/* Tanel Toova
 * 3-4
 * Kommenteeri kood
 */

#include <stdio.h>
#include <string.h>

#define NUM_OF_ELEMENTS 4

char *pszArray[NUM_OF_ELEMENTS]={
        "Särk",
        "Pikk-pikk-pikk-piiikkkkk string",
        "Värk",
        "Veel üks string"
        };
char *pszIdx[NUM_OF_ELEMENTS]; //this is the array where qsort puts sorted strings


void output(void *pfSort) //*pfSort points to the function qsort is going to  use to sort the pszArray 
{
        int i;
        char **ppszArray; //This array is used to display the sorted strings

        if(!pfSort){ //if pfSort is NULL then pszArray is not sorted
                ppszArray=pszArray;
        }
        else{
                qsort(&pszIdx[0], NUM_OF_ELEMENTS, sizeof(char*), pfSort); //qsort sorts the array pszIdx by using function pointed by pfsort
                ppszArray=pszIdx;
        }
        printf("\n");
        for(i=0;i<NUM_OF_ELEMENTS;i++){
                printf("%i: %s\n", i, ppszArray[i]); //displays sorted array
        }
}

int by_len(const char **pszS1, const char **pszS2) //function used by qsort to sort the strings by their lenght in ascending order
{ // function returns 0 if the strings have same length, negative integer when first string is shorter or positive integer when first string is longer
        return (strlen(*pszS1) - strlen(*pszS2));
}

int by_alpha(const char **pszS1, const char **pszS2) //function used by qsort to put the strings to alphabetical order
{// function returns 0 if strings are identical, negative integer when first string is before the second string in alphabetical order or positive string when it's not. 
        return strcmp(*pszS1, *pszS2);
}

int by_ralpha(const char **pszS1, const char **pszS2) // function used by qsort to put the strings to reversed alphabetical order
{ // works like the previous function only returned values are vice versa
        return strcmp(*pszS2, *pszS1);
}

int main(void)
{
        int iChr;
        int i;

        for(i=0;i<NUM_OF_ELEMENTS;i++){ //makes arrays pszIdx and pszArray identical
                pszIdx[i]=pszArray[i];
        }

        for(;;){ 
                printf("\n U - unsorted, L - by length, A - by alpha, R - by reverse alpha, Q - quit : ");
                iChr=tolower(getchar()); //puts inserted char to lowercase
                getchar(); //lets user isert a char
                switch(iChr){
                        case 'u':
                                output(NULL);
                                break;
                        case 'l':
                                output(by_len);
                                break;
                        case 'a':
                                output(by_alpha);
                                break;
                        case 'r':
                                output(by_ralpha);
                                break;
                        case 'q':
                                return 0;
                }
        }
}