Copyright (c) 2000, 2018 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
    Brock Janiczak  - Bug 181919 LineReader creating unneeded garbage
/*******************************************************************************
 * Copyright (c) 2000, 2018 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
 *     Brock Janiczak <brockj@tpg.com.au> - Bug 181919 LineReader creating unneeded garbage
 *******************************************************************************/
package org.eclipse.compare.internal.core.patch;

import java.io.BufferedReader;
import java.io.IOException;
import java.util.*;

import org.eclipse.compare.internal.core.ComparePlugin;
import org.eclipse.compare.patch.ReaderCreator;
import org.eclipse.core.runtime.Assert;
import org.eclipse.core.runtime.CoreException;

public class LineReader {
	
Reads the contents and returns them as a List of lines.
/**
	 * Reads the contents and returns them as a List of lines.
	 */
	public static List<String> load(ReaderCreator content, boolean create) {
		List<String> lines = null;
		BufferedReader bufferedReader = null;
		if (!create && content != null && content.canCreateReader()) {
			// read current contents
			try {
				bufferedReader = new BufferedReader(content.createReader());
				lines = readLines(bufferedReader);
			} catch (CoreException ex) {
				ComparePlugin.log(ex);
			} finally {
				if (bufferedReader != null) {
					try {
						bufferedReader.close();
					} catch (IOException ex) {
						// silently ignored
					}
				}
			}
		}

		if (lines == null)
			lines = new ArrayList<>();
		return lines;
	}

	public static List<String> readLines(BufferedReader reader) {
		List<String> lines;
		LineReader lr= new LineReader(reader);
		lr.ignoreSingleCR(); // Don't treat single CRs as line feeds to be consistent with command line patch
		lines= lr.readLines();
		return lines;
	}

	/*
	 * Concatenates all strings found in the given List.
	 */
	public static String createString(boolean preserveLineDelimeters, List<String> lines) {
		StringBuilder sb= new StringBuilder();
		Iterator<String> iter= lines.iterator();
		if (preserveLineDelimeters) {
			while (iter.hasNext())
				sb.append(iter.next());
		} else {
			String lineSeparator= System.getProperty("line.separator"); //$NON-NLS-1$
			while (iter.hasNext()) {
				String line= iter.next();
				int l= length(line);
				if (l < line.length()) {	// line has delimiter
					sb.append(line.substring(0, l));
					sb.append(lineSeparator);
				} else {
					sb.append(line);
				}
			}
		}
		return sb.toString();
	}

	/*
	 * Returns the length (excluding a line delimiter CR, LF, CR/LF)
	 * of the given string.
	 */
	static int length(String s) {
		int l= s.length();
		if (l > 0) {
			char c= s.charAt(l-1);
			if (c == '\r')
				return l-1;
			if (c == '\n') {
				if (l > 1 && s.charAt(l-2) == '\r')
					return l-2;
				return l-1;
			}
		}
		return l;
	}

	private boolean fHaveChar= false;
	private int fLastChar;
	private boolean fSawEOF= false;
	private BufferedReader fReader;
	private boolean fIgnoreSingleCR= false;
	private StringBuilder fBuffer= new StringBuilder();

	public LineReader(BufferedReader reader) {
		this.fReader= reader;
		Assert.isNotNull(reader);
	}

	public void ignoreSingleCR() {
		this.fIgnoreSingleCR= true;
	}

	
Reads a line of text. A line is considered to be terminated by any one
of a line feed ('\n'), a carriage return ('\r'), or a carriage return
followed immediately by a line-feed.
Throws:
IOException – If an I/O error occurs
Returns:
A string containing the contents of the line including
the line-termination characters, or null if the end of the
stream has been reached/**
	 * Reads a line of text. A line is considered to be terminated by any one
	 * of a line feed ('\n'), a carriage return ('\r'), or a carriage return
	 * followed immediately by a line-feed.
	 * @return A string containing the contents of the line including
	 *	the line-termination characters, or <code>null</code> if the end of the
	 *	stream has been reached
	 * @exception IOException If an I/O error occurs
	 */
	String readLine() throws IOException {
		try {
			while (!this.fSawEOF) {
				int c= readChar();
				if (c == -1) {
					this.fSawEOF= true;
					break;
				}
				this.fBuffer.append((char)c);
				if (c == '\n')
					break;
				if (c == '\r') {
					c= readChar();
					if (c == -1) {
						this.fSawEOF= true;
						break;	// EOF
					}
					if (c != '\n') {
						if (this.fIgnoreSingleCR) {
							this.fBuffer.append((char)c);
							continue;
						}
						this.fHaveChar= true;
						this.fLastChar= c;
					} else
						this.fBuffer.append((char)c);
					break;
				}
			}

			if (this.fBuffer.length() != 0) {
				return this.fBuffer.toString();
			}
			return null;
		} finally {
			this.fBuffer.setLength(0);
		}
	}

	void close() {
		try {
			this.fReader.close();
		} catch (IOException ex) {
			// silently ignored
		}
	}

	public List<String> readLines() {
		try {
			List<String> lines= new ArrayList<>();
			String line;
			while ((line= readLine()) != null)
				lines.add(line);
			return lines;
		} catch (IOException ex) {
			// NeedWork
			//System.out.println("error while reading file: " + fileName + "(" + ex + ")");
		} finally {
			close();
		}
		return null;
	}

	/*
	 * Returns the number of characters in the given string without
	 * counting a trailing line separator.
	 */
	int lineContentLength(String line) {
		if (line == null)
			return 0;
		int length= line.length();
		for (int i= length-1; i >= 0; i--) {
			char c= line.charAt(i);
			if (c =='\n' || c == '\r')
				length--;
			else
				break;
		}
		return length;
	}

	//---- private

	private int readChar() throws IOException {
		if (this.fHaveChar) {
			this.fHaveChar= false;
			return this.fLastChar;
		}
		return this.fReader.read();
	}
}