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package org.apache.wicket.util.diff;

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

/**
 * Holds a information about a part of the text involved in a differencing or patching operation.
 * 
 * @version $Id: Chunk.java,v 1.1 2006/03/12 00:24:21 juanca Exp $
 * @author <a href="mailto:[email protected]">Juanco Anez</a>
 * @see Diff
 * @see Delta
 */
public class Chunk extends ToString
{

        protected int anchor;

        protected int count;

        protected List<Object> chunk;

        /**
         * Creates a chunk that doesn't copy the original text.
         * 
         * @param pos
         *            the start position in the text.
         * @param count
         *            the size of the chunk.
         */
        public Chunk(final int pos, final int count)
        {
                anchor = pos;
                this.count = (count >= 0 ? count : 0);
        }

        /**
         * Creates a chunk and saves a copy the original chunk's text.
         * 
         * @param iseq
         *            the original text.
         * @param pos
         *            the start position in the text.
         * @param count
         *            the size of the chunk.
         */
        public Chunk(final Object[] iseq, final int pos, final int count)
        {
                this(pos, count);
                chunk = slice(iseq, pos, count);
        }

        /**
         * Creates a chunk that will be displaced in the resulting text, and saves a copy the original
         * chunk's text.
         * 
         * @param iseq
         *            the original text.
         * @param pos
         *            the start position in the text.
         * @param count
         *            the size of the chunk.
         * @param offset
         *            the position the chunk should have in the resulting text.
         */
        public Chunk(final Object[] iseq, final int pos, final int count, final int offset)
        {
                this(offset, count);
                chunk = slice(iseq, pos, count);
        }

        /**
         * Creates a chunk and saves a copy the original chunk's text.
         * 
         * @param iseq
         *            the original text.
         * @param pos
         *            the start position in the text.
         * @param count
         *            the size of the chunk.
         */
        public Chunk(final List<Object> iseq, final int pos, final int count)
        {
                this(pos, count);
                chunk = slice(iseq, pos, count);
        }

        /**
         * Creates a chunk that will be displaced in the resulting text, and saves a copy the original
         * chunk's text.
         * 
         * @param iseq
         *            the original text.
         * @param pos
         *            the start position in the text.
         * @param count
         *            the size of the chunk.
         * @param offset
         *            the position the chunk should have in the resulting text.
         */
        public Chunk(final List<Object> iseq, final int pos, final int count, final int offset)
        {
                this(offset, count);
                chunk = slice(iseq, pos, count);
        }

        /**
         * Returns the anchor position of the chunk.
         * 
         * @return the anchor position.
         */
        public int anchor()
        {
                return anchor;
        }

        /**
         * Returns the size of the chunk.
         * 
         * @return the size.
         */
        public int size()
        {
                return count;
        }

        /**
         * Returns the index of the first line of the chunk.
         * 
         * @return int
         */
        public int first()
        {
                return anchor();
        }

        /**
         * Returns the index of the last line of the chunk.
         * 
         * @return int
         */
        public int last()
        {
                return anchor() + size() - 1;
        }

        /**
         * Returns the <i>from</i> index of the chunk in RCS terms.
         * 
         * @return int
         */
        public int rcsfrom()
        {
                return anchor + 1;
        }

        /**
         * Returns the <i>to</i> index of the chunk in RCS terms.
         * 
         * @return int
         */
        public int rcsto()
        {
                return anchor + count;
        }

        /**
         * Returns the text saved for this chunk.
         * 
         * @return the text.
         */
        public List<Object> chunk()
        {
                return chunk;
        }

        /**
         * Verifies that this chunk's saved text matches the corresponding text in the given sequence.
         * 
         * @param target
         *            the sequence to verify against.
         * @return true if the texts match.
         */
        public boolean verify(final List<Object> target)
        {
                if (chunk == null)
                {
                        return true;
                }
                if (last() > target.size())
                {
                        return false;
                }
                for (int i = 0; i < count; i++)
                {
                        if (!target.get(anchor + i).equals(chunk.get(i)))
                        {
                                return false;
                        }
                }
                return true;
        }

        /**
         * Delete this chunk from he given text.
         * 
         * @param target
         *            the text to delete from.
         */
        public void applyDelete(final List<Object> target)
        {
                for (int i = last(); i >= first(); i--)
                {
                        target.remove(i);
                }
        }

        /**
         * Add the text of this chunk to the target at the given position.
         * 
         * @param start
         *            where to add the text.
         * @param target
         *            the text to add to.
         */
        public void applyAdd(int start, final List<Object> target)
        {
                for (Object aChunk : chunk)
                {
                        target.add(start++, aChunk);
                }
        }

        /**
         * Provide a string image of the chunk using the an empty prefix and postfix.
         * 
         * @param s
         */
        @Override
        public void toString(final StringBuilder s)
        {
                toString(s, "", "");
        }

        /**
         * Provide a string image of the chunk using the given prefix and postfix.
         * 
         * @param s
         *            where the string image should be appended.
         * @param prefix
         *            the text that should prefix each line.
         * @param postfix
         *            the text that should end each line.
         * @return StringBuilder
         */
        public StringBuilder toString(final StringBuilder s, final String prefix, final String postfix)
        {
                if (chunk != null)
                {
                        for (Object aChunk : chunk)
                        {
                                s.append(prefix);
                                s.append(aChunk);
                                s.append(postfix);
                        }
                }
                return s;
        }

        /**
         * Retrieves the specified part from a {@link List List}.
         * 
         * @param <T>
         *            the type of objects contained in <code>seq</code>
         * 
         * @param seq
         *            the list to retrieve a slice from.
         * @param pos
         *            the start position.
         * @param count
         *            the number of items in the slice.
         * @return a {@link List List} containing the specified items.
         */
        public static <T> List<T> slice(final List<T> seq, final int pos, final int count)
        {
                if (count <= 0)
                {
                        return new ArrayList<>();
                }
                else
                {
                        return new ArrayList<>(seq.subList(pos, pos + count));
                }
        }

        /**
         * Retrieves a slice from an {@link Object Object} array.
         * 
         * @param seq
         *            the list to retrieve a slice from.
         * @param pos
         *            the start position.
         * @param count
         *            the number of items in the slice.
         * @return a {@link List List} containing the specified items.
         */
        public static List<Object> slice(final Object[] seq, final int pos, final int count)
        {
                return slice(Arrays.asList(seq), pos, count);
        }

        /**
         * Provide a string representation of the numeric range of this chunk.
         * 
         * @return String
         */
        public String rangeString()
        {
                StringBuilder result = new StringBuilder();
                rangeString(result);
                return result.toString();
        }

        /**
         * Provide a string representation of the numeric range of this chunk.
         * 
         * @param s
         *            where the string representation should be appended.
         */
        public void rangeString(final StringBuilder s)
        {
                rangeString(s, ",");
        }

        /**
         * Provide a string representation of the numeric range of this chunk.
         * 
         * @param s
         *            where the string representation should be appended.
         * @param separ
         *            what to use as line separator.
         */
        public void rangeString(final StringBuilder s, final String separ)
        {
                if (size() <= 1)
                {
                        s.append(Integer.toString(rcsfrom()));
                }
                else
                {
                        s.append(Integer.toString(rcsfrom()));
                        s.append(separ);
                        s.append(Integer.toString(rcsto()));
                }
        }
}