#include "src/world.hpp"
#include "src/tile-defs.hpp"
#include "src/tile-atlas.hpp"
#include "binary-serializer.inl"

#include <bit>
#include <cerrno>
#include <cstdio>
#include <array>
#include <vector>
#include <limits>
#include <unordered_map>

#include <Corrade/Containers/ArrayView.h>
#include <Corrade/Utility/Path.h>

namespace floormat::Serialize {

namespace {

using tilemeta  = std::uint8_t;
using imgvar    = std::uint8_t;
using atlasid   = std::uint16_t;
using enum tile::pass_mode;

template<typename T> constexpr inline T int_max = std::numeric_limits<T>::max();

constexpr inline std::size_t atlas_name_max = 128;
constexpr inline auto null_atlas = (atlasid)-1LL;

#define file_magic ".floormat.save"
constexpr inline std::uint16_t proto_version = 1;
constexpr inline auto chunk_magic = (std::uint16_t)~0xc0d3;

constexpr inline std::underlying_type_t<tile::pass_mode> pass_mask = pass_blocked | pass_shoot_through | pass_ok;
constexpr inline auto pass_bits = std::bit_width(pass_mask);

enum : tilemeta {
    meta_ground     = 1 << (pass_bits + 0),
    meta_wall_n     = 1 << (pass_bits + 1),
    meta_wall_w     = 1 << (pass_bits + 2),
};

struct interned_atlas final {
    const tile_atlas* img;
    atlasid index;
};

struct state final {
    state(const world& world);
    atlasid intern_atlas(const tile_image& img);
    atlasid maybe_intern_atlas(const tile_image& img);
    void serialize_chunk(const chunk& c, chunk_coords coord);
    void serialize_atlases();
    ArrayView<const char> serialize_world();

    fm_DECLARE_DEFAULT_MOVE_ASSIGNMENT_(state);
    fm_DECLARE_DEPRECATED_COPY_ASSIGNMENT(state);

private:
    const struct world* world;
    std::vector<char> atlas_buf, chunk_buf, file_buf;
    std::vector<std::vector<char>> chunk_bufs;
    std::unordered_map<const void*, interned_atlas> tile_images;
};

constexpr auto tile_size = sizeof(tilemeta) + sizeof(atlasid)*3;

constexpr auto chunkbuf_size =
    sizeof(chunk_magic) + sizeof(chunk_coords) + tile_size * TILE_COUNT;

#ifdef __GNUG__
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
#endif

state::state(const struct world& world) : world{&world}
{
    chunk_buf.reserve(chunkbuf_size);
    chunk_bufs.reserve(world.chunks().size());
    atlas_buf.reserve(atlas_name_max * 64);
}

#ifdef __GNUG__
#pragma GCC diagnostic pop
#endif

atlasid state::intern_atlas(const tile_image& img)
{
    const void* const ptr = img.atlas.get();
    fm_assert_debug(ptr != nullptr);
    if (auto it = tile_images.find(ptr); it != tile_images.end())
        return it->second.index;
    else
        return (tile_images[ptr] = { &*img.atlas, (atlasid)tile_images.size() }).index;
}

atlasid state::maybe_intern_atlas(const tile_image& img)
{
    return img ? intern_atlas(img) : null_atlas;
}

void state::serialize_chunk(const chunk& c, chunk_coords coord)
{
    fm_assert(chunk_buf.empty());
    chunk_buf.resize(chunkbuf_size);

    auto s = binary_writer{chunk_buf.begin()};

    s << chunk_magic << coord.x << coord.y;

    for (std::size_t i = 0; i < TILE_COUNT; i++)
    {
        const tile& x = c[i];

        [[maybe_unused]] constexpr auto tile_size = sizeof(atlasid)*3 + sizeof(tilemeta);
        fm_assert_debug(s.bytes_written() + tile_size <= chunkbuf_size);

        auto img_g = maybe_intern_atlas(x.ground_image);
        auto img_n = maybe_intern_atlas(x.wall_north);
        auto img_w = maybe_intern_atlas(x.wall_north);

        tilemeta flags = {};
        flags |= meta_ground * (img_g != null_atlas);
        flags |= meta_wall_n * (img_n != null_atlas);
        flags |= meta_wall_w * (img_w != null_atlas);

        fm_assert_debug((x.passability & pass_mask) == x.passability);
        flags |= x.passability;

        s << flags;

        if (img_g != null_atlas)
            s << img_g;
        if (img_n != null_atlas)
            s << img_n;
        if (img_w != null_atlas)
            s << img_w;
    }

    const auto nbytes = s.bytes_written();
    fm_assert(nbytes <= chunkbuf_size);

    chunk_buf.resize(nbytes);
    chunk_bufs.push_back(chunk_buf);
    chunk_buf.clear();
}

void state::serialize_atlases()
{
    const std::size_t sz = tile_images.size();
    fm_assert(sz < int_max<atlasid>);
    const auto atlasbuf_size = sizeof(sz) + atlas_name_max*sz;
    atlas_buf.resize(atlasbuf_size);
    auto s = binary_writer{atlas_buf.begin()};
    fm_assert(sz <= int_max<atlasid>);

    s << sz;

    for (const auto& [p, t] : tile_images)
    {
        const auto& [atlas, index] = t;
        const auto name = atlas->name();
        const auto namesiz = name.size();
        fm_assert_debug(s.bytes_written() + namesiz + 1 <= atlasbuf_size);
        fm_assert(namesiz <= atlas_name_max - 1); // null terminated
        fm_assert_debug(name.find('\0') == name.cend());
        s.write_asciiz_string(name);
    }
    fm_assert(s.bytes_written() <= atlasbuf_size);
}

#ifdef __GNUG__
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
#endif

ArrayView<const char> state::serialize_world()
{
    for (const auto& [pos, c] : world->chunks())
    {
#ifndef FM_NO_DEBUG
        if (c.empty(true))
            fm_warn("chunk %hd:%hd is empty", pos.x, pos.y);
#endif
        serialize_chunk(c, pos);
    }
    serialize_atlases();

    std::size_t len = 0;
    len += std::size(file_magic)-1;
    len += sizeof(proto_version);
    for (const auto& buf : chunk_bufs)
        len += buf.size();
    len += atlas_buf.size();
    file_buf.resize(len);
    auto it = file_buf.begin();
    const auto copy = [&](const auto& in) {
#ifndef FM_NO_DEBUG
        auto len1 = std::distance(std::cbegin(in), std::cend(in)),
             len2 = std::distance(it, file_buf.end());
        fm_assert(len1 <= len2);
#endif
        it = std::copy(std::cbegin(in), std::cend(in), it);
    };
    copy(Containers::StringView{file_magic, std::size(file_magic)-1});
    copy(std::initializer_list<char>{ char(proto_version & 0xff), char((proto_version >> 8) & 0xff) });
    copy(atlas_buf);
    for (const auto& buf : chunk_bufs)
        copy(buf);
    return {file_buf.data(), file_buf.size()};
}

#ifdef __GNUG__
#pragma GCC diagnostic pop
#endif

} // namespace

} // namespace floormat::Serialize

namespace floormat {

namespace Path = Corrade::Utility::Path;

struct FILE_raii final {
    FILE_raii(FILE* s) noexcept : s{s} {}
    ~FILE_raii() noexcept { if (s) ::fclose(s); }
    operator FILE*() noexcept { return s; }
    void close() noexcept { if (s) ::fclose(s); s = nullptr; }
private:
    FILE* s;
};

void world::serialize(StringView filename)
{
    collect(true);
    char errbuf[128];
    constexpr auto strerror = []<std::size_t N> (char (&buf)[N]) -> const char* {
        ::strerror_s(buf, std::size(buf), errno);
        return buf;
    };
    fm_assert(filename.flags() & StringViewFlag::NullTerminated);
    if (Path::exists(filename))
        Path::remove(filename);
    FILE_raii file = ::fopen(filename.data(), "w");
    if (!file)
        fm_abort("fopen(\"%s\", \"w\"): %s", filename.data(), strerror(errbuf));
    Serialize::state s{*this};
    const auto array = s.serialize_world();
    if (auto len = ::fwrite(array.data(), array.size(), 1, file); len != 1)
        fm_abort("fwrite: %s", strerror(errbuf));
    if (int ret = ::fflush(file); ret != 0)
        fm_abort("fflush: %s", strerror(errbuf));
}

world world::deserialize(StringView filename)
{
    (void)filename;
    return world();
}

} // namespace floormat