#include "terrain_files.h"

#include "m2_tokvec.h" // read_file

#include <cstring>

namespace fmt {

namespace {
uint16_t rd_u16(const uint8_t* p) { return uint16_t(p[0]) | (uint16_t(p[1]) << 8); }
} // namespace

bool load_height_map(const std::string& path, HeightMap& out, std::string* err) {
    std::string buf;
    if (!read_file(path, buf)) { if (err) *err = "打不开 " + path; return false; }
    const size_t need = size_t(HEIGHTMAP_RAW_XY) * HEIGHTMAP_RAW_XY * 2;
    if (buf.size() != need) {
        if (err) *err = "height.raw 大小 " + std::to_string(buf.size()) +
                        " != " + std::to_string(need) + "（131*131*2）";
        return false;
    }
    out.raw.resize(size_t(HEIGHTMAP_RAW_XY) * HEIGHTMAP_RAW_XY);
    const auto* p = reinterpret_cast<const uint8_t*>(buf.data());
    for (size_t i = 0; i < out.raw.size(); ++i) out.raw[i] = rd_u16(p + i * 2);
    return true;
}

bool load_tile_map(const std::string& path, TileMap& out, std::string* err) {
    std::string buf;
    if (!read_file(path, buf)) { if (err) *err = "打不开 " + path; return false; }
    const size_t need = size_t(TILEMAP_RAW_XY) * TILEMAP_RAW_XY;
    if (buf.size() != need) {
        if (err) *err = "tile.raw 大小 " + std::to_string(buf.size()) +
                        " != " + std::to_string(need) + "（258*258）";
        return false;
    }
    out.raw.assign(buf.begin(), buf.end());
    return true;
}

bool load_attr_map(const std::string& path, AttrMap& out, std::string* err) {
    std::string buf;
    if (!read_file(path, buf)) { if (err) *err = "打不开 " + path; return false; }
    const size_t payload = size_t(ATTRMAP_XY) * ATTRMAP_XY;
    if (buf.size() != 6 + payload) {
        if (err) *err = "attr.atr 大小 " + std::to_string(buf.size()) +
                        " != " + std::to_string(6 + payload) + "（6B 头 + 256*256）";
        return false;
    }
    const auto* p = reinterpret_cast<const uint8_t*>(buf.data());
    uint16_t magic = rd_u16(p), w = rd_u16(p + 2), h = rd_u16(p + 4);
    if (magic != ATTR_MAGIC) {
        if (err) *err = "attr.atr magic " + std::to_string(magic) + " != 2634";
        return false;
    }
    if (w != ATTRMAP_XY || h != ATTRMAP_XY) {
        if (err) *err = "attr.atr 尺寸头 " + std::to_string(w) + "x" + std::to_string(h) +
                        " != 256x256";
        return false;
    }
    out.data.assign(buf.begin() + 6, buf.end());
    return true;
}

bool load_water_map(const std::string& path, WaterMap& out, std::string* err) {
    std::string buf;
    if (!read_file(path, buf)) { if (err) *err = "打不开 " + path; return false; }
    if (buf.size() < 7) { if (err) *err = "water.wtr 太小"; return false; }
    const auto* p = reinterpret_cast<const uint8_t*>(buf.data());
    uint16_t magic = rd_u16(p), w = rd_u16(p + 2), h = rd_u16(p + 4);
    uint8_t layers = p[6];
    if (magic != WATER_MAGIC) {
        if (err) *err = "water.wtr magic " + std::to_string(magic) + " != 5426";
        return false;
    }
    if (w != WATERMAP_XY || h != WATERMAP_XY) {
        if (err) *err = "water.wtr 尺寸头 != 128x128";
        return false;
    }
    const size_t ids = size_t(WATERMAP_XY) * WATERMAP_XY;
    const size_t rest = buf.size() - 7;
    // Terrain.cpp 接受两种：u16 层高 或 long(u32) 层高。
    size_t hsize = 0;
    if (rest == ids + size_t(layers) * 2) hsize = 2;
    else if (rest == ids + size_t(layers) * 4) hsize = 4;
    else if (rest == ids && layers == 0) hsize = 0;
    else {
        if (err) *err = "water.wtr 数据段大小 " + std::to_string(rest) +
                        " 与 layers=" + std::to_string(layers) + " 不符";
        return false;
    }
    out.layer_count = layers;
    out.ids.assign(buf.begin() + 7, buf.begin() + 7 + ids);
    out.heights.clear();
    const auto* hp = p + 7 + ids;
    for (int i = 0; i < layers; ++i) {
        if (hsize == 2) out.heights.push_back((int16_t)rd_u16(hp + i * 2));
        else if (hsize == 4)
            out.heights.push_back((int32_t)(uint32_t(hp[i * 4]) | (uint32_t(hp[i * 4 + 1]) << 8) |
                                            (uint32_t(hp[i * 4 + 2]) << 16) |
                                            (uint32_t(hp[i * 4 + 3]) << 24)));
    }
    return true;
}

} // namespace fmt