/*******************************************************************************
 * Copyright (c) 2000, 2017 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.core.tests.internal.builders;

import java.io.*;
import java.util.ArrayList;
import java.util.Map;
import org.eclipse.core.internal.resources.ResourceException;
import org.eclipse.core.resources.*;
import org.eclipse.core.runtime.*;

/**
 * A <code>SortBuilder</code> maintains a collection of files located
 * under a project's "sorted" folder.  These files mirror another
 * collection of files located under the project's "unsorted" folder.
 * The content (bytes) of each sorted file is the content of the
 * unsorted file it mirrors, but sorted in either ascending or
 * descending order depending on the build command.
 * @see SortBuilderPlugin
 */
public class SortBuilder extends TestBuilder {
	public static final String BUILDER_NAME = "org.eclipse.core.tests.resources.sortbuilder";
	/**
	 * The most recently created instance
	 */
	protected static SortBuilder singleton;

	/**
	 * All instances.
	 */
	protected static final ArrayList<SortBuilder> allInstances = new ArrayList<>();

	/**
	 * Build command parameters.
	 */
	public static String SORT_ORDER = "SortOrder";

	public static String ASCENDING = "Ascending";
	public static String DESCENDING = "Descending";

	public static String SORTED_FOLDER = "SortedFolder";

	public static String UNSORTED_FOLDER = "UnsortedFolder";
	/**
	 * Default folders
	 */
	public static String DEFAULT_SORTED_FOLDER = "SortedFolder";
	public static String DEFAULT_UNSORTED_FOLDER = "UnsortedFolder";
	/**
	 * Whether the last build was full, auto or incremental
	 */
	private int triggerForLastBuild = -1;
	/**
	 * Whether the last build provided a null delta.
	 */
	private boolean wasDeltaNull = false;

	/**
	 * List of the resources that were in the last delta, if any.
	 */
	protected final ArrayList<IResource> changedResources = new ArrayList<>();
	private boolean requestForgetState = false;

	/**
	 * Returns all instances of the SortBuilder that have ever been instantiated.
	 * The returned array is in the order in which the builders were first instantiated.
	 */
	public static SortBuilder[] allInstances() {
		return allInstances.toArray(new SortBuilder[allInstances.size()]);
	}

	/**
	 * Returns the most recently created instance.
	 */
	public static SortBuilder getInstance() {
		return singleton;
	}

	public static void resetSingleton() {
		singleton = null;
	}

	public SortBuilder() {
		singleton = this;
		allInstances.add(this);
	}

	/**
	 * Sort the given unsorted file in either ascending or descending
	 * order (depending on the build command) and update its corresponding
	 * sorted file with the result.
	 * @param unsortedFile
	 * @exception Exception if the build can't proceed
	 */
	private void build(IFile unsortedFile) throws CoreException {
		InputStream is = unsortedFile.getContents();
		ByteArrayOutputStream bos = new ByteArrayOutputStream();

		try {
			try {
				int c;
				while ((c = is.read()) != -1) {
					bos.write(c);
				}
			} finally {
				is.close();
			}
		} catch (IOException e) {
			throw new ResourceException(IResourceStatus.BUILD_FAILED, null, "IOException sorting file", e);
		}

		byte[] bytes = bos.toByteArray();

		quicksort(bytes, 0, bytes.length - 1, isSortOrderAscending());

		IFile sortedFile = (IFile) convertToSortedResource(unsortedFile);
		createResource(sortedFile);

		ByteArrayInputStream bis = new ByteArrayInputStream(bytes);
		sortedFile.setContents(bis, true, false, null);
	}

	/**
	 * Implements the inherited abstract method in
	 * <code>BaseBuilder</code>.
	 * @see BaseBuilder#build(IResourceDelta,int,IProgressMonitor)
	 */
	@Override
	protected IProject[] build(int kind, Map<String, String> args, IProgressMonitor monitor) throws CoreException {
		arguments = args;
		super.build(kind, args, monitor);
		triggerForLastBuild = kind;
		IResourceDelta delta = getDelta(getProject());
		recordChangedResources(delta);
		wasDeltaNull = delta == null;

		if (delta == null || kind == IncrementalProjectBuilder.FULL_BUILD) {
			fullBuild();
		} else {
			try {
				incrementalBuild(delta);
			} catch (Exception e) {
				throw new CoreException(new Status(IStatus.ERROR, "tests", IResourceStatus.BUILD_FAILED, "Incremental build failed due to internal error", e));
			}
		}
		//forget last built state if requested to do so
		if (requestForgetState) {
			requestForgetState = false;
			forgetLastBuiltState();
		}
		String project = arguments.get(INTERESTING_PROJECT);
		if (project != null) {
			return new IProject[] {getProject().getWorkspace().getRoot().getProject(project)};
		}
		return new IProject[0];
	}

	/**
	 * Converts the given unsorted resource handle to its corresponding
	 * sorted resource handle.  Neither resources need exist, but their
	 * types must be a folder (FOLDER) or a file (FILE).
	 * @param IResource
	 * @exception Exception if the resource is not a folder or a file
	 */
	private IResource convertToSortedResource(IResource unsortedResource) throws CoreException {
		IPath sortedFolderRelativePath = unsortedResource.getProjectRelativePath().removeFirstSegments(1);

		int type = unsortedResource.getType();

		if (type == IResource.FOLDER) {
			return getSortedFolder().getFolder(sortedFolderRelativePath);
		} else if (type == IResource.FILE) {
			return getSortedFolder().getFile(sortedFolderRelativePath);
		} else {
			throw new ResourceException(IResourceStatus.RESOURCE_WRONG_TYPE, null, "Wrong resource type", null);
		}
	}

	/**
	 * Creates the given resource, and its parent if necessary.  The
	 * resource must not be a solution and its project must exist.
	 * @param resource
	 * @exception Exception if the resource is not a folder or a file
	 */
	private void createResource(IResource resource) throws CoreException {
		if (resource.exists()) {
			return;
		}

		createResource(resource.getParent());

		int type = resource.getType();

		if (type == IResource.FOLDER) {
			((IFolder) resource).create(true, true, null);
		} else if (type == IResource.FILE) {
			((IFile) resource).create(null, true, null);
		} else {
			throw new ResourceException(IResourceStatus.RESOURCE_WRONG_TYPE, null, "Wrong resource type", null);
		}
	}

	/**
	 * Deletes the given resource, and its children if necessary.  The
	 * resource must not be a solution and its project must exist.
	 * @param resource
	 * @exception CoreException if the resource is not a folder or a file
	 */
	private void deleteResource(IResource resource) throws CoreException {
		if (!resource.exists()) {
			return;
		}

		int type = resource.getType();

		if (type == IResource.FOLDER) {
			IFolder folder = (IFolder) resource;
			IResource[] members = folder.members();
			for (IResource member : members) {
				deleteResource(member);
			}
			folder.delete(true, null);
		} else if (type == IResource.FILE) {
			((IFile) resource).delete(true, null);
		} else {
			throw new ResourceException(IResourceStatus.RESOURCE_WRONG_TYPE, null, "Wrong resource type", null);
		}
	}

	/**
	 * Performs a full build by discarding the results of the previous
	 * build and sorting all files in the unsorted folder.
	 * @exception CoreException if the build can't proceed
	 */
	private void fullBuild() throws CoreException {
		try {
			IFolder sortedFolder = getSortedFolder();
			IFolder unsortedFolder = getUnsortedFolder();

			if (sortedFolder.exists()) {
				//delete all sorted files
				IResource[] members = sortedFolder.members();
				for (IResource member : members) {
					deleteResource(member);
				}
			}

			if (unsortedFolder.exists()) {
				fullBuild(unsortedFolder);
			}
		} catch (Exception e) {
			throw new ResourceException(IResourceStatus.BUILD_FAILED, null, "Sort builder failed", e);
		}
	}

	/**
	 * Performs a full build on the given unsorted resource by sorting
	 * it, if it is a file, and sorting its children, if it is a folder.
	 * @exception Exception if the build can't proceed
	 */
	private void fullBuild(IResource unsortedResource) throws Exception {
		if (unsortedResource.getType() == IResource.FILE) {
			build((IFile) unsortedResource);
		} else {
			IResource[] members = ((IFolder) unsortedResource).members();
			for (IResource member : members) {
				fullBuild(member);
			}
		}
	}

	/**
	 * Returns the set of resources that were affected in the last delta.
	 * Affected means that resource changed or one of its children changed.
	 */
	public IResource[] getAffectedResources() {
		return changedResources.toArray(new IResource[changedResources.size()]);
	}

	/**
	 * Returns the folder under which sorted resources are found.
	 * @return IFolder
	 */
	private IFolder getSortedFolder() {
		String sortedFolder = arguments.get(SORTED_FOLDER);
		if (sortedFolder == null) {
			sortedFolder = DEFAULT_SORTED_FOLDER;
		}
		return getProject().getFolder(sortedFolder);
	}

	/**
	 * Returns the folder under which unsorted resources are found.
	 * @return IFolder
	 */
	private IFolder getUnsortedFolder() {
		String unsortedFolder = arguments.get(UNSORTED_FOLDER);
		if (unsortedFolder == null) {
			unsortedFolder = DEFAULT_UNSORTED_FOLDER;
		}
		return getProject().getFolder(unsortedFolder);
	}

	/**
	 * Performs an incremental build by leveraging the result of the
	 * previous build.
	 * @param delta describes how the resources have changed since
	 * the last build
	 * @exception Exception if the build can't proceed
	 */
	private void incrementalBuild(IResourceDelta delta) throws CoreException {
		IResource unsortedResource = delta.getResource();
		IPath unsortedFolderPath = getUnsortedFolder().getFullPath();
		IPath deltaPath = delta.getResource().getFullPath();

		boolean isUnderUnsortedFolder = unsortedFolderPath.isPrefixOf(deltaPath);

		boolean isOverUnsortedFolder = deltaPath.isPrefixOf(unsortedFolderPath);

		if (isUnderUnsortedFolder) {
			int status = delta.getKind();
			int changeFlags = delta.getFlags();

			int type = unsortedResource.getType();

			IResource sortedResource = convertToSortedResource(unsortedResource);

			if (status == IResourceDelta.REMOVED) {
				if (sortedResource.exists()) {
					sortedResource.delete(false, null);
				}
			} else if (type == IResource.FILE && status == IResourceDelta.ADDED) {
				build((IFile) unsortedResource);
			} else if (type == IResource.FILE && status == IResourceDelta.CHANGED && (changeFlags & IResourceDelta.CONTENT) != 0) {
				build((IFile) unsortedResource);
			}
		}

		if (isUnderUnsortedFolder || isOverUnsortedFolder) {
			IResourceDelta[] affectedChildren = delta.getAffectedChildren();
			for (IResourceDelta element : affectedChildren) {
				incrementalBuild(element);
			}
		}
	}

	/**
	 * Returns true if the unsorted files are to be sorted in ascending
	 * order, or false if they are to be sorted in descending order.
	 * @return boolean
	 */
	private boolean isSortOrderAscending() {
		String sortOrder = arguments.get(SORT_ORDER);
		return !DESCENDING.equals(sortOrder);
	}

	/**
	 * Sorts the specified bytes in either ascending or descending order.
	 * @param bytes
	 * @param start position of first byte
	 * @param end position of last byte
	 * @param ascendingOrder true if the bytes are to be sorted in
	 * ascending order, false if the bytes are to be sorted in
	 * descending order
	 */
	private void quicksort(byte[] bytes, int start, int end, boolean ascendingOrder) {
		if (start >= end || start < 0 || end >= bytes.length) {
			return;
		}

		int pos = start;
		int mid = (start + end) / 2;
		swap(bytes, start, mid);

		for (int i = start + 1; i <= end; ++i) {
			if (ascendingOrder && bytes[i] < bytes[start] || !ascendingOrder && bytes[i] > bytes[start]) {
				++pos;
				swap(bytes, pos, i);
			}
		}

		swap(bytes, start, pos);
		quicksort(bytes, start, pos, ascendingOrder);
		quicksort(bytes, pos + 1, end, ascendingOrder);
	}

	/**
	 * Remember all resources that appeared in the delta.
	 */
	private void recordChangedResources(IResourceDelta delta) throws CoreException {
		changedResources.clear();
		if (delta == null) {
			return;
		}
		delta.accept(delta1 -> {
			changedResources.add(delta1.getResource());
			return true;
		});
	}

	/**
	 * Requests that the next invocation of build() will call
	 * forgetLastBuiltState().
	 */
	public void requestForgetLastBuildState() {
		requestForgetState = true;
	}

	/**
	 * Swaps the specified bytes in the given byte array.
	 * @param bytes
	 * @param pos1 the position of the first byte
	 * @param pos2 the position of the second byte
	 */
	private void swap(byte[] bytes, int pos1, int pos2) {
		byte temp = bytes[pos1];
		bytes[pos1] = bytes[pos2];
		bytes[pos2] = temp;
	}

	@Override
	public String toString() {
		return "SortBuilder(" + getProject() + ')';
	}

	public boolean wasAutoBuild() {
		return triggerForLastBuild == IncrementalProjectBuilder.AUTO_BUILD;
	}

	/**
	 * Returns true if this builder has ever been built, and false otherwise.
	 */
	public boolean wasBuilt() {
		return triggerForLastBuild != -1;
	}

	public boolean wasDeltaNull() {
		return wasDeltaNull;
	}

	public boolean wasFullBuild() {
		return triggerForLastBuild == IncrementalProjectBuilder.FULL_BUILD;
	}

	public boolean wasIncrementalBuild() {
		return triggerForLastBuild == IncrementalProjectBuilder.INCREMENTAL_BUILD;
	}
}