#include <stdio.h>
#include <string.h>
#include <limits.h>

char *firstMatch (char *string, int offset, int *digit);
char *lastMatch (char *string, int *digit);

// array of strings with all digits and human-numbers
const char *numbers[] = {"one", "two", "three", "four", "five", "six",
                         "seven", "eight", "nine",
                         "0", "1", "2", "3", "4", "5", "6", "7", "8", "9"};

int main() 
{
	FILE *input;
	input = fopen("./input", "r");
	
	int digit = 0;
	int value = 0;
	int sum = 0;
	char row[100];

	// use fgets
	while ((fgets(row, 100, input)) != 0) {
		firstMatch(row, 0, &digit);
		value = digit * 10;

		lastMatch(row, &digit);
		value += digit;

		printf("value: %d\n", value);
		sum += value;
	}
	
	fclose(input);
	printf("%u\n", sum);
}

// function with input offset and string, returns offset (and val?)
// looks for every string / char, return lowest offset
// to find rightmost, repeatedly call this function with offset + 1
char *firstMatch (char *string, int offset, int *digit)
{
	// this ptr is 1 step outside of the array, because the
	// relational operators in C are only defined if both pointers
	// point within the same array or one step beyond the last member
	char *first = &string[99] + 1;

	// looks for each number string from numbers[]
	// and remembers the lowest pointer
	char *match; 
	for (int i = 0; i < sizeof(numbers) / 8; i++) {
		match = strstr(string + offset, numbers[i]);
		if (match == 0) continue;
		if (match < first) {
			first = match;
			if (i <= 8) {
				*digit = i + 1;
			} else {
				*digit = i - 9;
			}
		}
	}

	// Pointer unchanged? No match, return NULL
	if (first == &string[99] + 1) first = NULL;
	return first;
}

char *lastMatch (char *string, int *digit)
{
	char *last = &string[0];
	int offset = 0;
	while (firstMatch(string, offset, digit) >= last) {
		if (firstMatch(string, offset, digit) == NULL) break;
		last = firstMatch(string, offset, digit);
		offset++;
	}
	return last;
}