#include <fmt/core.h>
#include <numbers>
#include <algorithm>
#include <cmath>
#include "matrix.hpp"
#include <cstdlib>
#include "fenster/fenster.h"
#include "dbc.hpp"

using matrix::Matrix;
using namespace fmt;

Matrix MAP{
  {2,2,2,2,2,2,2,2,2},
  {2,0,8,0,0,0,0,0,2},
  {2,0,7,0,0,5,6,0,2},
  {2,0,0,0,0,0,0,0,2},
  {2,2,0,0,0,0,0,2,2},
  {2,0,0,1,3,4,0,0,2},
  {2,0,0,0,0,0,2,2,2},
  {2,2,2,2,2,2,2,2,2}
};

const int SCREEN_HEIGHT=480;
const int SCREEN_WIDTH=SCREEN_HEIGHT * 2;

const int THREED_VIEW_WIDTH=480;
const int THREED_VIEW_HEIGHT=480;
const int MAP_SIZE=matrix::width(MAP);
const int TILE_SIZE=(SCREEN_WIDTH/2) / MAP_SIZE;
const float FOV = std::numbers::pi / 3.0;
const float HALF_FOV = FOV / 2;
const int CASTED_RAYS=120;
const float STEP_ANGLE = FOV / CASTED_RAYS;
const int MAX_DEPTH = MAP_SIZE * TILE_SIZE;
const float SCALE = (SCREEN_WIDTH / 2) / CASTED_RAYS;
int PITCH=25;

float player_x = SCREEN_WIDTH / 4;
float player_y = SCREEN_WIDTH / 4;

// x and y start position
double posX = player_x / TILE_SIZE;
double posY = player_y / TILE_SIZE;

// initial direction vector
double dirX = -1;
double dirY = 0;

// the 2d raycaster version of camera plane
double planeX = 0;
double planeY = 0.66;

#define rgba_color(r,g,b,a) (b<<(0*8))|(g<<(1*8))|(r<<(2*8))|(a<<(3*8))
#define gray_color(c) rgba_color(c, c, c, 255)

std::vector<uint32_t> texture[8];
#define texWidth 64
#define texHeight 64


void load_textures() {
  for(int i = 0; i < 8; i++) {
    texture[i].resize(texWidth * texHeight);
  }

  for(int x = 0; x < texWidth; x++) {
    for(int y = 0; y < texHeight; y++)
    {
      int xorcolor = (x * 256 / texWidth) ^ (y * 256 / texHeight);
      //int xcolor = x * 256 / texWidth;
      int ycolor = y * 256 / texHeight;
      int xycolor = y * 128 / texHeight + x * 128 / texWidth;
      texture[0][texWidth * y + x] = 65536 * 254 * (x != y && x != texWidth - y); //flat red texture with black cross
      texture[1][texWidth * y + x] = xycolor + 256 * xycolor + 65536 * xycolor; //sloped greyscale
      texture[2][texWidth * y + x] = 256 * xycolor + 65536 * xycolor; //sloped yellow gradient
      texture[3][texWidth * y + x] = xorcolor + 256 * xorcolor + 65536 * xorcolor; //xor greyscale
      texture[4][texWidth * y + x] = 256 * xorcolor; //xor green
      texture[5][texWidth * y + x] = 65536 * 192 * (x % 16 && y % 16); //red bricks
      texture[6][texWidth * y + x] = 65536 * ycolor; //red gradient
      texture[7][texWidth * y + x] = 128 + 256 * 128 + 65536 * 128; //flat grey texture
    }
  }
}

void draw_rect(Fenster &window, Point pos, Point size, uint32_t color) {
  size_t x_start = size_t(pos.x);
  size_t y_start = size_t(pos.y);
  size_t width = size_t(size.x);
  size_t height = size_t(size.y);

  dbc::check(x_start <= size_t(window.f.width), format("pos.x {} is greater than width {}", x_start, window.f.width));
  dbc::check(y_start <= size_t(window.f.height), format("pos.y {} is greater than height {}", y_start, window.f.height));
  dbc::check(x_start + width <= size_t(window.f.width), format("size width {} is greater than width {}", x_start + width, window.f.width));
  dbc::check(y_start + height <= size_t(window.f.height), format("size height {} is greater than height {}", y_start + height, window.f.height));

  for(size_t y = y_start; y < y_start + height; y++) {
    for(size_t x = x_start; x < x_start + width; x++) {
      window.px(x, y) = color;
    }
  }
}

void draw_map_rect(Fenster &window, int x, int y, uint32_t color) {
  draw_rect(window,
      {size_t(x * TILE_SIZE), size_t(y * TILE_SIZE)},
      {size_t(TILE_SIZE-1), size_t(TILE_SIZE-1)},
      color);
}

void draw_map(Fenster &window, Matrix &map) {
  uint32_t light_grey = gray_color(191);
  uint32_t dark_grey = gray_color(65);

  for(size_t y = 0; y < matrix::height(map); y++) {
    for(size_t x = 0; x < matrix::width(map); x++) {
      draw_map_rect(window, x, y, map[y][x] == 0 ? dark_grey : light_grey);
    }
  }
}

void draw_line(Fenster &window, Point start, Point end, uint32_t color) {
  int x = int(start.x);
  int y = int(start.y);
  int x1 = int(end.x);
  int y1 = int(end.y);
  int dx = std::abs(x1 - x);
  int sx = x < x1 ? 1 : -1;
  int dy = std::abs(y1 - y) * -1;
  int sy = y < y1 ? 1 : -1;
  int error = dx + dy;

  while(x != x1 || y != y1) {
    int e2 = 2 * error;

    if(e2 >= dy) {
      error = error + dy;
      x = x + sx;
    }

    if(e2 <= dx) {
      error = error + dx;
      y = y + sy;
    }

    window.px(x, y) = color;
  }
}

void clear(Fenster &window) {
  for(int y = 0; y < window.f.height; y++) {
    for(int x = 0; x < window.f.width; x++) {
      window.px(x, y) = 0;
    }
  }
}

void draw_map_blocks(Fenster &window, int col, int row) {
  draw_map_rect(window, col, row, rgba_color(100, 20, 20, 255));
}

void ray_casting(Fenster &window, Matrix& map) {
  int w = THREED_VIEW_WIDTH;
  int h = THREED_VIEW_HEIGHT;

  for(int x = 0; x < w; x++) {
    // calculate ray position and direction
    double cameraX = 2 * x / double(w) - 1; // x-coord in camera space
    double rayDirX = dirX + planeX * cameraX;
    double rayDirY = dirY + planeY * cameraX;

    // which box of the map we're in
    int mapX = int(posX);
    int mapY = int(posY);

    // length of ray from current pos to next x or y-side
    double sideDistX;
    double sideDistY;

    // length of ray from one x or y-side to next x or y-side
    double deltaDistX = std::abs(1.0 / rayDirX);
    double deltaDistY = std::abs(1.0 / rayDirY);
    double perpWallDist;

    int stepX = 0;
    int stepY = 0;
    int hit = 0;
    int side = 0;

    // calculate step and initial sideDist
    if(rayDirX < 0) {
      stepX = -1;
      sideDistX = (posX - mapX) * deltaDistX;
    } else {
      stepX = 1;
      sideDistX = (mapX + 1.0 - posX) * deltaDistX;
    }

    if(rayDirY < 0) {
      stepY = -1;
      sideDistY = (posY - mapY) * deltaDistY;
    } else {
      stepY = 1;
      sideDistY = (mapY + 1.0 - posY) * deltaDistY;
    }

    // perform DDA
    while(hit == 0) {
      if(sideDistX < sideDistY) {
        sideDistX += deltaDistX;
        mapX += stepX;
        side = 0;
      } else {
        sideDistY += deltaDistY;
        mapY += stepY;
        side = 1;
      }

      if(map[mapY][mapX] > 0) hit = 1;
    }

    if(side == 0) {
      perpWallDist = (sideDistX - deltaDistX);
    } else {
      perpWallDist = (sideDistY - deltaDistY);
    }

    draw_map_blocks(window, mapX, mapY);


    // player direction ray
    draw_line(window, {size_t(posX * TILE_SIZE), size_t(posY * TILE_SIZE)},
        {(size_t)mapX * TILE_SIZE, (size_t)mapY * TILE_SIZE}, rgba_color(0, 255, 0, 255));

    int lineHeight = int(h / perpWallDist);

    int drawStart = -lineHeight / 2 + h / 2 + PITCH;
    if(drawStart < 0) drawStart = 0;

    int drawEnd = lineHeight / 2 + h / 2 + PITCH;
    if(drawEnd >= h) drawEnd = h - 1;

    int texNum = MAP[mapY][mapX] - 1;

    // calculate value of wallX
    double wallX;  // where exactly the wall was hit
    if(side == 0) {
      wallX = posY + perpWallDist * rayDirY;
    } else {
      wallX = posX + perpWallDist * rayDirX;
    }
    wallX -= floor((wallX));

    // x coorindate on the texture
    int texX = int(wallX * double(texWidth));
    if(side == 0 && rayDirX > 0) texX = texWidth - texX - 1;
    if(side == 1 && rayDirY < 0) texX = texWidth - texX - 1;

    // LODE: an integer-only bresenham or DDA like algorithm could make the texture coordinate stepping faster

    // How much to increase the texture coordinate per screen pixel
    double step = 1.0 * texHeight / lineHeight;
    // Starting texture coordinate
    double texPos = (drawStart - PITCH - h / 2 + lineHeight / 2) * step;

    for(int y = drawStart; y < drawEnd; y++) {
      // BUG? Why bitwise and here?
      int texY = (int)texPos & (texHeight - 1);
      texPos += step;
      uint32_t color = texture[texNum][texHeight * texY + texX];

      if(side == 1) color = (color >> 1) & 8355711;
      window.px(x + THREED_VIEW_WIDTH, y) = color;
    }
  }
}

void draw_ceiling_floor(Fenster &window) {
  draw_rect(window,
      {size_t(window.width() / 2), size_t(window.height() / 2)},
      {size_t(window.width() / 2), size_t(window.height() / 2)},
      gray_color(200));

  draw_rect(window,
      {size_t(window.width() / 2), 0},
      {size_t(window.height()), size_t(window.height() / 2 + PITCH)},
      gray_color(100));
}

void draw_everything(Fenster &window) {
  clear(window);
  draw_map(window, MAP);
  draw_ceiling_floor(window);
  ray_casting(window, MAP);
}

bool empty_space(int new_x, int new_y) {
  dbc::check((size_t)new_x < matrix::width(MAP),
      format("x={} too wide={}", new_x, matrix::width(MAP)));
  dbc::check((size_t)new_y < matrix::height(MAP),
      format("y={} too high={}", new_y, matrix::height(MAP)));

  return MAP[new_y][new_x] == 0;
}

int main() {
  Fenster window(SCREEN_WIDTH, SCREEN_HEIGHT, "Fenscaster");
  const int fps = 60;
  double moveSpeed = 0.1;
  double rotSpeed = 0.1;

  load_textures();

  while(window.loop(fps)) {
    draw_everything(window);

    if(window.key('W')) {
        if(empty_space(int(posX + dirX * moveSpeed), int(posY))) posX += dirX * moveSpeed;
        if(empty_space(int(posX), int(posY + dirY * moveSpeed))) posY += dirY * moveSpeed;
    } else if(window.key('S')) {
        if(empty_space(int(posX - dirX * moveSpeed), int(posY))) posX -= dirX * moveSpeed;
        if(empty_space(int(posX), int(posY - dirY * moveSpeed))) posY -= dirY * moveSpeed;
    }

    if(window.key('D')) {
      double oldDirX = dirX;
      dirX = dirX * cos(-rotSpeed) - dirY * sin(-rotSpeed);
      dirY = oldDirX * sin(-rotSpeed) + dirY * cos(-rotSpeed);

      double oldPlaneX = planeX;
      planeX = planeX * cos(-rotSpeed) - planeY * sin(-rotSpeed);
      planeY = oldPlaneX * sin(-rotSpeed) + planeY * cos(-rotSpeed);
    } else if(window.key('A')) {
      double oldDirX = dirX;
      dirX = dirX * cos(rotSpeed) - dirY * sin(rotSpeed);
      dirY = oldDirX * sin(rotSpeed) + dirY * cos(rotSpeed);

      double oldPlaneX = planeX;
      planeX = planeX * cos(rotSpeed) - planeY * sin(rotSpeed);
      planeY = oldPlaneX * sin(rotSpeed) + planeY * cos(rotSpeed);
    }

    if(window.key('E')) {
      PITCH = std::clamp(PITCH + 10, -60, 240);
    } else if(window.key('Q')) {
      PITCH = std::clamp(PITCH - 10, -60, 240);
    }
  }

  return 0;
}

#if defined(_WIN32)
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR pCmdLine,
                   int nCmdShow) {
  (void)hInstance, (void)hPrevInstance, (void)pCmdLine, (void)nCmdShow;
  return main();
}
#endif