//
// Created by Lennart on 02/12/2023.
//

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

int find_digits(FILE *f, bool replace_letters);
int solve(const char *fileName, bool replace_letters);

char *buffer;
int bufferLen = 64;
const char* digitsAsLetters[] = {
    "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine"
};

int main() {
    buffer = malloc(bufferLen * sizeof (char));

    printf("Result #1: %i\n", solve("day_1.txt", false));
    printf("Result #2: %i\n", solve("day_1.txt", true));

    free(buffer);
    return 0;
}

int solve(const char *fileName, bool replace_letters) {
    FILE *f = fopen(fileName, "r");
    if(f == NULL) {
        printf("Error! Missing input file!");
        exit(-1);
    }

    int sum = 0;
    while(!feof(f)) {
        sum += find_digits(f, replace_letters);
    }
    fclose(f);
    return sum;
}

// Read all digits form the next line in a file
int find_digits(FILE *f, bool replace_letters) {
    int first = -1, last = 10; // Use first=-1 to detect unset value and last=10 to return 0 (-10 + 10) when no values are set

    // Read the entire line as a string
    int position = 0;
    do {
        if(position >= bufferLen - 1) {
            buffer = realloc(buffer, 2 * sizeof(char) * bufferLen);
            bufferLen *= 2;
        }
        fgets(&buffer[position], bufferLen - position, f);
        position = bufferLen - 1;
    } while(buffer[strlen(buffer) - 1] != '\n' && !feof(f));

    for(int i = 0; i < bufferLen; i++) {
        if(buffer[i] == 0) {
            break;
        }

        int digit = -1;
        if(sscanf(&buffer[i], "%1d", &digit) != 1 && replace_letters) {
            for(int j = 1; j < 10; j++) {
                if(strncmp(&buffer[i], digitsAsLetters[j], strlen(digitsAsLetters[j])) == 0) {
                    digit = j;
                    break;
                }
            }
        }

        if(digit >= 0) {
            if(first == -1) {
                first = digit;
            }
            last = digit;
        }
    }

    return first * 10 + last;
}