#include "render.h"

static struct {
	Colour pixels[renderer_w * renderer_h];
} renderer;

Colour make_colour(unsigned rgb, unsigned char a) {
	Colour r;
	r.r = (unsigned char)(rgb >> 16);
	r.g = (unsigned char)(rgb >> 8);
	r.b = (unsigned char)rgb;
	r.a = a;
	return r;
}

Colour make_black() {
	Colour r = { 0, 0, 0, 255 };
	return r;
}

Colour make_white() {
	return make_colour(0xffffff, 255);
}

void init_bitmap(
	Bitmap* bitmap,
	Colour* pixels,
	int w,
	int h
) {
	bitmap->pixels = pixels;
	bitmap->w = w;
	bitmap->h = h;
}

void init_renderer() {
}

void renderer_begin_frame() {
	int i;

	for (i = 0; i < renderer_w * renderer_h; i++) {
		renderer.pixels[i] = make_black();
	}
}

Colour* get_render_pixels() {
	return renderer.pixels;
}

Colour blend(Colour dst, Colour src) {
	int ima;

	ima = 0xff - src.a;
	dst.r = (unsigned char)(((src.r * src.a) + (dst.r * ima)) >> 8);
	dst.g = (unsigned char)(((src.g * src.a) + (dst.g * ima)) >> 8);
	dst.b = (unsigned char)(((src.b * src.a) + (dst.b * ima)) >> 8);

	return dst;
}

Colour blend_mod(Colour dst, Colour src, Colour mod) {
	int ima;

	src.a = (src.a * mod.a) >> 8;
	ima = 0xff - src.a;
	dst.r = (unsigned char)(((src.r * mod.r * src.a) >> 16) + ((dst.r * ima) >> 8));
	dst.g = (unsigned char)(((src.g * mod.g * src.a) >> 16) + ((dst.g * ima) >> 8));
	dst.b = (unsigned char)(((src.b * mod.b * src.a) >> 16) + ((dst.b * ima) >> 8));

	return dst;
}

void init_font(
	BM_Font* font,
	const Bitmap* bmp,
	int char_w,
	int char_h,
	int chars_across
) {
	font->bmp = bmp;
	font->char_w = char_w;
	font->char_h = char_h;
	font->chars_across = chars_across;
}

void rfont_char(const BM_Font* font, int x, int y, char c) {
	Rectangle rect;

	c -= ' ';

	rect.x = (c % font->chars_across) * font->char_w;
	rect.y = (c / font->chars_across) * font->char_h;
	rect.w = font->char_w;
	rect.h = font->char_h;

	render_bitmap(font->bmp, x, y, &rect);
}

void rfont_char_col(
	const BM_Font* font,
	int x,
	int y,
	char c,
	Colour colour
) {
	Rectangle rect;

	c -= ' ';

	rect.x = (c % font->chars_across) * font->char_w;
	rect.y = (c / font->chars_across) * font->char_h;
	rect.w = font->char_w;
	rect.h = font->char_h;

	render_bitmap_col(font->bmp, x, y, &rect, colour);
}

void rfont_text(
	const BM_Font* font,
	int x,
	int y,
	const char* text
) {
	const char* c;

	for (c = text; *c; c++) {
		rfont_char(font, x, y, *c);
		x += font->char_w;
	}
}

void rfont_text_col(
	const BM_Font* font,
	int x,
	int y,
	const char* text,
	Colour colour
) {
	const char* c;

	for (c = text; *c; c++) {
		rfont_char_col(font, x, y, *c, colour);
		x += font->char_w;
	}
}

void render_bitmap(
	const Bitmap* bitmap,
	int x,
	int y,
	const Rectangle* rect
) {
	int i, j, stride, sstride, n;
	Colour* dst;
	const Colour* src;
	Rectangle sub;

	sub = *rect;

	if (sub.w <= 0) { return; }
	if (sub.h <= 0) { return; }
	if (sub.w > bitmap->w) { return; }
	if (sub.h > bitmap->h) { return; }

	if ((n = -x) > 0) {
		sub.w -= n;
		sub.x += n;
		x += n;
	}
	
	if ((n = -y) > 0) {
		sub.h -= n;
		sub.y += n;
		y += n;
	}
	
	if ((n = x + sub.w - renderer_w) > 0) {
		sub.w -= n;
	}

	if ((n = y + sub.h - renderer_h) > 0) {
		sub.h -= n;
	}

	if (sub.w <= 0) { return; }
	if (sub.h <= 0) { return; }

	dst = renderer.pixels + (x + y * renderer_w);
	src = bitmap->pixels + (sub.x + sub.y * bitmap->w);

	stride = renderer_w - sub.w;
	sstride = bitmap->w - sub.w;

	for (i = 0; i < sub.h; i++) {
		for (j = 0; j < sub.w; j++) {
			*dst = blend(*dst, *src);
			dst++;
			src++;
		}
		dst += stride;
		src += sstride;
	}
}

void render_bitmap_col(
	const Bitmap* bitmap,
	int x,
	int y,
	const Rectangle* rect,
	Colour colour
) {
	int i, j, stride, sstride, n;
	Colour* dst;
	const Colour* src;
	Rectangle sub;

	sub = *rect;

	if (sub.w <= 0) { return; }
	if (sub.h <= 0) { return; }
	if (sub.w > bitmap->w) { return; }
	if (sub.h > bitmap->h) { return; }

	if ((n = -x) > 0) {
		sub.w -= n;
		sub.x += n;
		x += n;
	}
	
	if ((n = -y) > 0) {
		sub.h -= n;
		sub.y += n;
		y += n;
	}
	
	if ((n = x + sub.w - renderer_w) > 0) {
		sub.w -= n;
	}

	if ((n = y + sub.h - renderer_h) > 0) {
		sub.h -= n;
	}

	if (sub.w <= 0) { return; }
	if (sub.h <= 0) { return; }

	dst = renderer.pixels + (x + y * renderer_w);
	src = bitmap->pixels + (sub.x + sub.y * bitmap->w);

	stride = renderer_w - sub.w;
	sstride = bitmap->w - sub.w;

	for (i = 0; i < sub.h; i++) {
		for (j = 0; j < sub.w; j++) {
			*dst = blend_mod(*dst, *src, colour);
			dst++;
			src++;
		}
		dst += stride;
		src += sstride;
	}
}

void blit(
	Bitmap* to,
	const Bitmap* from,
	int x,
	int y,
	const Rectangle* rect
) {
	int i, j, stride, sstride, n;
	Colour* dst;
	const Colour* src;
	Rectangle sub;

	sub = *rect;

	if (sub.w <= 0) { return; }
	if (sub.h <= 0) { return; }
	if (sub.w > from->w) { return; }
	if (sub.h > from->h) { return; }

	if ((n = -x) > 0) {
		sub.w -= n;
		sub.x += n;
		x += n;
	}
	
	if ((n = -y) > 0) {
		sub.h -= n;
		sub.y += n;
		y += n;
	}
	
	if ((n = x + sub.w - to->w) > 0) {
		sub.w -= n;
	}

	if ((n = y + sub.h - to->h) > 0) {
		sub.h -= n;
	}

	if (sub.w <= 0) { return; }
	if (sub.h <= 0) { return; }

	dst = to->pixels   + (x     + y     * to->w);
	src = from->pixels + (sub.x + sub.y * from->w);

	stride = to->w - sub.w;
	sstride = from->w - sub.w;

	for (i = 0; i < sub.h; i++) {
		for (j = 0; j < sub.w; j++) {
			*dst = blend(*dst, *src);
			dst++;
			src++;
		}
		dst += stride;
		src += sstride;
	}
}

void blit_col(
	Bitmap* to,
	const Bitmap* from,
	int x,
	int y,
	const Rectangle* rect,
	Colour colour
) {
	int i, j, stride, sstride, n;
	Colour* dst;
	const Colour* src;
	Rectangle sub;

	sub = *rect;

	if (sub.w <= 0) { return; }
	if (sub.h <= 0) { return; }
	if (sub.w > from->w) { return; }
	if (sub.h > from->h) { return; }

	if ((n = -x) > 0) {
		sub.w -= n;
		sub.x += n;
		x += n;
	}
	
	if ((n = -y) > 0) {
		sub.h -= n;
		sub.y += n;
		y += n;
	}
	
	if ((n = x + sub.w - to->w) > 0) {
		sub.w -= n;
	}

	if ((n = y + sub.h - to->h) > 0) {
		sub.h -= n;
	}

	if (sub.w <= 0) { return; }
	if (sub.h <= 0) { return; }

	dst = to->pixels   + (x     + y     * to->w);
	src = from->pixels + (sub.x + sub.y * from->w);

	stride = to->w - sub.w;
	sstride = from->w - sub.w;

	for (i = 0; i < sub.h; i++) {
		for (j = 0; j < sub.w; j++) {
			*dst = blend_mod(*dst, *src, colour);
			dst++;
			src++;
		}
		dst += stride;
		src += sstride;
	}
}