// Swarm.java
// Written by THC for CS 5 Lab Assignment #2.
// Maintains information about a swarm of bugs.

import java.awt.*;

public class Swarm {
  private Bug[] insects;    // array of Bug objects
  private int bugCount;     // only entries 0 to bugCount-1 reference existing Bug objects
  
  // Constructor.  Given how many Bug objects we'll ever have at once, create
  // the array and initialize bugCount to 0.
  public Swarm(int howMany) {
    insects = new Bug[howMany];
    bugCount = 0;
  }
  
  // Return how many Bugs currently exist.
  public int getBugCount() {
    return bugCount;
  }
  
  // Draw every Bug that currently exists.
  public void draw(Graphics page) {
    for (int i = 0; i < bugCount; i++)
      insects[i].draw(page);
  }
  
  // Move every Bug that currently exists.
  // Any Bug that moves fully off the top of the window no longer exists.
  public void move() {
    int thisBug = 0;          // index into insects array
    
    while (thisBug < bugCount) {
      // Move a Bug.  If it's still in the window, go on to the next one.
      // Otherwise, terminate this Bug.
      if (insects[thisBug].move())
        thisBug++;            // still in the window
      else
        terminate(thisBug);   // moved fully off the top
    }
  }
  
  // Terminate a Bug.  Do so by moving the last Bug that exists in the insects
  // array to the index of this Bug, making that last entry be null, and decrementing
  // bugCount.  Note that this method works even if whichBug == bugCount-1.
  private void terminate(int whichBug) {
    insects[whichBug] = insects[bugCount-1];
    insects[bugCount-1] = null;
    bugCount--;
  }
  
  // Add a new Bug to the Swarm, but only if there's room.
  public void add(Point where) {
    if (bugCount < insects.length) {        // is there room?
      insects[bugCount] = new Bug(where);   // yes, so add the Bug
      bugCount++;                           // and record that we've got one more
    }
  }
  
  // Hit all bugs that fall under a given Point.
  // All bugs whose bounding box contains the Point are terminated.
  public void hitBugs(Point where) {
    int thisBug = 0;  // index into insects array
    
    while (thisBug < bugCount) {
      // See if this Bug is hit.
      // If not, then go on to the next one.
      // If it is hit, terminate this Bug.
      if (insects[thisBug].isHit(where))
        terminate(thisBug);
      else
        thisBug++;
    }
  }
}