/**
 *
 *
 * @author     Francisco, Graham
 * @assignment ICS 212 Assignment 10
 * @date       2/19/2019
 */

#include <stdio.h>
#include "getdouble.h"  //allows the program to use getdouble() function

/*
  Recursively displays all the numbers in sorted order from the first parameter
  to the second parameter. The recursive method, prints the first parameter,
  increments it and then prints it again until the base case is reached.
*/
void recursiveCount(int first, int second) {
    if (first <= second) {
        printf("%d ", first);
        recursiveCount(first + 1, second);
    }
}

/*
  Recursively adds all the numbers from the first parameter to the second
  parameter. The recursive method adds the first parameter with an incremented
  first parameter until it reaches the base case (first > second).
 */
int recursiveAdd(int first, int second) {
    if (first > second) {
        return 0;   // returns 0, so that it doesn't affect result at the end
    } else {
        return first + recursiveAdd(first + 1, second);
    }
}

/*
  Recursively multiplies all the numbers from the first parameter to the second
  parameter. The recursive method multiplies the first parameter with an
  incremented first parameter until it reaches the base case (first > second).
 */
int recursiveMultiply(int first, int second) {
    if (first > second) {
        return 1;   // returns 1, so that it doesn't affect result at the end
    } else {
        return first * recursiveMultiply(first + 1, second);
    }
}

/*
  Recursively multiplies the first parameter by itself. The number of times it's
  gonna multiply itself is determined by the second parameter.
 */
int recursivePower(int first, int second) {
    if (second < 1) {
        return 1;   // returns 1, signifying that first has been multiplied enough times
    } else {
        return first * recursivePower(first, second - 1);
    }
}

/*
  Recursively calculates the Greatest Commond Divisor of the first and second
  parameter. The recursive method utilizes the "Euclidean algorithm" where it
  does modular arithmetic until first mod second = 0, then returns second.
 */
int recursiveGcd(int first, int second) {
    if (first % second == 0) {
        return second;
    } else {
        return recursiveGcd(second, first % second);
    }
}

/*Main function*/
int main() {

    printf("Enter two positive integers, separated by a space, the first smaller than the second: ");

    int firstInput = (int) getdouble();
    int secondInput = (int) getdouble();

    /*
      Error Checking. If first input or second input is less than 1, or if first
      input is bigger than the second input, throw an error. Otherwise, run the
      recursive functions
     */
    if (firstInput < 1) {
        printf("ERROR: %d is not positive", firstInput);
    } else if (secondInput < 1) {
        printf("ERROR: %d is not positive", secondInput);
    } else if (firstInput > secondInput){
        printf("ERROR: %d is not smaller than %d", firstInput, secondInput);
    } else {

        /*
          for organization purposes, we assign variables for functions with
          return values
         */
        int add = recursiveAdd(firstInput, secondInput);
        int multiply = recursiveMultiply(firstInput, secondInput);
        int power = recursivePower(firstInput, secondInput);
        int gcd = recursiveGcd(firstInput, secondInput);

        //prints the recursiveCount from firstInput to secondInput
        printf("Counting from %d to %d: ", firstInput, secondInput);
        recursiveCount(firstInput, secondInput);

        //prints the recursiveAdd from firstInput to secondInput
        printf("\nThe sum of %d to %d = %d", firstInput, secondInput, add);

        //prints the recursiveMultiply from firstInput to secondInput
        printf("\nThe product of %d to %d = %d", firstInput, secondInput, multiply);

        //prints the recursivePower of firstInput and secondInput
        printf("\n%d to power of %d = %d", firstInput, secondInput, power);

        //prints the recursiveGcd of firstInput and secondInput
        printf("\nThe gcd of %d and %d = %d", firstInput, secondInput, gcd);

    }

    return 0;
}