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

using matrix::Matrix;
using namespace fmt;

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

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=0;

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

std::vector<uint32_t> texture[8];
#define texWidth 64 // must be power of two
#define texHeight 64 // must be power of two

#define pixcoord(X, Y) ((Y) * SCREEN_HEIGHT) + (X)

uint32_t pixels[SCREEN_HEIGHT * SCREEN_HEIGHT] = {0};

sf::Texture view_texture;
sf::Sprite view_sprite;

void loadImage(std::vector<uint32_t>& texture, const char *filename) {
  sf::Image img;
  bool good = img.loadFromFile(filename);
  dbc::check(good, format("failed to load {}", filename));
  uint32_t *pixbuf = (uint32_t *)img.getPixelsPtr();
  std::copy_n(pixbuf, texture.size(), texture.begin());
}

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

  loadImage(texture[0], "pics/eagle.png");
  loadImage(texture[1], "pics/redbrick.png");
  loadImage(texture[2], "pics/purplestone.png");
  loadImage(texture[3], "pics/greystone.png");
  loadImage(texture[4], "pics/bluestone.png");
  loadImage(texture[5], "pics/mossy.png");
  loadImage(texture[6], "pics/wood.png");
  loadImage(texture[7], "pics/colorstone.png");
}

void draw_sfml_rect(sf::RenderWindow &window, sf::Vector2f pos, sf::Vector2f size, uint8_t color) {
  sf::RectangleShape rect(size);
  rect.setFillColor({color, color, color});
  rect.setPosition(pos);
  window.draw(rect);
}

void draw_pixel_rect(sf::RenderWindow &window, Point pos, Point size, uint32_t color) {
  size_t x_start = size_t(pos.x - SCREEN_HEIGHT);
  size_t y_start = size_t(pos.y);
  size_t width = size_t(size.x);
  size_t height = size_t(size.y);

  for(size_t y = y_start; y < y_start + height; y++) {
    for(size_t x = x_start; x < x_start + width; x++) {
      size_t pixel_index = (y * SCREEN_HEIGHT) + x;
      pixels[pixel_index] = color;
    }
  }
}

void draw_pixel_buffer(sf::RenderWindow &window) {
  view_texture.update((uint8_t *)pixels, SCREEN_HEIGHT, SCREEN_HEIGHT, 0, 0);
  // BUG: can I do this once and just update it?
  window.draw(view_sprite);
}

void draw_map_rect(sf::RenderWindow &window, int x, int y, uint32_t color) {
  draw_sfml_rect(window,
      {float(x * TILE_SIZE), float(y * TILE_SIZE)},
      {float(TILE_SIZE-1), float(TILE_SIZE-1)},
      color);
}

void draw_map(sf::RenderWindow &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(sf::RenderWindow &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;
    }

    pixels[pixcoord(x,y)] = color;
  }
}

void clear(sf::RenderWindow &window) {
  std::fill_n(pixels, SCREEN_HEIGHT * SCREEN_HEIGHT, 0);
  window.clear();
}

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

void ray_casting(sf::RenderWindow &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);

    // TODO: player direction ray

    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];

      pixels[pixcoord(x, y)] = color;
    }
  }
}

void draw_ceiling_floor(sf::RenderWindow &window) {
  int screenHeight = THREED_VIEW_HEIGHT;
  int screenWidth = THREED_VIEW_HEIGHT;

  for(int y = screenHeight / 2 + 1; y < screenHeight; ++y) {
    float rayDirX0 = dirX - planeX;
    float rayDirY0 = dirY - planeY;
    float rayDirX1 = dirX + planeX;
    float rayDirY1 = dirY + planeY;

    int p = y - screenHeight / 2;

    float posZ = 0.5 * screenHeight;
    float rowDistance = posZ / p;

    float floorStepX = rowDistance * (rayDirX1 - rayDirX0) / screenWidth;
    float floorStepY = rowDistance * (rayDirY1 - rayDirY0) / screenWidth;

    float floorX = posX + rowDistance * rayDirX0;
    float floorY = posY + rowDistance * rayDirY0;

    for(int x = 0; x < screenWidth; ++x) {
      int cellX = int(floorX);
      int cellY = int(floorY);

      int tx = int(texWidth * (floorX - cellX)) & (texWidth - 1);
      int ty = int(texWidth * (floorY - cellY)) & (texHeight - 1);

      floorX += floorStepX;
      floorY += floorStepY;

      int checkerBoardPattern = int(cellX + cellY) & 1;
      int floorTexture = checkerBoardPattern == 0 ? 3 : 4;

      int ceilingTexture = 6;

      uint32_t color;
      color = texture[floorTexture][texWidth * ty + tx];
      pixels[pixcoord(x, y)] = color;

      color = texture[ceilingTexture][texWidth * ty + tx];
      pixels[pixcoord(x, screenHeight - y - 1)] = color;
    }
  }
}

void draw_everything(sf::RenderWindow &window) {
  clear(window);
  draw_map(window, MAP);
  draw_ceiling_floor(window);
  ray_casting(window, MAP);
  draw_pixel_buffer(window);
  window.display();
}

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() {
  using KB = sf::Keyboard;
  sf::RenderWindow window(sf::VideoMode(SCREEN_WIDTH, SCREEN_HEIGHT), "SFMLCaster");

  window.setVerticalSyncEnabled(true);
  view_texture.create(SCREEN_HEIGHT, SCREEN_HEIGHT);
  view_sprite.setTexture(view_texture);
  view_sprite.setPosition(THREED_VIEW_WIDTH, 0);

  load_textures();

  double moveSpeed = 0.1;
  double rotSpeed = 0.1;

  while(window.isOpen()) {
    draw_everything(window);

    if(KB::isKeyPressed(KB::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(KB::isKeyPressed(KB::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(KB::isKeyPressed(KB::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(KB::isKeyPressed(KB::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(KB::isKeyPressed(KB::E)) {
      println("PITCH DISABLED");
      // PITCH = std::clamp(PITCH + 10, -60, 240);
    } else if(KB::isKeyPressed(KB::Q)) {
      println("PITCH DISABLED");
      // PITCH = std::clamp(PITCH - 10, -60, 240);
    }

    sf::Event event;
    while(window.pollEvent(event)) {
      if(event.type == sf::Event::Closed) {
        window.close();
      }
    }

  }

  return 0;
}