/*******************************************************************************
 * Copyright (c) 2000, 2015 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.corext.refactoring.util;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.eclipse.core.runtime.CoreException;

import org.eclipse.jdt.core.IBuffer;
import org.eclipse.jdt.core.IJavaProject;
import org.eclipse.jdt.core.JavaCore;
import org.eclipse.jdt.core.ToolFactory;
import org.eclipse.jdt.core.compiler.IScanner;
import org.eclipse.jdt.core.compiler.ITerminalSymbols;
import org.eclipse.jdt.core.dom.ASTNode;
import org.eclipse.jdt.core.dom.CompilationUnit;
import org.eclipse.jdt.core.dom.rewrite.TargetSourceRangeComputer;
import org.eclipse.jdt.core.formatter.IndentManipulation;

import org.eclipse.jdt.internal.corext.dom.ASTNodes;
import org.eclipse.jdt.internal.corext.dom.TokenScanner;

public class SelectionAwareSourceRangeComputer extends TargetSourceRangeComputer {

	private ASTNode[] fSelectedNodes;
	private int fSelectionStart;
	private int fSelectionLength;

	private Map<ASTNode, SourceRange> fRanges;
	private String fDocumentPortionToScan;

	public SelectionAwareSourceRangeComputer(ASTNode[] selectedNodes, IBuffer buffer, int selectionStart, int selectionLength) {
		fSelectedNodes= selectedNodes;
		fSelectionStart= selectionStart;
		fSelectionLength= selectionLength;
		fDocumentPortionToScan= buffer.getText(fSelectionStart, fSelectionLength);
	}

	@Override
	public SourceRange computeSourceRange(ASTNode node) {
		try {
			if (fRanges == null)
				initializeRanges();
			SourceRange result= fRanges.get(node);
			if (result != null)
				return result;
			return super.computeSourceRange(node);
		} catch (CoreException e) {
			// fall back to standard implementation
			fRanges= new HashMap<>();
		}
		return super.computeSourceRange(node);
	}

	private void initializeRanges() throws CoreException {
		fRanges= new HashMap<>();
		if (fSelectedNodes.length == 0)
			return;

		fRanges.put(fSelectedNodes[0], super.computeSourceRange(fSelectedNodes[0]));
		int last= fSelectedNodes.length - 1;
		fRanges.put(fSelectedNodes[last], super.computeSourceRange(fSelectedNodes[last]));

		IJavaProject javaProject= ((CompilationUnit) fSelectedNodes[0].getRoot()).getTypeRoot().getJavaProject();
		String sourceLevel= javaProject.getOption(JavaCore.COMPILER_SOURCE, true);
		String complianceLevel= javaProject.getOption(JavaCore.COMPILER_COMPLIANCE, true);
		IScanner scanner= ToolFactory.createScanner(true, false, false, sourceLevel, complianceLevel);
		char[] source= fDocumentPortionToScan.toCharArray();
		scanner.setSource(source);
		fDocumentPortionToScan= null; // initializeRanges() is only called once

		TokenScanner tokenizer= new TokenScanner(scanner);
		int pos= tokenizer.getNextStartOffset(0, false);

		ASTNode currentNode= fSelectedNodes[0];
		int newStart= Math.min(fSelectionStart + pos, currentNode.getStartPosition());
		SourceRange range= fRanges.get(currentNode);
		fRanges.put(currentNode, new SourceRange(newStart, range.getLength() + range.getStartPosition() - newStart));

		currentNode= fSelectedNodes[last];
		int scannerStart= currentNode.getStartPosition() + currentNode.getLength() - fSelectionStart;
		tokenizer.setOffset(scannerStart);
		pos= scannerStart;
		int token= -1;
		try {
			while (true) {
				token= tokenizer.readNext(false);
				pos= tokenizer.getCurrentEndOffset();
			}
		} catch (CoreException e) {
		}
		if (token == ITerminalSymbols.TokenNameCOMMENT_LINE) {
			int index= pos - 1;
			while (index >= 0 && IndentManipulation.isLineDelimiterChar(source[index])) {
				pos--;
				index--;
			}
		}

		int newEnd= Math.max(fSelectionStart + pos, currentNode.getStartPosition() + currentNode.getLength());
		range= fRanges.get(currentNode);
		fRanges.put(currentNode, new SourceRange(range.getStartPosition(), newEnd - range.getStartPosition()));

		// The extended source range of the last child node can end after the selection.
		// We have to ensure that the source range of such child nodes is also capped by the selection range.
		// Example: (/*]*/TRANSFORMER::transform/*[*/)
		// Selection is between /*]*/ and /*[*/, but the extended range of the "transform" node actually includes /*[*/ as well.
		while (true) {
			List<ASTNode> children= ASTNodes.getChildren(currentNode);
			if (!children.isEmpty()) {
				ASTNode lastChild= children.get(children.size() - 1);
				SourceRange extRange= super.computeSourceRange(lastChild);
				if (extRange.getStartPosition() + extRange.getLength() > newEnd) {
					fRanges.put(lastChild, new SourceRange(extRange.getStartPosition(), newEnd - extRange.getStartPosition()));
					currentNode= lastChild;
					continue;
				}
			}
			break;
		}
	}
}
