/*
 * crypt_args.cpp
 *
 * Notes: since argv[] array contains c-style char strings, I chose to use C
 *        functions to work on them instead of dealing with C++ class string
 *        conversions.
 *
 */

#include "crypt_args.h"

char *fname;
char *keyfname;
char *outfname;

int crypt_args(int argc, char **argv)
{
    /* flags */
    int fname_f         = 0;
    int keyfname_f      = 0;
    int resultfile_f    = 0;
    int usage_f         = 0;
    int fname_args      = 0;
    int keyfname_args   = 0;
    int resultfile_args = 0;
    int opt_args        = 0;

    int i;
    for (i = 1; i < argc; i++)
    {
        if (argc > 7)
        {
            fprintf(stderr, "too many options\n");
            usage_f = 1;
            break;
        }

        /* skip non option arguments */
        if (!strchr(argv[i], '-'))
        {
            opt_args++;

            if (fname_f)
            {
                if (i-1 == fname_f)
                    fname_args++;

                /* not allowed to have 2 args */
                if ((i-2 == fname_f) && argv[i-1][0] != '-')
                {
                    fprintf(stderr, "too many arguments to \"-f\" option\n");
                    usage_f = 1;
                    break;
                }
            }

            if (keyfname_f)
            {
                if (i-1 == keyfname_f)
                    keyfname_args++;

                /* not allowed to have 2 args */
                if ((i-2 == keyfname_f) && argv[i-1][0] != '-')
                {
                    fprintf(stderr, "too many arguments to \"-k\" option\n");
                    usage_f = 1;
                    break;
                }
            }

            if (resultfile_f)
            {
                if (i-1 == resultfile_f)
                    resultfile_args++;

                /* not allowed to have 2 args */
                if ((i-2 == resultfile_f) && argv[i-1][0] != '-')
                {
                    fprintf(stderr, "too many arguments to \"-o\" option\n");
                    usage_f = 1;
                    break;
                }
            }

            continue;
        }
        else if (strcmp(argv[i], "-f") == 0)
            fname_f = i;
        else if (strcmp(argv[i], "-k") == 0)
            keyfname_f = i;
        else if (strcmp(argv[i], "-o") == 0)
            resultfile_f = i;
        else
        {
            fprintf(stderr, "unknown option \"%s\"\n", argv[i]);
            usage_f = 1;
            break;
        }
    }

    /* error checking */
    if (usage_f || opt_args > 3 || (fname_f && !fname_args) || (resultfile_f &&
        !resultfile_args) || (keyfname_f && !keyfname_args) || (!fname_f && 
        !keyfname_f && !resultfile_f && opt_args))
    {
        printf("usage: %s [-f] file [-k] key [-o ] output\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    /* used for line reading */
    ssize_t amount_read = 0;
    int args_parsed = 0;
    size_t line_sz = 0;
    char *line_ptr = NULL;

    if (fname_f)
        fname = strdup(argv[fname_f+1]);
    else
    {
        /* ask user for the filename */
        printf("please provide the file to be encrypted/decrypted: ");
        fname = (char *) malloc(sizeof(char) * 100);
        if (!fname)
        {
            perror("malloc");
            exit(EXIT_FAILURE);
        }

        do
        {
            fflush(stdin);
            amount_read = getline(&line_ptr, &line_sz, stdin);
            args_parsed = sscanf(line_ptr, "%s", fname);
            if (args_parsed != 1)
                fprintf(stderr, "invalid input, please try again: ");
        } while (args_parsed != 1);
    }

    if (keyfname_f)
        keyfname = strdup(argv[keyfname_f+1]);
    else
    {
        /* ask user for the filename */
        printf("please provide the file that contains the key: ");
        keyfname = (char *) malloc(sizeof(char) * 100);
        if (!keyfname)
        {
            perror("malloc");
            exit(EXIT_FAILURE);
        }

        do
        {
            fflush(stdin);
            amount_read = getline(&line_ptr, &line_sz, stdin);
            args_parsed = sscanf(line_ptr, "%s", keyfname);
            if (args_parsed != 1)
                fprintf(stderr, "invalid input, please try again: ");
        } while (args_parsed != 1);
    }

    if (resultfile_f)
        outfname = strdup(argv[resultfile_f+1]);
    else
    {
        /* ask user for the filename */
        printf("please specify the output file: ");
        outfname = (char *) malloc(sizeof(char) * 100);
        if (!outfname)
        {
            perror("malloc");
            exit(EXIT_FAILURE);
        }

        do
        {
            fflush(stdin);
            amount_read = getline(&line_ptr, &line_sz, stdin);
            args_parsed = sscanf(line_ptr, "%s", outfname);
            if (args_parsed != 1)
                fprintf(stderr, "invalid input, please try again: ");
        } while (args_parsed != 1);
    }

    if (line_ptr)
        free(line_ptr);

    return 0;
}