// This Source Code is in the Public Domain per: http://litesoft.org/License.txt
package org.litesoft.core.util;

import java.util.*;

/**
 * In implementing classes, any bulk operations should be synchronized and probably call LLincModificationVersion!
 */
public abstract class NoEqualsCollection<E, C extends Comparable<C>> extends NoEqualsBase<E, C> implements Collection<E>
{
    private int mModificationVersion = 0;
    private Wrapper<E, C>[] mCachedWrappedEntries = null;

    protected NoEqualsCollection( NoEqualsHelper<E, C> pHelper )
    {
        super( pHelper );
    }

    abstract protected Collection<Wrapper<E, C>> LLgetCollection();

    protected final synchronized Wrapper<E, C>[] getWrappedEntries()
    {
        if ( mCachedWrappedEntries == null )
        {
            mCachedWrappedEntries = LLgetCollection().toArray( array( size() ) );
        }
        return mCachedWrappedEntries;
    }

    protected final synchronized void LLincModificationVersion()
    {
        mCachedWrappedEntries = null;
        mModificationVersion++;
    }

    protected final synchronized int LLgetModificationVersion()
    {
        return mModificationVersion;
    }

    /**
     * @param pWrap !null
     */
    protected final boolean LLadd( Wrapper<E, C> pWrap )
    {
        return LLgetCollection().add( pWrap );
    }

    /**
     * @param pWrap !null
     */
    protected final boolean LLremove( Wrapper<E, C> pWrap )
    {
        return LLgetCollection().remove( pWrap );
    }

    protected final int LLsize()
    {
        return LLgetCollection().size();
    }

    protected final void LLclear()
    {
        LLgetCollection().clear();
    }

    private boolean LLcontains( Wrapper<E, C>[] pWrappers, Object o )
    {
        E zObject = castNotNull( o );
        return LLobjectIsIn( zObject, pWrappers );
    }

    protected final boolean LLobjectIsIn( E pNotNullObject, Wrapper<E, C>[] pWrappers )
    {
        C toFind = mHelper.getProxyValue( pNotNullObject );
        for ( Wrapper<E, C> zWrapper : pWrappers )
        {
            if ( (pNotNullObject == zWrapper.getObject()) || areEqual( toFind, zWrapper.getProxyValue() ) )
            {
                return true;
            }
        }
        return false;
    }

    @SuppressWarnings({"ConstantConditions"})
    protected final E[] toTypedArray( Wrapper<E, C>[] pWrappers )
    {
        int zLength = (pWrappers != null) ? pWrappers.length : 0;
        E[] zEntries = mHelper.createArray( zLength );
        for ( int i = 0; i < zLength; i++ )
        {
            zEntries[i] = pWrappers[i].getObject();
        }
        return zEntries;
    }

    protected final boolean LLmodified( boolean pModified )
    {
        if ( pModified )
        {
            LLincModificationVersion();
        }
        return pModified;
    }

    /**
     * Returns the number of elements in this collection.  If this collection
     * contains more than <tt>Integer.MAX_VALUE</tt> elements, returns
     * <tt>Integer.MAX_VALUE</tt>.
     *
     * @return the number of elements in this collection
     */
    @Override
    public final synchronized int size()
    {
        return LLsize();
    }

    /**
     * Removes all of the elements from this collection (optional operation).
     * The collection will be empty after this method returns.
     *
     * @throws UnsupportedOperationException if the <tt>clear</tt> operation
     *                                       is not supported by this collection
     */
    @Override
    public final synchronized void clear()
    {
        if ( 0 != LLsize() )
        {
            LLclear();
            LLincModificationVersion();
        }
    }

    /**
     * Returns <tt>true</tt> if this collection contains no elements.
     *
     * @return <tt>true</tt> if this collection contains no elements
     */
    @Override
    public final boolean isEmpty()
    {
        return size() == 0;
    }

    /**
     * Returns <tt>true</tt> if this collection contains the specified element.
     * More formally, returns <tt>true</tt> if and only if this collection
     * contains at least one element <tt>e</tt> such that
     * <tt>(o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;o.equals(e))</tt>.
     *
     * @param o element whose presence in this collection is to be tested
     *
     * @return <tt>true</tt> if this collection contains the specified
     *         element
     *
     * @throws ClassCastException   if the type of the specified element
     *                              is incompatible with this collection (optional)
     * @throws NullPointerException if the specified element is null and this
     *                              collection does not permit null elements (optional)
     */
    @Override
    public final synchronized boolean contains( Object o )
    {
        return LLcontains( getWrappedEntries(), o );
    }

    /**
     * Returns an array containing all of the elements in this collection.
     * If this collection makes any guarantees as to what order its elements
     * are returned by its iterator, this method must return the elements in
     * the same order.
     * <p/>
     * <p>The returned array will be "safe" in that no references to it are
     * maintained by this collection.  (In other words, this method must
     * allocate a new array even if this collection is backed by an array).
     * The caller is thus free to modify the returned array.
     * <p/>
     * <p>This method acts as bridge between array-based and collection-based
     * APIs.
     *
     * @return an array containing all of the elements in this collection
     */
    @Override
    public final Object[] toArray()
    {
        return toTypedArray( getWrappedEntries() );
    }

    /**
     * Returns an array containing all of the elements in this collection;
     * the runtime type of the returned array is that of the specified array.
     * If the collection fits in the specified array, it is returned therein.
     * Otherwise, a new array is allocated with the runtime type of the
     * specified array and the size of this collection.
     * <p/>
     * <p>If this collection fits in the specified array with room to spare
     * (i.e., the array has more elements than this collection), the element
     * in the array immediately following the end of the collection is set to
     * <tt>null</tt>.  (This is useful in determining the length of this
     * collection <i>only</i> if the caller knows that this collection does
     * not contain any <tt>null</tt> elements.)
     * <p/>
     * <p>If this collection makes any guarantees as to what order its elements
     * are returned by its iterator, this method must return the elements in
     * the same order.
     * <p/>
     * <p>Like the {@link #toArray()} method, this method acts as bridge between
     * array-based and collection-based APIs.  Further, this method allows
     * precise control over the runtime type of the output array, and may,
     * under certain circumstances, be used to save allocation costs.
     * <p/>
     * <p>Suppose <tt>x</tt> is a collection known to contain only strings.
     * The following code can be used to dump the collection into a newly
     * allocated array of <tt>String</tt>:
     * <p/>
     * <pre>
     *     String[] y = x.toArray(new String[0]);</pre>
     *
     * Note that <tt>toArray(new Object[0])</tt> is identical in function to
     * <tt>toArray()</tt>.
     *
     * @param a the array into which the elements of this collection are to be
     *          stored, if it is big enough; otherwise, a new array of the same
     *          runtime type is allocated for this purpose.
     *
     * @return an array containing all of the elements in this collection
     *
     * @throws ArrayStoreException  if the runtime type of the specified array
     *                              is not a supertype of the runtime type of every element in
     *                              this collection
     * @throws NullPointerException if the specified array is null
     */
    @Override
    public final <T> T[] toArray( T[] a )
    {
        Wrapper<E, C>[] zWrappers = getWrappedEntries();
        List<Object> collector = new ArrayList<Object>( zWrappers.length );
        for ( Wrapper<E, C> zWrapper : zWrappers )
        {
            collector.add( zWrapper.getObject() );
        }
        //noinspection SuspiciousToArrayCall
        return collector.toArray( a );
    }

    /**
     * Ensures that this collection contains the specified element (optional
     * operation).  Returns <tt>true</tt> if this collection changed as a
     * result of the call.  (Returns <tt>false</tt> if this collection does
     * not permit duplicates and already contains the specified element.)<p>
     * <p/>
     * Collections that support this operation may place limitations on what
     * elements may be added to this collection.  In particular, some
     * collections will refuse to add <tt>null</tt> elements, and others will
     * impose restrictions on the type of elements that may be added.
     * Collection classes should clearly specify in their documentation any
     * restrictions on what elements may be added.<p>
     * <p/>
     * If a collection refuses to add a particular element for any reason
     * other than that it already contains the element, it <i>must</i> throw
     * an exception (rather than returning <tt>false</tt>).  This preserves
     * the invariant that a collection always contains the specified element
     * after this call returns.
     *
     * @param e element whose presence in this collection is to be ensured
     *
     * @return <tt>true</tt> if this collection changed as a result of the
     *         call
     *
     * @throws UnsupportedOperationException if the <tt>add</tt> operation
     *                                       is not supported by this collection
     * @throws ClassCastException            if the class of the specified element
     *                                       prevents it from being added to this collection
     * @throws NullPointerException          if the specified element is null and this
     *                                       collection does not permit null elements
     * @throws IllegalArgumentException      if some property of the element
     *                                       prevents it from being added to this collection
     * @throws IllegalStateException         if the element cannot be added at this
     *                                       time due to insertion restrictions
     */
    @Override
    public final synchronized boolean add( E e )
    {
        return LLmodified( LLadd( wrapNotNull( e ) ) );
    }

    /**
     * Removes a single instance of the specified element from this
     * collection, if it is present (optional operation).  More formally,
     * removes an element <tt>e</tt> such that
     * <tt>(o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;o.equals(e))</tt>, if
     * this collection contains one or more such elements.  Returns
     * <tt>true</tt> if this collection contained the specified element (or
     * equivalently, if this collection changed as a result of the call).
     *
     * @param o element to be removed from this collection, if present
     *
     * @return <tt>true</tt> if an element was removed as a result of this call
     *
     * @throws ClassCastException            if the type of the specified element
     *                                       is incompatible with this collection (optional)
     * @throws NullPointerException          if the specified element is null and this
     *                                       collection does not permit null elements (optional)
     * @throws UnsupportedOperationException if the <tt>remove</tt> operation
     *                                       is not supported by this collection
     */
    @Override
    public final synchronized boolean remove( Object o )
    {
        return LLmodified( LLremove( wrap( castNotNull( o ) ) ) );
    }

    /**
     * Returns <tt>true</tt> if this collection contains all of the elements
     * in the specified collection.
     *
     * @param c collection to be checked for containment in this collection
     *
     * @return <tt>true</tt> if this collection contains all of the elements
     *         in the specified collection
     *
     * @throws ClassCastException   if the types of one or more elements
     *                              in the specified collection are incompatible with this
     *                              collection (optional)
     * @throws NullPointerException if the specified collection contains one
     *                              or more null elements and this collection does not permit null
     *                              elements (optional), or if the specified collection is null
     * @see #contains(Object)
     */
    @Override
    public final boolean containsAll( Collection<?> c )
    {
        Object[] zObjects = c.toArray();
        synchronized ( this )
        {
            Wrapper<E, C>[] zWrappers = getWrappedEntries();
            for ( Object zEntry : zObjects )
            {
                if ( !LLcontains( zWrappers, zEntry ) )
                {
                    return false;
                }
            }
        }
        return true;
    }

    /**
     * Adds all of the elements in the specified collection to this collection
     * (optional operation).  The behavior of this operation is undefined if
     * the specified collection is modified while the operation is in progress.
     * (This implies that the behavior of this call is undefined if the
     * specified collection is this collection, and this collection is
     * nonempty.)
     *
     * @param c collection containing elements to be added to this collection
     *
     * @return <tt>true</tt> if this collection changed as a result of the call
     *
     * @throws UnsupportedOperationException if the <tt>addAll</tt> operation
     *                                       is not supported by this collection
     * @throws ClassCastException            if the class of an element of the specified
     *                                       collection prevents it from being added to this collection
     * @throws NullPointerException          if the specified collection contains a
     *                                       null element and this collection does not permit null elements,
     *                                       or if the specified collection is null
     * @throws IllegalArgumentException      if some property of an element of the
     *                                       specified collection prevents it from being added to this
     *                                       collection
     * @throws IllegalStateException         if not all the elements can be added at
     *                                       this time due to insertion restrictions
     * @see #add(Object)
     */
    @Override
    public final boolean addAll( Collection<? extends E> c )
    {
        E[] zEntries = c.toArray( mHelper.createArray( 0 ) );
        synchronized ( this )
        {
            boolean modified = false;
            for ( E zEntry : zEntries )
            {
                modified |= LLadd( wrapNotNull( zEntry ) );
            }
            return LLmodified( modified );
        }
    }

    /**
     * Removes all of this collection's elements that are also contained in the
     * specified collection (optional operation).  After this call returns,
     * this collection will contain no elements in common with the specified
     * collection.
     *
     * @param c collection containing elements to be removed from this collection
     *
     * @return <tt>true</tt> if this collection changed as a result of the
     *         call
     *
     * @throws UnsupportedOperationException if the <tt>removeAll</tt> method
     *                                       is not supported by this collection
     * @throws ClassCastException            if the types of one or more elements
     *                                       in this collection are incompatible with the specified
     *                                       collection (optional)
     * @throws NullPointerException          if this collection contains one or more
     *                                       null elements and the specified collection does not support
     *                                       null elements (optional), or if the specified collection is null
     * @see #remove(Object)
     * @see #contains(Object)
     */
    @Override
    public final boolean removeAll( Collection<?> c )
    {
        // Default Implementation uses modifiable Iterator!
        //
        //        boolean modified = false;
        //        Iterator<?> e = iterator();
        //        while ( e.hasNext() )
        //        {
        //            if ( c.contains( e.next() ) )
        //            {
        //                e.remove();
        //                modified = true;
        //            }
        //        }
        //        return modified;
        Object[] zObjects = c.toArray();
        synchronized ( this )
        {
            boolean modified = false;
            for ( Object zToRemove : zObjects )
            {
                if ( mHelper.isInstance( zToRemove ) )
                {
                    modified |= LLremove( wrap( castNullOK( zToRemove ) ) );
                }
            }
            return LLmodified( modified );
        }
    }

    /**
     * Retains only the elements in this collection that are contained in the
     * specified collection (optional operation).  In other words, removes from
     * this collection all of its elements that are not contained in the
     * specified collection.
     *
     * @param c collection containing elements to be retained in this collection
     *
     * @return <tt>true</tt> if this collection changed as a result of the call
     *
     * @throws UnsupportedOperationException if the <tt>retainAll</tt> operation
     *                                       is not supported by this collection
     * @throws ClassCastException            if the types of one or more elements
     *                                       in this collection are incompatible with the specified
     *                                       collection (optional)
     * @throws NullPointerException          if this collection contains one or more
     *                                       null elements and the specified collection does not permit null
     *                                       elements (optional), or if the specified collection is null
     * @see #remove(Object)
     * @see #contains(Object)
     */
    @Override
    public final synchronized boolean retainAll( Collection<?> c )
    {
        // Default Implementation uses modifiable Iterator!
        //
        //        boolean modified = false;
        //        Iterator<E> e = iterator();
        //        while ( e.hasNext() )
        //        {
        //            if ( !c.contains( e.next() ) )
        //            {
        //                e.remove();
        //                modified = true;
        //            }
        //        }
        //        return modified;
        boolean modified = false;
        for ( Wrapper<E, C> zWrapper : getWrappedEntries() )
        {
            if ( !c.contains( zWrapper.getObject() ) )
            {
                modified |= LLremove( zWrapper );
            }
        }
        return LLmodified( modified );
    }

    /**
     * Returns the hash code value for this collection.
     * <p/>
     * The hash code is defined to be the sum of the hash codes of the
     * elements in the collection.  While this calculation is sub-optimal for
     * lists, it is required for sets, and is adequate for lists.
     * <p/>
     * This ensures that collections that are equal have the same hashcode,
     * as required by the general contract of {@link Object#hashCode}.
     *
     * @return the hash code value for this list
     */
    public final int hashCode()
    {
        int hashcode = 1;
        for ( Wrapper<E, C> zWrapper : getWrappedEntries() )
        {
            C zProxyValue = zWrapper.getProxyValue();
            if ( zProxyValue != null )
            {
                hashcode += zProxyValue.hashCode();
            }
        }
        return hashcode;
    }

    /**
     * Returns a string representation of this collection.  The string
     * representation consists of a list of the collection's elements in the
     * order they are returned by its iterator, enclosed in square brackets
     * (<tt>"[]"</tt>).  Adjacent elements are separated by the characters
     * <tt>", "</tt> (comma and space).  Elements are converted to strings as
     * by {@link String#valueOf(Object)}.
     *
     * @return a string representation of this collection
     */
    public String toString()
    {
        if ( isEmpty() )
        {
            return "[]";
        }

        StringBuilder sb = new StringBuilder();
        String prefix = "[";
        for ( Object zEntry : toArray() )
        {
            sb.append( prefix ).append( zEntry == this ? "(this Collection)" : zEntry );
            prefix = ", ";
        }
        return sb.append( ']' ).toString();
    }

    /**
     * Returns an iterator over the elements in this collection.  There are no
     * guarantees concerning the order in which the elements are returned
     * (unless this collection is an instance of some class that provides a
     * guarantee).
     *
     * @return an <tt>Iterator</tt> over the elements in this collection
     */
    @Override
    public final Iterator<E> iterator()
    {
        ModVersionedEntries<E, C> zModVersionedEntries = getModVersionedEntries();
        return new OurIterator( 0, zModVersionedEntries.getWrappers().length, 0, zModVersionedEntries );
    }

    protected final Object getSynchronizedObject()
    {
        return this;
    }

    protected final synchronized ModVersionedEntries<E, C> getModVersionedEntries()
    {
        return new ModVersionedEntries<E, C>( LLgetModificationVersion(), getWrappedEntries() );
    }

    protected static class ModVersionedEntries<E, C extends Comparable<C>>
    {
        private int mModificationVersion;
        private Wrapper<E, C>[] mWrappers;

        public ModVersionedEntries( int pModificationVersion, Wrapper<E, C>[] pWrappers )
        {
            mModificationVersion = pModificationVersion;
            mWrappers = pWrappers;
        }

        public int getModificationVersion()
        {
            return mModificationVersion;
        }

        public Wrapper<E, C>[] getWrappers()
        {
            return mWrappers;
        }
    }

    protected final void LLcheckForComodification( int mExpectedModificationVersion )
    {
        if ( mExpectedModificationVersion != LLgetModificationVersion() )
        {
            throw new ConcurrentModificationException();
        }
    }

    protected class OurIterator implements Iterator<E>
    {
        protected void checkForComodification()
        {
            LLcheckForComodification( mModificationVersion );
        }

        private final int mModificationVersion;
        protected final E[] mEntries;
        protected final int mToIndex;
        protected int mNextIndex;

        protected OurIterator( int pFromIndex, int pSize, int pNextIndex, ModVersionedEntries<E, C> pModVersionedEntries )
        {
            mNextIndex = pFromIndex + pNextIndex;
            mModificationVersion = pModVersionedEntries.getModificationVersion();
            mEntries = toTypedArray( pModVersionedEntries.getWrappers() );
            mToIndex = pFromIndex + pSize;
        }

        /**
         * Returns <tt>true</tt> if the iteration has more elements. (In other
         * words, returns <tt>true</tt> if <tt>next</tt> would return an element
         * rather than throwing an exception.)
         *
         * @return <tt>true</tt> if the iterator has more elements.
         */
        @Override
        public boolean hasNext()
        {
            return (mNextIndex < mToIndex);
        }

        /**
         * Returns the next element in the iteration.
         *
         * @return the next element in the iteration.
         *
         * @throws NoSuchElementException iteration has no more elements.
         */
        @Override
        public E next()
        {
            checkForComodification();
            if ( !hasNext() )
            {
                throw new NoSuchElementException();
            }
            return mEntries[mNextIndex++];
        }

        /**
         * Removes from the underlying collection the last element returned by the
         * iterator (optional operation).  This method can be called only once per
         * call to <tt>next</tt>.  The behavior of an iterator is unspecified if
         * the underlying collection is modified while the iteration is in
         * progress in any way other than by calling this method.
         *
         * @throws UnsupportedOperationException if the <tt>remove</tt>
         *                                       operation is not supported by this Iterator.
         * @throws IllegalStateException         if the <tt>next</tt> method has not
         *                                       yet been called, or the <tt>remove</tt> method has already
         *                                       been called after the last call to the <tt>next</tt>
         *                                       method.
         */
        @Override
        public void remove()
        {
            throw new UnsupportedOperationException();
        }
    }
}