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

struct list {
	int xy[2];
	struct list *next;
};

int score_trail(int x, int y, int width, int height, char **map, struct list *peaks)
{
	int dir[4][2] = {{0, -1}, {1, 0}, {0, 1}, {-1, 0}};
	int score = 0;
	int first = map[x][y];

	// init list
	if (peaks == NULL) {
		peaks = malloc(sizeof(struct list));
		peaks->xy[0] = -1;
		peaks->xy[1] = -1;
		peaks->next = NULL;
	}

	// if find 9, check if its already in list, else append it
	// could have been its own func
	if (map[x][y] == '9') {
		printf("found %dx%d\n", x, y);
		if (peaks->xy[0] == -1 ) {
			printf("was first, init first trail\n");
			peaks->xy[0] = x;
			peaks->xy[1] = y;
			return 1;
		}
		// while (!(peaks->xy[0] == x && peaks->xy[1] == y) && peaks->next) {
		while (peaks->next) {
			printf("checking next peaklist...\n");
			peaks = peaks->next;
		}
		/*
		if (peaks->xy[0] == x && peaks->xy[1] == y) {
			printf("found same, exit\n");
			return 0;
		}
		*/
		// printf("allocate new peak, jump to it, and set it\n");
		peaks->next = malloc(sizeof(struct list));
		peaks = peaks->next;
		peaks->xy[0] = x;
		peaks->xy[1] = y;
		peaks->next = NULL;
		return 1;
	}

	// look in every direction for grid[j][i] + 1, recurse it
	for (int i = 0; i < 4; i++) {
		if (x + dir[i][0] >= 0 &&
		    x + dir[i][0] < width &&
		    y + dir[i][1] >= 0 &&
		    y + dir[i][1] < height) {
			if (map[x + dir[i][0]][y + dir[i][1]] == map[x][y] + 1)
				score_trail(x + dir[i][0], y + dir[i][1],
				            width, height, map, peaks);
		}
	}

	// please count and cleanup the list
	if (first == '0') {
		struct list *tmp;
		while (peaks) {
			score++;
			tmp = peaks;
			peaks = peaks->next;
			free(tmp);
		}
		return score;
	}
	return 0;
}

int main ()
{

	// figure out data dimensions
	FILE *input = fopen("./input", "r");
	int width =  0;
	int height = 1;
	while (fgetc(input) != '\n') width++;
	for (char c = fgetc(input); c != EOF; c = fgetc(input)) {
		if (c == '\n')
			height++;
	}
	rewind(input);
	printf("Dimensions: %d x %d\n", width, height);

	// make 2d array
	char **map = malloc(width * sizeof(char*));
	map[0] = malloc(width * height);
	for (int i = 1; i < width; i++) {
		map[i] = map[0] + i * height;
	}

	// put the data in the array
	for (int i = 0; i < height; i++) {
		for (int j = 0; j < width; j++) {
			map[j][i] = fgetc(input);
		}
		fgetc(input);
	}
	fclose(input);

	// sum it
	int scoreSum = 0;
	// find trailheads, check their score, sumit (hehehe)
	for (int i = 0; i < height; i++) {
		for (int j = 0; j < width; j++) {
			if (map[j][i] == '0') {
				printf("\tExamining %dx%d:\n", j, i);
				int score = score_trail(j, i, width, height, map, NULL);
				scoreSum += score;
				if (score)
					printf("score sum trail head %dx%d: %d\n", j, i, score);
			}
		}
	}
	printf("total score: %d\n", scoreSum);
}