package tmcsim.paramicscommunicator;

import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Observable;
import java.util.Timer;
import java.util.TimerTask;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import tmcsim.common.CADProtocol.PARAMICS_ACTIONS;
import tmcsim.common.CADProtocol.PARAMICS_COMM_TAGS;
import tmcsim.paramicscommunicator.FileIOUpdate.IO_TYPE;

/**
 * The ParamicsFileReader handles reading fom a target file which is written to
 * by Paramics. Once initialized, a timer task is started which periodically
 * checks the target file for updates. If the file has been modified, it is read
 * and cleared. The read data is transmitted to the CAD Simulator.
 *
 * @author Matthew Cechini
 * @version 0.1 Notes by jdalbey: Paramics modeler is licensed third-party
 * software and apparently we don't have an SDK for it. So it seems the
 * workaround was to communicate with it via data files that the modeler
 * produces. Wacky, but it works for now. Look at the run() method below: if
 * (lastModified < inputFile.lastModified()) Means it's watching the file to
 * see if it has been updated by the modeler.
 */
public class ParamicsFileReader extends Observable
{

    /**
     * Error Logger.
     */
    private Logger paramLogger = Logger.getLogger("tmcsim.paramicscommunicator");
    /**
     * FileReader ID used for creation of the ParamicsCommMessage
     */
    private String readerID = null;
    /**
     * File reference to the file where data is read.
     */
    private File inputFile = null;
    /**
     * FileReader used to read data from the input file.
     */
    private FileReader fileReader = null;
    /**
     * FileWriter used to clear the input file.
     */
    private FileWriter fileWriter = null;
    /**
     * Value (seconds since 1/1/1970) of input file's last modification time.
     */
    private long lastModified = 0;
    /**
     * Timer used to schedule file reading tasks.
     */
    private Timer readerTimer = null;
    /**
     * Duration (in seconds) that the TimerTask will be scheduled to read from
     * the target file.
     */
    private long readerInterval;

    /**
     * A TimerTask to read from the target file. If the file has been modified
     * since last read, read the file and transmit the data to the CAD
     * Simulator.
     *
     * @author Matthew Cechini
     */
    private class ReaderTimerTask extends TimerTask
    {

        public void run()
        {

            if (lastModified < inputFile.lastModified())
            {

                try
                {
                    Document readerDoc = DocumentBuilderFactory.newInstance()
                            .newDocumentBuilder().newDocument();

                    Element readerElem = readerDoc.createElement(PARAMICS_COMM_TAGS.READER.tag);
                    readerElem.setAttribute(PARAMICS_COMM_TAGS.ID.tag, readerID);
                    readerElem.setAttribute(PARAMICS_COMM_TAGS.ACTION.tag,
                            PARAMICS_ACTIONS.READ_FILE.action);

                    Element messageElem = readerDoc.createElement(PARAMICS_COMM_TAGS.MESSAGE.tag);
                    String fileContents = readFromFile();
                    messageElem.appendChild(readerDoc.createTextNode(fileContents));
                    readerElem.appendChild(messageElem);

                    readerDoc.appendChild(readerElem);

                    setChanged();
                    notifyObservers(readerDoc);
                } catch (Exception e)
                {
                    paramLogger.logp(Level.SEVERE,
                            "ParamicsFileReader.ReaderTimerTask", "run()",
                            "Exception in reading from file: "
                            + inputFile.getName(), e);
                }
            }
        }
    }

    /**
     * Constructor. Set the reader id and interval from the parsed
     * ParamicsCommMessage. The interval is found within the first three
     * characters of the object's "message" data member. Create a file object
     * for the target file, and create a new file if it does not already exist.
     * Instantiate the timer and ReaderTimerTask to begin periodic reading of
     * the file.
     *
     * @param workingDir Target working directory. // Oops, the following seem
     * obsolete
     * @param mess ParamicsCommMessage object containing registration data.
     * @param theComm Reference to the ParamicsCommunicator.
     */
    public ParamicsFileReader(String workingDir, String id, Integer interval, String targetFile)
    {

        try
        {
            readerID = id;
            readerInterval = interval;

            inputFile = new File(workingDir + targetFile);

            if (!inputFile.exists())
            {
                inputFile.createNewFile();
            }

            readerTimer = new Timer();
            readerTimer.scheduleAtFixedRate(new ReaderTimerTask(),
                    0L, readerInterval * 1000);

        } catch (IOException ioe)
        {
            paramLogger.logp(Level.SEVERE, "ParamicsFileReader",
                    "Constructor()", "Exception in initializing file reading.", ioe);
        }
    }

    /**
     * Method opens the target file and reads all contents. The file is then
     * cleared.
     *
     * @returns
     * @throws IOException if there is an error in reading or writing to the
     * file.
     */
    private String readFromFile() throws IOException
    {

        char[] input = new char[(int) inputFile.length()];

        fileReader = new FileReader(inputFile);
        fileReader.read(input);
        fileReader.close();

        //make sure the new file has a modified time that is different
        try
        {
            Thread.sleep(1000);
        } catch (Exception e)
        {
        }

        //clear file after reading contents
        fileWriter = new FileWriter(inputFile);
        fileWriter.write("");
        fileWriter.close();

        lastModified = inputFile.lastModified();

        setChanged();
        notifyObservers(new FileIOUpdate(IO_TYPE.READ, readerID, (long) input.length));

        return new String(input);
    }
}