#ifndef GBAEXP_BITMAP_H
#define GBAEXP_BITMAP_H

#include "common.h"

// Draws a line with the given color between (x0,y0) and (x1,y1) using the
// Bresenham's line drawing algorithm using exclusively integer arithmetic.
static void
draw_line(int x0, int y0, int x1, int y1, Color clr) {
    // Pointer to the initial position of the screen buffer where we will start
    // writing our data.
    vu16 *destination = (u16*)(SCREEN_BUFFER + y0 * SCREEN_WIDTH + x0);

    // Adjust the step direction and calculate deltas.
    int x_step;
    int y_step;
    int dx;
    int dy;
    if (x0 > x1) {
        x_step = -1;
        dx = x0 - x1;
    } else {
        x_step = 1;
        dx = x1 - x0;
    }
    if (y0 > y1) {
        y_step = -SCREEN_WIDTH;
        dy = y0 - y1;
    } else {
        y_step = +SCREEN_WIDTH;
        dy = y1 - y0;
    }

    if(dy == 0) {
        // Horizontal line.
        for(int i = 0; i <= dx; i++) {
            destination[i * x_step] = clr;
        }
    } else if(dx == 0) {
        // Vertical line.
        for(int i = 0; i <= dy; i++) {
            destination[i * y_step] = clr;
        }
    } else if (dx >= dy){
        // Positive slope.
        int diff = 2 * dy - dx;
        for (int i = 0; i <= dx; ++i) {
            *destination = clr;
            if (diff >= 0) {
                destination += y_step;
                diff -= 2 * dx;
            }
            destination += x_step;
            diff += 2 * dy;
        }
    } else {
        // Negative slope.
        int diff = 2 * dx - dy;
        for (int i = 0; i <= dy; ++i) {
            *destination = clr;
            if (diff >= 0) {
                destination += x_step;
                diff -= 2 * dy;
            }
            destination += y_step;
            diff += 2 * dx;
        }
    }
}

static inline void
draw_rect(int x0, int y0, int x1, int y1, Color clr) {
    if (x0 > x1) {
        int tmp = x0;
        x0 = x1;
        x1 = tmp;
    }
    if (y0 > y1) {
        int tmp = y0;
        y0 = y1;
        y1 = tmp;
    }
    int dx = x1 - x0;
    int dy = y1 - y0;
    for (int i = 0; i <= dx; ++i) {
        int x = x0 + i;
        FRAMEBUFFER[y0][x] = clr;
        FRAMEBUFFER[y1][x] = clr;
    }
    for (int j = 0; j <= dy; ++j) {
        int y = y0 + j;
        FRAMEBUFFER[y][x0] = clr;
        FRAMEBUFFER[y][x1] = clr;
    }
}

static inline void
draw_fill_rect(int x0, int y0, int x1, int y1, Color clr) {
    if (x0 > x1) {
        int tmp = x0;
        x0 = x1;
        x1 = tmp;
    }
    if (y0 > y1) {
        int tmp = y0;
        y0 = y1;
        y1 = tmp;
    }
    int dx = x1 - x0;
    int dy = y1 - y0;
    for (int i = 0; i <= dx; ++i) {
        for (int j = 0; j <= dy; ++j) {
            int x = x0 + i;
            int y = y0 + j;
            FRAMEBUFFER[y][x] = clr;
        }
    }
}

// In Mode4 the buffer is of 8 bytes per pixel instead of 16. We can't write the
// color directly, instead the color is stored in the palette memory at
// `MEM_PAL`. Note that in this mode MEM_PAL[0] is the background color. This
// plotter takes an index to a color stored in MEM_PAL[col_index]. Because the
// GBA needs to meet memory alignment requirements, we can't write a u8 into
// memory, instead we need to read a u16 word, mask and or the corresponding
// bits and wave the updated u16.
static inline void
put_pixel_m4(int x, int y, u8 clr_idx, vu16 *buffer) {
    int buffer_index = (y * SCREEN_WIDTH + x) / 2;
    vu16 *destination = &buffer[buffer_index];
    // Odd pixels will go to the top 8 bits of the destination. Even pixels to
    // the lower 8 bits.
    int odd = x & 0x1;
    if(odd) {
        *destination= (*destination & 0xFF) | (clr_idx << 8);
    } else {
        *destination= (*destination & ~0xFF) |  clr_idx;
    }
}

static inline void
put_pixel_m3(int x, int y, u16 color, Scanline *buffer) {
    buffer[y][x] = color;
}

static inline void
clear_screen_m4() {
    size_t size = SCREEN_WIDTH * SCREEN_HEIGHT / 4;
    u32 *buf = backbuffer;
    for (size_t i = 0; i < size; ++i) {
        buf[i] = 0;
    }
}

static inline void
clear_screen_m3() {
    size_t size = SCREEN_WIDTH * SCREEN_HEIGHT / 4;
    u32 *buf = FRAMEBUFFER;
    for (size_t i = 0; i < size; ++i) {
        buf[i] = 0;
    }
}

static inline void
draw_fill_rect_m4(int x0, int y0, int x1, int y1, u8 col_index, vu16 *buffer) {
    int ix, iy;
    for(iy = y0; iy < y1; iy++) {
        for(ix = x0; ix < x1; ix++) {
            put_pixel_m4(ix, iy, col_index, buffer);
        }
    }
}

void
draw_logo(void) {
    int side = 60;
    int line = 35;
    int height = side * 0.5;
    int x = SCREEN_WIDTH / 2 - height / 2;
    int y = SCREEN_HEIGHT / 2;

    // Draw red triangle.
    draw_line(x + height - 1, y - side / 2, x, y - 1, COLOR_RED);
    draw_line(x + height - 1, y + side / 2, x, y + 1, COLOR_RED);
    draw_line(x + height - 1, y - side / 2 + 1, x, y, COLOR_RED);
    draw_line(x + height - 1, y + side / 2 - 1, x, y, COLOR_RED);

    // Draw white triangle.
    draw_line(x, y - side / 2, x, y + side / 2, COLOR_WHITE);
    draw_line(x + 1, y - side / 2, x + height, y - 1, COLOR_WHITE);
    draw_line(x + 1, y + side / 2, x + height, y + 1, COLOR_WHITE);

    // Draw white line at triangle tip.
    draw_line(x + height, y - side / 2, x + height, y + side / 2, COLOR_WHITE);
    draw_line(x + height + 1, y - side / 2, x + height + 1, y + side / 2, COLOR_WHITE);

    // Double triangle line.
    draw_line(x - 1, y - side / 2, x - 1, y + side / 2, COLOR_WHITE);
    draw_line(x + 1, y - side / 2 + 1, x + height, y, COLOR_WHITE);
    draw_line(x + 1, y + side / 2 - 1, x + height, y, COLOR_WHITE);

    // Draw white lines.
    draw_line(x - line, y, x, y, COLOR_WHITE);
    draw_line(x + height, y, x + height + line, y, COLOR_WHITE);
    draw_line(x - line, y + 1, x, y + 1, COLOR_WHITE);
    draw_line(x + height, y + 1, x + height + line, y + 1, COLOR_WHITE);
}

#endif // GBAEXP_BITMAP_H