/*
 *  FlatCharArrayRope.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.Arrays;
import java.util.Iterator;

import org.ahmadsoft.ropes.Rope;

/**
 * A rope constructed from a character array. This rope is even
 * flatter than a regular flat rope.
 * @author Amin Ahmad
 */
public final class FlatCharArrayRope extends AbstractRope implements FlatRope {

	private final char[] sequence;

	/**
	 * Constructs a new rope from a character array.
	 * @param sequence the character array.
	 */
	public FlatCharArrayRope(final char[] sequence) {
		this(sequence, 0, sequence.length);
	}

	/**
	 * Constructs a new rope from a character array range.
	 * @param sequence the character array.
	 * @param offset the offset in the array.
	 * @param length the length of the array.
	 */
	public FlatCharArrayRope(final char[] sequence, final int offset, final int length) {
		if (length > sequence.length)
			throw new IllegalArgumentException("Length must be less than " + sequence.length);
		this.sequence = new char[length];
		System.arraycopy(sequence, offset, this.sequence, 0, length);
	}

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

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

	/*
	 * Implementation Note: This is a reproduction of the AbstractRope
	 * indexOf implementation. Calls to charAt have been replaced
	 * with direct array access to improve speed.
	 */
	@Override
	public int indexOf(final char ch) {
		for (int j=0; j<this.sequence.length; ++j)
			if (this.sequence[j] == ch)
				return j;
		return -1;
	}

	/*
	 * Implementation Note: This is a reproduction of the AbstractRope
	 * indexOf implementation. Calls to charAt have been replaced
	 * with direct array access to improve speed.
	 */
	@Override
	public int indexOf(final char ch, final int fromIndex) {
		if (fromIndex < 0 || fromIndex >= this.length())
			throw new IndexOutOfBoundsException("Rope index out of range: " + fromIndex);
		for (int j=fromIndex; j<this.sequence.length; ++j)
			if (this.sequence[j] == ch)
				return j;
		return -1;
	}

	/*
	 * Implementation Note: This is a reproduction of the AbstractRope
	 * indexOf implementation. Calls to charAt have been replaced
	 * with direct array access to improve speed.
	 */
	@Override
	public int indexOf(final CharSequence sequence, final int fromIndex) {
		// Implementation of Boyer-Moore-Horspool algorithm with
		// special support for unicode.

		// step 0. sanity check.
		final int length = sequence.length();
		if (length == 0)
			return -1;
		if (length == 1)
			return this.indexOf(sequence.charAt(0), fromIndex);

		final int[] bcs = new int[256]; // bad character shift
		Arrays.fill(bcs, length);

		// step 1. preprocessing.
		for (int j=0; j<length-1; ++j) {
			final char c = sequence.charAt(j);
			final int l = (c & 0xFF);
			bcs[l] = Math.min(length - j - 1, bcs[l]);
		}

		// step 2. search.
		for (int j=fromIndex+length-1; j<this.length();) {
			int x=j, y=length-1;
			while (true) {
				if (sequence.charAt(y) != this.sequence[x]) {
					j += bcs[(this.sequence[x] & 0xFF)];
					break;
				}
				if (y == 0)
					return x;
				--x; --y;
			}

		}

		return -1;
	}

	@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 < FlatCharArrayRope.this.length();
			}

			@Override
			public Character next() {
				return FlatCharArrayRope.this.sequence[this.current++];
			}

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

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

	@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 = FlatCharArrayRope.this.length() - start;
			@Override
			public boolean hasNext() {
				return this.current > 0;
			}

			@Override
			public Character next() {
				return FlatCharArrayRope.this.sequence[--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 < 16) {
			return new FlatCharArrayRope(this.sequence, start, end-start);
		} else {
			return new SubstringRope(this, start, end-start);
		}
	}

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


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

	@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 {
		out.write(this.sequence, offset, length);
	}
}