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/*
@VaadinApache2LicenseForJavaFiles@
 */
package com.vaadin.terminal.gwt.client.ui;

import com.google.gwt.core.client.Scheduler.ScheduledCommand;
import com.google.gwt.user.client.Timer;

/**
 * Executes the given command {@code delayMs} milliseconds after a call to
 * {@link #trigger()}. Calling {@link #trigger()} again before the command has
 * been executed causes the execution to be rescheduled to {@code delayMs} after
 * the second call.
 * 
 */
public class VLazyExecutor {

    private Timer timer;
    private int delayMs;
    private ScheduledCommand cmd;

    /**
     * @param delayMs
     *            Delay in milliseconds to wait before executing the command
     * @param cmd
     *            The command to execute
     */
    public VLazyExecutor(int delayMs, ScheduledCommand cmd) {
        this.delayMs = delayMs;
        this.cmd = cmd;
    }

    /**
     * Triggers execution of the command. Each call reschedules any existing
     * execution to {@link #delayMs} milliseconds from that point in time.
     */
    public void trigger() {
        if (timer == null) {
            timer = new Timer() {
                @Override
                public void run() {
                    timer = null;
                    cmd.execute();
                }
            };
        }
        // Schedule automatically cancels any old schedule
        timer.schedule(delayMs);

    }

}