package directory;

import java.util.Scanner;

/** An application that prompts the user for operations stack of persons
  * and performs these operations.
  * This contract must be provided by a stack implementation.
  * @author Jan Stelovsky, UH ICS AMI Lab */
public class StackUI {

  /** Constants that represent operations on stack.
    * As the push operation needs a string attribute, the constants 
    * provide for setting and getting such attribute. */
  enum Operation {push, pop, empty, list, quit;
  
    /** The string to store. */
    private String string;
    
    /** Stores a string. 
      * @param string to store */
    public void setString (String string) {this.string = string;}
    
    /** Returns the stored string. 
      * @return the stored string */
    public String getString () {return string;}
  }

  /** The user's input from the console. */
  private Scanner scanner = new Scanner (System.in);
  /** Prompt to the user displayed in the console. */
  private static final String prompt = "push (+ name), pop (-), empty (?) or quit (!)>";
  
  /** Creates and starts a new StackUI application. */
  public StackUI () {
    BinarySearch search = new BinarySearch ();
    Stack stack = new StackAsArray ();
    // prompt the user for operation 
    Operation operation = promptForOperation (prompt);
    while (operation != Operation.quit) {
      switch (operation) {
        case push:
          // search the database for the last name of the person entered 
          Person person = search.binarySearch (Operation.push.name ().toLowerCase ());
          if (person != null) {stack.push (person);
          } else {System.out.println ("there is no person whose last name starts with '" + string + "'");}
          break;
        case pop:
          System.out.println (stack.pop ());
          break;
        case empty: 
          System.out.println ("stack is" + (stack.empty () ? "" : "n't") + " empty");
          break;
        case list: 
          System.out.println (stack);
          break;
      }
      // prompt the user for operation 
      operation = promptForOperation (prompt);
    }
  }

  /** Prompts the user and returns the operation requested possibly with a stored string.
    * @param prompt to display in the console
    * @return the operation incl. it's string argument */
  private Operation promptForOperation (String prompt) {
    // prompt the user
    System.out.println (prompt);
    // read the user's entry from the console; strip surrounding whitespace
    String line = scanner.nextLine ().trim ();
    // determine operation based on the 1st character
    switch (line.charAt (0)) {
      case '+': // interpret the remainder of the line as string to search for
        Operation.push.setString (line.substring (1).trim ());
        return Operation.push;
      case '-': return Operation.pop;
      case '?': return Operation.empty;
      case ':': return Operation.list;
      default: return Operation.quit;
    }
  }

  /** Creates and executes the StackUI application.
    * @param arguments no used */
  public static void main (String [] arguments) {
    new StackUI ();
  }

}