/* Copyright (C) 2018  C. McEnroe <june@causal.agency>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <err.h>
#include <fcntl.h>
#include <math.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sysexits.h>
#include <unistd.h>

#include "gfx.h"
#include "png.h"

#define MAX(a, b) ((a) > (b) ? (a) : (b))
#define MASK(b) ((1 << (b)) - 1)

static uint32_t rgb(uint8_t r, uint8_t g, uint8_t b) {
	return (uint32_t)r << 16 | (uint32_t)g << 8 | (uint32_t)b;
}
static uint32_t gray(uint8_t n) {
	return rgb(n, n, n);
}

static enum {
	ColorIndexed,
	ColorGrayscale,
	ColorRGB,
	ColorCount,
} space = ColorRGB;
static const char *ColorStr[ColorCount] = { "indexed", "grayscale", "rgb" };
static uint32_t palette[256];

static enum {
	EndianLittle,
	EndianBig,
} byteOrder, bitOrder;

enum { Pad, R, G, B };
static uint8_t bits[4] = { 8, 8, 8, 8 };

static uint8_t bitsColor(void) {
	return bits[R] + bits[G] + bits[B];
}
static uint8_t bitsTotal(void) {
	return bits[Pad] + bitsColor();
}

static size_t offset;
static size_t width = 16;
static bool flip;
static bool mirror;
static size_t scale = 1;

static const char *prefix = "gfxx";

static size_t size;
static uint8_t *data;

int init(int argc, char *argv[]) {
	const char *pal = NULL;
	const char *path = NULL;

	int opt;
	while (0 < (opt = getopt(argc, argv, "c:p:b:e:E:n:fmw:z:o:"))) {
		switch (opt) {
			break; case 'c':
				switch (optarg[0]) {
					break; case 'i': space = ColorIndexed;
					break; case 'g': space = ColorGrayscale;
					break; case 'r': space = ColorRGB;
					break; default: return EX_USAGE;
				}
			break; case 'p': pal = optarg;
			break; case 'e':
				switch (optarg[0]) {
					break; case 'l': byteOrder = EndianLittle;
					break; case 'b': byteOrder = EndianBig;
					break; default: return EX_USAGE;
				}
			break; case 'E':
				switch (optarg[0]) {
					break; case 'l': bitOrder = EndianLittle;
					break; case 'b': bitOrder = EndianBig;
					break; default: return EX_USAGE;
				}
			break; case 'b': {
				if (strlen(optarg) < 4) return EX_USAGE;
				for (int i = 0; i < 4; ++i) {
					bits[i] = optarg[i] - '0';
				}
			}
			break; case 'n': offset = strtoul(optarg, NULL, 0);
			break; case 'f': flip ^= true;
			break; case 'm': mirror ^= true;
			break; case 'w': width = strtoul(optarg, NULL, 0);
			break; case 'z': scale = strtoul(optarg, NULL, 0);
			break; case 'o': prefix = optarg;
			break; default: return EX_USAGE;
		}
	}
	if (argc > optind) path = argv[optind];
	if (!width || !scale) return EX_USAGE;

	if (pal) {
		FILE *file = fopen(pal, "r");
		if (!file) err(EX_NOINPUT, "%s", pal);
		fread(palette, 4, 256, file);
		if (ferror(file)) err(EX_IOERR, "%s", pal);
		fclose(file);
	} else {
		for (int i = 0; i < 256; ++i) {
			double h = i / 256.0 * 6.0;
			double x = 1.0 - fabs(fmod(h, 2.0) - 1.0);
			double r = 255.0, g = 255.0, b = 255.0;
			if      (h <= 1.0) { g *= x; b = 0.0; }
			else if (h <= 2.0) { r *= x; b = 0.0; }
			else if (h <= 3.0) { r = 0.0; b *= x; }
			else if (h <= 4.0) { r = 0.0; g *= x; }
			else if (h <= 5.0) { r *= x; g = 0.0; }
			else if (h <= 6.0) { g = 0.0; b *= x; }
			palette[i] = (uint32_t)r << 16 | (uint32_t)g << 8 | (uint32_t)b;
		}
	}

	if (path) {
		int fd = open(path, O_RDONLY);
		if (fd < 0) err(EX_NOINPUT, "%s", path);

		struct stat stat;
		int error = fstat(fd, &stat);
		if (error) err(EX_IOERR, "%s", path);
		size = stat.st_size;

		data = mmap(NULL, size, PROT_READ, MAP_SHARED, fd, 0);
		if (data == MAP_FAILED) err(EX_IOERR, "%s", path);

	} else {
		size = 1024 * 1024;
		data = malloc(size);
		if (!data) err(EX_OSERR, "malloc(%zu)", size);

		size = fread(data, 1, size, stdin);
		if (ferror(stdin)) err(EX_IOERR, "(stdin)");
	}

	return EX_OK;
}

static char options[128];
static void formatOptions(void) {
	snprintf(
		options, sizeof(options),
		"gfxx -c %s -e%c -E%c -b %hhu%hhu%hhu%hhu -n 0x%zX %s%s-w %zu -z %zu",
		ColorStr[space],
		"lb"[byteOrder],
		"lb"[bitOrder],
		bits[Pad], bits[R], bits[G], bits[B],
		offset,
		flip ? "-f " : "",
		mirror ? "-m " : "",
		width,
		scale
	);
}

const char *status(void) {
	formatOptions();
	return options;
}

struct Iter {
	uint32_t *buf;
	size_t bufWidth;
	size_t bufHeight;
	size_t left;
	size_t x;
	size_t y;
};

static struct Iter iter(uint32_t *buf, size_t bufWidth, size_t bufHeight) {
	struct Iter it = { .buf = buf, .bufWidth = bufWidth, .bufHeight = bufHeight };
	if (mirror) it.x = width - 1;
	if (flip) it.y = bufHeight / scale - 1;
	return it;
}

static bool nextX(struct Iter *it) {
	if (mirror) {
		if (it->x == it->left) return false;
		it->x--;
	} else {
		it->x++;
		if (it->x == it->left + width) return false;
	}
	return true;
}

static bool nextY(struct Iter *it) {
	if (flip) {
		if (it->y == 0) {
			it->left += width;
			it->y = it->bufHeight / scale;
		}
		it->y--;
	} else {
		it->y++;
		if (it->y == it->bufHeight / scale) {
			it->left += width;
			it->y = 0;
		}
	}
	it->x = it->left;
	if (mirror) it->x += width - 1;
	return (it->left < it->bufWidth / scale);
}

static bool next(struct Iter *it) {
	return nextX(it) || nextY(it);
}

static void put(const struct Iter *it, uint32_t pixel) {
	size_t scaledX = it->x * scale;
	size_t scaledY = it->y * scale;
	for (size_t fillY = scaledY; fillY < scaledY + scale; ++fillY) {
		if (fillY >= it->bufHeight) break;
		for (size_t fillX = scaledX; fillX < scaledX + scale; ++fillX) {
			if (fillX >= it->bufWidth) break;
			it->buf[fillY * it->bufWidth + fillX] = pixel;
		}
	}
}

static uint8_t interp(uint8_t b, uint32_t n) {
	if (b == 8) return n;
	if (b == 0) return 0;
	return n * MASK(8) / MASK(b);
}

static uint32_t interpolate(uint32_t orig) {
	uint32_t r, g, b;
	if (bitOrder == EndianLittle) {
		b = orig & MASK(bits[B]);
		g = (orig >>= bits[B]) & MASK(bits[G]);
		r = (orig >>= bits[G]) & MASK(bits[R]);
	} else {
		r = orig & MASK(bits[R]);
		g = (orig >>= bits[R]) & MASK(bits[G]);
		b = (orig >>= bits[G]) & MASK(bits[B]);
	}
	return rgb(interp(bits[R], r), interp(bits[G], g), interp(bits[B], b));
}

static void drawBits(struct Iter *it) {
	for (size_t i = offset; i < size; ++i) {
		for (uint8_t b = 0; b < 8; b += bitsTotal()) {
			uint8_t n;
			if (byteOrder == EndianBig) {
				n = data[i] >> (8 - bitsTotal() - b) & MASK(bitsTotal());
			} else {
				n = data[i] >> b & MASK(bitsTotal());
			}

			if (space == ColorIndexed) {
				put(it, palette[n]);
			} else if (space == ColorGrayscale) {
				put(it, gray(interp(bitsColor(), n & MASK(bitsColor()))));
			} else if (space == ColorRGB) {
				put(it, interpolate(n));
			}

			if (!next(it)) return;
		}
	}
}

static void drawBytes(struct Iter *it) {
	uint8_t bytes = (bitsTotal() + 7) / 8;
	for (size_t i = offset; i + bytes <= size; i += bytes) {
		uint32_t n = 0;
		for (size_t b = 0; b < bytes; ++b) {
			n <<= 8;
			n |= (byteOrder == EndianBig) ? data[i + b] : data[i + bytes - b - 1];
		}

		if (space == ColorIndexed) {
			put(it, palette[n & 0xFF]);
		} else if (space == ColorGrayscale) {
			put(it, gray(interp(bitsColor(), n & MASK(bitsColor()))));
		} else if (space == ColorRGB) {
			put(it, interpolate(n));
		}

		if (!next(it)) return;
	}
}

static struct {
	unsigned counter;
	char path[FILENAME_MAX];
	FILE *file;
} out;
static void outOpen(const char *ext) {
	snprintf(out.path, sizeof(out.path), "%s%04u.%s", prefix, ++out.counter, ext);
	out.file = fopen(out.path, "wx");
	if (out.file) {
		printf("%s\n", out.path);
	} else {
		warn("%s", out.path);
	}
}

static void pngDump(uint32_t *src, size_t srcWidth, size_t srcHeight) {
	int error;

	size_t stride = 1 + 3 * srcWidth;
	uint8_t data[stride * srcHeight];
	for (size_t y = 0; y < srcHeight; ++y) {
		data[y * stride] = 0;
		for (size_t x = 0; x < srcWidth; ++x) {
			uint8_t *p = &data[y * stride + 1 + 3 * x];
			p[0] = src[y * srcWidth + x] >> 16;
			p[1] = src[y * srcWidth + x] >> 8;
			p[2] = src[y * srcWidth + x];
		}
	}

	outOpen("png");
	if (!out.file) return;

	const char Software[] = "Software";
	formatOptions();
	uint8_t sbit[3] = { MAX(bits[R], 1), MAX(bits[G], 1), MAX(bits[B], 1) };

	pngHead(out.file, srcWidth, srcHeight, 8, PNGTruecolor);

	pngChunk(out.file, "tEXt", sizeof(Software) + strlen(options));
	pngWrite(out.file, (uint8_t *)Software, sizeof(Software));
	pngWrite(out.file, (uint8_t *)options, strlen(options));
	pngInt32(out.file, ~pngCRC);

	pngChunk(out.file, "sBIT", sizeof(sbit));
	pngWrite(out.file, sbit, sizeof(sbit));
	pngInt32(out.file, ~pngCRC);

	pngData(out.file, data, sizeof(data));
	pngTail(out.file);

	error = fclose(out.file);
	if (error) err(EX_IOERR, "%s", out.path);
}

static enum {
	DumpNone,
	DumpOne,
	DumpAll,
} dump;

void draw(uint32_t *buf, size_t bufWidth, size_t bufHeight) {
	memset(buf, 0, 4 * bufWidth * bufHeight);
	struct Iter it = iter(buf, bufWidth, bufHeight);
	if (bitsTotal() >= 8) {
		drawBytes(&it);
	} else {
		drawBits(&it);
	}
	if (dump) pngDump(buf, bufWidth, bufHeight);
	if (dump == DumpOne) dump = DumpNone;
}

static void palSample(void) {
	size_t temp = scale;
	scale = 1;
	draw(palette, 256, 1);
	scale = temp;
}

static void palDump(void) {
	outOpen("dat");
	if (!out.file) return;

	fwrite(palette, 4, 256, out.file);
	if (ferror(out.file)) err(EX_IOERR, "%s", out.path);

	int error = fclose(out.file);
	if (error) err(EX_IOERR, "%s", out.path);
}

static const uint8_t Presets[][4] = {
	{ 0, 0, 1, 0 },
	{ 0, 1, 1, 0 },
	{ 1, 1, 1, 1 },
	{ 2, 2, 2, 2 },
	{ 0, 3, 3, 2 },
	{ 4, 4, 4, 4 },
	{ 1, 5, 5, 5 },
	{ 0, 5, 6, 5 },
	{ 0, 8, 8, 8 },
	{ 8, 8, 8, 8 },
};
static const size_t PresetsLen = sizeof(Presets) / sizeof(Presets[0]);

static uint8_t preset = PresetsLen - 1;
static void setPreset(void) {
	bits[Pad] = Presets[preset][Pad];
	bits[R] = Presets[preset][R];
	bits[G] = Presets[preset][G];
	bits[B] = Presets[preset][B];
}

static void setBit(char in) {
	static uint8_t bit = 0;
	bits[bit++] = in - '0';
	bit &= 3;
}

bool input(char in) {
	size_t pixel = (bitsTotal() + 7) / 8;
	size_t row = width * bitsTotal() / 8;
	switch (in) {
		break; case 'q': return false;
		break; case 'x': dump = DumpOne;
		break; case 'X': dump ^= DumpAll;
		break; case 'o': formatOptions(); printf("%s\n", options);
		break; case '[': if (!space--) space = ColorCount - 1;
		break; case ']': if (++space == ColorCount) space = 0;
		break; case 'p': palSample();
		break; case 'P': palDump();
		break; case '{': if (!preset--) preset = PresetsLen - 1; setPreset();
		break; case '}': if (++preset == PresetsLen) preset = 0; setPreset();
		break; case 'e': byteOrder ^= EndianBig;
		break; case 'E': bitOrder ^= EndianBig;
		break; case 'h': if (offset) offset--;
		break; case 'j': offset += pixel;
		break; case 'k': if (offset >= pixel) offset -= pixel;
		break; case 'l': offset++;
		break; case 'H': if (offset >= row) offset -= row;
		break; case 'J': offset += width * row;
		break; case 'K': if (offset >= width * row) offset -= width * row;
		break; case 'L': offset += row;
		break; case '.': width++;
		break; case ',': if (width > 1) width--;
		break; case '>': width *= 2;
		break; case '<': if (width > 1) width /= 2;
		break; case 'f': flip ^= true;
		break; case 'm': mirror ^= true;
		break; case '+': scale++;
		break; case '-': if (scale > 1) scale--;
		break; default: if (in >= '0' && in <= '9') setBit(in);
	}
	return true;
}