/* This is the complete line count program from Lecture 09.
 * It shows how a simple C program is laid out, including taking command-line
 * arguments, printing to stdout and stderr, and reading from a file.
 */

#include <stdio.h> // standard library stuff for printing and file I/O
#include <string.h> // standard library string functions

// during compilation MAX_LINE_LENGTH will get replaced with 500
#define MAX_LINE_LENGTH 500 

// prototype for count_lines, so main can use it
int count_lines(FILE *file, int *c_count);

int main(int argc, char **argv) {
    // we expect exactly two arguments
    //    argv[0] is the command (i.e., "./line_count")
    //    argv[1] FILE
    if (argc != 2) {
        // use fprintf to print to stderr
        fprintf(stderr, "usage: ./line_count FILE\n");
        return 1; // exit status of 1 indicates error
    }

    FILE *file = fopen(argv[1], "r"); // try to open the file in "read" mode
    // check if we were able to open the file (fopen returns NULL if it fails)
    if (file != NULL) {
        int c_count; // character count
        int lines = count_lines(file, &c_count); // pass &c_count so count_lines can modify the value of c_count
        if (lines == -1) { // -1 indicates an error while reading
            fprintf(stderr, "line_count: error reading %s\n", argv[1]);
            return 3;
        }
        // could use fprintf(stdout, ...) to print to stdout, but printf is easier
        printf("%d %d\n", lines, c_count); // %d is the format string for an int
        return 0; // exit status of 0 for success
    } else {
        // %s is the format string for a string
        fprintf(stderr, "line_count: error opening %s\n", argv[1]);
        return 2;
    }
}


/*
 * Reads file and returns the number of lines.
 * Lines are assumed to be at most MAX_LINE_LENGTH characters long.
 * The number of characters in the file is stored in c_count
 */
int count_lines(FILE *file, int *c_count) {
    int count = 0;
    *c_count = 0;
    char line[MAX_LINE_LENGTH]; // will get turned into char line[500] at compilation
    /* fgets reads up to MAX_LINE_LENGTH characters from file and stores them in line, stopping at newlines
     * file keeps track of what has been read, so the next call to fgets will pick up where it left off
     * if successful, fgets returns line, which gets treated as true
     * if it fails (e.g., there are no more characters to read), fgets returns NULL, which gets treated as false
     */
    while(fgets(line, MAX_LINE_LENGTH, file)) {
        count++;
        *c_count += strlen(line);
    }
    return count;
}