/* 
 * guessprime9.c - a C version of our bash demo program
 *  (interpret words like 'quit' on input; usage of stderr)
 * usage: guessprime [maxPrime]
 * 
 * David Kotz, April 2016, 2017
 * CS50, Fall 2022
 */

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <time.h>
#include "readline.h"

// function prototype *declarations*
int pickPrime(const int max);
int readGuess(const int max);
bool isPrime(const int p);

// Main loop - ask for a guess, quit when it matches the answer
int main(const int argc, const char *argv[]) {
  int answer; // the secret prime to guess
  int guess;  // the user's guess
  int max;    // we'll pick a prime in [1..max]

  // interpret arguments
  if (argc == 1) {
    // no arguments (other than the command) - use default value
    max = 100;
  } else if (argc == 2) {
    // one argument - should be the maxPrime
    if (sscanf(argv[1], "%d", &max) < 1 || max < 2 || max > 100) {
      fprintf(stderr, "usage: %s [maxPrime]; your maxPrime is out of range\n", argv[0]);
      exit(1);
    }
  } else {
    // too many arguments
    fprintf(stderr, "usage: %s [maxPrime]\n", argv[0]);
    exit(2);
  }

  answer = pickPrime(max);

  guess = readGuess(max);
  while (guess != 0 && guess != answer) {
    printf("Wrong! try again\n");
    guess = readGuess(max);
  }

  if (guess == 0) {
    printf("Hah! you gave up; the answer was %d\n", answer);
  }
  if (guess == answer) {
    printf("You win!\n");
  }

  return 0;  // exit status
}

// pick a random prime between 1..max
int pickPrime(const int max) {
  int p;

  srand(time(NULL)); // seed the random-number sequence

  // keep picking random numbers until we find a prime
  for (p = 0; !isPrime(p); p = (rand() % max + 1))
    ;

  return p;
}

// Prompt for, and read, one guess
// return 0 if they gave up
int readGuess(const int max) {
  const int bufsize = 20;	// the buffer size
  char inputline[bufsize];	// the buffer for user input
  int guess;			// the user's guess
  
  printf("Enter a prime between 1-%d (give up? enter 'quit'): ", max);
  if (!readLine(inputline, bufsize)) {
    if (feof(stdin)) {		// end of file
      printf("EOF\n");
      return 0;
    } else {			// error in input
      printf("Hey! input error\n");
      return -1;
    }
  }

  if (strcmp(inputline, "quit\n") == 0) {
    return 0;
  }

  // this could be improved; see our Section meeting exercise
  if (sscanf(inputline, "%d", &guess) < 1) {
    printf("Hey! invalid number.\n");
    return -1;
  }

  if (guess < 1 || guess > max) {
    printf("Hey! %d is out of range [1..%d].\n", guess, max);
    return -1;
  }
    
  if (!isPrime(guess)) {
    printf("Hey! %d is not even a prime number.\n", guess);
    return -1;
  }

  return guess;
}


// determine whether the number is prime
// (assumes n <= 100)
bool isPrime(const int n) {
  if (n < 2) return false;
  if (n > 2 && n%2 == 0) return false;
  if (n > 3 && n%3 == 0) return false;
  if (n > 5 && n%5 == 0) return false;
  if (n > 7 && n%7 == 0) return false;
  return true;
}