/*******************************************************************************
 * Copyright (c) 2000, 2008 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.springframework.ide.vscode.commons.util.text.linetracker;

import java.util.ArrayList;
import java.util.List;

import org.springframework.ide.vscode.commons.util.BadLocationException;
import org.springframework.ide.vscode.commons.util.text.IRegion;
import org.springframework.ide.vscode.commons.util.text.Region;
import org.springframework.ide.vscode.commons.util.text.linetracker.AbstractLineTracker.DelimiterInfo;

/**
 * Abstract, read-only implementation of <code>ILineTracker</code>. It lets the definition of
 * line delimiters to subclasses. Assuming that '\n' is the only line delimiter, this abstract
 * implementation defines the following line scheme:
 * <ul>
 * <li> "" -> [0,0]
 * <li> "a" -> [0,1]
 * <li> "\n" -> [0,1], [1,0]
 * <li> "a\n" -> [0,2], [2,0]
 * <li> "a\nb" -> [0,2], [2,1]
 * <li> "a\nbc\n" -> [0,2], [2,3], [5,0]
 * </ul>
 * This class must be subclassed.
 *
 * @since 3.2
 */
abstract class ListLineTracker implements ILineTracker {

	/** The line information */
	private final List<Line> fLines= new ArrayList<>();
	/** The length of the tracked text */
	private int fTextLength;

	/**
	 * Creates a new line tracker.
	 */
	protected ListLineTracker() {
	}

	/**
	 * Binary search for the line at a given offset.
	 *
	 * @param offset the offset whose line should be found
	 * @return the line of the offset
	 */
	private int findLine(int offset) {

		if (fLines.size() == 0)
			return -1;

		int left= 0;
		int right= fLines.size() - 1;
		int mid= 0;
		Line line= null;

		while (left < right) {

			mid= (left + right) / 2;

			line= fLines.get(mid);
			if (offset < line.offset) {
				if (left == mid)
					right= left;
				else
					right= mid - 1;
			} else if (offset > line.offset) {
				if (right == mid)
					left= right;
				else
					left= mid + 1;
			} else if (offset == line.offset) {
				left= right= mid;
			}
		}

		line= fLines.get(left);
		if (line.offset > offset)
			--left;
		return left;
	}

	/**
	 * Returns the number of lines covered by the specified text range.
	 *
	 * @param startLine the line where the text range starts
	 * @param offset the start offset of the text range
	 * @param length the length of the text range
	 * @return the number of lines covered by this text range
	 * @exception BadLocationException if range is undefined in this tracker
	 */
	private int getNumberOfLines(int startLine, int offset, int length) throws BadLocationException {

		if (length == 0)
			return 1;

		int target= offset + length;

		Line l= fLines.get(startLine);

		if (l.delimiter == null)
			return 1;

		if (l.offset + l.length > target)
			return 1;

		if (l.offset + l.length == target)
			return 2;

		return getLineNumberOfOffset(target) - startLine + 1;
	}

	@Override
	public final int getLineLength(int line) throws BadLocationException {
		int lines= fLines.size();

		if (line < 0 || line > lines)
			throw new BadLocationException();

		if (lines == 0 || lines == line)
			return 0;

		Line l= fLines.get(line);
		return l.length;
	}

	@Override
	public final int getLineNumberOfOffset(int position) throws BadLocationException {
		if (position < 0 || position > fTextLength)
			throw new BadLocationException();

		if (position == fTextLength) {

			int lastLine= fLines.size() - 1;
			if (lastLine < 0)
				return 0;

			Line l= fLines.get(lastLine);
			return (l.delimiter != null ? lastLine + 1 : lastLine);
		}

		return findLine(position);
	}

	@Override
	public final IRegion getLineInformationOfOffset(int position) throws BadLocationException {
		if (position > fTextLength)
			throw new BadLocationException();

		if (position == fTextLength) {
			int size= fLines.size();
			if (size == 0)
				return new Region(0, 0);
			Line l= fLines.get(size - 1);
			return (l.delimiter != null ? new Line(fTextLength, 0) : new Line(fTextLength - l.length, l.length));
		}

		return getLineInformation(findLine(position));
	}

	@Override
	public final IRegion getLineInformation(int line) throws BadLocationException {
		int lines= fLines.size();

		if (line < 0 || line > lines)
			throw new BadLocationException();

		if (lines == 0)
			return new Line(0, 0);

		if (line == lines) {
			Line l= fLines.get(line - 1);
			return new Line(l.offset + l.length, 0);
		}

		Line l= fLines.get(line);
		return (l.delimiter != null ? new Line(l.offset, l.length - l.delimiter.length()) : l);
	}

	@Override
	public final int getLineOffset(int line) throws BadLocationException {
		int lines= fLines.size();

		if (line < 0 || line > lines)
			throw new BadLocationException();

		if (lines == 0)
			return 0;

		if (line == lines) {
			Line l= fLines.get(line - 1);
			if (l.delimiter != null)
				return l.offset + l.length;
			throw new BadLocationException();
		}

		Line l= fLines.get(line);
		return l.offset;
	}

	@Override
	public final int getNumberOfLines() {
		int lines= fLines.size();

		if (lines == 0)
			return 1;

		Line l= fLines.get(lines - 1);
		return (l.delimiter != null ? lines + 1 : lines);
	}

	@Override
	public final int getNumberOfLines(int position, int length) throws BadLocationException {

		if (position < 0 || position + length > fTextLength)
			throw new BadLocationException();

		if (length == 0) // optimization
			return 1;

		return getNumberOfLines(getLineNumberOfOffset(position), position, length);
	}

	@Override
	public final int computeNumberOfLines(String text) {
		int count= 0;
		int start= 0;
		DelimiterInfo delimiterInfo= nextDelimiterInfo(text, start);
		while (delimiterInfo != null && delimiterInfo.delimiterIndex > -1) {
			++count;
			start= delimiterInfo.delimiterIndex + delimiterInfo.delimiterLength;
			delimiterInfo= nextDelimiterInfo(text, start);
		}
		return count;
	}

	@Override
	public final String getLineDelimiter(int line) throws BadLocationException {
		int lines= fLines.size();

		if (line < 0 || line > lines)
			throw new BadLocationException();

		if (lines == 0)
			return null;

		if (line == lines)
			return null;

		Line l= fLines.get(line);
		return l.delimiter;
	}

	/**
	 * Returns the information about the first delimiter found in the given text starting at the
	 * given offset.
	 *
	 * @param text the text to be searched
	 * @param offset the offset in the given text
	 * @return the information of the first found delimiter or <code>null</code>
	 */
	protected abstract DelimiterInfo nextDelimiterInfo(String text, int offset);

	/**
	 * Creates the line structure for the given text. Newly created lines are inserted into the line
	 * structure starting at the given position. Returns the number of newly created lines.
	 *
	 * @param text the text for which to create a line structure
	 * @param insertPosition the position at which the newly created lines are inserted into the
	 *        tracker's line structure
	 * @param offset the offset of all newly created lines
	 * @return the number of newly created lines
	 */
	private int createLines(String text, int insertPosition, int offset) {

		int count= 0;
		int start= 0;
		DelimiterInfo delimiterInfo= nextDelimiterInfo(text, 0);

		while (delimiterInfo != null && delimiterInfo.delimiterIndex > -1) {

			int index= delimiterInfo.delimiterIndex + (delimiterInfo.delimiterLength - 1);

			if (insertPosition + count >= fLines.size())
				fLines.add(new Line(offset + start, offset + index, delimiterInfo.delimiter));
			else
				fLines.add(insertPosition + count, new Line(offset + start, offset + index, delimiterInfo.delimiter));

			++count;
			start= index + 1;
			delimiterInfo= nextDelimiterInfo(text, start);
		}

		if (start < text.length()) {
			if (insertPosition + count < fLines.size()) {
				// there is a line below the current
				Line l= fLines.get(insertPosition + count);
				int delta= text.length() - start;
				l.offset-= delta;
				l.length+= delta;
			} else {
				fLines.add(new Line(offset + start, offset + text.length() - 1, null));
				++count;
			}
		}

		return count;
	}

	@Override
	public final void replace(int position, int length, String text) throws BadLocationException {
		throw new UnsupportedOperationException();
	}

	@Override
	public final void set(String text) {
		fLines.clear();
		if (text != null) {
			fTextLength= text.length();
			createLines(text, 0, 0);
		}
	}

	/**
	 * Returns the internal data structure, a {@link List} of {@link Line}s. Used only by
	 * {@link TreeLineTracker#TreeLineTracker(ListLineTracker)}.
	 *
	 * @return the internal list of lines.
	 */
	final List<Line> getLines() {
		return fLines;
	}
}
