/*
 * Program to expand tabs in input.
 *
 * Command-line argument specifies infile
 * (later we can maybe figure out how to also specify spaces per tab).
 */
#include <stdio.h>
#include <stdlib.h>

#define LINE_WIDTH 80

void print_header(int spaces_per_tab);

int main(int argc, char * argv[]) {
    if (argc < 2) {
        fprintf(stderr, "usage: %s infile spaces_per_tab\n", argv[0]);
        return EXIT_FAILURE;
    }
    FILE * infile = fopen(argv[1], "r");
    if (infile == NULL) {
        fprintf(stderr, "cannot open input file %s\n", argv[2]);
        return EXIT_FAILURE;
    }

    int spaces_per_tab = 8;
    print_header(spaces_per_tab);
    
    int ch;
    int tab_count = 0;
    int position_in_line = 0;
    while ((ch = fgetc(infile)) != EOF) {
        if (ch == '\t') {
            tab_count += 1;
            do {
                fputc(' ', stdout);
                position_in_line += 1;
            } while ((position_in_line % spaces_per_tab) != 0); 
        }
        else if (ch == '\n') {
            fputc(ch, stdout);
            position_in_line = 0;
        }
        else {
            fputc(ch, stdout);
            position_in_line += 1;
        }
    }
    fclose(infile);
    printf("%d tabs found\n", tab_count);

    return EXIT_SUCCESS;
}

void print_header(int spaces_per_tab) {
    for (int i = 0; i < LINE_WIDTH; ++i) {
        if ((i % spaces_per_tab) == 0) {
            fputc('+', stdout);
        } else {
            fputc('-', stdout);
        }
    }
    fputc('\n', stdout);
}