/* SPDX-License-Identifier: Apache-2.0 */

/* Copyright 2025 Thorsten Töpper
 *
 * I noticed GNU uniq -u not always removed all overlaps, instead
 * of spending hours in creating a reproducable test case and code
 * review, a simple custom implementation of that mode.
 *
 * vim:ts=4:sw=4:expandtab
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <stdbool.h>
#include <stdint.h>
#include <errno.h>

#include "trace_macros.h"

#define LINE_LENGTH 4096

/* prev=(cur)?0:1; less cycles? */
#define INDEXSWITCH cur=(cur+1)%2; prev=(prev+1)%2;

int main(int argc, char **argv) {
    FILE *fdin = stdin;
    char *lines[2];
    int cur = 1, prev = 0;
    bool duplicate = false;

    if (argc > 1) {
        if (strncmp(argv[1], "-", 2) != 0) {
            if ((fdin=fopen(argv[1], "r")) == NULL) {
                LOGERR("ERROR: Failed to open file %s: %s\n",
                        argv[1], strerror(errno));
                return EXIT_FAILURE;
            }
        }
    }

    lines[0] = calloc(LINE_LENGTH, sizeof(char));
    lines[1] = calloc(LINE_LENGTH, sizeof(char));
    if (lines[0] == NULL || lines[1] == NULL) {
        LOGERR("ERROR: Failed to allocate 8kiB...\n");
        return EXIT_FAILURE;
    }

    /* preparation */
    if (fgets(lines[prev], LINE_LENGTH, fdin) == NULL) {
        LOGERR("ERROR: Failed to read input line.\n");
        return EXIT_FAILURE;
    }

    /* parsing input */
    while (fgets(lines[cur], LINE_LENGTH, fdin) != NULL) {
        if (strcmp(lines[cur], lines[prev]) == 0) {
            duplicate = true;
            continue;
        }

        if ( ! duplicate ) {
            fputs(lines[prev], stdout);
        } else {
            duplicate = false;
        }

        INDEXSWITCH;
    }

    /* last line */
    if ( ! duplicate ) {
        fputs(lines[prev], stdout);
    }


    if (fdin != stdin)
        fclose(fdin);

    return EXIT_SUCCESS;
}