/*
 *  FlatCharSequenceRope.java
 *  Copyright (C) 2007 Amin Ahmad.
 *
 *  This file is part of Java Ropes.
 *
 *  Java Ropes is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  Java Ropes is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with Java Ropes.  If not, see <http://www.gnu.org/licenses/>.
 *
 *  Amin Ahmad can be contacted at amin.ahmad@gmail.com or on the web at
 *  www.ahmadsoft.org.
 */
package org.ahmadsoft.ropes.impl;

import java.io.IOException;
import java.io.Writer;
import java.util.Iterator;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.ahmadsoft.ropes.Rope;

/**
 * A rope constructed from an underlying character sequence.
 * @author Amin Ahmad
 */
public final class FlatCharSequenceRope extends AbstractRope implements FlatRope {

	private final CharSequence sequence;

	/**
	 * Constructs a new rope from an underlying character sequence.
	 * @param sequence
	 */
	public FlatCharSequenceRope(final CharSequence sequence) {
		this.sequence = sequence;
	}

	@Override
	public char charAt(final int index) {
		return this.sequence.charAt(index);
	}

	@Override
	public byte depth() {
		return 0;
	}

	@Override
	public Iterator<Character> iterator(final int start) {
		if (start < 0 || start > this.length())
			throw new IndexOutOfBoundsException("Rope index out of range: " + start);
		return new Iterator<Character>() {
			int current = start;
			@Override
			public boolean hasNext() {
				return this.current < FlatCharSequenceRope.this.length();
			}

			@Override
			public Character next() {
				return FlatCharSequenceRope.this.sequence.charAt(this.current++);
			}

			@Override
			public void remove() {
				throw new UnsupportedOperationException("Rope iterator is read-only.");
			}
		};
	}

	@Override
	public int length() {
		return this.sequence.length();
	}

	@Override
	public Matcher matcher(final Pattern pattern) {
		// optimized to return a matcher directly on the underlying sequence.
		return pattern.matcher(this.sequence);
	}

	@Override
	public Rope reverse() {
		return new ReverseRope(this);
	}

	@Override
	public Iterator<Character> reverseIterator(final int start) {
		if (start < 0 || start > this.length())
			throw new IndexOutOfBoundsException("Rope index out of range: " + start);
		return new Iterator<Character>() {
			int current = FlatCharSequenceRope.this.length() - start;
			@Override
			public boolean hasNext() {
				return this.current > 0;
			}

			@Override
			public Character next() {
				return FlatCharSequenceRope.this.sequence.charAt(--this.current);
			}

			@Override
			public void remove() {
				throw new UnsupportedOperationException("Rope iterator is read-only.");
			}
		};
	}

	@Override
	public Rope subSequence(final int start, final int end) {
		if (start == 0 && end == this.length())
			return this;
		if (end - start < 8 || this.sequence instanceof String /* special optimization for String */) {
			return new FlatCharSequenceRope(this.sequence.subSequence(start, end));
		} else {
			return new SubstringRope(this, start, end-start);
		}
	}

	@Override
	public String toString() {
		return this.sequence.toString();
	}

	public String toString(final int offset, final int length) {
		return this.sequence.subSequence(offset, offset + length).toString();
	}

	@Override
	public void write(final Writer out) throws IOException {
		this.write(out, 0, this.length());
	}

	@Override
	public void write(final Writer out, final int offset, final int length) throws IOException {
		if (offset < 0 || offset + length > this.length())
			throw new IndexOutOfBoundsException("Rope index out of bounds:" + (offset < 0 ? offset: offset + length));

		if (this.sequence instanceof String) {	// optimization for String
			out.write(((String) this.sequence).substring(offset, offset+length));
			return;
		}
		for (int j=offset; j<offset + length; ++j)
			out.write(this.sequence.charAt(j));
	}
}