#include <stdio.h>
#include <stdlib.h>
#include <SDL2/SDL.h>

#define WINDOW_W 1280
#define WINDOW_H 720

void renderMaskedTexture(SDL_Renderer *context, SDL_Texture *result, SDL_Texture *mask, SDL_Texture *diffuse) {
	SDL_SetRenderTarget(context, result);
	SDL_SetRenderDrawColor(context, 0, 0, 0, 0);
	SDL_RenderClear(context);
	SDL_RenderCopy(context, mask, 0, 0);
	SDL_RenderCopy(context, diffuse, 0, 0);
	SDL_SetRenderTarget(context, 0);
}

SDL_Texture *createTiledTexture(SDL_Renderer *context, const char *filename) {
	SDL_Surface *texture_surface = SDL_LoadBMP(filename);
	SDL_Texture *texture_tile = SDL_CreateTextureFromSurface(context, texture_surface);
	int tile_w = texture_surface->w;
	int tile_h = texture_surface->h;
	SDL_FreeSurface(texture_surface);

	SDL_Texture *texture = SDL_CreateTexture(context,
			SDL_PIXELFORMAT_RGBA8888,
			SDL_TEXTUREACCESS_TARGET,
			WINDOW_W, WINDOW_H);
	SDL_SetRenderTarget(context, texture);
	for (int y = 0; y < WINDOW_H; y += tile_h) {
		for (int x = 0; x < WINDOW_W; x += tile_w) {
			SDL_Rect tile_rect = { x, y, tile_w, tile_h };
			SDL_RenderCopy(context, texture_tile, 0, &tile_rect);
		}
	}
	SDL_DestroyTexture(texture_tile);
	SDL_SetRenderTarget(context, 0);
	return texture;
}

int main() {
	SDL_Init(SDL_INIT_VIDEO);

	SDL_Window *window = SDL_CreateWindow("Cannons",
			SDL_WINDOWPOS_UNDEFINED,
			SDL_WINDOWPOS_UNDEFINED,
			WINDOW_W,
			WINDOW_H,
			0);

	SDL_Renderer *context = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED);

	SDL_Texture *background = createTiledTexture(context, "background.bmp");

	SDL_Texture *foreground = createTiledTexture(context, "foreground.bmp");
	SDL_SetTextureBlendMode(foreground, SDL_BLENDMODE_MOD);

	SDL_Texture *terrain = SDL_CreateTexture(context,
			SDL_PIXELFORMAT_RGBA8888,
			SDL_TEXTUREACCESS_TARGET,
			WINDOW_W, WINDOW_H);
	SDL_SetTextureBlendMode(terrain, SDL_BLENDMODE_BLEND);

	// Terrain generation
	SDL_Surface *mask_surface = SDL_CreateRGBSurfaceWithFormat(0,
			WINDOW_W, WINDOW_H, 32, SDL_PIXELFORMAT_RGBA8888);
	SDL_LockSurface(mask_surface);
	for (int i = 0; i < mask_surface->w * mask_surface->h; i++) {
		((Uint32 *)mask_surface->pixels)[i] = 0x00000000;
	}
	for (int i = mask_surface->w * 500; i < mask_surface->w * mask_surface->h; i++) {
		((Uint32 *)mask_surface->pixels)[i] = 0xffffffff;
	}
	SDL_UnlockSurface(mask_surface);
	SDL_Texture *mask_texture = SDL_CreateTextureFromSurface(context, mask_surface);
	renderMaskedTexture(context, terrain, mask_texture, foreground);

	// Player variables
	float player_x = 100;
	float player_y = 100;
	float player_vy = 0;
	float player_ay = 1;

	// Timer variables
	float old_t = 0.0;

	// Event handling
	int exit = 0;
	while (!exit) {
		SDL_Event event = {0};
		while (SDL_PollEvent(&event)) {
			if (event.type == SDL_QUIT) {
				exit = 1;
			}
		}
		int mouse_x, mouse_y;
		Uint32 mouse_state = SDL_GetMouseState(&mouse_x, &mouse_y);
		if (mouse_state & SDL_BUTTON_LMASK) {
			SDL_LockSurface(mask_surface);
			unsigned size = 100;
			for (int j = mouse_y - size / 2; j < mouse_y + size / 2; j++) {
				for (int i = mouse_x - size / 2; i < mouse_x + size / 2; i++) {
					size_t index = i + j * WINDOW_W;
					((Uint32 *)mask_surface->pixels)[index] = 0xffffffff;
				}
			}
			SDL_UnlockSurface(mask_surface);
			SDL_DestroyTexture(mask_texture);
			mask_texture = SDL_CreateTextureFromSurface(context, mask_surface);

			renderMaskedTexture(context, terrain, mask_texture, foreground);
		} else if (mouse_state & SDL_BUTTON_RMASK) {
			SDL_LockSurface(mask_surface);
			unsigned size = 100;
			for (int j = mouse_y - size / 2; j < mouse_y + size / 2; j++) {
				for (int i = mouse_x - size / 2; i < mouse_x + size / 2; i++) {
					size_t index = i + j * WINDOW_W;
					((Uint32 *)mask_surface->pixels)[index] = 0x00000000;
				}
			}
			SDL_UnlockSurface(mask_surface);
			SDL_DestroyTexture(mask_texture);
			mask_texture = SDL_CreateTextureFromSurface(context, mask_surface);

			renderMaskedTexture(context, terrain, mask_texture, foreground);
		}

		// Main loop
		SDL_SetRenderDrawColor(context, 40, 40, 40, 255);
		SDL_RenderClear(context);

		SDL_RenderCopy(context, background, 0, 0);
		SDL_RenderCopy(context, terrain, 0, 0);

		// Time delta calculation
		double new_t = (double) SDL_GetTicks64() / 1000.0;
		double dt = new_t - old_t;
		old_t = new_t;

		// Player logic
		player_y += player_vy * dt;
		player_vy += player_ay * dt;

		// Draw player
		SDL_SetRenderDrawColor(context, 255, 0, 0, 255);
		SDL_Rect player_rect = {player_x - 5, WINDOW_H - player_y - 10, 10, 10 };
		SDL_RenderFillRect(context, &player_rect);

		SDL_RenderPresent(context);
		SDL_Delay(1);
	}

	SDL_DestroyRenderer(context);
	SDL_DestroyWindow(window);
	SDL_Quit();
	return 0;
}