// City program for ISM001 homework 2
import java.util.Scanner;

public class City {

  //----------------------------
  // Attributes of the city:
  //----------------------------
  private String name="My City";
  private int population=500;
  private int wealth=population;

  //----------------------------
  // Constructors
  //----------------------------
  public City( String name ){ this.name = name; }
  public City( String name, int population ){ 
    this(name);
    this.population = population;
  }
  public City( String name, int population, int wealth ){
    this(name, population);
    this.wealth = wealth;
  }

  //----------------------------
  // Get methods
  //----------------------------
  public String toString(){ return name; }
  public int getPopulation(){ return population; }
  public int getWealth(){ return wealth; }

  //----------------------------
  // Change the attributes
  // (another form of set methods)
  //----------------------------

  // Add citizens to the city
  // When n < 0, it will remove citizens.
  // It will also guarantee that population will not be negative.
  public void addPopulation(int n){
    population += (population + n > 0)? n: (-population);
  }

  // Add n units of wealth to the city
  public void addWealth(int n){ wealth += n; }
  
  //----------------------------
  // Check the attributes
  //----------------------------

  // Check if the city is empty
  public boolean isEmpty(){ return (population<10); }

  // Check if there is any debt
  public boolean isDebit(){ return (wealth<0); }

  //----------------------------
  // Events
  //----------------------------

  // Earthquake
  public void earthquake(){
    addPopulation( (int)(getPopulation() * -.8) );
    addWealth(-1000);
  }

  // Trade with city c
  public boolean tradeWith( City c ){
    if(!isEmpty() && !c.isEmpty() && !c.isDebit()){
      addWealth(500); addPopulation(100);
      c.addWealth(500); c.addPopulation(100);
      return true;
    }
    return false;
  }

  //----------------------------
  // Other methods
  //----------------------------

  public void displayMessage(){
    System.out.printf("%s (%d, %d)\n", toString(), getPopulation(), getWealth());
  }

  //--------------------------------------
  // Main program to test the code
  //--------------------------------------
  public static void main( String args [] ){
  
    City city[] = { new City("Hong Kong"), new City("Macau", 50), new City("Shanghai", 2000, 1000) };

    // Initial
    System.out.println("\nInitial:");
    for( City c: city ) c.displayMessage();

    // Events:
    System.out.println("\nAfter some events:");
    city[0].tradeWith(city[2]);
    city[1].earthquake();
    city[2].earthquake();
    for( City c: city ) c.displayMessage();

    // More changes:
    System.out.println("\nAfter some more changes");
    city[0].addPopulation(200);
    city[1].addPopulation(-100);
    city[2].addPopulation(300);
    city[2].addWealth(-1400);

    for( City c: city ) c.displayMessage();

    for( City c: city ){
      if( c.isEmpty() ) System.out.printf("There are no more citizens in %s!\n", c);
      if( c.isDebit() ) System.out.printf("%s is in debt!\n", c);
    }
    
  }

 }