#include "types.h"
#include <math.h>
#include <stdbool.h>
#include <stdio.h>

void read_print_quadratic() {
  // TODO 1. Read 3 numbers: a, b and c which represent known numbers for
  // quadratic equation in standard format (ax^2 + bx + c = 0) from stdin.
  printf("Enter numbers a, b and c of equation ax^2 +bx + c = 0:\n");
  int a, b, c;
  scanf("%d %d %d", &a, &b, &c);

  // TODO 2. Check if equation is quadratic. If so, calculate its discriminant
  // and, if possible, print all roots to stdout.
  if (a == 0 || (a == 0 && b == 0 && c == 0)) {
    printf("Please enter a cooler formula");
    return;
  }

  double d = b * b + (-4) * a * c;
  printf("Discriminant: %.2f\n", d);

  if (d < 0) {
    printf("Discriminant is lower than 0, cannot solve equation in R");
    return;
  }

  double rootA, rootB;

  rootA = (-b + sqrt(d)) / (2*a);
  rootB = (-b - sqrt(d)) / (2*a);

  if (rootA == rootB) {
    printf("Equation has one solution: %.2f", rootA);
  } else {
    printf("Equation has two solution: %.2f and %.2f", rootA, rootB);
  }
  return;
}

void read_print_is_character() {
  // TODO 1. Read one character from stdin.
  printf("Enter a character:\n");
  char l;
  scanf(" %c", &l);
  // TODO 2. Determine whether the character represents a letter (a-z, A-Z) or
  // not and print the result to stdout.
  if ((l >= 'a' && l <= 'z') || (l >= 'A' && l <= 'Z')) {
    printf("%c IS a letter (a-z or A-Z)", l);
  } else {
    printf("%c is NOT a letter (a-z or A-Z)", l);
  }
  return;
}

void read_print_factorial() {
  printf("Enter a number for calcuation of factorial:\n");
  // TODO 1. Read one number from stdin.
  int a;
  scanf("%d", &a);

  // TODO 2. Print its factorial (!) to stdout.
  for (int i = a - 1; i != 0; --i) {
    a *= i;
  }
  printf("Factorial: %d", a);
  return;
}

void read_print_gcd() {
  // TODO 1. Read two numbers from stdin.
  printf("Enter two numbers to calculate gcd:\n");
  int a, b;
  scanf("%d %d", &a, &b);

  // see https://en.wikipedia.org/wiki/Greatest_common_divisor#Euclidean_algorithm
  while (b != 0) {
        int temp = b;
        b = a % b;
        a = temp;
    }

  printf("gcd is %d\n", a);
  return;
}

#ifndef TEST_BUILD

int main() {
  printf("\n--read_print_quadratic--\n");
  read_print_quadratic();

  printf("\n--read_print_is_character--\n");
  read_print_is_character();

  printf("\n--read_print_factorial--\n");
  read_print_factorial();

  printf("\n--read_print_gcd--\n");
  read_print_gcd();

  return 0;
}

#endif