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/*
 * Copyright 2016-2017 Axioma srl.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
package com.holonplatform.vaadin7.data;

import java.io.Serializable;
import java.util.Collection;
import java.util.Optional;

import com.holonplatform.core.exceptions.DataAccessException;
import com.holonplatform.core.internal.utils.ObjectUtils;
import com.holonplatform.core.query.QueryConfigurationProvider;
import com.holonplatform.core.query.QuerySort;
import com.holonplatform.vaadin7.internal.data.DefaultItemSort;

/**
 * Represents an item set data source, providing operations to retrieve items by id and change the item set composition
 * adding a removing items.
 * 
 * Items values are accessed using a defined set of properties.
 * 
 * 
 * Item set modifications can be persisted in a backend data store using a {@link CommitHandler}, triggered through the
 * {@link #commit()} method.
 * 
 * 
 * @param  Item type
 * @param  Item property type
 * 
 * @since 5.0.0
 * 
 * @see ItemDataProvider
 */
public interface ItemDataSource extends Serializable {

	/**
	 * Get the data source configuration.
	 * @return Data source configuration (never null)
	 */
	Configuration getConfiguration();

	/**
	 * Refresh data source items.
	 * @throws DataAccessException Error performing concrete items loading operations
	 */
	void refresh();

	/**
	 * Clear data source contents (current item set)
	 */
	void clear();

	/**
	 * Returns current data source size (considering any applied filter), i.e. the total number of available items.
	 * @return the total number of available items in data source
	 */
	int size();

	/**
	 * Get all item ids available from this data source
	 * @return Item ids, empty if none
	 */
	Collection getItemIds();

	/**
	 * Get the identifier of given item
	 * @param item Item to get the identifier for
	 * @return Item identifier
	 */
	Object getId(ITEM item);

	/**
	 * Get the item identified by given itemId.
	 * @param itemId Item id (not null)
	 * @return Optional item identified by given itemId, empty if not found
	 */
	Optional get(Object itemId);

	/**
	 * Adds an item to the data source.
	 * @param item The item to add (not null)
	 * @return Id of the added item
	 */
	Object add(ITEM item);

	/**
	 * Update given item in data source.
	 * @param item Item to update (not null)
	 */
	void update(ITEM item);

	/**
	 * Removes given item from the data source.
	 * @param item Item to remove (not null)
	 * @return true if the item was successfully removed from data source
	 */
	boolean remove(ITEM item);

	/**
	 * Refresh given item in data source
	 * @param item Item to refresh (not null)
	 * @throws UnsupportedOperationException If the refresh operation is not supported by concrete data store
	 */
	void refresh(ITEM item);

	/**
	 * Updates all changes since the previous commit.
	 */
	void commit();

	/**
	 * Discards all changes since last commit.
	 */
	void discard();

	/**
	 * Get whether the data source is in buffered mode.
	 * @return whether the data source is in buffered mode
	 */
	boolean isBuffered();

	/**
	 * Sort the data source items using given {@link ItemSort} directives.
	 * @param sorts Item sorts to apply
	 */
	@SuppressWarnings("unchecked")
	void sort(ItemSort... sorts);

	/**
	 * Item actions enumeration.
	 */
	public enum ItemAction {

		/**
		 * An item was loaded
		 */
		LOADED,

		/**
		 * An item was added
		 */
		ADDED,

		/**
		 * An item was modified
		 */
		MODIFIED,

		/**
		 * An item was modified
		 */
		REFRESHED,

		/**
		 * An item was removed
		 */
		REMOVED,

		/**
		 * The item set changed
		 */
		SET_CHANGED;

	}

	// Data source configuration

	public interface Configuration extends QueryConfigurationProvider, Serializable {

		/**
		 * Get available item properties.
		 * @return Available item properties iterable
		 */
		Iterable getProperties();

		/**
		 * Gets the data type of the given data source property.
		 * @param property Property (not null)
		 * @return Property data type
		 */
		Class getPropertyType(PROPERTY property);

		/**
		 * Get whether the given property is read only.
		 * @param property Property (not null)
		 * @return true if property is read only, false otherwise
		 */
		boolean isPropertyReadOnly(PROPERTY property);

		/**
		 * Get whether the given property is sortable.
		 * @param property Property (not null)
		 * @return true if property is sortable, false otherwise
		 */
		boolean isPropertySortable(PROPERTY property);

		/**
		 * Get the default value for the given property.
		 * @param property Property (not null)
		 * @return Property default value, or null if not available
		 */
		Object getPropertyDefaultValue(PROPERTY property);

	}

	/**
	 * An item sort directive.
	 * @param  Item property type
	 */
	public interface ItemSort extends Serializable {

		/**
		 * Item property to sort
		 * @return Item property to sort
		 */
		PROPERTY getProperty();

		/**
		 * Sort direction
		 * @return true if ascending, false if descending
		 */
		boolean isAscending();

		/**
		 * Create an {@link ItemSort} using given property and sort direction.
		 * @param  Property type
		 * @param property Property to sort (not null)
		 * @param ascending true to sort ascending, false for descending
		 * @return Item sort
		 */
		static  ItemSort of(PROPERTY property, boolean ascending) {
			ObjectUtils.argumentNotNull(property, "Sort property must be not null");
			return new DefaultItemSort<>(property, ascending);
		}

		/**
		 * Create an ascending {@link ItemSort} using given property.
		 * @param  Property type
		 * @param property Property to sort (not null)
		 * @return Item sort
		 */
		static  ItemSort asc(PROPERTY property) {
			return of(property, true);
		}

		/**
		 * Create an descending {@link ItemSort} using given property.
		 * @param  Property type
		 * @param property Property to sort (not null)
		 * @return Item sort
		 */
		static  ItemSort desc(PROPERTY property) {
			return of(property, false);
		}

	}

	/**
	 * {@link QuerySort} generator to provide query sorts for an item property.
	 */
	@FunctionalInterface
	public interface PropertySortGenerator extends Serializable {

		/**
		 * Get the {@link QuerySort} to use for given property with specified sort direction.
		 * @param property Property to sort
		 * @param ascending Sort direction
		 * @return QuerySort
		 */
		QuerySort getQuerySort(PROPERTY property, boolean ascending);

	}

	/**
	 * Data source commit handler to perform concrete persistence operations when data is committed invoking
	 * {@link ItemDataSource#commit()}.
	 * @param  Item type
	 */
	@FunctionalInterface
	public interface CommitHandler extends Serializable {

		/**
		 * Commit item modifications.
		 * @param addedItems Added items: an empty collection if none
		 * @param modifiedItems Modified items: an empty collection if none
		 * @param removedItems Removed items: an empty collection if none
		 */
		void commit(Collection addedItems, Collection modifiedItems, Collection removedItems);

	}

}