package com.waldura.servlet;

import java.io.File;


/**
 * This class does the asynchronous generation of a report.
 * It is used by {@link HandleGenReportRequest}
 * to generate the report asynchronously.
 *
 * @see HandleGenReportRequest
 * @author Renaud Waldura, 7/21/2001
 */

public class ReportGeneration
	implements Runnable
{
	/**
	 * The name of the thread generating the report.
	 */
	public static final String REPORT_GENERATION_THREAD_NAME = "ReportGenerator-";

	// used only for the thread name
	private static int n = 0;
	private static synchronized int threadNumber() { return ++n; }

	private Thread t;
	private Exception e;
	private GenReport reportEngine;

	/**
	 * Constructor.
	 */
	public ReportGeneration(GenReport reportEngine)
	{
		this.reportEngine = reportEngine;
		t = new Thread(this, REPORT_GENERATION_THREAD_NAME + threadNumber());
	}

	/*
	 * The file this report is written to.
	 */
	private String reportFile;
	public void setReportFile(String s) { reportFile = s; }
	public String getReportFile() { return reportFile; }

	/*
	 * The URL mapping to that file above.
	 */
	private String reportURL;
	public void setReportURL(String s) { reportURL = s; }
	public String getReportURL() { return reportURL; }

	/**
	 * Returns the error that may have occurred while generating
	 * the report.
	 */
	public Exception getException()
	{
		return e;
	}

	/**
	 * Start report generation.
	 */
	public void start()
	{
		t.start();
	}

	/**
	 * Wait for report generation to complete.
	 * This method times out and returns if report generation hasn't completed
	 * in the imparted <code>delay</code>.
	 * {@link #isFinished()} then returns <code>false</code>,
	 * indicating that this method timed-out -- the report isn't ready yet.
	 *
	 * @param delay how long to wait for the thread to complete,
	 * in seconds.
	 */
	public void waitForCompletion(int delay)
		throws InterruptedException
	{
		t.join(delay * 1001);
	}

	/**
	 * Returns whether {@link #waitForCompletion(int)}
	 * timed-out or completed normally -- <code>false</code> when it timed-out,
	 * indicating that the report generation thread is still running.
	 */
	public boolean isFinished()
	{
		return !t.isAlive();
	}

	/**
	 * Generates the report by calling
	 * {@link GenReport#execute(File)}. Any errors
	 * are caught and saved; use
	 * {@link #getException()} to retrieve the error.
	 */
	public void run()
	{
		try
		{
			reportEngine.execute( new File(reportFile) );

			/*
			 * THIS FOR TESTING ONLY: make the report generation take a long time.
			 *
			try
			{
				Thread.sleep(3 * 60 * 1000);
			}
			catch (InterruptedException ie) {}
			 */

		}
		catch (Exception e)
		{
			this.e = e;
		}
	}
}