#include "path-search.hpp"
#include "global-coords.hpp"
#include "world.hpp"
#include "pass-mode.hpp"
#include "RTree-search.hpp"
#include "compat/function2.hpp"
#include <Corrade/Containers/PairStl.h>
#include <Magnum/Math/Functions.h>
#include <Magnum/Math/Range.h>

namespace floormat {

namespace {

constexpr auto div = path_search::subdivide_factor;
constexpr int div_BITS = 2;
static_assert(1 << div_BITS == div);

constexpr auto never_continue_1 = [](collision_data) constexpr { return path_search_continue::blocked; };
constexpr auto never_continue_ = path_search::pred{never_continue_1};
constexpr auto always_continue_1 = [](collision_data) constexpr { return path_search_continue::pass; };
constexpr auto always_continue_ = path_search::pred{always_continue_1};

constexpr Pair<Vector2i, Vector2i> get_value(Vector2ub sz, Vector2ub div, rotation r)
{
    const int offset_W = iTILE_SIZE2.x()/(int)div.x(), offset_N = iTILE_SIZE2.y()/(int)div.y();

    const auto r_ = (uint8_t)r;
    CORRADE_ASSUME(r_ <= (uint8_t)rotation_COUNT);

    switch (r_)
    {
    case (uint8_t)rotation::N: {
        auto min_N = Vector2i(-sz.x()/2,                        -offset_N - sz.y()/2            );
        auto max_N = Vector2i(min_N.x() + sz.x(),               sz.y() - sz.y()/2               );
        return {min_N, max_N};
    }
    case (uint8_t)rotation::S: {
        auto min_S = Vector2i(-sz.x()/2,                        -sz.y()                         );
        auto max_S = Vector2i(min_S.x() + sz.x(),               offset_N + sz.y() - sz.y()/2    );
        return {min_S, max_S};
    }
    case (uint8_t)rotation::W: {
        auto min_W = Vector2i(-offset_W - sz.x()/2,             -sz.y()/2                       );
        auto max_W = Vector2i(sz.x() - sz.x()/2,                min_W.y() + sz.y()              );
        return {min_W, max_W};
    }
    case (uint8_t)rotation::E: {
        auto min_E = Vector2i(-sz.x()/2,                        -sz.y()/2                       );
        auto max_E = Vector2i(offset_W + sz.x() - sz.x()/2,     min_E.y() + sz.y()              );
        return {min_E, max_E};
    }
    case (uint8_t)rotation_COUNT: {
        auto min_C = Vector2i(-sz.x()/2,                        -sz.y()/2                       );
        auto max_C = min_C + Vector2i(sz);
        return {min_C, max_C};
    }
    default:
        fm_abort("wrong 4-way rotation enum '%d'", (int)r);
    }
}

#if 0
[[maybe_unused]] constexpr bool test_offsets()
{
    constexpr auto sz_  = Vector2ub(path_search::min_size);
    constexpr Vector2i shift = Vector2i(0, 0) * iTILE_SIZE2 + Vector2i(0, 0);

    [[maybe_unused]] constexpr auto N = get_value(sz_, {1,1}, rotation::N);
    [[maybe_unused]] constexpr auto min_N = N.first() + shift, max_N = N.second() + shift;
    [[maybe_unused]] constexpr auto N_min_x = min_N.x(), N_min_y = min_N.y();
    [[maybe_unused]] constexpr auto N_max_x = max_N.x(), N_max_y = max_N.y();

    [[maybe_unused]] constexpr auto E = get_value(sz_, {1,1}, rotation::E);
    [[maybe_unused]] constexpr auto min_E = E.first() + shift, max_E = E.second() + shift;
    [[maybe_unused]] constexpr auto E_min_x = min_E.x(), E_min_y = min_E.y();
    [[maybe_unused]] constexpr auto E_max_x = max_E.x(), E_max_y = max_E.y();

    [[maybe_unused]] constexpr auto S = get_value(sz_, {1,1}, rotation::S);
    [[maybe_unused]] constexpr auto min_S = S.first() + shift, max_S = S.second() + shift;
    [[maybe_unused]] constexpr auto S_min_x = min_S.x(), S_min_y = min_S.y();
    [[maybe_unused]] constexpr auto S_max_x = max_S.x(), S_max_y = max_S.y();

    [[maybe_unused]] constexpr auto W = get_value(sz_, {1,1}, rotation::W);
    [[maybe_unused]] constexpr auto min_W = W.first() + shift, max_W = W.second() + shift;
    [[maybe_unused]] constexpr auto W_min_x = min_W.x(), W_min_y = min_W.y();
    [[maybe_unused]] constexpr auto W_max_x = max_W.x(), W_max_y = max_W.y();

    return true;
}
static_assert(test_offsets());
#endif

#if 0
[[maybe_unused]] constexpr bool test_offsets2()
{
    using enum rotation;
    constexpr auto tile_start = iTILE_SIZE2/-2;
    constexpr auto sz = Vector2ub(8, 16);

    {
        constexpr auto bb = get_value(sz, Vector2ub(div), N);
        constexpr auto min = tile_start + bb.first(), max = tile_start + bb.second();
        static_assert(min.x() == -32 - sz.x()/2);
        static_assert(max.x() == -32 + sz.x()/2);
        static_assert(min.y() == -48 - sz.y()/2);
        static_assert(max.y() == -32 + sz.y()/2);
    }
    {
        constexpr auto bb = get_value(sz, Vector2ub(div), W);
        constexpr auto min = tile_start + bb.first(), max = tile_start + bb.second();
        static_assert(min.x() == -32 - 16 - sz.x()/2);
        static_assert(max.x() == -32 + sz.x()/2);
        static_assert(min.y() == -32 - sz.y()/2);
        static_assert(max.y() == -32 + sz.y()/2);
    }

    return true;
}
static_assert(test_offsets2());
#endif

} // namespace



path_search::neighbors::operator ArrayView<const global_coords>() const { return {data.data(), size}; }
auto path_search::never_continue() noexcept -> const pred& { return never_continue_; }
auto path_search::always_continue() noexcept -> const pred& { return always_continue_; }

bool path_search::is_passable_1(chunk& c, Vector2 min, Vector2 max, object_id own_id, const pred& p)
{
    auto& rt = *c.rtree();
    bool is_passable = true;
    rt.Search(min.data(), max.data(), [&](uint64_t data, const auto&) {
        [[maybe_unused]] auto x = std::bit_cast<collision_data>(data);
        if (x.data != own_id)
        {
            if (x.pass != (uint64_t)pass_mode::pass && p(x) != path_search_continue::pass)
            {
                is_passable = false;
                //[[maybe_unused]] auto obj = c.world().find_object(x.data);
                return false;
            }
        }
        return true;
    });
    return is_passable;
}

bool path_search::is_passable_(chunk* c0, const std::array<world::neighbor_pair, 8>& neighbors,
                               Vector2 min, Vector2 max, object_id own_id, const pred& p)
{
    fm_debug_assert(max >= min);

    if (c0)
        // it's not correct to return true if c == nullptr
        // because neighbors can still contain bounding boxes for that tile
        if (!is_passable_1(*c0, min, max, own_id, p))
            return false;

    for (auto i = 0uz; i < 8; i++)
    {
        auto nb = world::neighbor_offsets[i];
        auto* c2 = neighbors[i].c;

        if (c2)
        {
            static_assert(std::size(world::neighbor_offsets) == 8);
            constexpr auto chunk_size = iTILE_SIZE2 * TILE_MAX_DIM;
            constexpr auto bbox_size = Vector2i(1 << sizeof(Vector2b::Type)*8);
            constexpr auto chunk_max = chunk_size + bbox_size;

            const auto off = Vector2(nb)*Vector2(chunk_size);
            const auto min_ = min - off, max_ = max - off;

            if (min_.x() > chunk_max.x() || min_.y() > chunk_max.y())
                continue;
            if (max_.x() < -bbox_size.x() || max_.y() < -bbox_size.y())
                continue;

            if (!is_passable_1(*c2, min_, max_, own_id, p))
                return false;
        }
    }

    return true;
}

bool path_search::is_passable(world& w, chunk_coords_ ch0, Vector2 min, Vector2 max, object_id own_id, const pred& p)
{
    auto* c = w.at(ch0);
    auto neighbors = w.neighbors(ch0);
    return is_passable_(c, neighbors, min, max, own_id, p);
}

bool path_search::is_passable(world& w, global_coords coord, Vector2b offset, Vector2ub size_,
                              object_id own_id, const pred& p)
{
    auto center = iTILE_SIZE2 * Vector2i(coord.local()) + Vector2i(offset);
    auto size = Vector2(size_);
    auto min = Vector2(center) - size*.5f, max = min + size;
    return is_passable(w, coord, min, max, own_id, p);
}

bool path_search::is_passable(world& w, chunk_coords_ ch, const bbox<float>& bb, object_id own_id, const pred& p)
{
    return is_passable(w, ch, bb.min, bb.max, own_id, p);
}

auto path_search::neighbor_tile_bbox(Vector2i coord, Vector2ub own_size, Vector2ub div, rotation r) -> bbox<float>
{
    own_size = Math::max(own_size, Vector2ub(min_size));
    const auto shift = coord * iTILE_SIZE2;
    auto [min, max] = get_value(own_size, div, r);
    return { Vector2(min + shift), Vector2(max + shift) };
}

auto path_search::neighbor_tiles(world& w, global_coords coord, Vector2ub size, object_id own_id, const pred& p) -> neighbors
{
    auto ch = chunk_coords_{ coord.chunk(), coord.z() };
    auto pos = Vector2i(coord.local());
    constexpr auto min_size = Vector2ub(iTILE_SIZE2/4);
    size = Math::max(size, min_size);

    neighbors ns;

    using enum rotation;
    constexpr struct {
        Vector2i off;
        rotation r = {};
    } nbs[] = {
        { {  0, -1 }, N },
        { {  1,  0 }, E },
        { {  0,  1 }, S },
        { { -1,  0 }, W },
    };

    for (auto [off, r] : nbs)
    {
        auto [min, max] = neighbor_tile_bbox(pos, size, { 1, 1 }, r);
        if (is_passable(w, ch, min, max, own_id, p))
            ns.data[ns.size++] = { coord + off, {} };
    }

    return ns;
}

} // namespace floormat