'use strict';

const ELEMENT_ROCK = "Rock";
const ELEMENT_PAPER = "Paper";
const ELEMENT_SCISSORS = "Scissors";

const ELEMENTS = [ELEMENT_ROCK, ELEMENT_PAPER, ELEMENT_SCISSORS];

const PLAYER_HUMAN = "Player";
const PLAYER_CPU = "CPU";

// in codewars testable function
const getWinningElement = function(element, otherElement) {
  if (element === otherElement)
    // no winning element -> tie
    return null;
  
  switch (element) {
    case ELEMENT_ROCK:
      if (otherElement === ELEMENT_PAPER)
        return otherElement;
      if (otherElement === ELEMENT_SCISSORS)
        return element;

      break;
    case ELEMENT_PAPER:
      if (otherElement === ELEMENT_ROCK)
        return element;
      if (otherElement === ELEMENT_SCISSORS)
        return otherElement;
      
      break;
    case ELEMENT_SCISSORS:
      if (otherElement === ELEMENT_ROCK)
        return otherElement;
      if (otherElement === ELEMENT_PAPER)
        return element;

      break;
  }  
}

// in codewars testable function
const getWinnerOfRound = function(playerElement, cpuElement) {
  let winningElement = getWinningElement(playerElement, cpuElement);
  
  let winner;  
  switch (winningElement) {
    case playerElement:
        winner = PLAYER_HUMAN;

      break;
    case cpuElement:
        winner = PLAYER_CPU;
      
      break;
    default:
      // no winner -> tie
      winner = null;

      break;
  }
  
  return winner;
}

// in codewars testable function
const describeRound = function(winner, winnersElement, losersElement) {
  let verbForElement = {};
  verbForElement[ELEMENT_ROCK] = 'crushes';
  verbForElement[ELEMENT_PAPER] = 'covers';
  verbForElement[ELEMENT_SCISSORS] = 'cuts';
  
  let verb = verbForElement[winnersElement];
  
  let message;
  
  switch(winner) {
    case PLAYER_HUMAN:
      message = `Your ${winnersElement} ${verb} CPU's ${losersElement}: YOU WIN!!`;
      break;
    
    case PLAYER_CPU:
      message = `CPU's ${winnersElement} ${verb} your ${losersElement}: YOU LOSE!!!`;
      break;
    
    default:
      message = `Both players choose ${winnersElement}: ITS A TIE...!`;
  }

  
  return message;
}

// function contains user interaction (prompt, alert) -> NOT unit-testable
// BUT: most of the initial code got refactored out into testable functions above
const rpsInteractiveGame = function () {
  let playerElement = prompt(`Rock Paper Scissors Game, which shape you go with:`);
  let cpuElement = ELEMENTS[ Math.trunc(Math.random() * 3) ];

  if (!ELEMENTS.includes(playerElement))
    return alert(`Wrong! Please choose from Rock, Paper or Scissors`);
  
  let winner = getWinnerOfRound(playerElement, cpuElement);
  let winnersElement = getWinningElement(playerElement, cpuElement);
  let losersElement = null;
  
  if (winner != null && winner === PLAYER_HUMAN)
    losersElement = cpuElement;
  else
    losersElement = playerElement;   
    
  alert(describeRound(winner, winnersElement, losersElement));
};