/*
 * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 * author: Jerome Glisse
 */
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main(int argc, char *argv[])
{
    char line[256], tmp[256];
    FILE **files;
    unsigned i;

    if (argc <= 2) {
        fprintf(stderr, "%s FILES - FILES\n", argv[0]);
        return -EINVAL;
    }

    files = malloc(sizeof(void*) * argc);
    if (files == NULL) {
        return -ENOMEM;
    }

    for (i = 1; i < argc; i++) {
        if (!strcmp(argv[i], "-")) {
            files[i] = NULL;
            continue;
        }
        files[i] = fopen(argv[i], "r");
        if (files[i] == NULL) {
            fprintf(stderr, "failed opening %s\n", argv[i]);
            return -EINVAL;
        }
    }

    do {
        unsigned diff, skip;

        fgets(line, 256, files[1]);
        for (i = 2, diff = 0, skip = 0; i < argc; i++) {
            if (files[i] == NULL) {
                diff = 1;
                continue;
            }
            if (feof(files[i])) {
                return 0;
            }
            fgets(tmp, 256, files[i]);
            if (skip) {
                continue;
            }
            if (diff) {
                if (strcmp(line, tmp)) {
                    printf("- %s", line);
                    printf("+ %s", tmp);
                }
            } else {
                if (strcmp(line, tmp)) {
                    skip = 1;
                }
            }
        }
    } while (!feof(files[1]));

    return 0;
}