/*******************************************************************************
 * Copyright (c) 2000, 2018 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 *******************************************************************************/
package org.eclipse.dltk.internal.corext.util;

import java.net.URI;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import org.eclipse.core.filebuffers.FileBuffers;
import org.eclipse.core.filebuffers.ITextFileBuffer;
import org.eclipse.core.filebuffers.ITextFileBufferManager;
import org.eclipse.core.filebuffers.LocationKind;
import org.eclipse.core.filesystem.EFS;
import org.eclipse.core.filesystem.IFileInfo;
import org.eclipse.core.resources.IResource;
import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IProgressMonitor;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.OperationCanceledException;
import org.eclipse.core.runtime.Status;
import org.eclipse.core.runtime.jobs.Job;
import org.eclipse.dltk.core.DLTKCore;
import org.eclipse.dltk.core.ElementChangedEvent;
import org.eclipse.dltk.core.IElementChangedListener;
import org.eclipse.dltk.core.IMethod;
import org.eclipse.dltk.core.IModelElement;
import org.eclipse.dltk.core.IModelElementDelta;
import org.eclipse.dltk.core.IProjectFragment;
import org.eclipse.dltk.core.ISourceModule;
import org.eclipse.dltk.core.ModelException;
import org.eclipse.dltk.core.ScriptModelUtil;
import org.eclipse.dltk.core.search.MethodNameMatch;
import org.eclipse.dltk.core.search.SearchEngine;
import org.eclipse.dltk.ui.DLTKUIPlugin;
import org.eclipse.dltk.ui.IDLTKUILanguageToolkit;
import org.w3c.dom.Element;

/**
 * History for the open type dialog. Object and keys are both
 * {@link MethodNameMatch}s.
 */
public class OpenMethodHistory extends History {

	// private IDLTKUILanguageToolkit fToolkit = null;
	MethodFilter fMethodFilter = null;

	private static Map sToolkitHistory = new HashMap();

	public static synchronized OpenMethodHistory getInstance(
			IDLTKUILanguageToolkit toolkit) {
		if (sToolkitHistory.containsKey(toolkit)) {
			return (OpenMethodHistory) sToolkitHistory.get(toolkit);
		}
		OpenMethodHistory his = new OpenMethodHistory(toolkit);
		sToolkitHistory.put(toolkit, his);
		return his;
	}

	private class MethodHistoryDeltaListener
			implements IElementChangedListener {
		@Override
		public void elementChanged(ElementChangedEvent event) {
			if (processDelta(event.getDelta())) {
				markAsInconsistent();
			}
		}

		/**
		 * Computes whether the history needs a consistency check or not.
		 *
		 * @param delta
		 *                  the Java element delta
		 *
		 * @return <code>true</code> if consistency must be checked
		 *         <code>false</code> otherwise.
		 */
		private boolean processDelta(IModelElementDelta delta) {
			IModelElement elem = delta.getElement();

			boolean isChanged = delta.getKind() == IModelElementDelta.CHANGED;
			boolean isRemoved = delta.getKind() == IModelElementDelta.REMOVED;

			switch (elem.getElementType()) {
			case IModelElement.SCRIPT_PROJECT:
				if (isRemoved || (isChanged && (delta.getFlags()
						& IModelElementDelta.F_CLOSED) != 0)) {
					return true;
				}
				return processChildrenDelta(delta);
			case IModelElement.PROJECT_FRAGMENT:
				if (isRemoved || (isChanged && ((delta.getFlags()
						& IModelElementDelta.F_ARCHIVE_CONTENT_CHANGED) != 0
						|| (delta.getFlags()
								& IModelElementDelta.F_REMOVED_FROM_BUILDPATH) != 0))) {
					return true;
				}
				return processChildrenDelta(delta);
			case IModelElement.METHOD:
				if (isRemoved || isChanged && (delta.getFlags()
						& IModelElementDelta.F_MODIFIERS) != 0) {
					return true;
				}
				return false;
			case IModelElement.SCRIPT_MODEL:
			case IModelElement.SCRIPT_FOLDER:
				if (isRemoved) {
					return true;
				}
				return processChildrenDelta(delta);
			case IModelElement.SOURCE_MODULE:
				// Not the primary compilation unit. Ignore it
				if (!ScriptModelUtil.isPrimary((ISourceModule) elem)) {
					return false;
				}

				if (isRemoved || (isChanged
						&& isUnknownStructuralChange(delta.getFlags()))) {
					return true;
				}
				return processChildrenDelta(delta);
			default:
				// fields, methods, imports ect
				return false;
			}
		}

		private boolean isUnknownStructuralChange(int flags) {
			if ((flags & IModelElementDelta.F_CONTENT) == 0)
				return false;
			return (flags & IModelElementDelta.F_FINE_GRAINED) == 0;
		}

		/*
		 * private boolean isPossibleStructuralChange(int flags) { return (flags
		 * & (IJavaElementDelta.F_CONTENT | IJavaElementDelta.F_FINE_GRAINED))
		 * == IJavaElementDelta.F_CONTENT; }
		 */

		private boolean processChildrenDelta(IModelElementDelta delta) {
			IModelElementDelta[] children = delta.getAffectedChildren();
			for (int i = 0; i < children.length; i++) {
				if (processDelta(children[i])) {
					return true;
				}
			}
			return false;
		}
	}

	private static final String FAMILY = UpdateJob.class.getName();

	private class UpdateJob extends Job {
		public UpdateJob() {
			super(CorextMessages.MethodInfoHistory_consistency_check);
		}

		@Override
		protected IStatus run(IProgressMonitor monitor) {
			internalCheckConsistency(monitor);
			return new Status(IStatus.OK, DLTKUIPlugin.getPluginId(),
					IStatus.OK, "", null); //$NON-NLS-1$
		}

		@Override
		public boolean belongsTo(Object family) {
			return FAMILY.equals(family);
		}
	}

	// Needs to be volatile since accesses aren't synchronized.
	private volatile boolean fNeedsConsistencyCheck;
	// Map of cached time stamps
	private Map fTimestampMapping;

	private final IElementChangedListener fDeltaListener;
	private final UpdateJob fUpdateJob;

	private static final String FILENAME = "OpenMethodHistory"; //$NON-NLS-1$
	private static final String NODE_ROOT = "methodInfoHistroy"; //$NON-NLS-1$
	private static final String NODE_TYPE_INFO = "methodInfo"; //$NON-NLS-1$
	private static final String NODE_HANDLE = "handle"; //$NON-NLS-1$
	private static final String NODE_MODIFIERS = "modifiers"; //$NON-NLS-1$
	private static final String NODE_TIMESTAMP = "timestamp"; //$NON-NLS-1$

	private OpenMethodHistory(IDLTKUILanguageToolkit toolkit) {
		super(FILENAME
				+ toolkit.getCoreToolkit().getNatureId().replace('.', '_')
				+ ".xml", NODE_ROOT, NODE_TYPE_INFO); //$NON-NLS-1$
		fTimestampMapping = new HashMap();
		fNeedsConsistencyCheck = true;
		load();
		fDeltaListener = new MethodHistoryDeltaListener();
		DLTKCore.addElementChangedListener(fDeltaListener);
		fUpdateJob = new UpdateJob();
		// It is not necessary anymore that the update job has a rule since
		// markAsInconsistent isn't synchronized anymore. See bugs
		// https://bugs.eclipse.org/bugs/show_bug.cgi?id=128399 and
		// https://bugs.eclipse.org/bugs/show_bug.cgi?id=135278
		// for details.
		fUpdateJob.setPriority(Job.SHORT);

		// this.fToolkit = toolkit;
		this.fMethodFilter = new MethodFilter(toolkit);
	}

	public void markAsInconsistent() {
		fNeedsConsistencyCheck = true;
		// cancel the old job. If no job is running this is a NOOP.
		fUpdateJob.cancel();
		fUpdateJob.schedule();
	}

	public boolean needConsistencyCheck() {
		return fNeedsConsistencyCheck;
	}

	public void checkConsistency(IProgressMonitor monitor)
			throws OperationCanceledException {
		if (!fNeedsConsistencyCheck)
			return;
		if (fUpdateJob.getState() == Job.RUNNING) {
			try {
				Job.getJobManager().join(FAMILY, monitor);
			} catch (OperationCanceledException e) {
				// Ignore and do the consistency check without
				// waiting for the update job.
			} catch (InterruptedException e) {
				// Ignore and do the consistency check without
				// waiting for the update job.
			}
		}
		if (!fNeedsConsistencyCheck)
			return;
		internalCheckConsistency(monitor);
	}

	public synchronized boolean contains(MethodNameMatch type) {
		return super.contains(type);
	}

	public synchronized void accessed(MethodNameMatch info) {
		// Fetching the timestamp might not be cheap (remote file system
		// external Jars. So check if we alreay have one.
		if (!fTimestampMapping.containsKey(info)) {
			fTimestampMapping.put(info,
					Long.valueOf(getContainerTimestamp(info)));
		}
		super.accessed(info);
	}

	public synchronized MethodNameMatch remove(MethodNameMatch info) {
		fTimestampMapping.remove(info);
		return (MethodNameMatch) super.remove(info);
	}

	public synchronized void replace(MethodNameMatch old,
			MethodNameMatch newMatch) {
		fTimestampMapping.remove(old);
		fTimestampMapping.put(newMatch,
				Long.valueOf(getContainerTimestamp(newMatch)));
		super.remove(old);
		super.accessed(newMatch);
	}

	public synchronized MethodNameMatch[] getTypeInfos() {
		Collection values = getValues();
		int size = values.size();
		MethodNameMatch[] result = new MethodNameMatch[size];
		int i = size - 1;
		for (Iterator iter = values.iterator(); iter.hasNext();) {
			result[i] = (MethodNameMatch) iter.next();
			i--;
		}
		return result;
	}

	public synchronized MethodNameMatch[] getFilteredTypeInfos(
			MethodInfoFilter filter) {
		Collection values = getValues();
		List<MethodNameMatch> result = new ArrayList<>();
		for (Iterator iter = values.iterator(); iter.hasNext();) {
			MethodNameMatch method = (MethodNameMatch) iter.next();
			if ((filter == null || filter.matchesHistoryElement(method))
					&& !fMethodFilter
							.isFiltered(method.getFullyQualifiedName()))
				result.add(method);
		}
		Collections.reverse(result);
		return result.toArray(new MethodNameMatch[result.size()]);

	}

	@Override
	protected Object getKey(Object object) {
		return object;
	}

	private synchronized void internalCheckConsistency(IProgressMonitor monitor)
			throws OperationCanceledException {
		// Setting fNeedsConsistencyCheck is necessary here since
		// markAsInconsistent isn't synchronized.
		fNeedsConsistencyCheck = true;
		List typesToCheck = new ArrayList(getKeys());
		monitor.beginTask(CorextMessages.MethodInfoHistory_consistency_check,
				typesToCheck.size());
		monitor.setTaskName(CorextMessages.MethodInfoHistory_consistency_check);
		for (Iterator iter = typesToCheck.iterator(); iter.hasNext();) {
			MethodNameMatch type = (MethodNameMatch) iter.next();
			long currentTimestamp = getContainerTimestamp(type);
			Long lastTested = (Long) fTimestampMapping.get(type);
			if (lastTested != null && currentTimestamp != IResource.NULL_STAMP
					&& currentTimestamp == lastTested.longValue()
					&& !isContainerDirty(type))
				continue;
			try {
				IMethod sMethod = type.getMethod();
				if (sMethod == null || !sMethod.exists()) {
					remove(type);
				} else {
					// copy over the modifiers since they may have changed
					int modifiers = sMethod.getFlags();
					if (modifiers != type.getModifiers()) {
						replace(type, SearchEngine
								.createMethodNameMatch(sMethod, modifiers));
					} else {
						fTimestampMapping.put(type,
								Long.valueOf(currentTimestamp));
					}
				}
			} catch (ModelException e) {
				remove(type);
			}
			if (monitor.isCanceled())
				throw new OperationCanceledException();
			monitor.worked(1);
		}
		monitor.done();
		fNeedsConsistencyCheck = false;
	}

	private long getContainerTimestamp(MethodNameMatch match) {
		try {
			IMethod method = match.getMethod();
			IResource resource = method.getResource();
			if (resource != null) {
				URI location = resource.getLocationURI();
				if (location != null) {
					IFileInfo info = EFS.getStore(location).fetchInfo();
					if (info.exists()) {
						// The element could be removed from the build path. So
						// check
						// if the Java element still exists.
						IModelElement element = DLTKCore.create(resource);
						if (element != null && element.exists())
							return info.getLastModified();
					}
				}
			} else { // external JAR
				IProjectFragment root = match.getProjectFragment();
				if (root.exists()) {
					IFileInfo info = EFS.getLocalFileSystem()
							.getStore(root.getPath()).fetchInfo();
					if (info.exists()) {
						return info.getLastModified();
					}
				}
			}
		} catch (CoreException e) {
			// Fall through
		}
		return IResource.NULL_STAMP;
	}

	public boolean isContainerDirty(MethodNameMatch match) {
		ISourceModule cu = match.getMethod().getSourceModule();
		if (cu == null) {
			return false;
		}
		IResource resource = cu.getResource();
		if (resource != null) {
			ITextFileBufferManager manager = FileBuffers
					.getTextFileBufferManager();
			ITextFileBuffer textFileBuffer = manager.getTextFileBuffer(
					resource.getFullPath(), LocationKind.NORMALIZE);
			if (textFileBuffer != null) {
				return textFileBuffer.isDirty();
			}
		}
		return false;
	}

	public void shutdown() {
		DLTKCore.removeElementChangedListener(fDeltaListener);
		save();
	}

	@Override
	protected Object createFromElement(Element type) {
		String handle = type.getAttribute(NODE_HANDLE);
		if (handle == null)
			return null;

		IModelElement element = DLTKCore.create(handle);
		if (!(element instanceof IMethod))
			return null;

		int modifiers = 0;
		try {
			modifiers = Integer.parseInt(type.getAttribute(NODE_MODIFIERS));
		} catch (NumberFormatException e) {
			// take zero
		}
		MethodNameMatch info = SearchEngine
				.createMethodNameMatch((IMethod) element, modifiers);
		long timestamp = IResource.NULL_STAMP;
		String timestampValue = type.getAttribute(NODE_TIMESTAMP);
		if (timestampValue != null && timestampValue.length() > 0) {
			try {
				timestamp = Long.parseLong(timestampValue);
			} catch (NumberFormatException e) {
				// take null stamp
			}
		}
		if (timestamp != IResource.NULL_STAMP) {
			fTimestampMapping.put(info, Long.valueOf(timestamp));
		}
		return info;
	}

	@Override
	protected void setAttributes(Object object, Element typeElement) {
		MethodNameMatch method = (MethodNameMatch) object;
		String handleId = method.getMethod().getHandleIdentifier();
		typeElement.setAttribute(NODE_HANDLE, handleId);
		typeElement.setAttribute(NODE_MODIFIERS,
				Integer.toString(method.getModifiers()));
		Long timestamp = (Long) fTimestampMapping.get(method);
		if (timestamp == null) {
			typeElement.setAttribute(NODE_TIMESTAMP,
					Long.toString(IResource.NULL_STAMP));
		} else {
			typeElement.setAttribute(NODE_TIMESTAMP, timestamp.toString());
		}
	}

}