package org.webswing.classloader;

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.RandomAccessFile;
import java.net.URI;
import java.net.URLEncoder;
import java.nio.channels.FileChannel;
import java.nio.channels.FileLock;
import java.util.HashSet;
import java.util.Scanner;
import java.util.Set;

import org.webswing.Constants;
import org.webswing.util.AppLogger;

public class ClassModificationRegister {
	private static FileLock lock;
	private Set<String> unmodifiedClassSet = new HashSet<>();
	private PrintWriter writer = null;

	public ClassModificationRegister() {
		//read set of unmodified classes from file
		readUnmodified();

		try {
			if (acquireLock()) {
				writer = new PrintWriter(new BufferedWriter(new FileWriter(getClassListFile(), true)));
				AppLogger.info("ClassModificationRegister: lock acquired.");
			} else {
			}
		} catch (IOException ex) {
			AppLogger.error("ClassModificationRegister: Failed to create unmodified class register map. " + ex.getMessage());
		}
	}

	private boolean acquireLock() throws IOException {
		if (lock == null) {
			RandomAccessFile lockFile = new RandomAccessFile(getClassListLockFile(), "rw");
			FileChannel channel = lockFile.getChannel();
			lock = channel.tryLock();
		}
		return lock != null;
	}

	private void readUnmodified() {
		Scanner sc = null;
		try {
			sc = new Scanner(getClassListFile());
			for (; sc.hasNextLine(); ) {
				unmodifiedClassSet.add(sc.nextLine());
			}
		} catch (FileNotFoundException e) {
			//do nothing. file not created yet
		} finally {
			if (sc != null) {
				sc.close();
			}
		}
	}

	File getClassListFile() {
		String blacklistFileName=System.getProperty(Constants.SWING_START_SYS_PROP_CLASS_MODIFICATION_BLACKLIST);
		if(blacklistFileName!=null){
			return new File(blacklistFileName);
		}else {
			String tempDir = System.getProperty(Constants.TEMP_DIR_PATH);
			String applicationName = URLEncoder.encode(System.getProperty(Constants.SWING_START_SYS_PROP_APP_ID));
			return new File(URI.create(tempDir + applicationName + ".unmodified_classes"));
		}
	}

	File getClassListLockFile() {
		return new File(getClassListFile().getAbsolutePath() + ".lock");
	}

	public boolean canSkipModification(String className) {
		return unmodifiedClassSet.contains(className);
	}

	public void notifyClassLoaded(String className) {
		unmodifiedClassSet.remove(className);
	}

	public void setModificationState(String className, boolean modified) {
		if (!modified && writer != null) {
			writer.println(className);
			writer.flush();
		}
	}

}