#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdint.h>

#define WIDTH 720
#define HEIGHT 720
#define BPP 4  // BGRA = 4 bytes per pixel

typedef struct {
    int fb_fd;
    uint8_t *framebuffer;
} FramebufferDemo;

// Initialize framebuffer
int fb_init(FramebufferDemo *fb) {
    // Open framebuffer device
    fb->fb_fd = open("/dev/fb0", O_RDWR);
    if (fb->fb_fd < 0) {
        fprintf(stderr, "Error: Cannot open framebuffer device /dev/fb0\n");
        fprintf(stderr, "Make sure you have permissions (try running with sudo)\n");
        return -1;
    }
    
    // Allocate framebuffer memory
    fb->framebuffer = (uint8_t*)malloc(WIDTH * HEIGHT * BPP);
    if (!fb->framebuffer) {
        fprintf(stderr, "Error: Cannot allocate framebuffer memory\n");
        close(fb->fb_fd);
        return -1;
    }
    
    printf("Framebuffer opened successfully\n");
    printf("Resolution: %dx%d, Format: BGRA\n", WIDTH, HEIGHT);
    
    return 0;
}

// Close framebuffer
void fb_close(FramebufferDemo *fb) {
    if (fb->framebuffer) {
        free(fb->framebuffer);
        fb->framebuffer = NULL;
    }
    if (fb->fb_fd >= 0) {
        close(fb->fb_fd);
        fb->fb_fd = -1;
    }
}

// Set a pixel at (x, y) with BGRA color
void set_pixel(FramebufferDemo *fb, int x, int y, uint8_t b, uint8_t g, uint8_t r, uint8_t a) {
    if (x < 0 || x >= WIDTH || y < 0 || y >= HEIGHT) {
        return;
    }
    
    int offset = (y * WIDTH + x) * BPP;
    fb->framebuffer[offset + 0] = b; // Blue
    fb->framebuffer[offset + 1] = g; // Green
    fb->framebuffer[offset + 2] = r; // Red
    fb->framebuffer[offset + 3] = a; // Alpha
}

// Fill entire screen with a color
void fill_screen(FramebufferDemo *fb, uint8_t b, uint8_t g, uint8_t r, uint8_t a) {
    for (int y = 0; y < HEIGHT; y++) {
        for (int x = 0; x < WIDTH; x++) {
            set_pixel(fb, x, y, b, g, r, a);
        }
    }
}

// Draw a rectangle
void draw_rectangle(FramebufferDemo *fb, int x, int y, int w, int h, 
                   uint8_t b, uint8_t g, uint8_t r, uint8_t a) {
    for (int dy = 0; dy < h; dy++) {
        for (int dx = 0; dx < w; dx++) {
            set_pixel(fb, x + dx, y + dy, b, g, r, a);
        }
    }
}

// Draw a circle
void draw_circle(FramebufferDemo *fb, int cx, int cy, int radius, 
                uint8_t b, uint8_t g, uint8_t r, uint8_t a) {
    for (int y = -radius; y <= radius; y++) {
        for (int x = -radius; x <= radius; x++) {
            if (x * x + y * y <= radius * radius) {
                set_pixel(fb, cx + x, cy + y, b, g, r, a);
            }
        }
    }
}

// Update the framebuffer (write to /dev/fb0)
void fb_update(FramebufferDemo *fb) {
    if (fb->fb_fd < 0) {
        fprintf(stderr, "Error: Framebuffer not opened\n");
        return;
    }
    
    // Seek to beginning of framebuffer
    lseek(fb->fb_fd, 0, SEEK_SET);
    
    // Write framebuffer data
    ssize_t written = write(fb->fb_fd, fb->framebuffer, WIDTH * HEIGHT * BPP);
    if (written < 0) {
        fprintf(stderr, "Error writing to framebuffer\n");
    }
}

int main(int argc, char *argv[]) {
    FramebufferDemo fb = {0};
    
    if (fb_init(&fb) < 0) {
        return 1;
    }
    
    printf("Drawing demo graphics...\n");
    
    // Fill screen with black
    fill_screen(&fb, 0, 0, 0, 255);
    
    // Draw a red rectangle
    draw_rectangle(&fb, 100, 100, 200, 150, 0, 0, 255, 255);
    
    // Draw a green circle
    draw_circle(&fb, 500, 200, 80, 0, 255, 0, 255);
    
    // Draw a blue rectangle
    draw_rectangle(&fb, 200, 400, 300, 100, 255, 0, 0, 255);
    
    // Draw a yellow circle
    draw_circle(&fb, 360, 360, 100, 0, 255, 255, 255);
    
    // Update the framebuffer
    fb_update(&fb);
    
    printf("Graphics drawn! Press Enter to clear and exit...\n");
    getchar();
    
    // Clear screen before exit
    fill_screen(&fb, 0, 0, 0, 255);
    fb_update(&fb);
    
    printf("Done!\n");
    
    fb_close(&fb);
    return 0;
}