nodes.size() / 8;

    auto way_hash = [&](const char* w, const char* nodes, size_t max_n) -> uint64_t {
        uint32_t node_offset, name_id; uint8_t node_count;
        memcpy(&node_offset, w, 4); node_count = (uint8_t)w[4]; memcpy(&name_id, w + name_off, 4);
        uint64_t h = 14695981039346656037ULL;
        h = fnv_mix(h, name_id); h = fnv_mix(h, node_count);
        for (uint8_t j = 0; j < node_count && (node_offset + j) < max_n; j++) {
            float lat, lng;
            memcpy(&lat, nodes + (node_offset + j) * 8, 4);
            memcpy(&lng, nodes + (node_offset + j) * 8 + 4, 4);
            h = fnv_mix(h, to_grid(lat)); h = fnv_mix(h, to_grid(lng));
        }
        return h;
    };

    std::unordered_multimap<uint64_t, uint32_t> new_map;
    new_map.reserve(new_n);
    for (uint32_t i = 0; i < new_n; i++)
        new_map.emplace(way_hash(new_ways.data() + i * stride, new_nodes.data(), new_nc), i);

    for (uint32_t i = 0; i < old_n; i++) {
        uint64_t h = way_hash(old_ways.data() + i * stride, old_nodes.data(), old_nc);
        auto it = new_map.find(h);
        if (it != new_map.end()) {
            // Fix node_offset to match new way
            uint32_t new_node_off;
            memcpy(&new_node_off, new_ways.data() + it->second * stride, 4);
            memcpy(old_ways.data() + i * stride, &new_node_off, 4);
            new_map.erase(it);
        }
    }
}

// Same for admin polygons (vertex_offset)
static void fixup_admin_offsets(std::vector<char>& old_polys, const std::vector<char>& old_verts,
                                  const std::vector<char>& new_polys, const std::vector<char>& new_verts,
                                  size_t stride) {
    size_t old_n = old_polys.size() / stride, new_n = new_polys.size() / stride;
    size_t old_vc = old_verts.size() / 8, new_vc = new_verts.size() / 8;

    auto poly_hash = [&](const char* p, const char* verts, size_t max_v) -> uint64_t {
        uint32_t vert_offset, vert_count, name_id;
        memcpy(&vert_offset, p, 4); memcpy(&vert_count, p + 4, 4); memcpy(&name_id, p + 8, 4);
        uint8_t level = (uint8_t)p[12]; uint16_t cc; memcpy(&cc, p + stride - 2, 2);
        uint64_t h = 14695981039346656037ULL;
        h = fnv_mix(h, name_id); h = fnv_mix(h, level); h = fnv_mix(h, cc); h = fnv_mix(h, vert_count);
        for (uint32_t j = 0; j < std::min(vert_count, 10u) && (vert_offset + j) < max_v; j++) {
            float lat, lng;
            memcpy(&lat, verts + (vert_offset + j) * 8, 4); memcpy(&lng, verts + (vert_offset + j) * 8 + 4, 4);
            h = fnv_mix(h, to_grid(lat)); h = fnv_mix(h, to_grid(lng));
        }
        return h;
    };

    std::unordered_multimap<uint64_t, uint32_t> new_map;
    new_map.reserve(new_n);
    for (uint32_t i = 0; i < new_n; i++)
        new_map.emplace(poly_hash(new_polys.data() + i * stride, new_verts.data(), new_vc), i);

    for (uint32_t i = 0; i < old_n; i++) {
        uint64_t h = poly_hash(old_polys.data() + i * stride, old_verts.data(), old_vc);
        auto it = new_map.find(h);
        if (it != new_map.end()) {
            uint32_t new_vert_off;
            memcpy(&new_vert_off, new_polys.data() + it->second * stride, 4);
            memcpy(old_polys.data() + i * stride, &new_vert_off, 4);
            new_map.erase(it);
        }
    }
}

// Same for interp ways
static void fixup_interp_offsets(std::vector<char>& old_data, const std::vector<char>& old_nodes,
                                   const std::vector<char>& new_data, const std::vector<char>& new_nodes,
                                   size_t stride) {
    size_t street_off = (stride >= 20) ? 8 : 5;
    size_t old_n = old_data.size() / stride, new_n = new_data.size() / stride;
    size_t old_nc = old_nodes.size() / 8, new_nc = new_nodes.size() / 8;

    auto ihash = [&](const char* p, const char* nodes, size_t max_n) -> uint64_t {
        uint32_t node_offset, street_id, start, end; uint8_t count, itype;
        memcpy(&node_offset, p, 4); count = (uint8_t)p[4];
        memcpy(&street_id, p + street_off, 4); memcpy(&start, p + street_off + 4, 4);
        memcpy(&end, p + street_off + 8, 4);
        itype = (street_off + 12 < stride) ? (uint8_t)p[street_off + 12] : 0;
        uint64_t h = 14695981039346656037ULL;
        h = fnv_mix(h, street_id); h = fnv_mix(h, start); h = fnv_mix(h, end);
        h = fnv_mix(h, itype); h = fnv_mix(h, count);
        for (uint8_t j = 0; j < count && (node_offset + j) < max_n; j++) {
            float lat, lng;
            memcpy(&lat, nodes + (node_offset + j) * 8, 4); memcpy(&lng, nodes + (node_offset + j) * 8 + 4, 4);
            h = fnv_mix(h, to_grid(lat)); h = fnv_mix(h, to_grid(lng));
        }
        return h;
    };

    std::unordered_multimap<uint64_t, uint32_t> new_map;
    new_map.reserve(new_n);
    for (uint32_t i = 0; i < new_n; i++)
        new_map.emplace(ihash(new_data.data() + i * stride, new_nodes.data(), new_nc), i);
    for (uint32_t i = 0; i < old_n; i++) {
        uint64_t h = ihash(old_data.data() + i * stride, old_nodes.data(), old_nc);
        auto it = new_map.find(h);
        if (it != new_map.end()) {
            uint32_t new_off; memcpy(&new_off, new_data.data() + it->second * stride, 4);
            memcpy(old_data.data() + i * stride, &new_off, 4);
            new_map.erase(it);
        }
    }
}

// --- Write helpers ---
static void wval(std::vector<char>& buf, const void* data, size_t size) {
    buf.insert(buf.end(), (const char*)data, (const char*)data + size);
}

int main(int argc, char* argv[]) {
    if (argc < 5 || std::string(argv[3]) != "-o") {
        std::cerr << "Usage: geocoder-diff <old-dir> <new-dir> -o <patch-file>" << std::endl;
        return 1;
    }
    std::string old_dir = argv[1], new_dir = argv[2], patch_path = argv[4];
    std::string tmpdir = "/tmp/geocoder-diff-" + std::to_string(getpid());
    ensure_dir(tmpdir);

    // Build string remap
    std::cerr << "Building string remap..." << std::endl;
    auto old_strings = read_file(old_dir + "/strings.bin");
    auto new_strings = read_file(new_dir + "/strings.bin");
    auto str_remap = build_string_remap(old_strings, new_strings);

    // Detect strides
    auto detect = [](const std::string& path, std::vector<size_t> cs) -> size_t {
        auto d = read_file(path);
        for (size_t s : cs) if (d.size() % s == 0 && d.size() > 0) return s;
        return cs[0];
    };
    size_t way_stride = detect(old_dir + "/street_ways.bin", {12, 9});
    size_t interp_stride = detect(old_dir + "/interp_ways.bin", {24, 20, 18});
    size_t admin_stride = detect(old_dir + "/admin_polygons.bin", {24, 20, 19});

    // Build patch data (uncompressed, will be zstd-compressed at the end)
    std::vector<char> patch;
    patch.insert(patch.end(), GCPATCH_MAGIC, GCPATCH_MAGIC + 8);
    uint32_t ver = 2, flags = 0; // version 2 = custom format
    wval(patch, &ver, 4); wval(patch, &flags, 4);

    // --- Section: String remap ---
    {
        std::vector<std::pair<uint32_t,uint32_t>> entries;
        size_t pos = 0;
        while (pos < old_strings.size()) {
            uint32_t old_off = static_cast<uint32_t>(pos);
            auto it = str_remap.find(old_off);
            entries.push_back({old_off, (it != str_remap.end()) ? it->second : old_off});
            pos += strlen(old_strings.data() + pos) + 1;
        }
        uint32_t marker = 0xFFFFFFFE, count = static_cast<uint32_t>(entries.size());
        wval(patch, &marker, 4); wval(patch, &count, 4);
        for (auto& [o, n] : entries) { wval(patch, &o, 4); wval(patch, &n, 4); }
        std::cerr << "  String remap: " << count << " entries (" << count * 8 << " bytes)" << std::endl;
    }

    // --- Section: Per-file merge sequences ---
    // Track fixups per file (applied before merge, included in patch for patch tool)
    std::unordered_map<uint32_t, std::vector<std::pair<uint32_t,uint32_t>>> file_fixups;

    auto write_merge = [&](PatchFileId id, const std::string& name,
                             const std::vector<char>& old_data, const std::vector<char>& new_data,
                             size_t stride) {
        auto seq = build_merge_seq(old_data, new_data, stride);
        uint32_t fid = static_cast<uint32_t>(id);
        uint64_t os = old_data.size(), ns = new_data.size(), ss = seq.data.size();

        // Check for fixups
        auto fit = file_fixups.find(fid);
        uint32_t n_fixups = fit != file_fixups.end() ? static_cast<uint32_t>(fit->second.size()) : 0;

        wval(patch, &fid, 4);
        uint32_t st = static_cast<uint32_t>(stride);
        wval(patch, &st, 4);
        wval(patch, &os, 8); wval(patch, &ns, 8);
        // Fixup count + data before merge sequence
        wval(patch, &n_fixups, 4);
        if (n_fixups > 0) {
            for (auto& [idx, val] : fit->second) { wval(patch, &idx, 4); wval(patch, &val, 4); }
        }
        wval(patch, &ss, 8);
        patch.insert(patch.end(), seq.data.begin(), seq.data.end());
        std::cerr << "  " << name << ": seq=" << ss << " fixups=" << n_fixups
                  << " (" << std::fixed << std::setprecision(2)
                  << (ns > 0 ? ss * 100.0 / ns : 0) << "%)" << std::endl;
    };

    // strings.bin: full new (small file)
    {
        uint32_t fid = static_cast<uint32_t>(PatchFileId::STRINGS);
        uint32_t st = 1; // byte stride
        uint64_t os = old_strings.size(), ns = new_strings.size();
        auto seq = build_merge_seq(old_strings, new_strings, 1);
        uint64_t ss = seq.data.size();
        wval(patch, &fid, 4); wval(patch, &st, 4);
        wval(patch, &os, 8); wval(patch, &ns, 8); wval(patch, &ss, 8);
        patch.insert(patch.end(), seq.data.begin(), seq.data.end());
        std::cerr << "  strings.bin: seq=" << ss << " bytes" << std::endl;
    }

    // addr_points.bin
    {
        auto old_data = read_file(old_dir + "/addr_points.bin");
        remap_addr_points(old_data, str_remap);
        auto new_data = read_file(new_dir + "/addr_points.bin");
        write_merge(PatchFileId::ADDR_POINTS, "addr_points.bin", old_data, new_data, 16);
    }

    // street_ways.bin (string remap + offset fixup for node_offset)
    {
        auto old_w = read_file(old_dir + "/street_ways.bin");
        remap_field(old_w, way_stride, way_stride == 12 ? 8 : 5, str_remap);
        auto new_w = read_file(new_dir + "/street_ways.bin");
        auto old_n = read_file(old_dir + "/street_nodes.bin");
        auto new_n = read_file(new_dir + "/street_nodes.bin");
        // Record fixups: (record_index, new_node_offset)
        auto& fixups = file_fixups[static_cast<uint32_t>(PatchFileId::STREET_WAYS)];
        // Save old offsets, apply fixups, then record changes
        size_t wn = old_w.size() / way_stride;
        std::vector<uint32_t> old_offsets(wn);
        for (size_t i = 0; i < wn; i++) memcpy(&old_offsets[i], old_w.data() + i * way_stride, 4);
        fixup_way_offsets(old_w, old_n, new_w, new_n, way_stride);
        for (size_t i = 0; i < wn; i++) {
            uint32_t new_off; memcpy(&new_off, old_w.data() + i * way_stride, 4);
            if (new_off != old_offsets[i]) fixups.push_back({static_cast<uint32_t>(i), new_off});
        }
        write_merge(PatchFileId::STREET_WAYS, "street_ways.bin", old_w, new_w, way_stride);
    }

    // street_nodes.bin (no remap)
    {
        auto old_data = read_file(old_dir + "/street_nodes.bin");
        auto new_data = read_file(new_dir + "/street_nodes.bin");
        write_merge(PatchFileId::STREET_NODES, "street_nodes.bin", old_data, new_data, 8);
    }

    // interp_ways.bin
    {
        auto old_data = read_file(old_dir + "/interp_ways.bin");
        remap_field(old_data, interp_stride, interp_stride >= 20 ? 8 : 5, str_remap);
        auto old_n = read_file(old_dir + "/interp_nodes.bin");
        auto new_data = read_file(new_dir + "/interp_ways.bin");
        auto new_n = read_file(new_dir + "/interp_nodes.bin");
        auto& fixups = file_fixups[static_cast<uint32_t>(PatchFileId::INTERP_WAYS)];
        size_t in_count = old_data.size() / interp_stride;
        std::vector<uint32_t> old_offsets(in_count);
        for (size_t i = 0; i < in_count; i++) memcpy(&old_offsets[i], old_data.data() + i * interp_stride, 4);
        fixup_interp_offsets(old_data, old_n, new_data, new_n, interp_stride);
        for (size_t i = 0; i < in_count; i++) {
            uint32_t new_off; memcpy(&new_off, old_data.data() + i * interp_stride, 4);
            if (new_off != old_offsets[i]) fixups.push_back({static_cast<uint32_t>(i), new_off});
        }
        write_merge(PatchFileId::INTERP_WAYS, "interp_ways.bin", old_data, new_data, interp_stride);
    }

    // interp_nodes.bin
    {
        auto old_data = read_file(old_dir + "/interp_nodes.bin");
        auto new_data = read_file(new_dir + "/interp_nodes.bin");
        write_merge(PatchFileId::INTERP_NODES, "interp_nodes.bin", old_data, new_data, 8);
    }

    // admin_polygons.bin (string remap + offset fixup)
    {
        auto old_data = read_file(old_dir + "/admin_polygons.bin");
        remap_field(old_data, admin_stride, 8, str_remap);
        auto old_v = read_file(old_dir + "/admin_vertices.bin");
        auto new_data = read_file(new_dir + "/admin_polygons.bin");
        auto new_v = read_file(new_dir + "/admin_vertices.bin");
        fixup_admin_offsets(old_data, old_v, new_data, new_v, admin_stride);
        write_merge(PatchFileId::ADMIN_POLYGONS, "admin_polygons.bin", old_data, new_data, admin_stride);
    }

    // admin_vertices.bin
    {
        auto old_data = read_file(old_dir + "/admin_vertices.bin");
        auto new_data = read_file(new_dir + "/admin_vertices.bin");
        write_merge(PatchFileId::ADMIN_VERTICES, "admin_vertices.bin", old_data, new_data, 8);
    }

    // --- Section: Entry/cell files as full new data ---
    // These are small relative to data files and rebuilt by patch tool isn't reliable.
    // Include them as full replacement. zstd transport compression handles the rest.
    for (auto& [id, name] : std::vector<std::pair<PatchFileId, std::string>>{
        {PatchFileId::GEO_CELLS, "geo_cells.bin"},
        {PatchFileId::STREET_ENTRIES, "street_entries.bin"},
        {PatchFileId::ADDR_ENTRIES, "addr_entries.bin"},
        {PatchFileId::INTERP_ENTRIES, "interp_entries.bin"},
        {PatchFileId::ADMIN_CELLS, "admin_cells.bin"},
        {PatchFileId::ADMIN_ENTRIES, "admin_entries.bin"}}) {
        auto data = read_file(new_dir + "/" + name);
        uint32_t fid = static_cast<uint32_t>(id);
        uint32_t st = 0; // stride 0 = full replacement
        uint64_t os = 0, ns = data.size(), ss = data.size();
        wval(patch, &fid, 4); wval(patch, &st, 4);
        wval(patch, &os, 8); wval(patch, &ns, 8); wval(patch, &ss, 8);
        patch.insert(patch.end(), data.begin(), data.end());
        std::cerr << "  " << name << ": full " << data.size() << " bytes" << std::endl;
    }

    // End marker
    uint32_t end_marker = 0xFFFFFFFF;
    wval(patch, &end_marker, 4);

    std::cerr << "\nUncompressed patch: " << patch.size() << " bytes ("
              << patch.size() / 1024 / 1024 << " MiB)" << std::endl;

    // Compress whole patch with zstd for transport
    {
        std::string raw_path = tmpdir + "/patch.raw";
        write_file(raw_path, patch);
        std::string cmd = "zstd -19 '" + raw_path + "' -o '" + patch_path + "' -f --quiet 2>/dev/null";
        system(cmd.c_str());
        auto compressed = read_file(patch_path);
        std::cerr << "Compressed patch: " << compressed.size() << " bytes ("
                  << compressed.size() / 1024 / 1024 << " MiB)" << std::endl;
        remove(raw_path.c_str());
    }

    std::string rm_cmd = "rm -rf '" + tmpdir + "'";
    system(rm_cmd.c_str());
    return 0;
}

-    // admin_polygons.bin (string remap + offset fixup)

+        auto& fixups = file_fixups[static_cast<uint32_t>(PatchFileId::ADMIN_POLYGONS)];

+        size_t an = old_data.size() / admin_stride;

+        std::vector<uint32_t> old_offsets(an);

+        for (size_t i = 0; i < an; i++) memcpy(&old_offsets[i], old_data.data() + i * admin_stride, 4);

+        for (size_t i = 0; i < an; i++) {

+            uint32_t new_off; memcpy(&new_off, old_data.data() + i * admin_stride, 4);

+            if (new_off != old_offsets[i]) fixups.push_back({static_cast<uint32_t>(i), new_off});


Also need to update the entry/cell full replacement to use the new header format (with n_fixups=0):


   240→        auto it = new_map.find(h);
   241→        if (it != new_map.end()) {
   242→            uint32_t new_vert_off;
   243→            memcpy(&new_vert_off, new_polys.data() + it->second * stride, 4);
   244→            memcpy(old_polys.data() + i * stride, &new_vert_off, 4);
   245→            new_map.erase(it);
   246→        }
   247→    }
   248→}
   249→
   250→// Same for interp ways
   251→static void fixup_interp_offsets(std::vector<char>& old_data, const std::vector<char>& old_nodes,
   252→                                   const std::vector<char>& new_data, const std::vector<char>& new_nodes,
   253→                                   size_t stride) {
   254→    size_t street_off = (stride >= 20) ? 8 : 5;

        auto it = new_map.find(h);
        if (it != new_map.end()) {
            uint32_t new_vert_off;
            memcpy(&new_vert_off, new_polys.data() + it->second * stride, 4);
            memcpy(old_polys.data() + i * stride, &new_vert_off, 4);
            new_map.erase(it);
        }
    }
}

// Same for interp ways
static void fixup_interp_offsets(std::vector<char>& old_data, const std::vector<char>& old_nodes,
                                   const std::vector<char>& new_data, const std::vector<char>& new_nodes,
                                   size_t stride) {
    size_t street_off = (stride >= 20) ? 8 : 5;


Now update the patch tool to read fixups and apply them:


        // Merge sequence: load old file, apply remap, replay sequence
        auto old_data = read_file(cur_dir + "/" + std::string(filename));
        size_t actual_stride = stride;
        if (file_id == (uint32_t)PatchFileId::STREET_WAYS) actual_stride = way_stride;
        else if (file_id == (uint32_t)PatchFileId::INTERP_WAYS) actual_stride = interp_stride;
        else if (file_id == (uint32_t)PatchFileId::ADMIN_POLYGONS) actual_stride = admin_stride;

        // Apply string remap to old data
        apply_str_remap(old_data, file_id, actual_stride);

        // Merge sequence: load old file, apply remap + fixups, replay sequence
        auto old_data = read_file(cur_dir + "/" + std::string(filename));
        size_t actual_stride = stride;
        if (file_id == (uint32_t)PatchFileId::STREET_WAYS) actual_stride = way_stride;
        else if (file_id == (uint32_t)PatchFileId::INTERP_WAYS) actual_stride = interp_stride;
        else if (file_id == (uint32_t)PatchFileId::ADMIN_POLYGONS) actual_stride = admin_stride;

        // Apply string remap to old data
        apply_str_remap(old_data, file_id, actual_stride);

        // Read and apply fixups (node_offset/vertex_offset fixes)
        uint32_t n_fixups; memcpy(&n_fixups, patch.data() + pos, 4); pos += 4;
        for (uint32_t i = 0; i < n_fixups; i++) {
            uint32_t idx, val;
            memcpy(&idx, patch.data() + pos, 4); pos += 4;
            memcpy(&val, patch.data() + pos, 4); pos += 4;
            size_t byte_pos = (size_t)idx * actual_stride;
            if (byte_pos + 4 <= old_data.size())
                memcpy(old_data.data() + byte_pos, &val, 4);
        }


The file /root/traccar-geocoder/builder/tools/geocoder_patch.cpp has been updated successfully.

        // Merge sequence: load old file, apply remap + fixups, replay sequence
        auto old_data = read_file(cur_dir + "/" + std::string(filename));
        size_t actual_stride = stride;
        if (file_id == (uint32_t)PatchFileId::STREET_WAYS) actual_stride = way_stride;
        else if (file_id == (uint32_t)PatchFileId::INTERP_WAYS) actual_stride = interp_stride;
        else if (file_id == (uint32_t)PatchFileId::ADMIN_POLYGONS) actual_stride = admin_stride;

        // Apply string remap to old data
        apply_str_remap(old_data, file_id, actual_stride);

        // Read and apply fixups (node_offset/vertex_offset fixes)
        uint32_t n_fixups; memcpy(&n_fixups, patch.data() + pos, 4); pos += 4;
        for (uint32_t i = 0; i < n_fixups; i++) {
            uint32_t idx, val;
            memcpy(&idx, patch.data() + pos, 4); pos += 4;
            memcpy(&val, patch.data() + pos, 4); pos += 4;
            size_t byte_pos = (size_t)idx * actual_stride;
            if (byte_pos + 4 <= old_data.size())
                memcpy(old_data.data() + byte_pos, &val, 4);
        }

// geocoder-patch v3: Apply custom patch format.
//
// Decompresses zstd transport layer, then:
// 1. Reads string remap, applies to old data files
// 2. Replays merge sequences to reconstruct new data files
// 3. Writes full-replacement entry/cell files
//
// Usage: geocoder-patch <current-dir> <patch-file> -o <output-dir>

#include <cstdint>
#include <cstdlib>
#include <cstring>
#include <fstream>
#include <iostream>
#include <string>
#include <unordered_map>
#include <unistd.h>
#include <vector>

#include "patch_format.h"

// Merge ops (must match diff tool)
enum MergeOp : uint8_t { OP_MATCH_RUN = 0, OP_INSERT_RUN = 1, OP_DELETE_RUN = 2 };

int main(int argc, char* argv[]) {
    if (argc < 5 || std::string(argv[3]) != "-o") {
        std::cerr << "Usage: geocoder-patch <current-dir> <patch-file> -o <output-dir>" << std::endl;
        return 1;
    }
    std::string cur_dir = argv[1], patch_path = argv[2], out_dir = argv[4];
    ensure_dir(out_dir);
    std::string tmpdir = "/tmp/geocoder-patch-" + std::to_string(getpid());
    ensure_dir(tmpdir);

    // Decompress zstd transport layer
    std::string raw_path = tmpdir + "/patch.raw";
    {
        std::string cmd = "zstd -d '" + patch_path + "' -o '" + raw_path + "' -f --quiet 2>/dev/null";
        if (system(cmd.c_str()) != 0) {
            std::cerr << "Failed to decompress patch" << std::endl; return 1;
        }
    }
    auto patch = read_file(raw_path);
    remove(raw_path.c_str());
    std::cerr << "Decompressed patch: " << patch.size() << " bytes" << std::endl;

    size_t pos = 0;
    auto read_u32 = [&]() -> uint32_t { uint32_t v; memcpy(&v, patch.data() + pos, 4); pos += 4; return v; };
    auto read_u64 = [&]() -> uint64_t { uint64_t v; memcpy(&v, patch.data() + pos, 8); pos += 8; return v; };

    // Check header
    if (memcmp(patch.data(), GCPATCH_MAGIC, 8) != 0) {
        std::cerr << "Invalid patch magic" << std::endl; return 1;
    }
    pos = 8;
    uint32_t version = read_u32();
    if (version != 2) { std::cerr << "Expected patch v2, got " << version << std::endl; return 1; }
    uint32_t flags = read_u32();
    (void)flags;

    // Read string remap
    std::unordered_map<uint32_t, uint32_t> str_remap;
    {
        uint32_t marker = read_u32();
        if (marker != 0xFFFFFFFE) { std::cerr << "Expected remap section" << std::endl; return 1; }
        uint32_t count = read_u32();
        for (uint32_t i = 0; i < count; i++) {
            uint32_t old_off = read_u32(), new_off = read_u32();
            if (old_off != new_off) str_remap[old_off] = new_off;
        }
        std::cerr << "Loaded " << str_remap.size() << " string remap entries" << std::endl;
    }

    // Detect strides
    auto detect = [&](const std::string& name, std::vector<size_t> cs) -> size_t {
        auto d = read_file(cur_dir + "/" + name);
        for (size_t s : cs) if (d.size() % s == 0 && d.size() > 0) return s;
        return cs[0];
    };
    size_t way_stride = detect("street_ways.bin", {12, 9});
    size_t interp_stride = detect("interp_ways.bin", {24, 20, 18});
    size_t admin_stride = detect("admin_polygons.bin", {24, 20, 19});

    // String remap functions
    auto apply_str_remap = [&](std::vector<char>& data, uint32_t file_id, size_t stride) {
        if (str_remap.empty()) return;
        std::vector<size_t> field_offsets;
        if (file_id == (uint32_t)PatchFileId::ADDR_POINTS) field_offsets = {8, 12};
        else if (file_id == (uint32_t)PatchFileId::STREET_WAYS) field_offsets = {(stride == 12) ? (size_t)8 : (size_t)5};
        else if (file_id == (uint32_t)PatchFileId::INTERP_WAYS) field_offsets = {(stride >= 20) ? (size_t)8 : (size_t)5};
        else if (file_id == (uint32_t)PatchFileId::ADMIN_POLYGONS) field_offsets = {8};
        else return;

        for (size_t i = 0; i + stride <= data.size(); i += stride)
            for (size_t off : field_offsets) {
                uint32_t v; memcpy(&v, data.data() + i + off, 4);
                auto it = str_remap.find(v);
                if (it != str_remap.end()) memcpy(data.data() + i + off, &it->second, 4);
            }
    };

    // Process sections
    while (pos < patch.size()) {
        uint32_t file_id = read_u32();
        if (file_id == 0xFFFFFFFF) break;

        uint32_t stride = read_u32();
        uint64_t old_size = read_u64(), new_size = read_u64(), seq_size = read_u64();

        if (file_id >= (uint32_t)PatchFileId::COUNT) {
            pos += seq_size;
            continue;
        }
        const char* filename = patch_file_names[file_id];

        if (stride == 0) {
            // Full replacement
            std::vector<char> data(patch.data() + pos, patch.data() + pos + seq_size);
            write_file(out_dir + "/" + std::string(filename), data);
            std::cerr << "  " << filename << ": full replacement " << data.size() << " bytes" << std::endl;
            pos += seq_size;
            continue;
        }

        // Merge sequence: load old file, apply remap, replay sequence
        auto old_data = read_file(cur_dir + "/" + std::string(filename));
        size_t actual_stride = stride;
        if (file_id == (uint32_t)PatchFileId::STREET_WAYS) actual_stride = way_stride;
        else if (file_id == (uint32_t)PatchFileId::INTERP_WAYS) actual_stride = interp_stride;
        else if (file_id == (uint32_t)PatchFileId::ADMIN_POLYGONS) actual_stride = admin_stride;

        // Apply string remap to old data
        apply_str_remap(old_data, file_id, actual_stride);

        // Note: offset fixups (node_offset/vertex_offset) are already baked into the
        // merge sequence — matched records from old have been compared WITH fixups applied
        // by the diff tool. The merge MATCH ops copy from the remapped old, which has
        // the ORIGINAL offset values. But the diff matched against the fixed-up version.
        //
        // Wait — this is a problem. The diff applied fixups to old, then matched.
        // The patch only applies string remap, not fixups. So matched bytes differ.
        //
        // For the merge to work, we need the old file to be in the same state as
        // when the diff computed the merge sequence. The diff applied string remap
        // + offset fixups. We applied string remap. We need to also apply fixups.
        //
        // But we don't have the fixup data in v2 format...
        //
        // Actually: the merge sequence copies bytes from old. If old bytes after string
        // remap don't match new bytes (because offsets differ), the diff would have
        // encoded them as DELETE+INSERT, not MATCH. So MATCH ops only fire when bytes
        // are identical after string remap. For ways with different node_offsets, the
        // diff tool fixed up node_offsets BEFORE comparing, so MATCH ops assume the
        // fixup was applied.
        //
        // The patch tool must apply the same fixups. Since we don't have fixup tables
        // in v2, the diff tool needs to NOT fix offsets and instead let the merge
        // handle the byte differences. This means ways with different node_offsets
        // become DELETE+INSERT pairs instead of MATCH.
        //
        // This is less optimal but correct. The diff tool should NOT fixup offsets
        // when using merge sequences. Let me fix this in a follow-up.

        // Replay merge sequence
        std::vector<char> output;
        output.reserve(new_size);
        size_t old_pos = 0;
        size_t seq_end = pos + seq_size;

        while (pos < seq_end) {
            uint8_t op = static_cast<uint8_t>(patch[pos]); pos++;
            uint32_t count; memcpy(&count, patch.data() + pos, 4); pos += 4;

            if (op == OP_MATCH_RUN) {
                // Copy count records from old
                size_t bytes = count * actual_stride;
                if (old_pos + bytes <= old_data.size()) {
                    output.insert(output.end(), old_data.data() + old_pos,
                                 old_data.data() + old_pos + bytes);
                }
                old_pos += bytes;
            } else if (op == OP_INSERT_RUN) {
                // Read count records from patch
                size_t bytes = count * actual_stride;
                output.insert(output.end(), patch.data() + pos, patch.data() + pos + bytes);
                pos += bytes;
            } else if (op == OP_DELETE_RUN) {
                // Skip count records in old
                old_pos += count * actual_stride;
            }
        }

        write_file(out_dir + "/" + std::string(filename), output);
        std::cerr << "  " << filename << ": " << output.size() << " bytes" << std::endl;
    }

    std::string rm_cmd = "rm -rf '" + tmpdir + "'";
    system(rm_cmd.c_str());
    std::cerr << "Patch applied. Output in " << out_dir << std::endl;
    return 0;
}

-        // Merge sequence: load old file, apply remap, replay sequence

+        // Merge sequence: load old file, apply remap + fixups, replay sequence

+        // Read and apply fixups (node_offset/vertex_offset fixes)

+        uint32_t n_fixups; memcpy(&n_fixups, patch.data() + pos, 4); pos += 4;

+        for (uint32_t i = 0; i < n_fixups; i++) {

+            memcpy(&idx, patch.data() + pos, 4); pos += 4;

+            memcpy(&val, patch.data() + pos, 4); pos += 4;

+            size_t byte_pos = (size_t)idx * actual_stride;

+            if (byte_pos + 4 <= old_data.size())

+                memcpy(old_data.data() + byte_pos, &val, 4);


Also need to update the merge sequence size reading (now comes after fixups):


   115→
   116→        if (stride == 0) {
   117→            // Full replacement
   118→            std::vector<char> data(patch.data() + pos, patch.data() + pos + seq_size);
   119→            write_file(out_dir + "/" + std::string(filename), data);
   120→            std::cerr << "  " << filename << ": full replacement " << data.size() << " bytes" << std::endl;
   121→            pos += seq_size;
   122→            continue;
   123→        }
   124→
   125→        // Merge sequence: load old file, apply remap + fixups, replay sequence
   126→        auto old_data = read_file(cur_dir + "/" + std::string(filename));
   127→        size_t actual_stride = stride;
   128→        if (file_id == (uint32_t)PatchFileId::STREET_WAYS) actual_stride = way_stride;
   129→        else if (file_id == (uint32_t)PatchFileId::INTERP_WAYS) actual_stride = interp_stride;

        if (stride == 0) {
            // Full replacement
            std::vector<char> data(patch.data() + pos, patch.data() + pos + seq_size);
            write_file(out_dir + "/" + std::string(filename), data);
            std::cerr << "  " << filename << ": full replacement " << data.size() << " bytes" << std::endl;
            pos += seq_size;
            continue;
        }

        // Merge sequence: load old file, apply remap + fixups, replay sequence
        auto old_data = read_file(cur_dir + "/" + std::string(filename));
        size_t actual_stride = stride;
        if (file_id == (uint32_t)PatchFileId::STREET_WAYS) actual_stride = way_stride;
        else if (file_id == (uint32_t)PatchFileId::INTERP_WAYS) actual_stride = interp_stride;


Wait, the section header format changed. The diff writes: fid, stride, old_size, new_size, n_fixups, [fixups], seq_size, [seq_data]. But the patch reads: fid, stride, old_size, new_size, seq_size. The seq_size is now AFTER fixups, not before. Let me fix the patch reading to match:


        uint32_t stride = read_u32();
        uint64_t old_size = read_u64(), new_size = read_u64(), seq_size = read_u64();

        if (file_id >= (uint32_t)PatchFileId::COUNT) {
            pos += seq_size;
            continue;
        }
        const char* filename = patch_file_names[file_id];

        if (stride == 0) {
            // Full replacement
            std::vector<char> data(patch.data() + pos, patch.data() + pos + seq_size);
            write_file(out_dir + "/" + std::string(filename), data);
            std::cerr << "  " << filename << ": full replacement " << data.size() << " bytes" << std::endl;
            pos += seq_size;
            continue;
        }

        uint32_t stride = read_u32();
        uint64_t old_size = read_u64(), new_size = read_u64();

        if (file_id >= (uint32_t)PatchFileId::COUNT) {
            std::cerr << "  Unknown file " << file_id << std::endl;
            break;
        }
        const char* filename = patch_file_names[file_id];

        if (stride == 0) {
            // Full replacement: n_fixups=0, then seq_size = data size
            uint32_t n_fix = read_u32(); (void)n_fix; // always 0 for full replacement
            uint64_t data_size = read_u64();
            std::vector<char> data(patch.data() + pos, patch.data() + pos + data_size);
            write_file(out_dir + "/" + std::string(filename), data);
            std::cerr << "  " << filename << ": full replacement " << data.size() << " bytes" << std::endl;
            pos += data_size;
            continue;
        }