// getopt() sample.
//
// Last updated: <2022/07/18 21:06:55 +0900>

#include <stdio.h>
#include <getopt.h>

void usage(char *name)
{
    printf("Usage:\n");
    printf("  %s -i IN.png -o OUT.png [-d N]\n", name);
    printf("\n");
    printf("  -i FILE, --input FILE   input png image file.\n");
    printf("  -o FILE, --output FILE  output png image file.\n");
    printf("  -d N, --dither N        dither map. N = 2/4/8 (2x2, 4x4, 8x8)\n");
    printf("  -h, --help              display help message\n");
    printf("\n");
}

int main(int argc, char **argv)
{
    // parse option
    char *infile = NULL;
    char *outfile = NULL;
    int dither = 4;

    struct option longopts[] = {
        {"help", no_argument, NULL, 'h'},
        {"input", required_argument, NULL, 'i'},
        {"output", required_argument, NULL, 'o'},
        {"dither", required_argument, NULL, 'd'},
        {0, 0, 0, 0}};

    int opt;
    int longindex;
    while ((opt = getopt_long(argc, argv, "hi:o:d:", longopts, &longindex)) != -1)
    {
        switch (opt)
        {
        case 'i': // input image filename
            infile = optarg;
            break;

        case 'o': // output image filename
            outfile = optarg;
            break;

        case 'd': // dither map size, 2 or 4 or 8
            switch (optarg[0])
            {
            case '2':
                dither = 2;
                break;

            case '4':
                dither = 4;
                break;

            case '8':
                dither = 8;
                break;

            default:
                printf("Error : Unknown dither mode = %s\n\n", optarg);
                dither = -1;
                break;
            }
            break;

        case 'h': // help
            usage(argv[0]);
            return 0;

        default:
            break;
        }
    }

    if (optind < argc)
    {
        for (; optind < argc; optind++)
            printf("Unknown option : %s\n", argv[optind]);
        usage(argv[0]);
        return 1;
    }

    printf("infile  : %s\n", infile);
    printf("outfile : %s\n", outfile);
    printf("dither  : %d\n", dither);

    if (infile == NULL || outfile == NULL || dither == -1)
    {
        usage(argv[0]);
        return 1;
    }
}