package org.simantics.scl.osgi.internal;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.nio.charset.Charset;
import java.nio.file.Files;
import java.nio.file.Path;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;

import org.eclipse.core.runtime.FileLocator;
import org.osgi.framework.Bundle;
import org.osgi.framework.wiring.BundleWiring;
import org.simantics.scl.compiler.internal.codegen.types.JavaReferenceValidatorFactory;
import org.simantics.scl.compiler.module.ImportDeclaration;
import org.simantics.scl.compiler.module.repository.UpdateListener;
import org.simantics.scl.compiler.source.EncodedTextualModuleSource;
import org.simantics.scl.compiler.types.Type;

import gnu.trove.set.hash.THashSet;

public class BundleModuleSource extends EncodedTextualModuleSource implements UpdateListener.Observable {

    public static final ImportDeclaration[] DEFAULT_IMPORTS = new ImportDeclaration[] {
        new ImportDeclaration("Builtin", ""),
        new ImportDeclaration("StandardLibrary", "")
    };
    
    public static final ImportDeclaration[] DEFAULT_IMPORTS_FOR_STANDARD_LIBRARY = new ImportDeclaration[] {
        new ImportDeclaration("Builtin", ""),
    };
    
    public final Bundle bundle;
    public final URL url;
    
    private byte[] digest;
    private THashSet<UpdateListener> listeners;
    
    public BundleModuleSource(String moduleName, Bundle bundle, URL url) {
        super(moduleName);
        this.bundle = bundle;
        this.url = url;
    }
    
    @Override
    public void removeListener(UpdateListener listener) {
        if(listeners != null)
            synchronized(listeners) {
                listeners.remove(listener);
            }
    }

    @Override
    public ImportDeclaration[] getBuiltinImports(UpdateListener listener) {
        if(bundle.getSymbolicName().equals("org.simantics.scl.runtime"))
            return DEFAULT_IMPORTS_FOR_STANDARD_LIBRARY;
        else
            return DEFAULT_IMPORTS;
    }
    
    private byte[] computeDigest() {
        try {
            InputStream stream = url.openStream();
            try {
                MessageDigest digest = MessageDigest.getInstance("SHA1");
                byte[] buffer = new byte[1024];
                while(true) {
                    int count = stream.read(buffer);
                    if(count <= 0)
                        break;
                    digest.update(buffer, 0, count);
                }
                return digest.digest();
            } catch (NoSuchAlgorithmException e) {
                e.printStackTrace();
                return new byte[0];
            } finally {
                stream.close();
            }
        } catch(IOException e) {
            e.printStackTrace();
            return new byte[0];
        }
    }
    
    @Override
    protected InputStream getSourceStream(UpdateListener listener)
            throws IOException {
        if(digest == null)
            digest = computeDigest();
        if(listener != null) {
            if(listeners == null)
                listeners = new THashSet<UpdateListener>(4);
            listeners.add(listener);
            listener.addObservable(this);
        }
        return url.openStream();
    }
    
    @Override
    public ClassLoader getClassLoader() {
        if(bundle.getSymbolicName().equals("org.simantics.scl.runtime"))
            return Type.class.getClassLoader();
        else {
            BundleWiring wiring = bundle.adapt(BundleWiring.class);
            if(wiring != null)
                return wiring.getClassLoader();
            else
                return getClass().getClassLoader();
        }
    }

    public void checkUpdates() {
        if(digest != null && listeners != null) {
            byte[] newDigest = computeDigest();
            if(!Arrays.equals(digest, newDigest)) {
                digest = newDigest;
                THashSet<UpdateListener> oldListeners = listeners;
                listeners = null;
                for(UpdateListener listener : oldListeners)
                    listener.notifyAboutUpdate();
            }
        }
    }

    /*
     * This code is a copy from org.simantics.utils.ui.BundleUtils
     */
    public static File resolveWritableBundleFile(URL url) throws IOException {
        // This returns file, jar, http etc. - essentially resolves the bundle protocol
        URL resolved = FileLocator.resolve(url);
        if (resolved.getProtocol().equals("file")) {
            return new File(resolved.getPath());
        }
        return null;
    }

    private Path getPath() throws IOException {
        File file = resolveWritableBundleFile(url);
        return file != null ? file.toPath() : null;
    }

    @Override
    public boolean isUpdateable() {
        try {
            Path path = getPath();
            if(path == null)
                return false;
            return Files.exists(path);
        } catch (IOException e) {
            return false;
        }
    }
    
    @Override
    public void update(String newSourceText) {
        try {
            Path path = getPath();
            if(path == null)
                return;
            Files.write(path, newSourceText.getBytes(Charset.forName("UTF-8")));
        } catch(IOException e) {
            e.printStackTrace();
        }
        checkUpdates();
    }

    public void clear() {
        if (listeners != null) {
            listeners.clear();
            listeners = null;
        }
    }

    public JavaReferenceValidatorFactory getJavaReferenceValidatorFactory() {
        return new OsgiJavaReferenceValidatorFactory(bundle);
    }
}