#include <games/Game.hpp>
#include <games/tetris/Tetromino.hpp>
#include <games/tetris/Tetris.hpp>
#include <renderer/Renderer.hpp>

#include <SDL3/SDL_events.h>
#include <SDL3/SDL_timer.h>
#include <imgui.h>

#include <fstream>
#include <iostream>


static 
std::u32string
int32_to_u32string(int32_t value)
{
    std::string str = std::to_string(value);
    return std::u32string(str.begin(), str.end());
}


Tetris::Tetris()
    : m_font{s_dejavu_sans_mono_filepath, 22}
    , m_active_tetromino{m_board.m_bitmap}
    , m_highscore {ReadHighscore()}
{
    m_frame_strings.reserve(s_frame_strings_capacity);
}

void
Tetris::Start()
{
    m_game_status = game_resuming;
    m_tlast_milliseconds = SDL_GetTicks();
    m_dt_remaining_seconds = 0.0f;

    m_board.Reset();
    m_active_tetromino.Reset(Tetromino::GenerateRandomId());
    m_next_tetromino_id = Tetromino::GenerateRandomId();

    memset(m_tetromino_counters, 0, sizeof(m_tetromino_counters));
    m_tetromino_counters[m_active_tetromino.GetId()] += 1;
    m_score = 0;
    m_line_counter = 0;
    m_starting_level = 0;
    m_level = 0;
    m_softdrop_counter = 0;
}

bool
Tetris::Update(std::vector<SDL_Event>& events)
{
    Color clear_color = {0.2f, 0.2f, 0.2f, 1.0f};
    g_renderer.SetCameraSize(4.0f, 3.0f);
    g_renderer.Clear(clear_color);

    m_frame_strings.clear();


    if (m_game_status == game_starting) {
        Start();
    }


    float dt = ProcessDt();


    if (m_game_status == game_resuming) {
        uint32_t softdrop_count = GetSoftdropCount(dt);
        for (uint32_t i{0}; i < softdrop_count; i++) {
            bool moved_down = m_active_tetromino.MaybeMoveDown();
            if (!moved_down) {
                HandleTetrominoPlacement();
            }
        }
    }


    for (auto& event : events) {
        switch (m_game_status) {
        case game_resuming: UpdateResumeState(event); break;
        case game_paused: UpdatePauseState(event); break;
        default:;
        }
    }


    if (m_game_status == game_exit) {
        return false;
    }


    Draw();

    assert((float)m_frame_strings.size() <= 0.8f * s_frame_strings_capacity);


    return true;
}

void Tetris::UpdateResumeState(SDL_Event& event) {
    switch (event.type) {
    case SDL_EVENT_KEY_DOWN: {
        auto key = event.key.key;
        if (key == SDLK_RIGHT) {
            m_active_tetromino.MaybeMoveHorizontally(Tetromino::right);
        } else if (key == SDLK_LEFT) {
            m_active_tetromino.MaybeMoveHorizontally(Tetromino::left);
        } else if (key == SDLK_DOWN) {
            bool moved_down = m_active_tetromino.MaybeMoveDown();
            if (!moved_down) {
                HandleTetrominoPlacement();
            }
            else {
                m_softdrop_counter++;
            }
        } else if (key == SDLK_X) {
            m_active_tetromino.MaybeRotate(Tetromino::rotate_clockwise);
        } else if (key == SDLK_Z || key == SDLK_Y) {
            m_active_tetromino.MaybeRotate(Tetromino::rotate_counter_clockwise);
        } else if (key == SDLK_ESCAPE) {
            m_game_status = game_paused;
        }
    }
    default:;
    }
}

void Tetris::UpdatePauseState(SDL_Event& event) {
    switch (event.type) {
    case SDL_EVENT_KEY_DOWN: {
        auto key = event.key.key;
        if (key == SDLK_ESCAPE) {
            m_game_status = game_resuming;
        }
    }
    default:;
    }
}

void
Tetris::HandleTetrominoPlacement()
{
    int32_t rows_cleared = m_board.PlaceTetromino(m_active_tetromino);


    m_active_tetromino.Reset(m_next_tetromino_id);
    m_next_tetromino_id = Tetromino::GenerateRandomId();


    if (m_active_tetromino.IsCollisionWithBoard()) {
        m_game_status = game_over;
        if (m_score > m_highscore) {
            m_highscore = m_score;
            WriteHighscore();
        }
    }


    m_line_counter += rows_cleared;
    m_tetromino_counters[m_active_tetromino.GetId()] += 1;

    if (rows_cleared == 1) {
        m_score += 40 * (m_level + 1);
    }
    else if (rows_cleared == 2) {
        m_score += 100 * (m_level + 1);
    }
    else if (rows_cleared == 3) {
        m_score += 300 * (m_level + 1);
    }
    else if (rows_cleared == 4) {
        m_score += 1200 * (m_level + 1);
    }

    m_score += m_softdrop_counter;
    m_softdrop_counter = 0;
    m_level = m_starting_level + m_line_counter / 10;
}

uint32_t
Tetris::GetSoftdropCount(float dt)
{
    float nes_frame_time = 1.0f / 60;
    int32_t nes_frames_per_cell;
    if      (m_level <= 8)  nes_frames_per_cell = 48 - m_level * 5;
    else if (m_level == 9)  nes_frames_per_cell = 6;
    else if (m_level <= 12) nes_frames_per_cell = 5;
    else if (m_level <= 15) nes_frames_per_cell = 4;
    else if (m_level <= 18) nes_frames_per_cell = 3;
    else if (m_level <= 28) nes_frames_per_cell = 2;
    else                    nes_frames_per_cell = 1;


    float dt_level = static_cast<float>(nes_frames_per_cell) * nes_frame_time;

    uint32_t softdrop_count = 0;
    while (dt > dt_level) {
        softdrop_count += 1;
        dt -= dt_level;
    }


    m_dt_remaining_seconds = dt;
    return softdrop_count;
}

int32_t
Tetris::ReadHighscore()
{
    int32_t highscore = 0;
    std::ifstream highscore_file_in {s_tetris_highscore_path};
    if (highscore_file_in) {
        highscore_file_in >> highscore;
        highscore_file_in.close();
    }
    else {
        SDL_LogInfo(0, "Tetris: cannot open %s for reading", s_tetris_highscore_path);
    }
    return highscore;
}

void
Tetris::WriteHighscore()
{
    std::ofstream highscore_file_out {s_tetris_highscore_path};
    if (highscore_file_out) {
        highscore_file_out << m_highscore << std::endl;
        highscore_file_out.close();
    }
    else {
        SDL_LogInfo(0, "Tetris: cannot open %s for writing", s_tetris_highscore_path);
    }
}

void
Tetris::Draw()
{
    m_board.Draw(m_level);
    m_active_tetromino.Draw();

    DrawNextTetromino();
    DrawStatistics();
    DrawLineCounter();
    DrawLevel();
    DrawScore();

    if (m_game_status  == game_paused) {
        DrawDefaultGamePausedMenu();
    }
    else if (m_game_status == game_over) {
        DrawGameOverMenu();
    }
}

void
Tetris::DrawGameOverMenu()
{
    ImGui::Begin("TetrisGameOver", nullptr, s_imgui_window_flags_menu);
    ImGui::Text("Score = %d", m_score);
    ImGui::Text("HighScore = %d", m_highscore);
    if (ImGui::Button("Restart")) {
        m_game_status = game_starting;
    }
    if (ImGui::Button("Exit")) {
        m_game_status = game_exit;
    }
    ImGui::End();
}

void
Tetris::DrawLineCounter()
{
    static std::u32string text = U"Lines: xxx";
    V3F32 pos = {0.5f, 2.6f, 4.0f};
    Color color = {0.9f, 0.9f, 0.9f, 1.0f};

    int line_count = std::min(m_line_counter, 999);

    text[9] = U'0' + char32_t(line_count % 10);
    line_count /= 10;
    text[8] = U'0' + char32_t(line_count % 10);
    line_count /= 10;
    text[7] = U'0' + char32_t(line_count % 10);
    line_count /= 10;


    g_renderer.PushText(text, m_font, pos, color);
    pos.x += 0.2f;
}

void
Tetris::DrawStatistics()
{
    V3F32 pos = {0.4f, 0.5f, s_text_z};


    static std::u32string title_text = U"Statistics";
    V3F32 title_pos = {pos.x + 0.02f, pos.y + 1.64f, pos.z};
    g_renderer.PushText(title_text, m_font, title_pos, s_text_color);


    float yadvance = -0.2f;
    float tetrominoes_x0 = pos.x;
    float tetrominoes_y0 = pos.y - (float)Tetromino::id_count * yadvance;
    V2F32 tetromino_pos = {tetrominoes_x0, tetrominoes_y0};

    Tetromino::Draw(Tetromino::t_piece, 0, tetromino_pos, 0.5f);
    tetromino_pos.y += yadvance;

    Tetromino::Draw(Tetromino::j_piece, 0, tetromino_pos, 0.5f);
    tetromino_pos.y += yadvance;

    Tetromino::Draw(Tetromino::z_piece, 0, tetromino_pos, 0.5f);
    tetromino_pos.y += yadvance;

    Tetromino::Draw(Tetromino::o_piece, 0, tetromino_pos, 0.5f);
    tetromino_pos.y += yadvance;

    Tetromino::Draw(Tetromino::s_piece, 0, tetromino_pos, 0.5f);
    tetromino_pos.y += yadvance;

    Tetromino::Draw(Tetromino::l_piece, 0, tetromino_pos, 0.5f);
    tetromino_pos.y += yadvance;

    Tetromino::Draw(Tetromino::i_piece, 0, tetromino_pos, 0.5f);
    tetromino_pos.y += yadvance;


    float counters_x0 = pos.x + 0.4f;
    float counters_y0 = pos.y + 0.05f - yadvance * (float)Tetromino::id_count;
    V3F32 counters_pos = {counters_x0, counters_y0, s_text_z};

    std::u32string& t_count = m_frame_strings.emplace_back(int32_to_u32string(m_tetromino_counters[Tetromino::t_piece]));
    std::u32string& j_count = m_frame_strings.emplace_back(int32_to_u32string(m_tetromino_counters[Tetromino::j_piece]));
    std::u32string& z_count = m_frame_strings.emplace_back(int32_to_u32string(m_tetromino_counters[Tetromino::z_piece]));
    std::u32string& o_count = m_frame_strings.emplace_back(int32_to_u32string(m_tetromino_counters[Tetromino::o_piece]));
    std::u32string& s_count = m_frame_strings.emplace_back(int32_to_u32string(m_tetromino_counters[Tetromino::s_piece]));
    std::u32string& l_count = m_frame_strings.emplace_back(int32_to_u32string(m_tetromino_counters[Tetromino::l_piece]));
    std::u32string& i_count = m_frame_strings.emplace_back(int32_to_u32string(m_tetromino_counters[Tetromino::i_piece]));

    g_renderer.PushText(t_count, m_font, counters_pos, s_text_color);
    counters_pos.y += yadvance;
    g_renderer.PushText(j_count, m_font, counters_pos, s_text_color);
    counters_pos.y += yadvance;
    g_renderer.PushText(z_count, m_font, counters_pos, s_text_color);
    counters_pos.y += yadvance;
    g_renderer.PushText(o_count, m_font, counters_pos, s_text_color);
    counters_pos.y += yadvance;
    g_renderer.PushText(s_count, m_font, counters_pos, s_text_color);
    counters_pos.y += yadvance;
    g_renderer.PushText(l_count, m_font, counters_pos, s_text_color);
    counters_pos.y += yadvance;
    g_renderer.PushText(i_count, m_font, counters_pos, s_text_color);
}

void
Tetris::DrawScore()
{
    V3F32 pos = {3.0f, 2.6f, s_text_z};


    std::u32string& top_label = m_frame_strings.emplace_back(U"Top");
    std::u32string& top_value = m_frame_strings.emplace_back(int32_to_u32string(m_highscore));

    std::u32string& score_label = m_frame_strings.emplace_back(U"Score");
    std::u32string& score_value = m_frame_strings.emplace_back(int32_to_u32string(m_score));


    g_renderer.PushText(top_label, m_font, pos, s_text_color);
    pos.y -= 0.1f;
    g_renderer.PushText(top_value, m_font, pos, s_text_color);
    pos.y -= 0.2f;

    g_renderer.PushText(score_label, m_font, pos, s_text_color);
    pos.y -= 0.1f;
    g_renderer.PushText(score_value, m_font, pos, s_text_color);
}

void
Tetris::DrawNextTetromino()
{
    V3F32 pos = {3.0f, 1.4f, s_text_z};


    V3F32 label_pos = {pos.x, pos.y + 0.4f, pos.z};
    std::u32string& label_text = m_frame_strings.emplace_back(U"Next:");
    g_renderer.PushText(label_text, m_font, label_pos, s_text_color);


    V2F32 tetromino_pos = {pos.x, pos.y};
    Tetromino::Draw(m_next_tetromino_id, 0, tetromino_pos, 0.5f);
}

void
Tetris::DrawLevel()
{
    V3F32 pos = {3.0f, 1.1f};

    std::u32string& label = m_frame_strings.emplace_back(U"Level");
    g_renderer.PushText(label, m_font, pos, s_text_color);
    pos.y -= 0.1f;

    std::u32string& level = m_frame_strings.emplace_back(int32_to_u32string(m_level));
    g_renderer.PushText(level, m_font, pos, s_text_color);
}