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 java.util.stream.Stream;

import org.simantics.acorn.GraphClientImpl2;
import org.simantics.db.Database;
import org.simantics.db.DatabaseUserAgent;
import org.simantics.db.ServiceLocator;
import org.simantics.db.server.DatabaseStartException;
import org.simantics.db.server.ProCoreException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import fi.vtt.simantics.procore.internal.StaticSessionProperties;

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

    private static final Logger LOGGER = LoggerFactory.getLogger(AcornDatabase.class);

    private static final String LOCK_FILE_NAME = "lock";

    private final Path folder;
    private final Path lockFile;

    private GraphClientImpl2 currentClient;

    private DatabaseUserAgent userAgent;

    private RandomAccessFile raLockFile;

    private FileLock lock;

    private boolean isRunning;

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

    @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.error("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);
        File vgPath = StaticSessionProperties.virtualGraphStoragePath;
        if (vgPath != null) {
            try (Stream<Path> vgs = Files.list(vgPath.toPath())) {
                for (Path p : vgs.toArray(Path[]::new))
                    deleteTree(p);
            } catch (IOException e) {
                throw new ProCoreException(e);
            }
        }
    }

    @Override
    public synchronized void start() throws ProCoreException {
        try {
            raLockFile = new RandomAccessFile(lockFile.toFile(), "rw");
            lock = raLockFile.getChannel().tryLock();
            if (lock == null) {
                safeLoggingClose(raLockFile, lockFile);
                throw new ProCoreException("The database in folder " + folder.toAbsolutePath() + " is already in use!");
            }
            isRunning = true;
        } catch (IOException e) {
            LOGGER.error("Failed to start database at " + folder.toAbsolutePath(), e);
            safeLoggingClose(raLockFile, lockFile);
            throw new ProCoreException("Failed to start database at " + folder.toAbsolutePath(), e);
        }
    }

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

    @Override
    public synchronized boolean tryToStop() throws ProCoreException {
        if (!isRunning)
            return false;
        try {
            safeLoggingClose(lock, lockFile);
            lock = null;
            safeLoggingClose(raLockFile, lockFile);
            raLockFile = null;
            Files.deleteIfExists(lockFile);
            isRunning = false;
            safeLoggingClose(currentClient, currentClient.getDbFolder());
            currentClient = null;
        } catch (IOException e) {
            LOGGER.error("Failed to start database at " + folder.toAbsolutePath(), e);
        }
        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();
    }

    static class Visitor extends SimpleFileVisitor<Path> {
        @Override
        public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
            try {
                Files.delete(file);
            } catch (IOException ioe) {
                LOGGER.error("Failed to delete file {}", file, ioe);
                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) {
                    LOGGER.error("Failed to delete directory {}", dir, ioe);
                    throw ioe;
                }
                return FileVisitResult.CONTINUE;
            }
            throw e;
        }
    }

    private static void deleteTree(Path path) throws ProCoreException {
        if (!Files.exists(path))
            return;
        try {
            Files.walkFileTree(path, EnumSet.noneOf(FileVisitOption.class), Integer.MAX_VALUE, new Visitor());
        } catch (IOException e) {
            throw new ProCoreException("Could not delete " + path, e);
        }
    }

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

    private static void safeLoggingClose(AutoCloseable closeable, Path file) {
        if (closeable == null)
            return;
        try (AutoCloseable c = closeable) {
        } catch (Exception e) {
            LOGGER.error("Failed to close " + closeable.getClass() + " of " + file.toAbsolutePath(), e);
        }
    }

    private static void safeLoggingClose(Database.Session session, Path file) {
        if (session == null)
            return;
        try {
            session.close();
        } catch (Exception e) {
            LOGGER.error("Failed to close " + session.getClass() + " of " + file.toAbsolutePath(), e);
        }
    }

}