#include "splat.h"

namespace fmt {

void build_splat(const TileMap& tile, int runtime_layer_count, SplatSet& out) {
    out = SplatSet{};
    const int S = SPLAT_RAW_XY; // 258
    const auto& t = tile.raw;   // 258*258
    if ((int)t.size() != S * S) return;

    // 直方图 + 出现过的图层
    int maxidx = 0;
    for (uint8_t v : t) maxidx = std::max(maxidx, (int)v);
    out.tile_histogram.assign(maxidx + 1, 0);
    for (uint8_t v : t) out.tile_histogram[v]++;

    const int limit = std::max(runtime_layer_count - 1, maxidx);
    for (int i = 1; i <= limit; ++i) {
        if (i >= (int)out.tile_histogram.size() || out.tile_histogram[i] == 0) continue;

        SplatLayer L;
        L.layer = i;
        L.alpha.resize(size_t(S) * S);
        int cov = 0;
        for (int y = 0; y < S; ++y) {
            const uint8_t* row = &t[size_t(y) * S];
            const uint8_t* up = y > 0 ? row - S : nullptr;
            const uint8_t* dn = y < S - 1 ? row + S : nullptr;
            uint8_t* a = &L.alpha[size_t(y) * S];
            for (int x = 0; x < S; ++x) {
                uint8_t tn = row[x];
                if (tn == i) {
                    a[x] = 0xFF;
                    ++cov;
                } else if (tn > i) {
                    bool found = false;
                    if (x > 0 && row[x - 1] == i) found = true;
                    else if (x < S - 1 && row[x + 1] == i) found = true;
                    else if (up) {
                        if (up[x] == i) found = true;
                        else if (x > 0 && up[x - 1] == i) found = true;
                        else if (x < S - 1 && up[x + 1] == i) found = true;
                    }
                    if (!found && dn) {
                        if (dn[x] == i) found = true;
                        else if (x > 0 && dn[x - 1] == i) found = true;
                        else if (x < S - 1 && dn[x + 1] == i) found = true;
                    }
                    a[x] = found ? 0xFF : 0x00;
                    if (found) ++cov;
                } else {
                    a[x] = 0x00;
                }
            }
        }
        L.coverage = cov;
        out.layers.push_back(std::move(L));
    }
}

} // namespace fmt