//Omar Khan
//CSE 143 Section AA

import java.util.*;
import java.io.*;

//This program builds a tree for a game similar to 20 questions using QuestionNodes
//and displays it using the passed UserInterface object. It also keeps track of the total
//games played and won for an instance of play.

public class QuestionTree{
   private UserInterface ui;
   private QuestionNode root;
   private int played;
   private int won;

   //Passes in the UserInterface and starts the tree with a single QuestionNode that contains the answer "Computer".
   //Throws an IllegalArgumentException if UserInterface is null
   public QuestionTree(UserInterface ui){
      //Checks if passed in ui is null and throws an exception accordingly
      if(ui == null){
         throw new IllegalArgumentException();
      }
      this.ui = ui;
      this.played = 0;
      this.won = 0;
      root = new QuestionNode("computer");
   }
   
   //This method is used to play a game, it builds the question tree as the game progresses.
   public void play(){
      played++;
      root = play(root);
   }
   
   //Helper method to play the game, returns a 
   //QuestionNode and requires a QuestionNode be passed in.
   private QuestionNode play(QuestionNode otherRoot){
      if(otherRoot.isAnswer()){
         ui.print("Would your object happen to be " + otherRoot.data + "?");
         if(ui.nextBoolean()){
            won++;
            ui.println("I win!");
            return otherRoot;
         }else{
            ui.print("I lose. What is your object?");
            String answer = ui.nextLine();
            ui.print("Type a yes/no question to distinguish your item from " + otherRoot.data + ":");
            String question = ui.nextLine();
            ui.print("And what is the answer for your object?");
            
            otherRoot = add(otherRoot, question, answer, ui.nextBoolean());
            return otherRoot;
         }
      }else{
         ui.print(otherRoot.data);
         if(ui.nextBoolean()){
            otherRoot.yes = play(otherRoot.yes);
         }else{
            otherRoot.no = play(otherRoot.no);
         }
      }
      return otherRoot;
   }
   
   //Helper method to add a new question and answer, used to expand the tree.
   private QuestionNode add(QuestionNode otherRoot,String question, String answer, boolean y){
      QuestionNode currQuestion = new QuestionNode(question);
      if(y){
         currQuestion.yes = new QuestionNode(answer);
         currQuestion.no = otherRoot;
      }else{
         currQuestion.yes = otherRoot;
         currQuestion.no = new QuestionNode(answer);
      }

      return currQuestion;
   }
   
   //This method saves the contents of the tree in an appropriate 
   //format to the passed in PrintStream object.
   //Throws an IllegalArgumentException if passed PrintStream is null
   public void save(PrintStream output){
      if(output == null){
         throw new IllegalArgumentException();
      }
      save(output, root);
   }
   
   //Helper method for save which takes in a PrintStream object and a QuestionNode.
   private void save(PrintStream output, QuestionNode otherRoot){
      if(otherRoot.isAnswer()){
         output.println("A:" + otherRoot.data);
      }else{
         output.println("Q:" + otherRoot.data);
         save(output, otherRoot.yes);
         save(output, otherRoot.no);
      }
   }
   
   //This method builds a new tree using the contents of a passed in Scanner object.
   //Throws an IllegalArgumentException if passed Scanner is null.
   public void load(Scanner input){
      if(input == null){
         throw new IllegalArgumentException();
      }
      root = load(input, root);
   }
   
   //Helper method that takes in a Scanner object 
   //and a QustionNode, also returns a QuestionNode.
   private QuestionNode load(Scanner input, QuestionNode otherRoot){
      if(!input.hasNextLine()){
         return otherRoot;
      }else{
         String data = input.nextLine();
         otherRoot = new QuestionNode(data.substring(2));
         if(data.startsWith("Q:")){
            otherRoot.yes = load(input, otherRoot.yes);
            otherRoot.no = load(input, otherRoot.no);
         }
      }
      return otherRoot;
   }
   
   //Returns the total games won.
   public int gamesWon(){
      return won;
   }
   
   //Returns total games played.
   public int totalGames(){
      return played;
   }
}

Began life as a copy of #1002516