/*******************************************************************************
 * Copyright (c) 2000, 2011 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.jdt.internal.ui.text.template.contentassist;

import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.graphics.Point;

import org.eclipse.core.runtime.Assert;

import org.eclipse.jface.text.BadLocationException;
import org.eclipse.jface.text.DocumentEvent;
import org.eclipse.jface.text.IDocument;
import org.eclipse.jface.text.ITextViewer;
import org.eclipse.jface.text.contentassist.ICompletionProposal;
import org.eclipse.jface.text.contentassist.ICompletionProposalExtension2;
import org.eclipse.jface.text.contentassist.IContextInformation;


/**
 * Global state for templates. Selecting a proposal for the master template variable
 * will cause the value (and the proposals) for the slave variables to change.
 *
 * @see MultiVariable
 */
public class MultiVariableGuess {

	/**
	 * Implementation of the <code>ICompletionProposal</code> interface and extension.
	 */
	private static class Proposal implements ICompletionProposal, ICompletionProposalExtension2 {

		/** The string to be displayed in the completion proposal popup */
		private String fDisplayString;
		/** The replacement string */
		String fReplacementString;
		/** The replacement offset */
		private int fReplacementOffset;
		/** The replacement length */
		private int fReplacementLength;
		/** The cursor position after this proposal has been applied */
		private int fCursorPosition;
		/** The image to be displayed in the completion proposal popup */
		private Image fImage;
		/** The context information of this proposal */
		private IContextInformation fContextInformation;
		/** The additional info of this proposal */
		private String fAdditionalProposalInfo;

		/**
		 * Creates a new completion proposal based on the provided information.  The replacement string is
		 * considered being the display string too. All remaining fields are set to <code>null</code>.
		 *
		 * @param replacementString the actual string to be inserted into the document
		 * @param replacementOffset the offset of the text to be replaced
		 * @param replacementLength the length of the text to be replaced
		 * @param cursorPosition the position of the cursor following the insert relative to replacementOffset
		 */
		public Proposal(String replacementString, int replacementOffset, int replacementLength, int cursorPosition) {
			this(replacementString, replacementOffset, replacementLength, cursorPosition, null, null, null, null);
		}

		/**
		 * Creates a new completion proposal. All fields are initialized based on the provided information.
		 *
		 * @param replacementString the actual string to be inserted into the document
		 * @param replacementOffset the offset of the text to be replaced
		 * @param replacementLength the length of the text to be replaced
		 * @param cursorPosition the position of the cursor following the insert relative to replacementOffset
		 * @param image the image to display for this proposal
		 * @param displayString the string to be displayed for the proposal
		 * @param contextInformation the context information associated with this proposal
		 * @param additionalProposalInfo the additional information associated with this proposal
		 */
		public Proposal(String replacementString, int replacementOffset, int replacementLength, int cursorPosition, Image image, String displayString, IContextInformation contextInformation, String additionalProposalInfo) {
			Assert.isNotNull(replacementString);
			Assert.isTrue(replacementOffset >= 0);
			Assert.isTrue(replacementLength >= 0);
			Assert.isTrue(cursorPosition >= 0);

			fReplacementString= replacementString;
			fReplacementOffset= replacementOffset;
			fReplacementLength= replacementLength;
			fCursorPosition= cursorPosition;
			fImage= image;
			fDisplayString= displayString;
			fContextInformation= contextInformation;
			fAdditionalProposalInfo= additionalProposalInfo;
		}

		/*
		 * @see ICompletionProposal#apply(IDocument)
		 */
		@Override
		public void apply(IDocument document) {
			try {
				document.replace(fReplacementOffset, fReplacementLength, fReplacementString);
			} catch (BadLocationException x) {
				// ignore
			}
		}

		/*
		 * @see ICompletionProposal#getSelection(IDocument)
		 */
		@Override
		public Point getSelection(IDocument document) {
			return new Point(fReplacementOffset + fCursorPosition, 0);
		}

		/*
		 * @see ICompletionProposal#getContextInformation()
		 */
		@Override
		public IContextInformation getContextInformation() {
			return fContextInformation;
		}

		/*
		 * @see ICompletionProposal#getImage()
		 */
		@Override
		public Image getImage() {
			return fImage;
		}

		/*
		 * @see ICompletionProposal#getDisplayString()
		 */
		@Override
		public String getDisplayString() {
			if (fDisplayString != null)
				return fDisplayString;
			return fReplacementString;
		}

		/*
		 * @see ICompletionProposal#getAdditionalProposalInfo()
		 */
		@Override
		public String getAdditionalProposalInfo() {
			return fAdditionalProposalInfo;
		}

		/*
		 * @see org.eclipse.jface.text.contentassist.ICompletionProposalExtension2#apply(org.eclipse.jface.text.ITextViewer, char, int, int)
		 */
		@Override
		public void apply(ITextViewer viewer, char trigger, int stateMask, int offset) {
			apply(viewer.getDocument());
		}

		/*
		 * @see org.eclipse.jface.text.contentassist.ICompletionProposalExtension2#selected(org.eclipse.jface.text.ITextViewer, boolean)
		 */
		@Override
		public void selected(ITextViewer viewer, boolean smartToggle) {
		}

		/*
		 * @see org.eclipse.jface.text.contentassist.ICompletionProposalExtension2#unselected(org.eclipse.jface.text.ITextViewer)
		 */
		@Override
		public void unselected(ITextViewer viewer) {
		}

		/*
		 * @see org.eclipse.jface.text.contentassist.ICompletionProposalExtension2#validate(org.eclipse.jface.text.IDocument, int, org.eclipse.jface.text.DocumentEvent)
		 */
		@Override
		public boolean validate(IDocument document, int offset, DocumentEvent event) {
			try {
				String content= document.get(fReplacementOffset, fReplacementLength);
				if (content.startsWith(fReplacementString))
					return true;
			} catch (BadLocationException e) {
				// ignore concurrently modified document
			}
			return false;
		}
	}

	private final Map<MultiVariable, Set<MultiVariable>> fDependencies= new HashMap<>();
	private final Map<MultiVariable, MultiVariable> fBackwardDeps= new HashMap<>();
	private final Map<MultiVariable, VariablePosition> fPositions= new HashMap<>();

	public MultiVariableGuess() {
	}

	public ICompletionProposal[] getProposals(final MultiVariable variable, int offset, int length) {
		MultiVariable master= fBackwardDeps.get(variable);
		Object[] choices;
		if (master == null)
			choices= variable.getChoices();
		else
			choices= variable.getChoices(master.getCurrentChoice());

		if (choices == null)
			return null;

		if (fDependencies.containsKey(variable)) {
			ICompletionProposal[] ret= new ICompletionProposal[choices.length];
			for (int i= 0; i < ret.length; i++) {
				final Object choice= choices[i];
				ret[i]= new Proposal(variable.toString(choice), offset, length, offset + length) {
					@Override
					public void apply(IDocument document) {
						super.apply(document);
						Object oldChoice= variable.getCurrentChoice();
						variable.setCurrentChoice(choice);
						updateSlaves(variable, document, oldChoice);
					}
				};
			}

			return ret;

		} else {
			if (choices.length < 2)
				return null;

			ICompletionProposal[] ret= new ICompletionProposal[choices.length];
			for (int i= 0; i < ret.length; i++)
				ret[i]= new Proposal(variable.toString(choices[i]), offset, length, offset + length);

			return ret;
		}
	}

	private void updateSlaves(MultiVariable variable, IDocument document, Object oldChoice) {
		Object choice= variable.getCurrentChoice();
		if (!oldChoice.equals(choice)) {
			for (MultiVariable slave : fDependencies.get(variable)) {
				VariablePosition pos= fPositions.get(slave);

				Object slavesOldChoice= slave.getCurrentChoice();
				slave.setKey(choice); // resets the current choice
				try {
					document.replace(pos.getOffset(), pos.getLength(), slave.getDefaultValue());
				} catch (BadLocationException x) {
					// ignore and continue
				}
				// handle slaves recursively
				if (fDependencies.containsKey(slave))
					updateSlaves(slave, document, slavesOldChoice);
			}
		}
	}

	/**
	 * @param position
	 */
	public void addSlave(VariablePosition position) {
		fPositions.put(position.getVariable(), position);
	}

	/**
	 * @param master
	 * @param slave
	 * @since 3.3
	 */
	public void addDependency(MultiVariable master, MultiVariable slave) {
		// check for cycles and multi-slaves
		if (fBackwardDeps.containsKey(slave))
			throw new IllegalArgumentException("slave can only serve one master"); //$NON-NLS-1$
		Object parent= master;
		while (parent != null) {
			parent= fBackwardDeps.get(parent);
			if (parent == slave)
				throw new IllegalArgumentException("cycle detected"); //$NON-NLS-1$
		}

		Set<MultiVariable> slaves= fDependencies.get(master);
		if (slaves == null) {
			slaves= new HashSet<>();
			fDependencies.put(master, slaves);
		}
		fBackwardDeps.put(slave, master);
		slaves.add(slave);
	}
}
