package org.simantics.acorn.internal;

import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.channels.FileLock;
import java.nio.file.DirectoryStream;
import java.nio.file.FileVisitOption;
import java.nio.file.FileVisitResult;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.SimpleFileVisitor;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.EnumSet;
import java.util.Properties;

import org.simantics.acorn.GraphClientImpl2;
import org.simantics.db.Database;
import org.simantics.db.DatabaseUserAgent;
import org.simantics.db.ServiceLocator;
import org.simantics.db.common.utils.Logger;
import org.simantics.db.exception.SDBException;
import org.simantics.db.server.DatabaseStartException;
import org.simantics.db.server.ProCoreException;
import org.simantics.db.server.internal.InternalException;

/**
 * @author Tuukka Lehtonen
 */
public class AcornDatabase implements Database {

    private final Path folder;
    
    private GraphClientImpl2 currentClient;

    private DatabaseUserAgent userAgent;

    private RandomAccessFile raLockFile;

    private FileLock lock;

    private boolean isRunning;

    public AcornDatabase(Path folder) {
        this.folder = folder;
    }

    @Override
    public DatabaseUserAgent getUserAgent() {
        return userAgent;
    }

    @Override
    public void setUserAgent(DatabaseUserAgent dbUserAgent) {
        userAgent = dbUserAgent;
    }

    @Override
    public Status getStatus() {
        return Status.Local;
    }

    @Override
    public File getFolder() {
        return folder.toFile();
    }

    @Override
    public boolean isFolderOk() {
        return isFolderOk(folder.toFile());
    }

    @Override
    public boolean isFolderOk(File aFolder) {
        if (!aFolder.isDirectory())
            return false;
        return true;
    }

    @Override
    public boolean isFolderEmpty() {
        return isFolderEmpty(folder.toFile());
    }

    @Override
    public boolean isFolderEmpty(File aFolder) {
        Path path = aFolder.toPath();
        if (!Files.isDirectory(path))
            return false;
        try (DirectoryStream<Path> folderStream = Files.newDirectoryStream(path)) {
            return !folderStream.iterator().hasNext();
        } catch (IOException e) {
            Logger.defaultLogError("Failed to open folder stream. folder=" + path, e);
            return false;
        }
    }

    @Override
    public void initFolder(Properties properties) throws ProCoreException {
        try {
            Files.createDirectories(folder);
        } catch (IOException e) {
            throw new ProCoreException(e);
        }
    }

    @Override
    public void deleteFiles() throws ProCoreException {
        deleteTree(folder);
    }

    @Override
    public void start() throws ProCoreException {
        Path lockFile = folder.resolve("lock");
        try {
            if (!Files.exists(lockFile))
                Files.createFile(lockFile);
            
            raLockFile = new RandomAccessFile(lockFile.toFile(), "rw");
            lock = raLockFile.getChannel().tryLock();
            if (lock == null) {
                throw new ProCoreException("The database in folder " + folder.toAbsolutePath() + " is already in use!");
            }
            
            isRunning = true;
            
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    @Override
    public boolean isRunning() throws ProCoreException {
        return isRunning;
    }

    @Override
    public boolean tryToStop() throws ProCoreException {
        try {
            lock.release();
            raLockFile.close();
            
            Files.deleteIfExists(folder.resolve("lock"));
            
            isRunning = false;
            
        } catch (IOException e) {
            e.printStackTrace();
        }
        
        return true;
    }

    @Override
    public void connect() throws ProCoreException {
    }

    @Override
    public boolean isConnected() throws ProCoreException {
        return isRunning;
    }

    @Override
    public String execute(String command) throws ProCoreException {
        throw new UnsupportedOperationException("execute(" + command + ")");
    }

    @Override
    public void disconnect() throws ProCoreException {
    }

    @Override
    public void clone(File to, int revision, boolean saveHistory) throws ProCoreException {
        // TODO: implement
        throw new UnsupportedOperationException();
    }

    @Override
    public Path createFromChangeSets(int revision) throws ProCoreException {
        // TODO: implement
        throw new UnsupportedOperationException();
    }

    @Override
    public void deleteGuard() throws ProCoreException {
        // TODO: implement
        throw new UnsupportedOperationException();
    }

    @Override
    public Path dumpChangeSets() throws ProCoreException {
        // TODO: implement
        throw new UnsupportedOperationException();
    }

    @Override
    public void purgeDatabase() throws ProCoreException {
    	if(currentClient == null) throw new IllegalStateException("No current session.");
    	currentClient.purgeDatabase();
    }

    @Override
    public long serverGetTailChangeSetId() throws ProCoreException {
    	if(currentClient == null) throw new IllegalStateException("No current session.");
    	return currentClient.getTailChangeSetId();
    }

    @Override
    public Session newSession(ServiceLocator locator) throws ProCoreException {
        try {
        	if(currentClient != null) throw new DatabaseStartException(folder.toFile(), "A session is already running. Only one session is supported.");
        	currentClient = new GraphClientImpl2(this, folder, locator); 
            return currentClient;
        } catch (IOException e) {
            throw new ProCoreException(e);
        }
    }

    @Override
    public Journal getJournal() throws ProCoreException {
        // TODO: implement
        throw new UnsupportedOperationException();
    }

    private static void deleteTree(Path path) throws ProCoreException {
        if (!Files.exists(path))
            return;

        class Visitor extends SimpleFileVisitor<Path> {
            @Override
            public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
                try {
                    Files.delete(file);
                } catch (IOException ioe) {
                    ioe.printStackTrace();
                    throw ioe;
                }
                return FileVisitResult.CONTINUE;
            }
            @Override
            public FileVisitResult postVisitDirectory(Path dir, IOException e) throws IOException {
                if (e == null) {
                    try {
                        Files.delete(dir);
                    } catch (IOException ioe) {
                        ioe.printStackTrace();
                        throw ioe;
                    }
                    return FileVisitResult.CONTINUE;
                }
                throw e;
            }
        }
        try {
            Visitor v = new Visitor();
            EnumSet<FileVisitOption> opts = EnumSet.noneOf(FileVisitOption.class);
            Files.walkFileTree(path, opts, Integer.MAX_VALUE, v);
        } catch (IOException e) {
            throw new ProCoreException("Could not delete " + path, e);
        }
    }

	@Override
	public String getCompression() {
		return "LZ4";
	}

}