/**
 * This file is part of the CRISTAL-iSE kernel.
 * Copyright (c) 2001-2014 The CRISTAL Consortium. All rights reserved.
 *
 * This library is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published
 * by the Free Software Foundation; either version 3 of the License, or (at
 * your option) any later version.
 *
 * This library is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; with out even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
 * License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
 *
 * http://www.fsf.org/licensing/licenses/lgpl.html
 */
package org.cristalise.kernel.collection;

import org.cristalise.kernel.common.InvalidCollectionModification;
import org.cristalise.kernel.common.ObjectAlreadyExistsException;
import org.cristalise.kernel.common.ObjectNotFoundException;
import org.cristalise.kernel.entity.C2KLocalObject;
import org.cristalise.kernel.graph.model.GraphModel;
import org.cristalise.kernel.lookup.ItemPath;
import org.cristalise.kernel.persistency.ClusterStorage;
import org.cristalise.kernel.utils.CastorHashMap;


/**
 * Collections are Item local objects that reference other Items.
 * 
 * <p>In parallel with the OO meta-model, Items can be linked to other Items in
 * different ways. These links are modelled with Collections, which are local
 * objects stored in an Item which reference a number of other Items in the same
 * server. The Collections holds a CollectionMember, sometimes known as a slot,
 * to reference each Item and store additional information about the link.
 * 
 * <p>Features:
 * <ul>
 * <li><b>Typing</b> - Collections can restrict membership of based on type 
 * information derived from Item, Property and Collection descriptions. This
 * restriction may be per-slot or apply to the whole Collection.
 * 
 * <li><b>Fixed or flexible slots</b> - The CollectionMember objects of a
 * Collection may be empty, individually typed, or created and removed as
 * required, simulating either array, structures or lists.
 * 
 * <li><b>Layout</b> - Collections can include a {@link GraphModel} to lay out
 * its slots on a two-dimensional canvas, for modelling real world compositions.
 * </ul>
 * 
 * <p>Collections are managed through predefined steps.
 */
abstract public class Collection<E extends CollectionMember> implements C2KLocalObject
{

	public static final short EMPTY = -1;
    private int mCounter = -1;      // Contains next available Member ID
    protected CollectionMemberList<E> mMembers = new CollectionMemberList<E>();
    protected String mName = "";     // Not checked for uniqueness
    protected Integer mVersion = null;

    /**
     * Fetch the current highest member ID of the collection. This is found by
     * scanning all the current members and kept in the mCounter field, but is 
     * not persistent.
     * @return the current highest member ID
     */
	public int getCounter()
    {
        if (mCounter == -1)
			for (E element : mMembers.list) {
            if (mCounter < element.getID())
                mCounter = element.getID();
        }
        return ++mCounter;
    }

	/**
	 * @return The total number of slots in this collection, including empty 
	 * ones 
	 */
	public int size()
    {
        return mMembers.list.size();
    }

	/**
	 * Sets the collection name
	 */
	@Override
	public void setName(String name)
    {
        mName = name;
    }

	/**
	 * @return The collection's name
	 */
	@Override
	public String getName()
    {
        return mName;
    }
	
	/**
	 * Get the collection version. Null if not set, and will be stored as 'last'
	 * @return Integer version
	 */
	public Integer getVersion() {
		return mVersion;
	}

	/**
	 * Set a named version for this collection. Must be an integer or null.
	 * Named versions will be stored separately to the current version ('last')
	 * and should not change once saved.
	 * 
	 * @param Integer version
	 */
	public void setVersion(Integer mVersion) {
		this.mVersion = mVersion;
	}

	/**
	 * Get the version name for storage, which is 'last' unless the version 
	 * number is set. 
	 * 
	 * @return 
	 */
	public String getVersionName() {
		return mVersion==null?"last":String.valueOf(mVersion);
	}
	
	@Override
	public String getClusterType()
    {
        return ClusterStorage.COLLECTION;
    }

	public void setMembers(CollectionMemberList<E> newMembers)
    {
    	mMembers = newMembers;
    }

    public boolean contains(ItemPath itemPath) {
        for (E element : mMembers.list) {
            if (element.getItemPath().equals(itemPath))
                return true;
        }
        return false;
    }
    
    /**
     * Gets the description version referenced by the given collection member. 
     * Assumes 'last' if version not given.
     * 
     * @param mem The member in question
     * @return String version tag
     */
    public String getDescVer(E mem) {
    	String descVer = "last";
    	Object descVerObj = mem.getProperties().get("Version");
    	if (descVerObj != null) descVer = descVerObj.toString();
    	return descVer;
    }

    /**
     * Check if all slots have an assigned Item
     * @return boolean
     */
    public boolean isFull()
    {
    	for (E element : mMembers.list) {
            if (element.getItemPath() == null)
                return false;
    	}
    	return true;
    }

    /**
     * Find collection member by integer ID
     * @param memberId to find
     * @return the CollectionMember with that ID
     * @throws ObjectNotFoundException when the ID wasn't found
     */
	public E getMember(int memberId) throws ObjectNotFoundException {
        for (E element : mMembers.list) {
            if (element.getID() == memberId)
                return element;
        }
        throw new ObjectNotFoundException("Member "+memberId+" not found in "+mName);
    }

	public CollectionMemberList<E> getMembers()
    {
        return mMembers;
    }

	/**
	 * Add a member to this collection, with the given property and class properties
	 * and optionally an Item to assign, which may be null if the collection allows 
	 * empty slots.
	 * 
	 * @param itemPath the Item to assign to the new slot. Optional for collections
	 * that allow empty slots
	 * @param props the Properties of the new member
	 * @param classProps the names of the properties that dictate the type of
	 * assigned Items.
	 * @return the new CollectionMember instance
	 * @throws InvalidCollectionModification when the assignment was invalid because 
	 * of collection constraints, such as global type constraints, or not allowing
	 * empty slots.
	 * @throws ObjectAlreadyExistsException some collections don't allow multiple 
	 * slots assigned to the same Item, and throw this Exception if it is attempted
	 */
	public abstract E addMember(ItemPath itemPath, CastorHashMap props, String classProps) throws InvalidCollectionModification, ObjectAlreadyExistsException;
	
	/**
	 * Removes the slot with the given ID from the collection.
	 * 
	 * @param memberId to remove
	 * @throws ObjectNotFoundException when there was no slot with this ID found.
	 */
	public abstract void removeMember(int memberId) throws ObjectNotFoundException;

	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		result = prime * result
				+ ((mMembers == null) ? 0 : mMembers.hashCode());
		result = prime * result + ((mName == null) ? 0 : mName.hashCode());
		return result;
	}

	@Override
	public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (obj == null)
			return false;
		if (getClass() != obj.getClass())
			return false;
		Collection<?> other = (Collection<?>) obj;
		if (mMembers == null) {
			if (other.mMembers != null)
				return false;
		} else if (!mMembers.equals(other.mMembers))
			return false;
		if (mName == null) {
			if (other.mName != null)
				return false;
		} else if (!mName.equals(other.mName))
			return false;
		return true;
	}
}