ProcessChain.java

/*
 * Copyright (C) 2016 Google Inc. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.google.android.apps.santatracker.doodles.shared;

import java.util.LinkedList;
import java.util.List;
import java.util.Queue;

/**
 * A chain of processes, which are executed in the order in which they are added. When a process
 * is finished, it is removed from the chain and the next process in line is executed.
 */
public class ProcessChain {
  private Queue<Process> processes;

  public ProcessChain(Process p) {
    processes = new LinkedList<>();
    processes.add(p);
  }

  public ProcessChain then(Process p) {
    processes.add(p);
    return this;
  }

  public ProcessChain then(ProcessChain pc) {
    processes.addAll(pc.processes);
    return this;
  }

  public void update(float deltaMs) {
    if (processes.isEmpty()) {
      return;
    }
    Process activeProcess = processes.peek();
    activeProcess.update(deltaMs);
    if (activeProcess.isFinished()) {
      processes.remove();
    }
  }

  public boolean isFinished() {
    return processes.isEmpty();
  }

  public static void updateChains(List<ProcessChain> processChains, float deltaMs) {
    // Remove finished chains.
    for (int i = processChains.size() - 1; i >= 0; i--) {
      ProcessChain chain = processChains.get(i);
      if (chain.isFinished()) {
        processChains.remove(i);
      }
    }
    // Update still-running chains.
    for (int i = 0; i < processChains.size(); i++) {
      processChains.get(i).update(deltaMs);
    }
  }
}