#include "fb.h"
#include <stddef.h>
#include "mem.h"

static struct {
    uint32_t * addr;
    uint32_t width;
    uint32_t height;
    uint32_t pitch;
} fb;

static inline uint32_t build_pixel(uint8_t r, uint8_t g, uint8_t b)
{
    return (r << 16u) | (g << 8u) | b;
}

static inline void fb_set_pixel(int x, int y, uint8_t r, uint8_t g, uint8_t b)
{
    fb.addr[fb.pitch * y + x] = build_pixel(r, g, b);
}

void fb_clear(void)
{
    memset32(fb.addr, 0u, fb.pitch * fb.height);
}

void fb_init(uint32_t * addr, uint32_t width, uint32_t height, uint32_t pitch)
{
    fb.addr = addr;
    fb.width = width;
    fb.height = height;
    fb.pitch = pitch / 4u;
    fb_clear();
}

uint32_t * fb_addr(void)
{
    return fb.addr;
}

bool fb_ready(void)
{
    return fb.addr != NULL;
}

uint32_t fb_width(void)
{
    return fb.width;
}

uint32_t fb_height(void)
{
    return fb.height;
}

void fb_blend_alpha8(const uint8_t * bitmap, int width, int height, int pitch, int x, int y, uint8_t r, uint8_t g, uint8_t b)
{
    if (((x + width) <= 0) || (x >= (int)fb.width) || ((y + height) <= 0) || (y >= (int)fb.height))
    {
        return;
    }
    if (x < 0)
    {
        width += x;
        bitmap += (-x);
        x = 0;
    }
    if (y < 0)
    {
        height += y;
        bitmap += ((-y) * pitch);
        y = 0;
    }
    if ((x + width) > (int)fb.width)
    {
        width = (int)fb.width - x;
    }
    if ((y + height) > (int)fb.height)
    {
        height = (int)fb.height - y;
    }
    uint32_t * target = &fb.addr[fb.pitch * y + x];
    for (int row = 0; row < height; row++)
    {
        for (int col = 0; col < width; col++)
        {
            uint32_t alpha = bitmap[col];
            uint32_t current_pixel = target[col];
            uint8_t cr = (current_pixel >> 16u) & 0xFFu;
            uint8_t cg = (current_pixel >> 8u) & 0xFFu;
            uint8_t cb = current_pixel & 0xFFu;
            uint8_t pr = alpha * r / 255u;
            uint8_t pg = alpha * g / 255u;
            uint8_t pb = alpha * b / 255u;
            uint32_t current_alpha = 255u - alpha;
            uint32_t pixel = build_pixel(
                    pr + current_alpha * cr / 255u,
                    pg + current_alpha * cg / 255u,
                    pb + current_alpha * cb / 255u);
            target[col] = pixel;
        }
        bitmap += pitch;
        target += fb.pitch;
    }
}

void fb_fill(int x, int y, int width, int height, uint8_t r, uint8_t g, uint8_t b)
{
    uint32_t * target = &fb.addr[fb.pitch * y + x];
    uint32_t pixel = build_pixel(r, g, b);
    for (int row = 0; row < height; row++)
    {
        memset32(target, pixel, width);
        target += fb.pitch;
    }
}