#include "stdio.h"
#include "stdlib.h"
#include "limits.h"
#include "sodium.h"
#include "strtoui.h"

/**
 * Maps a number that is between i_min and i_max to the range o_min and o_max
 */
int map(int i, int i_min, int i_max, int o_min, int o_max) {
    double r = (double)(o_max - o_min) / (double)(i_max - i_min);
    int j = (double) (i - i_min) * r + o_min;
    return j;
}

int main(int argc, char *argv[]) {
    //if doesnt have any argument just show a usage info
    if(argc == 1) {
        puts("Usage:\tchars [length]");
        puts("\t0 > lenght > UINT_MAX");
        puts("Description:");
        puts("\t Generates a random string with the specified length");
        exit(EXIT_SUCCESS);
    }

    //read the length argument and parse it to a an unsigned int
    unsigned int len;
    enum strtoui_error error = strtoui(&len, argv[1], 10);
    if(error == STRTOUI_OVERFLOW){
        fputs("The input is too big\n", stderr);
        exit(EXIT_FAILURE);
    }else if(error == STRTOUI_UNDERFLOW) {
        fputs("The input must be bigger than 0\n", stderr);
        exit(EXIT_FAILURE);
    }else if(error == STRTOUI_INCONVERTIBLE) {
        fputs("The input isn't valid\n", stderr);
        exit(EXIT_FAILURE);
    }

    //prints random numbers in the bounds specified as chars
    char lower_bound = 0x20;
    char upper_bound= 0x7e;
    for(int i = 0; i < len; i++) {
        int random = randombytes_uniform(upper_bound);
        printf("%c", map(random, 0, upper_bound, lower_bound, upper_bound));
    }
    printf("\n");

    exit(EXIT_SUCCESS);
}