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

int main(int argc, char *argv[]) {
    if (argc < 2) {
        fprintf(stderr, "Need a file name as first argument!\n");
        return EXIT_FAILURE;
    }

    FILE *file = fopen(argv[1], "rb");
    if (file == NULL) {
        fprintf(stderr, "File open failed!\n");
        return EXIT_FAILURE;
    }

    size_t buffer_size = 8;
    char *line = (char*)malloc(buffer_size);
    char *longest = (char*)malloc(buffer_size);
    size_t longest_on = 0;
    size_t longest_length = 0;
    size_t num_lines = 0;

    if (line == NULL || longest == NULL) {
        fprintf(stderr, "Memory allocation failed!\n");
        return EXIT_FAILURE;
    }

    long pos_before = ftell(file);
    for (num_lines = 1 ; fgets(line, buffer_size, file) ; ++num_lines) {
        long pos_after = ftell(file);
        size_t line_length = pos_after - pos_before - 1;
        pos_before = pos_after-1;
        while (line_length == buffer_size-1 && line[line_length-1] != '\n') {
            line = (char*)realloc(line, buffer_size*2);
            longest = (char*)realloc(longest, buffer_size*2);
            if (line == NULL || longest == NULL) {
                fprintf(stderr, "Memory allocation failed!\n");
                return EXIT_FAILURE;
            }
            if (fgets(&line[buffer_size-1], buffer_size+1, file) == NULL) {
                fprintf(stderr, "File read failed!\n");
                fclose(file);
                free(line);
                free(longest);
                return EXIT_FAILURE;
            }
            pos_after = ftell(file);
            line_length += pos_after - pos_before - 1;
            pos_before = pos_after-1;
            buffer_size *= 2;
        }
        if (line_length > longest_length) {
            char *tmp = longest;
            longest = line;
            line = tmp;
            longest_on = num_lines;
            longest_length = line_length;
        }
    }

    if (longest_on) {
        printf("File had total of %lu lines.\n", num_lines);
        printf("Longest line found on line %lu with %lu characters.\n", longest_on, longest_length);
        printf("The line was: ");
        fwrite(longest, 1, longest_length, stdout);
    }
    else {
        fprintf(stderr, "The file had no readable lines!\n");
    }
    
    fclose(file);
    free(line);
    free(longest);
    return EXIT_SUCCESS;
}