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

/* readLines reads contents of a text file and returns a dynamically allocated string
 * containing the longest line of the file. Line is a sequence of characters terminated by the newline character '\n'.
 *
 * The length of the line is stored to the integer pointed to by
 * "longest". If the file does not contain any lines or if the file cannot be opened, then the value 0
 * is stored to the target of longest  and NULL pointer is returned.
 *
 * If the file contains multiple lines with the longest length, then the first line encountered is returned.
 *
 * The returned value does not include the newline character. The caller of the function must free()
 * the returned value when it is no longer needed.
 */
char *readLines(const char *file, size_t *longest){
    FILE* input = fopen(file, "r");
    if(input == NULL){
        *longest = 0;
        return NULL;
    }
    char buffer[1024];
    char *textFile = malloc(1);
    textFile[0] ='\0';
    size_t size = 0;
    while(fgets(buffer,1024,input)){
        size += strlen(buffer);
        textFile = realloc(textFile, size+1);
        strcat(textFile,buffer);
    }
    *longest = 0;
    char* newLine;
    const char* it = textFile;
    const char* lline = textFile;
    newLine = strchr(it,'\n');
    while(newLine != NULL){
        if((size_t)(newLine-it)>*longest){
            *longest = newLine-it;
            lline = it;
        }
        it = newLine+1;
        newLine = strchr(it,'\n');
    }
    //printf("longest is %zu\n", *longest);
    char *string = malloc((*longest)*sizeof(char));
    strncpy(string,lline,*longest);
    fclose(input);
    return string;

}