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

/* 
Copyright (c) 2020 Devine Lu Linvega

Permission to use, copy, modify, and distribute this software for any
purpose with or without fee is hereby granted, provided that the above
copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
WITH REGARD TO THIS SOFTWARE.
*/

#define HOR 32
#define VER 16
#define PAD 8
#define ZOOM 2
#define color1 0x000000
#define color2 0x72DEC2
#define color3 0xFFFFFF
#define color4 0x444444
#define color0 0x111111

#define SZ (HOR * VER * 16)

typedef struct Brush {
	int x, y, px, py;
	int mode, size, color;
	int down, edit, erase;
} Brush;

int colors[] = {color1, color2, color3, color4, color0};
int WIDTH = 8 * HOR + PAD * 2;
int HEIGHT = 8 * VER + PAD * 2;
int FPS = 30, GUIDES = 1;

unsigned char chrbuf[SZ];
SDL_Window *gWindow;
SDL_Renderer *gRenderer;
SDL_Texture *gTexture;
Uint32 *pixels;

Brush brush;

/* helpers */

int
distance(int ax, int ay, int bx, int by)
{
	return (bx - ax) * (bx - ax) + (by - ay) * (by - ay);
}

int
spos(char *s, char *ss)
{
	int a = 0, b = 0;
	while(s[a] != '\0') {
		if(s[a] == ss[b]) {
			if(ss[b + 1] == '\0')
				return a - b;
			b++;
		} else
			b = 0;
		a++;
	}
	return -1;
}

int
getclr(int r, int g, int b)
{
	return r && g && b && r == g && g == b ? 1 : r > g && r > b ? 2 : g > r && g > b ? 3 : 0;
}

/* chr */

int
rowchr(int x, int y)
{
	return (y % 8) + ((x / 8 + y / 8 * HOR) * 16);
}

int
getchr(int x, int y)
{
	int ch1, ch2;
	int r = rowchr(x, y);
	int px = x % 8;
	if(r < 0 || r > SZ - 8)
		return 0;
	ch1 = (chrbuf[r] >> (7 - px)) & 1;
	ch2 = (chrbuf[r + 8] >> (7 - px)) & 1;
	return ch1 && !ch2 ? 1 : !ch1 && ch2 ? 2 : ch1 && ch2 ? 3 : 0;
}

void
putchr(int x, int y, int color)
{
	int r = rowchr(x, y), px = x % 8;
	if(r < 0 || r > SZ - 8)
		return;
	if(!color) {
		chrbuf[r] &= ~(1UL << (7 - px));
		chrbuf[r + 8] &= ~(1UL << (7 - px));
	} else if(color == 2) {
		chrbuf[r] |= 1UL << (7 - px);
		chrbuf[r + 8] &= ~(1UL << (7 - px));
	} else if(color == 1) {
		chrbuf[r] &= ~(1UL << (7 - px));
		chrbuf[r + 8] |= 1UL << (7 - px);
	} else if(color == 3) {
		chrbuf[r] |= 1UL << (7 - px);
		chrbuf[r + 8] |= 1UL << (7 - px);
	}
}

void
newchr(void)
{
	int i;
	for(i = 0; i < SZ; ++i)
		chrbuf[i] = 0x00;
}

int
jagg(int x, int y)
{
	int n = getchr(x, y + 1);
	int e = getchr(x + 1, y);
	int s = getchr(x, y - 1);
	int w = getchr(x - 1, y);
	int h = getchr(x, y);
	if(h == n && h == e && h != s && h != w)
		return 1;
	if(h == e && h == s && h != w && h != n)
		return 1;
	if(h == s && h == w && h != n && h != e)
		return 1;
	if(h == w && h == n && h != e && h != s)
		return 1;
	return 0;
}

int
patt(int x, int y, int mode, int size)
{
	if(mode == 1)
		return ((x + y) % 4) == 0 && ((y - x) % 4) == 0;
	if(mode == 2)
		return ((x + y) % 2) == 0 && ((y - x) % 2) == 0;
	if(mode == 3)
		return 1;
	if(mode == 4)
		return y % size == 0;
	if(mode == 5)
		return x % size == 0;
	if(mode == 6)
		return (x + y) % size == 0 || (x - y) % size == 0;
	return 0;
}

void
fill(int x, int y, int mode, int size, int color)
{
	int ox, oy;
	for(ox = x - (size / 2); ox < x + size; ++ox)
		for(oy = y - (size / 2); oy < y + size; ++oy)
			if(mode == 7 && jagg(ox, oy))
				putchr(ox, oy, 0);
			else if(patt(ox, oy, mode, size) && distance(x, y, ox, oy) < size)
				putchr(ox, oy, color);
}

void
line(int ax, int ay, int bx, int by, int color)
{
	int dx = abs(bx - ax), sx = ax < bx ? 1 : -1;
	int dy = -abs(by - ay), sy = ay < by ? 1 : -1;
	int err = dx + dy, e2;
	for(;;) {
		putchr(ax, ay, color);
		if(ax == bx && ay == by)
			break;
		e2 = 2 * err;
		if(e2 >= dy) {
			err += dy;
			ax += sx;
		}
		if(e2 <= dx) {
			err += dx;
			ay += sy;
		}
	}
}

/* draw */

void
drawchr(Uint32 *dst, int x, int y, int id)
{
	int v, h, offset = id * 16;
	for(v = 0; v < 8; v++)
		for(h = 0; h < 8; h++) {
			int px = (x * 8) + (8 - h);
			int py = (y * 8) + v;
			int ch1 = chrbuf[offset + v];
			int ch2 = chrbuf[offset + v + 8];
			int clr = ((ch1 >> h) & 0x1) + (((ch2 >> h) & 0x1) << 1);
			int key = (py + PAD) * WIDTH + (px + PAD);
			int guides = GUIDES && !clr && (x + y) % 2;
			dst[key] = colors[guides ? 4 : clr];
		}
}

void
draw(Uint32 *dst)
{
	int x, y;
	for(y = 0; y < VER; ++y)
		for(x = 0; x < HOR; ++x)
			drawchr(dst, x, y, x + y * HOR);
	SDL_UpdateTexture(gTexture, NULL, dst, WIDTH * sizeof(Uint32));
	SDL_RenderClear(gRenderer);
	SDL_RenderCopy(gRenderer, gTexture, NULL, NULL);
	SDL_RenderPresent(gRenderer);
}

/* options */

int
error(char *msg, const char *err)
{
	printf("Error %s: %s\n", msg, err);
	return 0;
}

void
setcolor(Brush *b, int c)
{
	b->color = c;
	printf("Set Color %d\n", b->color);
}

void
setmode(Brush *b, int m)
{
	b->mode = m;
	printf("Set Mode %d\n", b->mode);
}

void
modsize(Brush *b, int mod)
{
	int res = b->size + mod;
	if(res > 0 && res < 30)
		b->size = res;
	printf("Set Size %d\n", b->size);
}

void
toggleguide(void)
{
	GUIDES = !GUIDES;
	draw(pixels);
	printf("%s Guides\n", GUIDES ? "Show" : "Hide");
}

void
destroy(void)
{
	newchr();
	draw(pixels);
	puts("Destroy");
}

void
exportchr(Brush *b)
{
	FILE *f = fopen("nasu-export.chr", "wb");
	if(!fwrite(chrbuf, sizeof(chrbuf), 1, f))
		error("Save", "Invalid output file");
	fclose(f);
	b->edit = 0;
	puts("Exported nasu-export.chr");
}

void
renderbmp(void)
{
	SDL_Surface *surface = SDL_GetWindowSurface(gWindow);
	GUIDES = 0;
	draw(pixels);
	SDL_RenderReadPixels(gRenderer,
		NULL,
		SDL_PIXELFORMAT_ARGB8888,
		surface->pixels,
		surface->pitch);
	SDL_SaveBMP(surface, "nasu-render.bmp");
	SDL_FreeSurface(surface);
	puts("Rendered nasu-render.bmp");
}

void
loadchr(char *path)
{
	FILE *f = fopen(path, "rb");
	if(f == NULL)
		error("Load", "Invalid input file");
	if(!fread(chrbuf, sizeof(chrbuf), 1, f))
		error("Load", "Invalid input size");
	fclose(f);
}

void
loadbmp(char *path)
{
	FILE *f = fopen(path, "rb");
	int i, width = HOR * 8, height = VER * 8, size = 3 * width * height;
	unsigned char header[54];
	unsigned char data[4096 * 256];
	if(!fread(header, sizeof(unsigned char), 54, f))
		error("Load", "Invalid bmp header");
	if(!fread(data, sizeof(unsigned char), size, f))
		error("Load", "Invalid bmp body");
	for(i = 0; i < size; i += 3) {
		int x = (i / 3) % width, y = height - (i / 3) / width - 1;
		putchr(x, y, getclr(data[i + 2], data[i + 1], data[i]));
	}
	fclose(f);
}

void
quit(void)
{
	free(pixels);
	SDL_DestroyTexture(gTexture);
	gTexture = NULL;
	SDL_DestroyRenderer(gRenderer);
	gRenderer = NULL;
	SDL_DestroyWindow(gWindow);
	gWindow = NULL;
	SDL_Quit();
	exit(0);
}

void
domouse(SDL_Event *event, Brush *b)
{
	switch(event->type) {
	case SDL_MOUSEBUTTONUP:
		if(event->button.button == SDL_BUTTON_LEFT) {
			b->down = 0;
			b->px = 0;
			b->py = 0;
		}
		if(event->button.button == SDL_BUTTON_RIGHT)
			b->erase = 0;
		b->edit = 1;
		break;
	case SDL_MOUSEBUTTONDOWN:
		if(event->button.button == SDL_BUTTON_LEFT) {
			b->down = 1;
		}
		if(event->button.button == SDL_BUTTON_RIGHT)
			b->erase = 1;
		if(event->button.button == SDL_BUTTON_MIDDLE) {
			b->erase = 0;
			if(b->px != 0 && b->py != 0) {
				b->x = (event->motion.x - (PAD * ZOOM)) / ZOOM;
				b->y = (event->motion.y - (PAD * ZOOM)) / ZOOM;
				line(b->px, b->py, b->x, b->y, b->erase ? 0 : b->color);
				draw(pixels);
			}
		}
		b->px = (event->motion.x - (PAD * ZOOM)) / ZOOM;
		b->py = (event->motion.y - (PAD * ZOOM)) / ZOOM;
		if(b->down) {
			putchr(b->px, b->py, b->color);
			draw(pixels);
		}
		break;
	case SDL_MOUSEMOTION:
		if(b->down) {
			b->x = (event->motion.x - (PAD * ZOOM)) / ZOOM;
			b->y = (event->motion.y - (PAD * ZOOM)) / ZOOM;
			if(!b->mode)
				line(b->px, b->py, b->x, b->y, b->erase ? 0 : b->color);
			else
				fill(b->x, b->y, b->mode, b->size, b->erase ? 0 : b->color);
			draw(pixels);
			b->px = b->x;
			b->py = b->y;
		}
		break;
	}
}

void
dokey(SDL_Event *event, Brush *b)
{
	switch(event->key.keysym.sym) {
	case SDLK_ESCAPE: quit(); break;
	case SDLK_1: setmode(b, 0); break;
	case SDLK_2: setmode(b, 1); break;
	case SDLK_3: setmode(b, 2); break;
	case SDLK_4: setmode(b, 3); break;
	case SDLK_5: setmode(b, 4); break;
	case SDLK_6: setmode(b, 5); break;
	case SDLK_7: setmode(b, 6); break;
	case SDLK_e: exportchr(b); break;
	case SDLK_r: renderbmp(); break;
	case SDLK_a: setcolor(b, 0); break;
	case SDLK_s: setcolor(b, 1); break;
	case SDLK_d: setcolor(b, 2); break;
	case SDLK_f: setcolor(b, 3); break;
	case SDLK_h: toggleguide(); break;
	case SDLK_z: modsize(b, -1); break;
	case SDLK_x: modsize(b, 1); break;
	case SDLK_c: setmode(b, 7); break;
	case SDLK_n: destroy(); break;
	}
}

int
init(void)
{
	int i, j;
	if(SDL_Init(SDL_INIT_VIDEO) < 0)
		return error("Init", SDL_GetError());
	gWindow = SDL_CreateWindow("Nasu",
		SDL_WINDOWPOS_UNDEFINED,
		SDL_WINDOWPOS_UNDEFINED,
		WIDTH * ZOOM,
		HEIGHT * ZOOM,
		SDL_WINDOW_SHOWN);
	if(gWindow == NULL)
		return error("Window", SDL_GetError());
	gRenderer = SDL_CreateRenderer(gWindow, -1, 0);
	if(gRenderer == NULL)
		return error("Renderer", SDL_GetError());
	gTexture = SDL_CreateTexture(gRenderer,
		SDL_PIXELFORMAT_ARGB8888,
		SDL_TEXTUREACCESS_STATIC,
		WIDTH,
		HEIGHT);
	if(gTexture == NULL)
		return error("Texture", SDL_GetError());
	pixels = (Uint32 *)malloc(WIDTH * HEIGHT * sizeof(Uint32));
	if(pixels == NULL)
		return error("Pixels", "Failed to allocate memory");
	for(i = 0; i < HEIGHT; i++)
		for(j = 0; j < WIDTH; j++)
			pixels[i * WIDTH + j] = color1;
	return 1;
}

int
main(int argc, char **argv)
{
	int ticknext = 0;

	brush.erase = 0;
	brush.down = 0;
	brush.color = 1;
	brush.edit = 0;
	brush.size = 8;
	brush.mode = 0;

	if(!init())
		return error("Init", "Failure");

	if(argc > 1 && spos(argv[1], ".bmp") > -1)
		loadbmp(argv[1]);
	else if(argc > 1 && spos(argv[1], ".chr") > -1)
		loadchr(argv[1]);
	else
		newchr();

	draw(pixels);

	while(1) {
		int tick = SDL_GetTicks();
		SDL_Event event;
		if(tick < ticknext)
			SDL_Delay(ticknext - tick);
		ticknext = tick + (1000 / FPS);
		while(SDL_PollEvent(&event) != 0) {
			if(event.type == SDL_QUIT)
				quit();
			else if(event.type == SDL_MOUSEBUTTONUP ||
					event.type == SDL_MOUSEBUTTONDOWN ||
					event.type == SDL_MOUSEMOTION) {
				domouse(&event, &brush);
			} else if(event.type == SDL_KEYDOWN)
				dokey(&event, &brush);
			else if(event.type == SDL_WINDOWEVENT)
				if(event.window.event == SDL_WINDOWEVENT_EXPOSED)
					draw(pixels);
		}
	}
	quit();
	return 0;
}