package org.contactcompany.api.ui.textmenu;
import java.util.List;
import java.util.ArrayList;

/**
 * <p>
 * This class represents a text based menu consisting of
 * "menu items". Menu items consist of a text describing a menu option
 * (prepended by a number for the user to select) and a
 * MenuAction object which will be run if the user selects the corresponding
 * number of the menu item.
 * </p>
 * <p>
 * In order to create a menu object, use the constructor which takes
 * a String reference as the only argument, which should be the title text
 * of the menu, then add menu items using the addMenuItem() method.
 * </p>
 * <p>
 * To start the menu, call the start() method. Starting the menu object
 * will display all the menu items (prepending by their number) and wait
 * for the user to enter one of the numbers, which will trigger the code
 * in the MenuAction's onItemSelecte() method to be run.
 * </p>
 * <p>
 * The menu will automatically add a "quit" menu item as the last
 * option. Selecting the number for "quit" will make the start()
 * method return. The menu will run eternally until the user selects
 * the quit option.
 * </p>
 * <p>
 * Here's a code example for creating and running a simple example menu:
 * <pre>
 * Menu m = new Menu("this is a menu");
 * m.addMenuItem("Print today's date", new MenuAction(){
 *      public void onItemSelected(){
 *        System.out.println(new Date());
 *      }
 *    });
 * m.addMenuItem("Print system info", new MenuAction(){
 *      public void onItemSelected(){
 *        System.out.println(System.getProperties().get("os.name")
 *                           + " - Java: "
 *                           + System.getProperties().get("java.version"));
 *      }
 *    });
 * m.addMenuItem("Say hello", new MenuAction(){
 *      public void onItemSelected(){
 *        System.out.println("Hello");
 *      }
 *    });
 * m.start();
 *</pre>
 *</p>
 */
public class Menu{
  
  /* The menu has a list of menu items */
  private List<MenuItem> items;
  /* The menu has a title */
  private String title;

  /**
   * Creates a new Menu with the title provided.
   * @param title The titel which will be used as a heading for this menu
   */
  public Menu(String title){
    // Initialize the list
    items=new ArrayList<>();
    // Save the title
    this.title = title;
  }

  /**
   * Adds a menu item to this menu.
   * @param prompt The text describing this menu item
   * @param action The {@link MenuAction} to be run if the user selects this menu item
   */
  public void addMenuItem(String prompt, MenuAction action){
    // Add this text and action to the list of menu items
    items.add(new MenuItem(prompt, action));
  }

  /**
   * Starts this menu. The method will enter an eternal loop,
   * displaying the menu items and accepting input until the
   * user selects the item number for the automatically provided
   * quit option, which will make this method return.
   *
   * Each menu item will be prepended with a number for the
   * user to select. The last item is the provided quit item.
   *
   * When the user selects an item number, the corresponding
   * {@link MenuAction} {@link MenuAction#onItemSelected()} method will run.
   */
  public void start(){
    while(true){
      System.out.println("\n===="+title+"====\n");
      try{
        int index=0; // Used as the number connected to the item
        int reply=0; // Used to hold the user's reply (choice)

        /* Print a number as the option and the prompt of every item */
        for(MenuItem m : items){
          System.out.println(index++ + " " + m.prompt);
        }
        // Add an option for quitting (this would be the last number)
        System.out.println(index + " quit");
        // Prompt the user for a selection (a number from the list)
        System.out.print("Please enter a number from the menu: ");
        // Read the number from the user
        // This does not work with java on cygwin:
        //    reply = Integer.parseInt(System.console().readLine());
        // so we're using Scanner instead
        reply = Integer.parseInt(new java.util.Scanner(System.in).nextLine());
        // If the user wants to quit, then return from this method
        if (reply==index) {
          System.out.println("\nBye!\n");
          // Quit the menu
          return;
        }
        // Give feedback on the selection and run the action of the
        // corresponding menu item
        System.out.println("\nYou selected "+items.get(reply).prompt+"\n");
        items.get(reply).action.onItemSelected();

        // Deal with bad input (illegal number or non-numeric response)
      }catch(NumberFormatException | IndexOutOfBoundsException e){
        System.out.println("\n\n\n>>>Invalid choice, please try again.<<<");
        System.out.println(">>>Your selection must be a number from the menu.<<<");
      }
    }
  }

  /* 
   * Inner class wrapping a menu item as an object
   * with a prompt (text of the item) and an action
   * to be performed when the user selects this item.
   * 
   * An inner class is convenient when you need a class
   * but no one else needs to know about it.
   *
   * Making it private is an effective way to hide it from
   * everyone.
   */  
  private class MenuItem{
    private String prompt;
    private MenuAction action;
    public MenuItem(String prompt, MenuAction action){
      this.prompt = prompt;
      this.action = action;
    }
  }
  
}