#include "all.h"

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>

Image read_ppm_image(const char *filename) {
	Image img = {0};

	FILE *f = fopen(filename, "rb");
	if (!f) {
		perror("fopen");
		return (Image){};
	}

	int j = 0;
	int in_token = 0;
	int header_done = 0;

	size_t pixel_count = 0;
	size_t pixel_capacity = 0;

	unsigned char buf[4096];
	size_t nread;

	while ((nread = fread(buf, 1, sizeof buf, f)) > 0) {
		for (size_t i = 0; i < nread; ++i) {
			unsigned char c = buf[i];

			if (!header_done) {
				if (isspace(c)) {
					if (in_token) {
						j++;
						in_token = 0;

						if (j == 4) {
							header_done = 1;

							pixel_capacity = img.width * img.height * 3;
							img.pixels = malloc(pixel_capacity);

							if (!img.pixels) {
								perror("malloc");
								fclose(f);
								return (Image){};
							}
						}
					}

					continue;
				}

				in_token = 1;

				switch (j) {
					case 0:
						{
							size_t len = strlen(img.format);
							if (len + 1 < sizeof img.format) {
								img.format[len] = (char)c;
								img.format[len + 1] = '\0';
							}
						} break;

					case 1:
						{
							if (isdigit(c)) {
								img.width = img.width * 10 + (c - '0');
							}
						} break;

					case 2:
						{
							if (isdigit(c)) {
								img.height = img.height * 10 + (c - '0');
							}
						} break;

					case 3:
						{
							if (isdigit(c)) {
								img.color_space = img.color_space * 10 + (c - '0');
							}
						} break;
				}
			} else {
				if (pixel_count < pixel_capacity) {
					img.pixels[pixel_count++] = c;
				}
			}
		}
	}

	fclose(f);

	printf("Loading image: [%s] %s (%dx%d) %d (%zu/%zu)\n", filename, img.format, img.width, img.height, img.color_space, pixel_count, pixel_capacity);

	return img;
}