/*
 *  AbstractRope.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.ObjectStreamException;
import java.io.StringWriter;
import java.util.Arrays;
import java.util.Iterator;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.ahmadsoft.ropes.Rope;

/**
 * Abstract base class for ropes that implements many of the common operations.
 * @author Amin Ahmad
 */
public abstract class AbstractRope implements Rope {

	protected int hashCode = 0;

	@Override
	public Rope append(final char c) {
		return RopeUtilities.INSTANCE.concatenate(this, Rope.BUILDER.build(String.valueOf(c)));
	}

	@Override
	public Rope append(final CharSequence suffix) {
		return RopeUtilities.INSTANCE.concatenate(this, Rope.BUILDER.build(suffix));
	}

	@Override
	public Rope append(final CharSequence csq, final int start, final int end) {
		return RopeUtilities.INSTANCE.concatenate(this, Rope.BUILDER.build(csq).subSequence(start, end));
	}

	@Override
	public int compareTo(final CharSequence sequence) {
		final int compareTill = Math.min(sequence.length(), this.length());
		final Iterator<Character> i = this.iterator();
		for (int j=0; j<compareTill; ++j) {
			final char x = i.next();
			final char y = sequence.charAt(j);
			if (x != y)
				return x - y;
		}
		return this.length() - sequence.length();
	}

	@Override
	public Rope delete(final int start, final int end) {
		if (start == end)
			return this;
		return this.subSequence(0, start).append(this.subSequence(end, this.length()));
	}

	/*
	 * The depth of the current rope, as defined in "Ropes: an Alternative
	 * to Strings".
	 */
	public abstract byte depth();

	@Override
	public boolean equals(final Object other) {
		if (other instanceof Rope) {
			final Rope rope = (Rope) other;
			if (rope.hashCode() != this.hashCode() || rope.length() != this.length())
				return false;
			final Iterator<Character> i1 = this.iterator();
			final Iterator<Character> i2 = rope.iterator();

			while (i1.hasNext()) {
				final char a = i1.next();
				final char b = i2.next();
				if (a != b)
					return false;
			}
			return true;
		}
		return false;
	}

	/**
	 * A utility method that returns an instance of this rope optimized
	 * for sequential access.
	 * @return
	 */
	protected CharSequence getForSequentialAccess() {
		return this;
	}

	@Override
	public int hashCode() {
		if (this.hashCode == 0 && this.length() > 0) {
			if (this.length() < 6) {
				for (final char c: this)
					this.hashCode = 31 * this.hashCode + c;
			} else {
				final Iterator<Character> i = this.iterator();
				for (int j=0;j<5; ++j)
					this.hashCode = 31 * this.hashCode + i.next();
				this.hashCode = 31 * this.hashCode + this.charAt(this.length() - 1);
			}
		}
		return this.hashCode;
	}

	@Override
	public int indexOf(final char ch) {
		int index = -1;
		for (final char c: this) {
			++index;
			if (c == ch)
				return index;
		}
		return -1;
	}

    @Override
    public boolean startsWith(CharSequence prefix) {
    	return startsWith(prefix, 0);
    }
    
    @Override
    public boolean startsWith(CharSequence prefix, int offset) {
    	if (offset < 0 || offset > this.length())
    		throw new IndexOutOfBoundsException("Rope offset out of range: " + offset);
    	if (offset + prefix.length() > this.length())
    		return false;
    	
    	int x=0;
    	for (Iterator<Character> i=this.iterator(offset); i.hasNext() && x < prefix.length(); ) {
    		if (i.next().charValue() != prefix.charAt(x++))
    			return false;
    	}
    	return true;
    }
    
    @Override
    public boolean endsWith(CharSequence suffix) {
    	return endsWith(suffix, 0);
    }
    
    @Override
    public boolean endsWith(CharSequence suffix, int offset) {
    	return startsWith(suffix, length() - suffix.length() - offset);
    }

	@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);
		int index = fromIndex - 1;
		for (final Iterator<Character> i=this.iterator(fromIndex); i.hasNext(); ) {
			++index;
			if (i.next().charValue() == ch)
				return index;
		}
		return -1;
	}

	@Override
	public int indexOf(final CharSequence sequence) {
		return this.indexOf(sequence, 0);
	}

	@Override
	public int indexOf(final CharSequence sequence, final int fromIndex) {
		final CharSequence me = this.getForSequentialAccess();

		// 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) {
				final char c = me.charAt(x);
				if (sequence.charAt(y) != c) {
					j += bcs[(me.charAt(j) & 0xFF)];
					break;
				}
				if (y == 0)
					return x;
				--x; --y;
			}

		}

		return -1;
	}

	@Override
	public Rope insert(final int dstOffset, final CharSequence s) {
		final Rope r = (s == null) ? Rope.BUILDER.build("null"): Rope.BUILDER.build(s);
		if (dstOffset == 0)
			return r.append(this);
		else if (dstOffset == this.length())
			return this.append(r);
		else if (dstOffset < 0 || dstOffset > this.length())
			throw new IndexOutOfBoundsException(dstOffset + " is out of insert range [" + 0 + ":" + this.length() + "]");
		return this.subSequence(0, dstOffset).append(r).append(this.subSequence(dstOffset, this.length()));
	}

	@Override
	public Iterator<Character> iterator() {
		return this.iterator(0);
	}

	@Override
	public Rope trimStart() {
		int index = -1;
		for (final char c: this) {
			++index;
			if (c > 0x20 && !Character.isWhitespace(c))
				break;
		}
		if (index <= 0)
			return this;
		else
			return this.subSequence(index, this.length());
	}

	@Override
	public Matcher matcher(final Pattern pattern) {
		return pattern.matcher(this.getForSequentialAccess());
	}

	@Override
	public boolean matches(final Pattern regex) {
        return regex.matcher(this.getForSequentialAccess()).matches();
	}

	@Override
	public boolean matches(final String regex) {
        return Pattern.matches(regex, this.getForSequentialAccess());
	}

	@Override
	public Rope rebalance() {
		return this;
	}

	@Override
	public Iterator<Character> reverseIterator() {
		return this.reverseIterator(0);
	}

	@Override
	public Rope trimEnd() {
		int index = this.length() + 1;
		for (final Iterator<Character> i=this.reverseIterator(); i.hasNext();) {
			final char c = i.next();
			--index;
			if (c > 0x20 && !Character.isWhitespace(c))
				break;
		}
		if (index >= this.length())
			return this;
		else
			return this.subSequence(0, index);
	}

	@Override
	public String toString() {
		final StringWriter out = new StringWriter(this.length());
		try {
			this.write(out);
			out.close();
		} catch (final IOException e) {
			throw new RuntimeException(e);
		}
		return out.toString();
	}

	@Override
	public Rope trim() {
		return this.trimStart().trimEnd();
	}

	public Object writeReplace() throws ObjectStreamException {
		return new SerializedRope(this);
	}
	

	@Override
    public Rope padStart(final int toWidth) {
		return padStart(toWidth, ' ');
	}

	@Override
    public Rope padStart(final int toWidth, final char padChar) {
		final int toPad = toWidth - this.length();
		if (toPad < 1)
			return this;
		return RopeUtilities.INSTANCE.concatenate(
			Rope.BUILDER.build(new RepeatedCharacterSequence(padChar, toPad)), 
			this);
	}

	@Override
    public Rope padEnd(final int toWidth) {
		return padEnd(toWidth, ' ');
	}

	@Override
    public Rope padEnd(final int toWidth, final char padChar) {
		final int toPad = toWidth - this.length();
		if (toPad < 1)
			return this;
		return RopeUtilities.INSTANCE.concatenate( 
				this,
				Rope.BUILDER.build(new RepeatedCharacterSequence(padChar, toPad)));
	}
	
	@Override
    public boolean isEmpty() {
        return length() == 0;
    }
}