#include <SDL3/SDL.h>
#include <SDL3_image/SDL_image.h>
#include <stdlib.h>
#include "app.h"

#define MIN_TILES_TO_CLEAR 3  //More than this number of tiles per row or column will trigger clear

#define MAX_BOARD_WIDTH 10
#define MAX_BOARD_HEIGHT 10
#define MAX_PIECES 300

#define PIECE_SOURCE_YOFFSET 4
#define PIECE_SOURCE_WIDTH 32
#define PIECE_SOURCE_HEIGHT 32
#define PIECE_DEST_WIDTH 50
#define PIECE_DEST_HEIGHT 50
#define PIECE_LINEAR_SPEED 1.5
#define PIECE_SWAP_SPEED 3
#define PIECE_MAX_ROTATION 40
#define PIECE_ROTATION_SPEED 200
#define GRAVITY 2000.0
#define PIECE_MAX_FALL_XSPEED 200
#define PIECE_FALL_YSPEED_INITIAL -15
#define DELETE_PIECE_OFFSET 50

#define BOARD_WIDTH 8
#define BOARD_HEIGHT 6

#define BOARD_XOFFSET 200
#define BOARD_YOFFSET 150
#define BOARD_PADDING 4

#define BACKGROUND_SCROLL_SPEED 40

typedef enum {
  linear_move_state,
  fall_state,
  static_state
} piece_state;

typedef struct {
  int piece_id;
  piece_state state;

  SDL_FPoint position;
  float orientation;

  //Data for linear movement
  SDL_FPoint start_position;
  SDL_FPoint dest_position;
  float travel_speed;
  float fraction_travelled;

  //Data for falling animation
  float xvel, yvel;

  int piece_color;
  int piece_face;
} piece;

typedef enum {
  tile_filled,
  tile_currently_empty,
  tile_always_empty
} tile_state;

typedef struct {
  tile_state state;
  int piece_id;  //Only if tile_state == tile_filled
} tile;

typedef enum {
  intro_state,
  neutral_state,
  piece_held_state
} game_scene_state;

typedef struct {
  bool inited;
  SDL_Texture* spritesheet;
  game_scene_state state;

  piece pieces[MAX_PIECES];
  int num_pieces;

  tile board[MAX_BOARD_HEIGHT][MAX_BOARD_WIDTH];
  int board_width;
  int board_height;

  int selected_piece_id;

  SDL_Texture* background_texture;
  float background_offset;

  float background_scaled_width;
  float background_scaled_height;
} s_game;

extern SDL_Window* window;

s_game game = {0};

extern SDL_Window* window;

static inline float random_float_0to1() {
  return (float)rand() / RAND_MAX;
}

static inline bool filled_tile_at(int y, int x) {
  if (x < 0 || x >= game.board_width || y < 0 || y >= game.board_height)
    return false;

  return game.board[y][x].state == tile_filled;
}

SDL_FPoint board_position(int y, int x) {
  return (SDL_FPoint) {
    .x = (PIECE_DEST_WIDTH + BOARD_PADDING) * x + BOARD_XOFFSET,
    .y = (PIECE_DEST_HEIGHT + BOARD_PADDING) * y + BOARD_YOFFSET
  };
}

void piece_start_moving_to(piece* piece, SDL_FPoint dest_position, float speed) {
  piece->start_position = piece->position;
  piece->dest_position = dest_position;
  piece->travel_speed = speed;
  piece->state = linear_move_state;
  piece->fraction_travelled = 0;
}

int add_piece(piece piece) {
  static int last_piece_id = 0;

  if (game.num_pieces + 1 >= MAX_PIECES) {
    return -1;
  }

  piece.piece_id = last_piece_id++;
  game.pieces[game.num_pieces++] = piece;

  return piece.piece_id;
}

piece* retreive_piece(int piece_id) {
  for (int i = 0; i < game.num_pieces; i++) {
    if (game.pieces[i].piece_id == piece_id) {
      return &game.pieces[i];
    }
  }

  return NULL;
}

void delete_piece(int piece_id) {
  piece* to_be_deleted = retreive_piece(piece_id);

  if (to_be_deleted == NULL) {
    return;
  }

  SDL_memcpy(to_be_deleted, &game.pieces[game.num_pieces - 1], sizeof(piece));
  game.num_pieces--;
}

float rand_float() {
  return rand() / (float)RAND_MAX;
}

void add_piece_at(int y, int x) {
  int new_piece_id = add_piece((piece) {
      .position = {
        .x = (800 - PIECE_DEST_WIDTH) * rand_float(),
        .y = (600 - PIECE_DEST_HEIGHT) * rand_float()
      },
      .orientation = 0,
      .piece_color = rand() % 9,
      .piece_face = rand() % 6
    });

  if (new_piece_id == -1) {
    return;
  }

  float speed_diff = PIECE_LINEAR_SPEED * rand_float() - PIECE_LINEAR_SPEED / 2.0;

  piece* new_piece = retreive_piece(new_piece_id);
  piece_start_moving_to(new_piece, board_position(y, x), PIECE_LINEAR_SPEED + speed_diff);

  game.board[y][x] = (tile) {
    .state = tile_filled,
    .piece_id = new_piece_id
  };
}

void fill_board() {
  for (int i = 0; i < game.board_height; i++) {
    for (int j = 0; j < game.board_width; j++) {
      add_piece_at(i, j);
    }
  }
}

void clear_board() {
  game.num_pieces = 0;
}

void init_game(SDL_Renderer* renderer) {
  SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);

  if (game.spritesheet == NULL) {
    game.spritesheet = IMG_LoadTexture(renderer, "assets/match3_sheet.png");
    SDL_SetTextureScaleMode(game.spritesheet, SDL_SCALEMODE_NEAREST);
  }

  if (game.background_texture == NULL) {
    game.background_texture = IMG_LoadTexture(renderer, "assets/Full-background.png");
    /* SDL_SetTextureScaleMode(game.background_texture, SDL_SCALEMODE_NEAREST); */

    int window_height;
    float texture_width, texture_height;
    SDL_GetWindowSizeInPixels(window, NULL, &window_height);
    SDL_GetTextureSize(game.background_texture, &texture_width, &texture_height);

    float scale = window_height / texture_height;
    game.background_scaled_width = scale * texture_width;
    game.background_scaled_height = scale * texture_height;
  }

  game.board_width = BOARD_WIDTH;
  game.board_height = BOARD_HEIGHT;

  game.state = intro_state;
  game.selected_piece_id = -1;

  fill_board();
}

void free_game() {
  SDL_DestroyTexture(game.spritesheet);
  SDL_DestroyTexture(game.background_texture);
}

SDL_FPoint lerp_points(SDL_FPoint a, SDL_FPoint b, float fraction) {
  SDL_FPoint target;

  target.x = fraction * b.x + (1 - fraction) * a.x;
  target.y = fraction * b.y + (1 - fraction) * a.y;

  return target;
}

void piece_start_falling(piece* piece) {
  float xvel_multiplier = 2*random_float_0to1() - 1;

  piece->xvel = xvel_multiplier * PIECE_MAX_FALL_XSPEED;
  piece->yvel = PIECE_FALL_YSPEED_INITIAL;
  piece->state = fall_state;
}

void update_piece(piece* piece, float dt) {
  switch (piece->state) {

  case linear_move_state:
    piece->fraction_travelled += dt * piece->travel_speed;

    if (piece->fraction_travelled >= 1) {
      piece->fraction_travelled = 1;
      piece->position = piece->dest_position;
      piece->state = static_state;
    } else {
      piece->position =
        lerp_points(piece->start_position, piece->dest_position, piece->fraction_travelled);
    }
    break;

  case fall_state:
    piece->position.x += piece->xvel * dt;
    piece->yvel += GRAVITY * dt / 2;
    piece->position.y += piece->yvel * dt;
    piece->yvel += GRAVITY * dt / 2;

    break;

  default:
    break;
  }
}

int mouse_on_piece() {
  SDL_FPoint mouse_position;
  SDL_GetMouseState(&mouse_position.x, &mouse_position.y);

  for (int i = 0; i < game.num_pieces; i++) {
    const piece* piece = &game.pieces[i];

    SDL_FRect piece_box = (SDL_FRect){
      .x = piece->position.x,
      .y = piece->position.y,
      .w = PIECE_DEST_WIDTH,
      .h = PIECE_DEST_HEIGHT
    };

    if (SDL_PointInRectFloat(&mouse_position, &piece_box)) {
      for (int i = 0; i < game.board_height; i++) {
        for (int j = 0; j < game.board_width; j++) {
          if (game.board[i][j].state == tile_filled && game.board[i][j].piece_id == piece->piece_id)
            return piece->piece_id;
        }
      }
    }
  }

  return -1;
}

void update_intro_state() {
  for (int i = 0; i < game.num_pieces; i++) {
    if (game.pieces[i].state != static_state && game.pieces[i].state != fall_state) {
      return;
    }
  }

  game.state = neutral_state;
}

void handle_piece_rotation(float dt) {
  int selected_piece_id = mouse_on_piece();

  for (int i = 0; i < game.num_pieces; i++) {
    piece* piece = &game.pieces[i];

    if (piece->piece_id == selected_piece_id) {
      piece->orientation =
        SDL_min(piece->orientation + PIECE_ROTATION_SPEED * dt,
                PIECE_MAX_ROTATION);
    } else {
      piece->orientation =
        SDL_max(piece->orientation - PIECE_ROTATION_SPEED * dt,
                0);
    }
  }
}

void scroll_background(float dt) {
  game.background_offset -= BACKGROUND_SCROLL_SPEED * dt;

  while (game.background_offset < -game.background_scaled_width) {
    game.background_offset += game.background_scaled_width;
  }
}

void update_game(float dt) {
  int window_width, window_height;
  SDL_GetWindowSizeInPixels(window, &window_width, &window_height);

  for (int i = 0; i < game.num_pieces; i++) {
    update_piece(&game.pieces[i], dt);

    if (game.pieces[i].position.y > window_height + DELETE_PIECE_OFFSET) {
      delete_piece(game.pieces[i].piece_id);
    }
  }

  handle_piece_rotation(dt);

  scroll_background(dt);

  if (game.state == intro_state) {
    update_intro_state();
  }
}

void draw_piece(SDL_Renderer* renderer, const piece* piece) {
  const int piece_source_xoffs[] = {4, 209};

  SDL_RenderTextureRotated(renderer,
                           game.spritesheet,
                           &(SDL_FRect){
                             .x = piece_source_xoffs[piece->piece_color / 9] + piece->piece_face * (PIECE_SOURCE_WIDTH + 1),
                             .y = PIECE_SOURCE_YOFFSET + (piece->piece_color % 9) * (PIECE_SOURCE_HEIGHT + 1),
                             .w = PIECE_SOURCE_WIDTH,
                             .h = PIECE_SOURCE_HEIGHT
                           },
                           &(SDL_FRect){
                             .x = piece->position.x,
                             .y = piece->position.y,
                             .w = PIECE_DEST_WIDTH,
                             .h = PIECE_DEST_HEIGHT
                           },
                           piece->orientation,
                           NULL,
                           SDL_FLIP_NONE
                           );
}

void draw_background(SDL_Renderer* renderer) {
  int x_offset = game.background_offset;

  while (x_offset <= 800) {
    SDL_RenderTexture(renderer,
                      game.background_texture,
                      NULL,
                      &(SDL_FRect){
                        .x = x_offset,
                        .y = 0,
                        .w = game.background_scaled_width,
                        .h = game.background_scaled_height
                      });

    x_offset += game.background_scaled_width;
  }
}

void draw_game(SDL_Renderer* renderer) {
  SDL_RenderClear(renderer);

  draw_background(renderer);

  piece* selected_piece = NULL;
  for (int i = 0; i < game.num_pieces; i++) {
    if (game.pieces[i].piece_id == game.selected_piece_id) {
      selected_piece = &game.pieces[i];
      continue;
    }
    draw_piece(renderer, &game.pieces[i]);
  }

  //Gives it the apearance that you are sliding your tiles over
  if (selected_piece) {
    draw_piece(renderer, selected_piece);
  }

  SDL_RenderPresent(renderer);
}

void neutral_state_event(SDL_Event* e) {
  if (e->type == SDL_EVENT_MOUSE_BUTTON_DOWN && e->button.button == SDL_BUTTON_LEFT) {
    int selected_piece_id = mouse_on_piece();

    if (selected_piece_id >= 0) {
      game.selected_piece_id = selected_piece_id;
      game.state = piece_held_state;
    }
  }
}

void swap_pieces_at(int x1, int y1, int x2 , int y2) {
  int id1 = game.board[y1][x1].piece_id;
  int id2 = game.board[y2][x2].piece_id;

  piece* selected = retreive_piece(id1);
  piece* swap = retreive_piece(id2);

  if (selected && swap) {
    piece_start_moving_to(selected, board_position(y2, x2), PIECE_SWAP_SPEED);
    piece_start_moving_to(swap, board_position(y1, x1), PIECE_SWAP_SPEED);

    game.board[y2][x2].piece_id = id1;
    game.board[y1][x1].piece_id = id2;
  }
}

void find_last_color_matching_tile_in_direction(int* sy, int* sx, int dy, int dx) {
  if (!filled_tile_at(*sy, *sx))
    return;

  piece* start_piece = retreive_piece(game.board[*sy][*sx].piece_id);

  for(;;) {
    int ny = *sy + dy, nx = *sx + dx;

    if (!filled_tile_at(ny, nx))
      return;

    piece* next_piece = retreive_piece(game.board[ny][nx].piece_id);

    if (!next_piece || next_piece->piece_color != start_piece->piece_color)
      return;

    *sy = ny; *sx = nx;
  }
}

bool try_clear_at(int y, int x) {
  const int axes[2][2] = {
    {1, 0},    //Horizontal
    {0, 1}     //Vertical
  };

  for (int a = 0; a < 2; a++) {
    int sy = y, sx = x, dy = axes[a][1], dx = axes[a][0];
    find_last_color_matching_tile_in_direction(&sy, &sx, dy, dx);

    int ey = sy, ex = sx;
    find_last_color_matching_tile_in_direction(&ey, &ex, -dy, -dx);

    if (SDL_abs(ey-sy) + SDL_abs(ex-sx) + 1 < MIN_TILES_TO_CLEAR)
      continue;

    for (;;) {
      piece_start_falling(retreive_piece(game.board[ey][ex].piece_id));
      game.board[ey][ex].state = tile_currently_empty;

      if (ey == sy && ex == sx)
        break;

      ey += dy; ex += dx;
    }

    return true;
  }

  return false;
}

void cascade_pieces() {
  for (int j = 0; j < game.board_width; j++) {
    for (int i = 0; i < game.board_height; i++) {
      if (game.board[i][j].state != tile_currently_empty)
        continue;

      //Look for the first filled tile above and start moving it down
      for (int c = i-1; c >= 0; c--) {
        if (game.board[c][j].state == tile_filled) {
          piece* piece = retreive_piece(game.board[c][j].piece_id);
          piece_start_moving_to(piece,
                                board_position(c+1, j),
                                PIECE_LINEAR_SPEED
                                );
          game.board[c+1][j] = game.board[c][j];
        }
      }

      add_piece_at(0, j);
    }
  }
}

void piece_held_event(SDL_Event* e) {
  if (e->type == SDL_EVENT_MOUSE_BUTTON_UP && e->button.button == SDL_BUTTON_LEFT) {
    int swap_piece_id = mouse_on_piece();
    int selected_piece_id = game.selected_piece_id;

    if (swap_piece_id >= 0) {
      int selected_x, selected_y;
      int swap_x, swap_y;

      for (int i = 0; i < game.board_height; i++) {
        for (int j = 0; j < game.board_width; j++) {
          if (game.board[i][j].state != tile_filled)
            continue;

          if (game.board[i][j].piece_id == selected_piece_id) {
            selected_x = j;
            selected_y = i;
          } if (game.board[i][j].piece_id == swap_piece_id) {
            swap_x = j;
            swap_y = i;
          }

        }
      }

      if (SDL_abs(selected_x-swap_x) + SDL_abs(selected_y-swap_y) != 1 ||
          retreive_piece(selected_piece_id)->piece_color == retreive_piece(swap_piece_id)->piece_color) {
        game.state = neutral_state;
        return;
      }

      swap_pieces_at(selected_x, selected_y, swap_x, swap_y);

      bool tiles_cleared = try_clear_at(selected_y, selected_x);
      tiles_cleared = try_clear_at(swap_y, swap_x) || tiles_cleared; //sneaky short circuit glitch

      if (tiles_cleared) {
        cascade_pieces();
        game.state = intro_state;
        return;
      }
    }

    game.state = neutral_state;
  }
}

void game_event(SDL_Event* e) {
  if (game.state == neutral_state) {
    neutral_state_event(e);
  } else if (game.state == piece_held_state) {
    piece_held_event(e);
  }
}