/*******************************************************************************
 * Copyright (c) 2005, 2017 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.core;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

import org.eclipse.core.runtime.Assert;
import org.eclipse.core.runtime.IAdaptable;
import org.eclipse.core.runtime.IProgressMonitor;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.PlatformObject;
import org.eclipse.dltk.core.DLTKCore;
import org.eclipse.dltk.core.IField;
import org.eclipse.dltk.core.IModelElement;
import org.eclipse.dltk.core.IModelElementMemento;
import org.eclipse.dltk.core.IModelElementVisitor;
import org.eclipse.dltk.core.IModelElementVisitorExtension;
import org.eclipse.dltk.core.IModelStatus;
import org.eclipse.dltk.core.IModelStatusConstants;
import org.eclipse.dltk.core.IOpenable;
import org.eclipse.dltk.core.IParent;
import org.eclipse.dltk.core.IScriptModel;
import org.eclipse.dltk.core.IScriptProject;
import org.eclipse.dltk.core.ISourceModule;
import org.eclipse.dltk.core.ISourceRange;
import org.eclipse.dltk.core.ISourceReference;
import org.eclipse.dltk.core.ModelException;
import org.eclipse.dltk.core.ScriptModelUtil;
import org.eclipse.dltk.core.WorkingCopyOwner;
import org.eclipse.dltk.internal.core.util.MementoTokenizer;
import org.eclipse.dltk.internal.core.util.Util;
import org.eclipse.dltk.utils.CorePrinter;

/**
 * Root of model element handle hierarchy.
 *
 * @see IModelElement
 */

public abstract class ModelElement extends PlatformObject
		implements IModelElement, IModelElementMemento {

	public static final char JEM_ESCAPE = '\\';
	public static final char JEM_SCRIPTPROJECT = '=';
	public static final char JEM_PROJECTFRAGMENT = '/';
	public static final char JEM_SCRIPTFOLDER = '<';
	public static final char JEM_FIELD = '^';
	public static final char JEM_METHOD = '~';
	public static final char JEM_SOURCEMODULE = '{';
	public static final char JEM_TYPE = '[';
	public static final char JEM_IMPORTDECLARATION = '&';
	public static final char JEM_COUNT = '!';
	public static final char JEM_LOCALVARIABLE = '@';
	public static final char JEM_TYPE_PARAMETER = ']';
	public static final char JEM_PACKAGEDECLARATION = '%';

	/**
	 * This Item is for direct user element handle. Resolving of elements with
	 * such delimiter requires building of the model.
	 */
	public static final char JEM_USER_ELEMENT = '}';
	public static final String JEM_USER_ELEMENT_ENDING = "=/<^~{[&!@]%}";

	// Used to replace path / or \\ symbols in external package names and
	// archives.
	public static final char JEM_SKIP_DELIMETER = '>';

	/**
	 * This element's parent, or <code>null</code> if this element does not have
	 * a parent.
	 */
	protected final ModelElement parent;

	protected static final ModelElement[] NO_ELEMENTS = new ModelElement[0];
	protected static final Object NO_INFO = new Object();

	/**
	 * Constructs a handle for a model element with the given parent element.
	 *
	 * @param parent
	 *            The parent of model element
	 *
	 * @exception IllegalArgumentException
	 *                if the type is not one of the valid model element type
	 *                constants
	 *
	 */
	protected ModelElement(ModelElement parent)
			throws IllegalArgumentException {
		this.parent = parent;
	}

	/**
	 * @see IModelElement
	 */
	@Override
	public boolean exists() {

		try {
			getElementInfo();
			return true;
		} catch (ModelException e) {
			// element doesn't exist: return false
			if (DLTKCore.DEBUG) {
				e.printStackTrace();
			}
		}
		return false;
	}

	/**
	 * @see IModelElement
	 */
	@Override
	public IModelElement getAncestor(int ancestorType) {

		IModelElement element = this;
		while (element != null) {
			if (element.getElementType() == ancestorType)
				return element;
			element = element.getParent();
		}
		return null;
	}

	@Override
	@SuppressWarnings("unchecked")
	public <E extends IModelElement> E getAncestor(Class<E> elementClass) {
		IModelElement element = this;
		do {
			if (elementClass.isInstance(element)) {
				return (E) element;
			}
			element = element.getParent();
		} while (element != null);
		return null;
	}

	/**
	 * @see IOpenable
	 */
	public void close() throws ModelException {
		ModelManager.getModelManager().removeInfoAndChildren(this);
	}

	/**
	 * This element is being closed. Do any necessary cleanup.
	 */
	protected abstract void closing(Object info) throws ModelException;

	/**
	 * Returns the info for this handle. If this element is not already open, it
	 * and all of its parents are opened. Does not return null. NOTE: BinaryType
	 * infos are NOT rooted under ModelElementInfo.
	 *
	 * @exception ModelException
	 *                if the element is not present or not accessible
	 */
	public Object getElementInfo() throws ModelException {
		return getElementInfo(null);
	}

	/**
	 * Returns the info for this handle. If this element is not already open, it
	 * and all of its parents are opened. Does not return null. NOTE: BinaryType
	 * infos are NOT rooted under ModelElementInfo.
	 *
	 * @exception ModelException
	 *                if the element is not present or not accessible
	 */
	public Object getElementInfo(IProgressMonitor monitor)
			throws ModelException {

		ModelManager manager = ModelManager.getModelManager();
		Object info = manager.getInfo(this);
		if (info != null)
			return info;
		return openWhenClosed(createElementInfo(), monitor);
	}

	/*
	 * Opens an <code>Openable</code> that is known to be closed (no check for
	 * <code>isOpen()</code>). Returns the created element info.
	 */
	protected Object openWhenClosed(Object info, IProgressMonitor monitor)
			throws ModelException {
		ModelManager manager = ModelManager.getModelManager();
		boolean hadTemporaryCache = manager.hasTemporaryCache();
		try {
			HashMap newElements = manager.getTemporaryCache();
			generateInfos(info, newElements, monitor);
			if (info == null) {
				info = newElements.get(this);
			}
			if (info == null) { // a source ref element could not be opened
				// close the buffer that was opened for the openable parent
				// close only the openable's buffer (see
				// https://bugs.eclipse.org/bugs/show_bug.cgi?id=62854)
				Openable openable = (Openable) getOpenable();
				if (newElements.containsKey(openable)) {
					openable.closeBuffer();
				}
				throw newNotPresentException();
			}
			if (!hadTemporaryCache) {
				manager.putInfos(this, newElements);
			}
		} finally {
			if (!hadTemporaryCache) {
				manager.resetTemporaryCache();
			}
		}
		return info;
	}

	/*
	 * @see IModelElement
	 */
	@Override
	public IOpenable getOpenable() {
		return this.getOpenableParent();
	}

	/**
	 * Return the first instance of IOpenable in the parent hierarchy of this
	 * element.
	 *
	 * <p>
	 * Subclasses that are not IOpenable's must override this method.
	 */
	public IOpenable getOpenableParent() {
		return (IOpenable) this.parent;
	}

	/**
	 * @see IModelElement
	 */
	@Override
	public IModelElement getParent() {
		return this.parent;
	}

	/*
	 * Returns a new element info for this element.
	 */
	protected abstract Object createElementInfo();

	/**
	 * Generates the element infos for this element, its ancestors (if they are
	 * not opened) and its children (if it is an Openable). Puts the newly
	 * created element info in the given map.
	 */
	protected abstract void generateInfos(Object info, HashMap newElements,
			IProgressMonitor pm) throws ModelException;

	/**
	 * @see IAdaptable
	 */
	@Override
	public String getElementName() {
		return ""; //$NON-NLS-1$
	}

	/**
	 * Creates and returns a new not present exception for this element.
	 */
	public ModelException newNotPresentException() {
		return new ModelException(new ModelStatus(
				IModelStatusConstants.ELEMENT_DOES_NOT_EXIST, this));
	}

	/**
	 * Returns true if this handle represents the same model element as the
	 * given handle. By default, two handles represent the same element if they
	 * are identical or if they represent the same type of element, have equal
	 * names, parents, and occurrence counts.
	 *
	 * <p>
	 * If a subclass has other requirements for equality, this method must be
	 * overridden.
	 *
	 * @see Object#equals
	 */
	@Override
	public boolean equals(Object o) {
		if (this == o)
			return true;
		// model parent is null
		if (this.parent == null) {
			return super.equals(o);
		}
		if (o == null) {
			return false;
		}
		// assume instanceof check is done in subclass
		final ModelElement other = (ModelElement) o;
		return getElementName().equals(other.getElementName())
				&& this.parent.equals(other.parent);
	}

	/**
	 * Returns the hash code for this model element. By default, the hash code
	 * for an element is a combination of its name and parent's hash code.
	 * Elements with other requirements must override this method.
	 */
	@Override
	public int hashCode() {
		if (this.parent == null)
			return super.hashCode();
		return Util.combineHashCodes(getElementName().hashCode(),
				this.parent.hashCode());
	}

	/**
	 * Returns true if this element is an ancestor of the given element,
	 * otherwise false.
	 */
	public boolean isAncestorOf(IModelElement e) {
		IModelElement parentElement = e.getParent();
		while (parentElement != null && !parentElement.equals(this)) {
			parentElement = parentElement.getParent();
		}
		return parentElement != null;
	}

	/**
	 * @see IModelElement
	 */
	@Override
	public boolean isReadOnly() {
		return false;
	}

	/**
	 * Returns a collection of (immediate) children of this node of the
	 * specified type.
	 *
	 * @param type
	 *            - one of the EM_* constants defined by ModelElement
	 */
	protected List<IModelElement> getChildrenOfType(int type)
			throws ModelException {
		return getChildrenOfType(type, null);
	}

	protected List<IModelElement> getChildrenOfType(int type,
			IProgressMonitor monitor) throws ModelException {
		IModelElement[] children = getChildren(monitor);
		int size = children.length;
		List<IModelElement> list = new ArrayList<>(size);
		for (int i = 0; i < size; ++i) {
			IModelElement elt = children[i];
			if (elt.getElementType() == type) {
				list.add(elt);
			}
		}
		return list;
	}

	/**
	 * @see IParent
	 */
	public IModelElement[] getChildren() throws ModelException {
		return getChildren(null);
	}

	public IModelElement[] getChildren(IProgressMonitor monitor)
			throws ModelException {
		Object elementInfo = getElementInfo(monitor);
		if (elementInfo instanceof ModelElementInfo) {
			return ((ModelElementInfo) elementInfo).getChildren();
		} else {
			return NO_ELEMENTS;
		}
	}

	/**
	 * @see IModelElement
	 */
	@Override
	public IScriptModel getModel() {
		IModelElement current = this;
		do {
			if (current instanceof IScriptModel)
				return (IScriptModel) current;
		} while ((current = current.getParent()) != null);
		return null;
	}

	/**
	 * Creates and returns a new model exception for this element with the given
	 * status.
	 */
	public ModelException newModelException(IStatus status) {
		if (status instanceof IModelStatus)
			return new ModelException((IModelStatus) status);
		else
			return new ModelException(new ModelStatus(status.getSeverity(),
					status.getCode(), status.getMessage()));
	}

	/**
	 * @see IModelElement
	 */
	@Override
	public IScriptProject getScriptProject() {
		IModelElement current = this;
		do {
			if (current instanceof IScriptProject)
				return (IScriptProject) current;
		} while ((current = current.getParent()) != null);
		return null;
	}

	public boolean hasChildren() throws ModelException {
		// if I am not open, return true to avoid opening (case of a project, a
		// source module or a binary file).
		Object elementInfo = ModelManager.getModelManager().getInfo(this);
		if (elementInfo instanceof ModelElementInfo) {
			return ((ModelElementInfo) elementInfo).getChildren().length > 0;
		} else {
			return true;
		}
	}

	/**
	 * Debugging purposes
	 */
	protected String tabString(int tab) {
		StringBuffer buffer = new StringBuffer();
		for (int i = tab; i > 0; i--)
			buffer.append("  "); //$NON-NLS-1$
		return buffer.toString();
	}

	/**
	 * Debugging purposes
	 */
	public String toDebugString() {
		StringBuffer buffer = new StringBuffer();
		this.toStringInfo(0, buffer, NO_INFO, true/* show resolved info */);
		return buffer.toString();
	}

	/**
	 * Debugging purposes
	 */
	@Override
	public String toString() {
		StringBuffer buffer = new StringBuffer();
		toString(0, buffer);
		return buffer.toString();
	}

	/**
	 * Debugging purposes
	 */
	protected void toString(int tab, StringBuffer buffer) {
		Object info = this.toStringInfo(tab, buffer);
		if (tab == 0) {
			this.toStringAncestors(buffer);
		}
		this.toStringChildren(tab, buffer, info);
	}

	/**
	 * Debugging purposes
	 */
	public String toStringWithAncestors() {
		return toStringWithAncestors(true/* show resolved info */);
	}

	/**
	 * Debugging purposes
	 */
	public String toStringWithAncestors(boolean showResolvedInfo) {
		StringBuffer buffer = new StringBuffer();
		this.toStringInfo(0, buffer, NO_INFO, showResolvedInfo);
		this.toStringAncestors(buffer);
		return buffer.toString();
	}

	/**
	 * Debugging purposes
	 */
	protected void toStringAncestors(StringBuffer buffer) {
		ModelElement parentElement = (ModelElement) this.getParent();
		if (parentElement != null && parentElement.getParent() != null) {
			buffer.append(" [in "); //$NON-NLS-1$
			parentElement.toStringInfo(0, buffer, NO_INFO, false); // don't show
			// resolved
			// info
			parentElement.toStringAncestors(buffer);
			buffer.append("]"); //$NON-NLS-1$
		}
	}

	/**
	 * Debugging purposes
	 */
	protected void toStringChildren(int tab, StringBuffer buffer, Object info) {
		if (info == null || !(info instanceof ModelElementInfo))
			return;
		IModelElement[] children = ((ModelElementInfo) info).getChildren();
		for (int i = 0; i < children.length; i++) {
			buffer.append("\n"); //$NON-NLS-1$
			((ModelElement) children[i]).toString(tab + 1, buffer);
		}
	}

	/**
	 * Debugging purposes
	 */
	public Object toStringInfo(int tab, StringBuffer buffer) {
		Object info = ModelManager.getModelManager().peekAtInfo(this);
		this.toStringInfo(tab, buffer, info, true/* show resolved info */);
		return info;
	}

	/**
	 * Debugging purposes
	 *
	 * @param showResolvedInfo
	 *            TODO
	 */
	protected void toStringInfo(int tab, StringBuffer buffer, Object info,
			boolean showResolvedInfo) {
		buffer.append(this.tabString(tab));
		toStringName(buffer);
		if (info == null) {
			buffer.append(" (not open)"); //$NON-NLS-1$
		}
	}

	/**
	 * Debugging purposes
	 */
	protected void toStringName(StringBuffer buffer) {
		buffer.append(getElementName());
	}

	/**
	 * Returns the element that is located at the given source position in this
	 * element. This is a helper method for
	 * <code>ISourceModule#getElementAt</code>, and only works on compilation
	 * units and types. The position given is known to be within this element's
	 * source range already, and if no finer grained element is found at the
	 * position, this element is returned.
	 */
	protected IModelElement getSourceElementAt(int position)
			throws ModelException {
		IModelElement res = getSourceElementAtTop(position);
		if (res != this)
			return res;

		if (this instanceof ISourceReference) {
			IModelElement[] children = getChildren();
			for (int i = children.length - 1; i >= 0; i--) {
				IModelElement aChild = children[i];
				if (aChild instanceof SourceRefElement) {
					SourceRefElement child = (SourceRefElement) children[i];
					if (child instanceof IParent) {
						res = child.getSourceElementAt(position);
						if (res != child)
							return res;
					}
				}
			}
		} else {
			// should not happen
			Assert.isTrue(false);
		}
		return this;
	}

	/**
	 * Returns the element that is located at the given source position in this
	 * element. This is a helper method for
	 * <code>ISourceModule#getElementAt</code>, and only works on compilation
	 * units and types. The position given is known to be within this element's
	 * source range already, and if no finer grained element is found at the
	 * position, this element is returned.
	 */
	protected IModelElement getSourceElementAtTop(int position)
			throws ModelException {
		if (this instanceof ISourceReference) {
			IModelElement[] children = getChildren();
			for (int i = children.length - 1; i >= 0; i--) {
				IModelElement aChild = children[i];
				if (aChild instanceof SourceRefElement) {
					SourceRefElement child = (SourceRefElement) children[i];
					ISourceRange range = child.getSourceRange();
					int start = range.getOffset();
					int end = start + range.getLength();
					if (start <= position && position <= end) {
						if (child instanceof IField) {
							// check muti-declaration case (see
							// https://bugs.eclipse.org/bugs/show_bug.cgi?id=39943
							// )
							int declarationStart = start;
							SourceRefElement candidate = null;
							do {
								// check name range
								range = ((IField) child).getNameRange();
								if (position <= range.getOffset()
										+ range.getLength()) {
									candidate = child;
								} else {
									return candidate == null
											? child.getSourceElementAt(position)
											: candidate.getSourceElementAt(
													position);
								}
								child = --i >= 0
										? (SourceRefElement) children[i]
										: null;
							} while (child instanceof IField
									&& child.getSourceRange()
											.getOffset() == declarationStart);
							// position in field's type: use first field
							return candidate.getSourceElementAt(position);
						} else if (child instanceof IParent) {
							return child.getSourceElementAt(position);
						} else {
							return child;
						}
					}
				}
			}
		} else {
			// should not happen
			Assert.isTrue(false);
		}
		return this;
	}

	/**
	 * Returns element type and name. called from
	 * {@link #printNode(CorePrinter)} only.
	 *
	 * @return
	 */
	protected String describeElement() {
		return ScriptModelUtil.describeElementType(getElementType()) + ':'
				+ getElementName();
	}

	/**
	 * Only for testing. Used to print this node with all sub childs.
	 *
	 * @param output
	 */
	public void printNode(CorePrinter output) {
		output.formatPrint(describeElement());
		output.indent();
		try {
			IModelElement modelElements[] = this.getChildren();
			for (int i = 0; i < modelElements.length; ++i) {
				IModelElement element = modelElements[i];
				if (element instanceof ModelElement) {
					((ModelElement) element).printNode(output);
				} else {
					output.print("Unknown element:" + element); //$NON-NLS-1$
				}
			}
		} catch (ModelException ex) {
			output.formatPrint(ex.getLocalizedMessage());
		}
		output.dedent();
	}

	@Override
	public IModelElement getPrimaryElement() {
		return getPrimaryElement(true);
	}

	/*
	 * Returns the primary element. If checkOwner, and the cu owner is primary,
	 * return this element.
	 */
	public IModelElement getPrimaryElement(boolean checkOwner) {
		return this;
	}

	@Override
	public IModelElement getHandleFromMemento(MementoTokenizer memento,
			WorkingCopyOwner owner) {
		if (!memento.hasMoreTokens())
			return this;
		String token = memento.nextToken();
		return getHandleFromMemento(token, memento, owner);
	}

	@Override
	public abstract IModelElement getHandleFromMemento(String token,
			MementoTokenizer memento, WorkingCopyOwner owner);

	@Override
	public String getHandleIdentifier() {
		return getHandleMemento();
	}

	public String getHandleMemento() {
		StringBuffer buff = new StringBuffer();
		getHandleMemento(buff);
		return buff.toString();
	}

	public void getHandleMemento(StringBuffer buff) {
		((ModelElement) getParent()).getHandleMemento(buff);
		buff.append(getHandleMementoDelimiter());
		escapeMementoName(buff, getElementName());
	}

	protected abstract char getHandleMementoDelimiter();

	protected void escapeMementoName(StringBuffer buffer, String mementoName) {
		for (int i = 0, length = mementoName.length(); i < length; i++) {
			char character = mementoName.charAt(i);
			switch (character) {
			case JEM_ESCAPE:
			case JEM_COUNT:
			case JEM_SCRIPTPROJECT:
			case JEM_PROJECTFRAGMENT:
			case JEM_SCRIPTFOLDER:
			case JEM_FIELD:
			case JEM_METHOD:
			case JEM_SOURCEMODULE:
			case JEM_TYPE:
			case JEM_IMPORTDECLARATION:
			case JEM_LOCALVARIABLE:
			case JEM_TYPE_PARAMETER:
			case JEM_USER_ELEMENT:
				buffer.append(JEM_ESCAPE);
			}
			buffer.append(character);
		}
	}

	public ISourceModule getSourceModule() {
		return null;
	}

	@Override
	public void accept(IModelElementVisitor visitor) throws ModelException {
		if (visitor.visit(this)) {
			IModelElement[] elements = getChildren();
			for (int i = 0; i < elements.length; ++i) {
				elements[i].accept(visitor);
			}
			if (visitor instanceof IModelElementVisitorExtension) {
				((IModelElementVisitorExtension) visitor).endVisit(this);
			}
		}
	}
}