/*=============================================================================#
 # Copyright (c) 2016, 2019 Stephan Wahlbrink and others.
 # 
 # This program and the accompanying materials are made available under the
 # terms of the Eclipse Public License 2.0 which is available at
 # https://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
 # which is available at https://www.apache.org/licenses/LICENSE-2.0.
 # 
 # SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
 # 
 # Contributors:
 #     Stephan Wahlbrink <sw@wahlbrink.eu> - initial API and implementation
 #=============================================================================*/

package org.eclipse.statet.ltk.ui.sourceediting.assist;

import static org.eclipse.statet.jcommons.lang.ObjectUtils.nonNullAssert;

import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.Status;
import org.eclipse.jface.text.BadLocationException;
import org.eclipse.jface.text.DocumentEvent;
import org.eclipse.jface.text.IDocument;
import org.eclipse.jface.text.IInformationControlCreator;
import org.eclipse.jface.text.ITextOperationTarget;
import org.eclipse.jface.text.ITextViewer;
import org.eclipse.jface.text.Position;
import org.eclipse.jface.text.contentassist.BoldStylerProvider;
import org.eclipse.jface.text.contentassist.ICompletionProposalExtension;
import org.eclipse.jface.text.contentassist.ICompletionProposalExtension2;
import org.eclipse.jface.text.contentassist.ICompletionProposalExtension3;
import org.eclipse.jface.text.contentassist.ICompletionProposalExtension4;
import org.eclipse.jface.text.contentassist.ICompletionProposalExtension6;
import org.eclipse.jface.text.contentassist.ICompletionProposalExtension7;
import org.eclipse.jface.text.contentassist.IContextInformation;
import org.eclipse.jface.text.source.Annotation;
import org.eclipse.jface.text.source.ISourceViewer;
import org.eclipse.jface.text.source.SourceViewer;
import org.eclipse.jface.viewers.StyledString;
import org.eclipse.swt.SWT;
import org.eclipse.swt.custom.StyledText;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.widgets.Display;
import org.eclipse.ui.statushandlers.StatusManager;

import org.eclipse.statet.jcommons.lang.NonNullByDefault;
import org.eclipse.statet.jcommons.lang.Nullable;
import org.eclipse.statet.jcommons.text.core.BasicTextRegion;
import org.eclipse.statet.jcommons.text.core.SearchPattern;
import org.eclipse.statet.jcommons.text.core.TextRegion;

import org.eclipse.statet.ecommons.ui.SharedUIResources;
import org.eclipse.statet.ecommons.ui.viewers.ViewerLabelUtils;

import org.eclipse.statet.internal.ltk.ui.LTKUIPlugin;


@NonNullByDefault
public abstract class SourceProposal<TContext extends AssistInvocationContext> implements AssistProposal,
		ICompletionProposalExtension, ICompletionProposalExtension2, ICompletionProposalExtension3,
		ICompletionProposalExtension4,
		ICompletionProposalExtension6, ICompletionProposalExtension7 {
	
	
	public static class ProposalParameters<TContext extends AssistInvocationContext> {
		
		
		public final TContext context;
		
		public final int replacementOffset;
		
		public final SearchPattern namePattern;
		
		public int baseRelevance;
		
		public int matchRule;
		
		
		public ProposalParameters(final TContext context, final int replacementOffset,
				final SearchPattern namePattern, final int baseRelevance) {
			this.context= nonNullAssert(context);
			this.replacementOffset= replacementOffset;
			this.namePattern= nonNullAssert(namePattern);
			this.baseRelevance= baseRelevance;
		}
		
		public ProposalParameters(final TContext context, final int replacementOffset,
				final SearchPattern namePattern) {
			this(context, replacementOffset, namePattern, 0);
		}
		
		public ProposalParameters(final TContext context, final int replacementOffset,
				final int baseRelevance) {
			this.context= nonNullAssert(context);
			this.replacementOffset= replacementOffset;
			this.namePattern= null;
			this.matchRule= SearchPattern.OTHER_MATCH;
			this.baseRelevance= baseRelevance;
		}
		
		
		public boolean matchesNamePattern(final @Nullable String name) {
			if (name == null) {
				this.matchRule= 0;
				return false;
			}
			return ((this.matchRule= this.namePattern.matches(name)) != 0);
		}
		
		
	}
	
	protected static class ApplyData {
		
		
		private @Nullable TextRegion selectionToSet;
		
		private @Nullable IContextInformation contextInformation;
		
		
		public ApplyData() {
		}
		
		
		public void setSelection(final TextRegion region) {
			this.selectionToSet= region;
		}
		
		public void setSelection(final int offset) {
			this.selectionToSet= new BasicTextRegion(offset, offset);
		}
		
		public void setSelection(final int offset, final int length) {
			assert (length >= 0);
			this.selectionToSet= new BasicTextRegion(offset, offset + length);
		}
		
		public void clearSelection() {
			this.selectionToSet= null;
		}
		
		public @Nullable TextRegion getSelection() {
			return this.selectionToSet;
		}
		
		public void setContextInformation(final IContextInformation info) {
			this.contextInformation= info;
		}
		
		public @Nullable IContextInformation getContextInformation() {
			return this.contextInformation;
		}
		
	}
	
	
	private final TContext context;
	
	private final int replacementOffset;
	
	private final @Nullable SearchPattern namePattern;
	private int matchOffset;
	private String matchPattern;
	private int matchRule;
	private final int baseRelevance;
	
	private @Nullable StyledString styledText;
	
	private @Nullable Annotation rememberedOverwriteAnnotation;
	
	private @Nullable ApplyData applyData;
	
	
	public SourceProposal(final ProposalParameters<? extends TContext> parameters) {
		this.context= parameters.context;
		this.replacementOffset= parameters.replacementOffset;
		this.namePattern= parameters.namePattern;
		this.matchOffset= this.context.getInvocationOffset();
		this.matchPattern= (this.namePattern != null) ? this.namePattern.getPattern() : null;
		this.matchRule= parameters.matchRule;
		this.baseRelevance= parameters.baseRelevance;
	}
	
	
	private boolean isInOverwriteMode(final boolean toggle) {
		return toggle;
	}
	
	
	protected final TContext getInvocationContext() {
		return this.context;
	}
	
	/**
	 * @param pattern the pattern or <code>null</code> for pattern of last match
	 * @return
	 */
	private final SearchPattern getNamePattern(final @Nullable String pattern) {
		final SearchPattern namePattern= nonNullAssert(this.namePattern);
		namePattern.setPattern((pattern != null) ? pattern : this.matchPattern);
		return namePattern;
	}
	
	protected abstract String getName();
	
	protected final int getReplacementOffset() {
		return this.replacementOffset;
	}
	
	protected int computeReplacementLength(final int replacementOffset, final Point selection,
			final int caretOffset, final boolean overwrite) throws BadLocationException {
		final int end= Math.max(caretOffset, selection.x + selection.y);
		return (end - replacementOffset);
	}
	
	protected final ApplyData getApplyData() {
		ApplyData applyData= this.applyData;
		if (applyData == null) {
			applyData= createApplyData();
			this.applyData= applyData;
		}
		return applyData;
	}
	
	protected ApplyData createApplyData() {
		return new ApplyData();
	}
	
	
	//-- Validate --
	
	@Override
	@Deprecated
	public boolean isValidFor(final IDocument document, final int offset) {
		return false;
	}
	
	@Override
	public boolean validate(final IDocument document, final int offset,
			@Nullable final DocumentEvent event) {
		return (doValidate(offset, event) != 0);
	}
	
	protected int doValidate(final int offset, @Nullable final DocumentEvent event) {
		if (this.namePattern != null) {
			try {
	//			System.out.println("doValidate " + getName() + " [" + getClass() + "]");
				final String prefix= getValidationPrefix(offset);
				if (prefix != null) {
					return validatePattern(offset, prefix, getValidationName());
				}
				return 0;
			}
			catch (final BadLocationException e) {
				return 0;
			}
		}
		return (offset == getInvocationContext().getInvocationOffset()) ?
				this.matchRule : 0;
	}
	
	protected @Nullable String getValidationPrefix(final int offset) throws BadLocationException {
		final int startOffset= Math.max(getReplacementOffset(), 0);
		if (offset >= startOffset) {
			return getInvocationContext().getDocument().get(startOffset, offset - startOffset);
		}
		return null;
	}
	
	protected String getValidationName() {
		return getName();
	}
	
	protected int validatePattern(final int offset, final String pattern, final String name) {
		final SearchPattern namePattern= getNamePattern(pattern);
		final int matchRule= namePattern.matches(name);
//		System.out.println("  => " + pattern + " = " + matchRule);
		if (matchRule != 0) {
			this.matchOffset= offset;
			this.matchPattern= pattern;
			this.matchRule= matchRule;
		}
		return matchRule;
	}
	
	
	protected final int getMatchRule(final int offset) {
		if (this.matchOffset == offset) {
			return this.matchRule;
		}
		return doValidate(offset, null);
	}
	
	
	//-- Sorting --
	
	@Override
	public int getRelevance() {
		int relevance= this.baseRelevance;
		if ((this.matchRule & (SearchPattern.WORD_PREFIX_MATCH | SearchPattern.SUBSTRING_MATCH)) != 0) {
			relevance-= 10;
		}
		return relevance;
	}
	
	@Override
	public abstract String getSortingString();
	
	
	//-- Item Label --
	
	@Override
	public String getDisplayString() {
		return getName();
	}
	
	@Override
	public final StyledString getStyledDisplayString() {
		StyledString styledText= this.styledText;
		if (styledText == null) {
			styledText= computeStyledText();
			this.styledText= styledText;
		}
		return styledText;
	}
	
	protected StyledString computeStyledText() {
		return new StyledString(getDisplayString());
	}
	
	@Override
	public StyledString getStyledDisplayString(final IDocument document, final int offset,
			final BoldStylerProvider boldStylerProvider) {
		final int matchRule;
//		System.out.println("getString " + getName() + " " + offset + " = " + matchRule + " [" + getClass() + "]");
		if (this.namePattern != null && (matchRule= getMatchRule(offset)) != 0) {
			final StyledString styledText= new StyledString();
			styledText.append(getStyledDisplayString());
			
			final SearchPattern namePattern= getNamePattern(null);
			final int[] matchingRegions= namePattern.getMatchingRegions(getValidationName(), matchRule);
			if (matchingRegions !=  null) {
//				System.out.println("  => " + Arrays.toString(matchingRegions));
				styleMatchingRegions(styledText, matchRule, matchingRegions, boldStylerProvider);
			}
			return styledText;
		}
		return getStyledDisplayString();
	}
	
	protected void styleMatchingRegions(final StyledString styledText,
			final int matchRule, final int[] matchingRegions,
			final BoldStylerProvider boldStylerProvider) {
		ViewerLabelUtils.setStyle(styledText, matchingRegions, boldStylerProvider.getBoldStyler() );
	}
	
	@Override
	public Image getImage() {
		return SharedUIResources.getImages().get(SharedUIResources.PLACEHOLDER_IMAGE_ID);
	}
	
	
	//-- Item Selection & Info --
	
	@Override
	public void selected(final ITextViewer viewer, final boolean smartToggle) {
		if (isInOverwriteMode(smartToggle)) {
			addOverwriteStyle();
		}
		else {
			repairPresentation();
		}
	}
	
	@Override
	public void unselected(final ITextViewer viewer) {
		repairPresentation();
	}
	
	@Override
	public @Nullable String getAdditionalProposalInfo() {
		return null;
	}
	
	@Override
	public @Nullable IInformationControlCreator getInformationControlCreator() {
		return null;
	}
	
	
	//-- Completion Trigger --
	
	@Override
	public boolean isAutoInsertable() {
		return false;
	}
	
	@Override
	public char @Nullable [] getTriggerCharacters() {
		return null;
	}
	
	
	//-- Prefix Completion --
	
	@Override
	public int getPrefixCompletionStart(final IDocument document,
			final int offset) {
		return Math.max(getReplacementOffset(), 0);
	}
	
	@Override
	public @Nullable CharSequence getPrefixCompletionText(final IDocument document,
			final int offset) {
		return getName();
	}
	
	
	//-- Apply --
	
	/**
	 * Not supported, use {@link #apply(ITextViewer, char, int, int)}
	 */
	@Override
	@Deprecated
	public void apply(final IDocument document, final char trigger, final int offset) {
	}
	
	@Override
	public void apply(final ITextViewer viewer, final char trigger, final int stateMask, final int offset) {
		assert (getInvocationContext().getSourceViewer() == viewer);
		
		final boolean smartToggle= (stateMask & SWT.CTRL) != 0;
		try {
			final int replacementOffset= Math.max(getReplacementOffset(), 0);
			final int replacementLength= computeReplacementLength(replacementOffset, viewer.getSelectedRange(), offset, isInOverwriteMode(smartToggle));
			
			if (validate(viewer.getDocument(), offset, null)) {
				doApply(trigger, stateMask, offset, replacementOffset, replacementLength);
				return;
			}
		}
		catch (final BadLocationException e) {
			StatusManager.getManager().handle(new Status(IStatus.ERROR, LTKUIPlugin.BUNDLE_ID,
					"Failed to apply completion proposal (" + getClass().getName() +").",
					e ));
		}
		Display.getCurrent().beep();
	}
	
	protected void doApply(final char trigger, final int stateMask, final int caretOffset,
			final int replacementOffset, final int replacementLength)
			throws BadLocationException {
		final AssistInvocationContext context= getInvocationContext();
		final IDocument document= context.getDocument();
		final ApplyData applyData= getApplyData();
		
		final StringBuilder replacement= new StringBuilder(getName());
		final int cursor= replacement.length();
		
		document.replace(replacementOffset, replacementLength, replacement.toString());
		
		applyData.setSelection(replacementOffset + cursor);
	}
	
	protected void reinvokeAssist() {
		final ISourceViewer viewer= getInvocationContext().getSourceViewer();
		if (viewer instanceof ITextOperationTarget) {
			final ITextOperationTarget target= (ITextOperationTarget) viewer;
			Display.getCurrent().asyncExec(new Runnable() {
				@Override
				public void run() {
					if (target.canDoOperation(ISourceViewer.CONTENTASSIST_PROPOSALS)) {
						target.doOperation(ISourceViewer.CONTENTASSIST_PROPOSALS);
					}
				}
			});
		}
	}
	
	
	@Override
	public @Nullable Point getSelection(final IDocument document) {
		final ApplyData applyData= this.applyData;
		if (applyData != null) {
			final TextRegion selection= applyData.getSelection();
			if (selection != null) {
				return new Point(selection.getStartOffset(), selection.getLength());
			}
		}
		return null;
	}
	
	@Override
	public @Nullable IContextInformation getContextInformation() {
		final ApplyData applyData= this.applyData;
		if (applyData != null) {
			return applyData.getContextInformation();
		}
		return null;
	}
	
	@Override
	public int getContextInformationPosition() {
		// return the default reference position, not the context position directly
		return getInvocationContext().getSourceViewer().getSelectedRange().x;
	}
	
	
	private void addOverwriteStyle() {
		final SourceViewer viewer= getInvocationContext().getSourceViewer();
		final StyledText text= viewer.getTextWidget();
		if (text == null || text.isDisposed()) {
			return;
		}
		
		final int widgetCaret= viewer.getTextWidget().getCaretOffset();
		final int modelCaret= viewer.widgetOffset2ModelOffset(widgetCaret);
		final int replacementOffset= Math.max(getReplacementOffset(), 0);
		int replacementLength;
		try {
			replacementLength= computeReplacementLength(replacementOffset, viewer.getSelectedRange(), modelCaret, true);
		}
		catch (final BadLocationException e) {
			replacementLength= -1;
		}
		if (replacementLength < 0 || modelCaret >= replacementOffset + replacementLength) {
			repairPresentation();
			return;
		}
		
		final int offset= widgetCaret;
		final int length= replacementOffset + replacementLength - modelCaret;
		
		repairPresentation();
		final Annotation annotation= new Annotation("org.eclipse.statet.ecommons.text.editorAnnotations.ContentAssistOverwrite", false, "");
		viewer.getAnnotationModel().addAnnotation(annotation, new Position(offset, length));
		this.rememberedOverwriteAnnotation= annotation;
	}
	
	private void repairPresentation() {
		final Annotation rememberedOverwriteAnnotation= this.rememberedOverwriteAnnotation;
		if (rememberedOverwriteAnnotation != null) {
			final SourceViewer viewer= getInvocationContext().getSourceViewer();
			
			this.rememberedOverwriteAnnotation= null;
			viewer.getAnnotationModel().removeAnnotation(rememberedOverwriteAnnotation);
		}
	}
	
}