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

#define DEBUG false

/*
See also:
* <https://web.archive.org/web/20160201212501/coding.debuntu.org/c-implementing-str_replace-replace-all-occurrences-substring>
* https://github.com/irl/la-cucina/blob/master/str_replace.c
*/

int str_replace_start(const char* string, const char* target, const char* replacement, char* output)
{
    int l1 = strlen(string);
    int l2 = strlen(target);
    int l3 = strlen(replacement);
    int l4 = strlen(output);
    if (DEBUG)
        printf("%d,%d,%d,%d\n", l1, l2, l3, l4);
    // if(DEBUG) printf("%s,%s,%s,%s\n", string, target, replacement, output);

    if ((l4 < (l1 - l2 + l3)) || l4 < l1) {
        // Not enough memory in output string.
        if (DEBUG)
            printf("String not long enough.\n");
        return 1;
    }
    /* else if(l1 < l2){
    // Not even possible that there is a match.
    if(DEBUG) printf("Target larger than string.\n");
    strcpy(output, string);
  } */
    else {
        if (DEBUG)
            printf("Looking for a match for %s in %s.\n", target, string);
        int match = true;
        for (int i = 0; i < l2; i++) {
            if (string[i] != target[i]) {
                match = false;
                break;
            }
        }
        if (match) {
            if (DEBUG)
                printf("Found match.\n");
            for (int i = 0; i < l3; i++) {
                output[i] = replacement[i];
            }
            int counter = l3;
            for (int i = l2; i < l1; i++) {
                output[counter] = string[i];
                counter++;
            }
            output[counter] = '\0';
            return 2; // success
        } else {
            if (DEBUG)
                printf("Did not find match.\n");
            strcpy(output, string);
        }
    }

    return 0;
}