Copyright (c) 2000, 2016 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
/*******************************************************************************
 * Copyright (c) 2000, 2016 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.dom;

import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.Status;

import org.eclipse.jface.text.BadLocationException;
import org.eclipse.jface.text.IDocument;
import org.eclipse.jface.text.IRegion;

import org.eclipse.jdt.core.IBuffer;
import org.eclipse.jdt.core.IJavaProject;
import org.eclipse.jdt.core.ITypeRoot;
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.compiler.InvalidInputException;
import org.eclipse.jdt.core.manipulation.JavaManipulation;

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

Wraps a scanner and offers convenient methods for finding tokens
/**
 * Wraps a scanner and offers convenient methods for finding tokens
 */
public class TokenScanner {

	public static final int END_OF_FILE= 20001;
	public static final int LEXICAL_ERROR= 20002;
	public static final int DOCUMENT_ERROR= 20003;

	private IScanner fScanner;
	private IDocument fDocument;
	private int fEndPosition;

	
Creates a TokenScanner
Params:
scanner – The scanner to be wrapped. The scanner has to support line information
if the comment position methods are used./**
	 * Creates a TokenScanner
	 * @param scanner The scanner to be wrapped. The scanner has to support line information
	 * if the comment position methods are used.
	 */
	public TokenScanner(IScanner scanner) {
		this(scanner, null);
	}

	
Creates a TokenScanner
Params:
scanner – The scanner to be wrapped
document – The document used for line information if specified/**
	 * Creates a TokenScanner
	 * @param scanner The scanner to be wrapped
	 * @param document The document used for line information if specified
	 */
	public TokenScanner(IScanner scanner, IDocument document) {
		fScanner= scanner;
		fEndPosition= fScanner.getSource().length - 1;
		fDocument= document;
	}

	
Creates a TokenScanner
Params:
document – The textbuffer to create the scanner on
project – the current Java project/**
	 * Creates a TokenScanner
	 * @param document The textbuffer to create the scanner on
	 * @param project the current Java project
	 */
	public TokenScanner(IDocument document, IJavaProject project) {
		String sourceLevel= project.getOption(JavaCore.COMPILER_SOURCE, true);
		String complianceLevel= project.getOption(JavaCore.COMPILER_COMPLIANCE, true);
		fScanner= ToolFactory.createScanner(true, false, false, sourceLevel, complianceLevel); // no line info required
		fScanner.setSource(document.get().toCharArray());
		fDocument= document;
		fEndPosition= fScanner.getSource().length - 1;
	}

	
Creates a TokenScanner
Params:
typeRoot – The type root to scan on
Throws:
CoreException – thrown if the buffer cannot be accessed/**
	 * Creates a TokenScanner
	 * @param typeRoot The type root to scan on
	 * @throws CoreException thrown if the buffer cannot be accessed
	 */
	public TokenScanner(ITypeRoot typeRoot) throws CoreException {
		IJavaProject project= typeRoot.getJavaProject();
		IBuffer buffer= typeRoot.getBuffer();
		if (buffer == null) {
			throw new CoreException(createError(DOCUMENT_ERROR, "Element has no source", null)); //$NON-NLS-1$
		}
		String sourceLevel= project.getOption(JavaCore.COMPILER_SOURCE, true);
		String complianceLevel= project.getOption(JavaCore.COMPILER_COMPLIANCE, true);
		fScanner= ToolFactory.createScanner(true, false, true, sourceLevel, complianceLevel); // line info required

		fScanner.setSource(buffer.getCharacters());
		fDocument= null; // use scanner for line information
		fEndPosition= fScanner.getSource().length - 1;
	}

	
Returns the wrapped scanner
Returns:
IScanner/**
	 * Returns the wrapped scanner
	 * @return IScanner
	 */
	public IScanner getScanner() {
		return fScanner;
	}

	
Sets the scanner offset to the given offset.
Params:
offset – The offset to set/**
	 * Sets the scanner offset to the given offset.
	 * @param offset The offset to set
	 */
	public void setOffset(int offset) {
		fScanner.resetTo(offset, fEndPosition);
	}

	
Returns:
Returns the offset after the current token/**
	 * @return Returns the offset after the current token
	 */
	public int getCurrentEndOffset() {
		return fScanner.getCurrentTokenEndPosition() + 1;
	}

	
Returns:
Returns the start offset of the current token/**
	 * @return Returns the start offset of the current token
	 */
	public int getCurrentStartOffset() {
		return fScanner.getCurrentTokenStartPosition();
	}

	
Returns:
Returns the length of the current token/**
	 * @return Returns the length of the current token
	 */
	public int getCurrentLength() {
		return getCurrentEndOffset() - getCurrentStartOffset();
	}

	
Reads the next token.
Params:
ignoreComments – If set, comments will be overread
Throws:
CoreException – Thrown when the end of the file has been reached (code END_OF_FILE)
or a lexical error was detected while scanning (code LEXICAL_ERROR)
Returns:
Return the token id./**
	 * Reads the next token.
	 * @param ignoreComments If set, comments will be overread
	 * @return Return the token id.
	 * @exception CoreException Thrown when the end of the file has been reached (code END_OF_FILE)
	 * or a lexical error was detected while scanning (code LEXICAL_ERROR)
	 */
	public int readNext(boolean ignoreComments) throws CoreException {
		int curr= 0;
		do {
			try {
				curr= fScanner.getNextToken();
				if (curr == ITerminalSymbols.TokenNameEOF) {
					throw new CoreException(createError(END_OF_FILE, "End Of File", null)); //$NON-NLS-1$
				}
			} catch (InvalidInputException e) {
				throw new CoreException(createError(LEXICAL_ERROR, e.getMessage(), e));
			}
		} while (ignoreComments && isComment(curr));
		return curr;
	}

	
Reads the next token.
Params:
ignoreComments – If set, comments will be overread.
Throws:
CoreException – Thrown when the end of the file has been reached (code END_OF_FILE)
or a lexical error was detected while scanning (code LEXICAL_ERROR)
Returns:
Return the token id./**
	 * Reads the next token.
	 * @param ignoreComments If set, comments will be overread.
	 * @return Return the token id.
	 * @exception CoreException Thrown when the end of the file has been reached (code END_OF_FILE)
	 * or a lexical error was detected while scanning (code LEXICAL_ERROR)
	 */
	private int readNextWithEOF(boolean ignoreComments) throws CoreException {
		int curr= 0;
		do {
			try {
				curr= fScanner.getNextToken();
			} catch (InvalidInputException e) {
				throw new CoreException(createError(LEXICAL_ERROR, e.getMessage(), e));
			}
		} while (ignoreComments && isComment(curr));
		return curr;
	}

	
Reads the next token from the given offset.
Params:
offset – The offset to start reading from.
ignoreComments – If set, comments will be overread.
Throws:
CoreException – Thrown when the end of the file has been reached (code END_OF_FILE)
or a lexical error was detected while scanning (code LEXICAL_ERROR)
Returns:
Returns the token id./**
	 * Reads the next token from the given offset.
	 * @param offset The offset to start reading from.
	 * @param ignoreComments If set, comments will be overread.
	 * @return Returns the token id.
	 * @exception CoreException Thrown when the end of the file has been reached (code END_OF_FILE)
	 * or a lexical error was detected while scanning (code LEXICAL_ERROR)
	 */
	public int readNext(int offset, boolean ignoreComments) throws CoreException {
		setOffset(offset);
		return readNext(ignoreComments);
	}

	
Reads the next token from the given offset and returns the start offset of the token.
Params:
offset – The offset to start reading from.
ignoreComments – If set, comments will be overread
Throws:
CoreException – Thrown when the end of the file has been reached (code END_OF_FILE)
or a lexical error was detected while scanning (code LEXICAL_ERROR)
Returns:
Returns the start position of the next token./**
	 * Reads the next token from the given offset and returns the start offset of the token.
	 * @param offset The offset to start reading from.
	 * @param ignoreComments If set, comments will be overread
	 * @return Returns the start position of the next token.
	 * @exception CoreException Thrown when the end of the file has been reached (code END_OF_FILE)
	 * or a lexical error was detected while scanning (code LEXICAL_ERROR)
	 */
	public int getNextStartOffset(int offset, boolean ignoreComments) throws CoreException {
		readNext(offset, ignoreComments);
		return getCurrentStartOffset();
	}

	
Reads the next token from the given offset and returns the offset after the token.
Params:
offset – The offset to start reading from.
ignoreComments – If set, comments will be overread
Throws:
CoreException – Thrown when the end of the file has been reached (code END_OF_FILE)
or a lexical error was detected while scanning (code LEXICAL_ERROR)
Returns:
Returns the end position of the next token./**
	 * Reads the next token from the given offset and returns the offset after the token.
	 * @param offset The offset to start reading from.
	 * @param ignoreComments If set, comments will be overread
	 * @return Returns the end position of the next token.
	 * @exception CoreException Thrown when the end of the file has been reached (code END_OF_FILE)
	 * or a lexical error was detected while scanning (code LEXICAL_ERROR)
	 */
	public int getNextEndOffset(int offset, boolean ignoreComments) throws CoreException {
		readNext(offset, ignoreComments);
		return getCurrentEndOffset();
	}

	
Reads until a token is reached.
Params:
tok – The token to read to.
Throws:
CoreException – Thrown when the end of the file has been reached (code END_OF_FILE)
or a lexical error was detected while scanning (code LEXICAL_ERROR)/**
	 * Reads until a token is reached.
	 * @param tok The token to read to.
	 * @exception CoreException Thrown when the end of the file has been reached (code END_OF_FILE)
	 * or a lexical error was detected while scanning (code LEXICAL_ERROR)
	 */
	public void readToToken(int tok) throws CoreException {
		int curr= 0;
		do {
			curr= readNext(false);
		} while (curr != tok);
	}

	
Reads until a token is reached, starting from the given offset.
Params:
tok – The token to read to.
offset – The offset to start reading from.
Throws:
CoreException – Thrown when the end of the file has been reached (code END_OF_FILE)
or a lexical error was detected while scanning (code LEXICAL_ERROR)/**
	 * Reads until a token is reached, starting from the given offset.
	 * @param tok The token to read to.
	 * @param offset The offset to start reading from.
	 * @exception CoreException Thrown when the end of the file has been reached (code END_OF_FILE)
	 * or a lexical error was detected while scanning (code LEXICAL_ERROR)
	 */
	public void readToToken(int tok, int offset) throws CoreException {
		setOffset(offset);
		readToToken(tok);
	}

	
Reads from the given offset until a token is reached and returns the start offset of the token.
Params:
token – The token to be found.
startOffset – The offset to start reading from.
Throws:
CoreException – Thrown when the end of the file has been reached (code END_OF_FILE)
or a lexical error was detected while scanning (code LEXICAL_ERROR)
Returns:
Returns the start position of the found token./**
	 * Reads from the given offset until a token is reached and returns the start offset of the token.
	 * @param token The token to be found.
	 * @param startOffset The offset to start reading from.
	 * @return Returns the start position of the found token.
	 * @exception CoreException Thrown when the end of the file has been reached (code END_OF_FILE)
	 * or a lexical error was detected while scanning (code LEXICAL_ERROR)
	 */
	public int getTokenStartOffset(int token, int startOffset) throws CoreException {
		readToToken(token, startOffset);
		return getCurrentStartOffset();
	}

	
Reads from the given offset until a token is reached and returns the offset after the token.
Params:
token – The token to be found.
startOffset – Offset to start reading from
Throws:
CoreException – Thrown when the end of the file has been reached (code END_OF_FILE)
or a lexical error was detected while scanning (code LEXICAL_ERROR)
Returns:
Returns the end position of the found token./**
	 * Reads from the given offset until a token is reached and returns the offset after the token.
	 * @param token The token to be found.
	 * @param startOffset Offset to start reading from
	 * @return Returns the end position of the found token.
	 * @exception CoreException Thrown when the end of the file has been reached (code END_OF_FILE)
	 * or a lexical error was detected while scanning (code LEXICAL_ERROR)
	 */
	public int getTokenEndOffset(int token, int startOffset) throws CoreException {
		readToToken(token, startOffset);
		return getCurrentEndOffset();
	}

	
Reads from the given offset until a token is reached and returns the offset after the previous token.
Params:
token – The token to be found.
startOffset – The offset to start scanning from.
Throws:
CoreException – Thrown when the end of the file has been reached (code END_OF_FILE)
or a lexical error was detected while scanning (code LEXICAL_ERROR)
Returns:
Returns the end offset of the token previous to the given token./**
	 * Reads from the given offset until a token is reached and returns the offset after the previous token.
	 * @param token The token to be found.
	 * @param startOffset The offset to start scanning from.
	 * @return Returns the end offset of the token previous to the given token.
	 * @exception CoreException Thrown when the end of the file has been reached (code END_OF_FILE)
	 * or a lexical error was detected while scanning (code LEXICAL_ERROR)
	 */
	public int getPreviousTokenEndOffset(int token, int startOffset) throws CoreException {
		setOffset(startOffset);
		int res= startOffset;
		int curr= readNext(false);
		while (curr != token) {
			res= getCurrentEndOffset();
			curr= readNext(false);
		}
		return res;
	}

	
Evaluates the start offset of comments directly ahead of a token specified by its start offset
Params:
lastPos – An offset to before the node start offset. Can be 0 but better is the end location of the previous node.
nodeStart – Start offset of the node to find the comments for.
Throws:
CoreException – Thrown when a lexical error was detected while scanning (code LEXICAL_ERROR)
Returns:
Returns the start offset of comments directly ahead of a token./**
	 * Evaluates the start offset of comments directly ahead of a token specified by its start offset
	 *
	 * @param lastPos An offset to before the node start offset. Can be 0 but better is the end location of the previous node.
	 * @param nodeStart Start offset of the node to find the comments for.
	 * @return Returns the start offset of comments directly ahead of a token.
	 * @exception CoreException Thrown when a lexical error was detected while scanning (code LEXICAL_ERROR)
	 */
	public int getTokenCommentStart(int lastPos, int nodeStart) throws CoreException {
		setOffset(lastPos);

		int prevEndPos= lastPos;
		int prevEndLine= prevEndPos > 0 ? getLineOfOffset(prevEndPos - 1) : 0;
		int nodeLine= getLineOfOffset(nodeStart);

		int res= -1;

		int curr= readNextWithEOF(false);
		int currStartPos= getCurrentStartOffset();
		int currStartLine= getLineOfOffset(currStartPos);
		while (curr != ITerminalSymbols.TokenNameEOF && nodeStart > currStartPos) {
			if (TokenScanner.isComment(curr)) {
				int linesDifference= currStartLine - prevEndLine;
				if ((linesDifference > 1) || (res == -1 && (linesDifference != 0 || nodeLine == currStartLine))) {
					res= currStartPos; // begin new
				}
			} else {
				res= -1;
			}

			if (curr == ITerminalSymbols.TokenNameCOMMENT_LINE) {
				prevEndLine= currStartLine;
			} else {
				prevEndLine= getLineOfOffset(getCurrentEndOffset() - 1);
			}
			curr= readNextWithEOF(false);
			currStartPos= getCurrentStartOffset();
			currStartLine= getLineOfOffset(currStartPos);
		}
		if (res == -1 || curr == ITerminalSymbols.TokenNameEOF) {
			return nodeStart;
		}
		if (currStartLine - prevEndLine > 1) {
			return nodeStart;
		}
		return res;
	}

	
Looks for comments after a node and returns the end position of the comment still belonging to the node.
Params:
nodeEnd – The end position of the node
nextTokenStart – The start positoion of the next node. Optional, can be -1
the line information shoould be taken from the scanner object
Throws:
CoreException – Thrown when the end of the file has been reached (code END_OF_FILE)
or a lexical error was detected while scanning (code LEXICAL_ERROR)
Returns:
Returns returns the end position of the comment still belonging to the node./**
	 * Looks for comments after a node and returns the end position of the comment still belonging to the node.
	 * @param nodeEnd The end position of the node
	 * @param nextTokenStart The start positoion of the next node. Optional, can be -1
	 * the line information shoould be taken from the scanner object
	 * @return Returns returns the end position of the comment still belonging to the node.
	 * @exception CoreException Thrown when the end of the file has been reached (code END_OF_FILE)
	 * or a lexical error was detected while scanning (code LEXICAL_ERROR)
	 */
	public int getTokenCommentEnd(int nodeEnd, int nextTokenStart) throws CoreException {
		// assign comments to the previous comments as long they are all on the same line as the
		// node end position or if they are on the next line but there is a separation from the next
		// node
		// } //aa
		// // aa
		//
		// // bb
		// public void b...
		//
		// } /* cc */ /*
		// cc/*
		// /*dd*/
		// public void d...

		int prevEndLine= getLineOfOffset(nodeEnd - 1);
		int prevEndPos= nodeEnd;
		int res= nodeEnd;
		boolean sameLineComment= true;

		setOffset(nodeEnd);


		int curr= readNextWithEOF(false);
		while (curr == ITerminalSymbols.TokenNameCOMMENT_LINE || curr == ITerminalSymbols.TokenNameCOMMENT_BLOCK) {
			int currStartLine= getLineOfOffset(getCurrentStartOffset());
			int linesDifference= currStartLine - prevEndLine;

			if (linesDifference > 1) {
				return prevEndPos; // separated comments
			}

			if (curr == ITerminalSymbols.TokenNameCOMMENT_LINE) {
				prevEndPos= getLineEnd(currStartLine);
				prevEndLine= currStartLine;
			} else {
				prevEndPos= getCurrentEndOffset();
				prevEndLine= getLineOfOffset(prevEndPos - 1);
			}
			if (sameLineComment) {
				if (linesDifference == 0) {
					res= prevEndPos;
				} else {
					sameLineComment= false;
				}
			}
			curr= readNextWithEOF(false);
		}
		if (curr == ITerminalSymbols.TokenNameEOF) {
			return prevEndPos;
		}
		int currStartLine= getLineOfOffset(getCurrentStartOffset());
		int linesDifference= currStartLine - prevEndLine;
		if (linesDifference > 1) {
			return prevEndPos; // separated comments
		}
		return res;
	}

	public int getLineOfOffset(int offset) throws CoreException {
		if (fDocument != null) {
			try {
				return fDocument.getLineOfOffset(offset);
			} catch (BadLocationException e) {
				String message= "Illegal offset: " + offset; //$NON-NLS-1$
				throw new CoreException(createError(DOCUMENT_ERROR, message, e));
			}
		}
		return getScanner().getLineNumber(offset);
	}

	public int getLineEnd(int line) throws CoreException {
		if (fDocument != null) {
			try {
				IRegion region= fDocument.getLineInformation(line);
				return region.getOffset() + region.getLength();
			} catch (BadLocationException e) {
				String message= "Illegal line: " + line; //$NON-NLS-1$
				throw new CoreException(createError(DOCUMENT_ERROR, message, e));
			}
		}
		return getScanner().getLineEnd(line);
	}

	public static boolean isComment(int token) {
		return token == ITerminalSymbols.TokenNameCOMMENT_BLOCK || token == ITerminalSymbols.TokenNameCOMMENT_JAVADOC
			|| token == ITerminalSymbols.TokenNameCOMMENT_LINE;
	}

	public static boolean isModifier(int token) {
		switch (token) {
			case ITerminalSymbols.TokenNamepublic:
			case ITerminalSymbols.TokenNameprotected:
			case ITerminalSymbols.TokenNameprivate:
			case ITerminalSymbols.TokenNamestatic:
			case ITerminalSymbols.TokenNamefinal:
			case ITerminalSymbols.TokenNameabstract:
			case ITerminalSymbols.TokenNamenative:
			case ITerminalSymbols.TokenNamevolatile:
			case ITerminalSymbols.TokenNamestrictfp:
			case ITerminalSymbols.TokenNametransient:
			case ITerminalSymbols.TokenNamesynchronized:
				return true;
			default:
				return false;
		}
	}

	private IStatus createError(int code, String message, Throwable e) {
		return new Status(IStatus.ERROR, JavaManipulation.ID_PLUGIN, code, message, e);
	}
}