/*
 * Copyright 2004-2012 the original author or authors.
 *
 * 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 org.springframework.webflow.execution.repository.snapshot;

import java.io.Serializable;

import org.springframework.util.Assert;
import org.springframework.webflow.conversation.Conversation;
import org.springframework.webflow.conversation.ConversationManager;
import org.springframework.webflow.core.collection.MutableAttributeMap;
import org.springframework.webflow.execution.FlowExecution;
import org.springframework.webflow.execution.FlowExecutionKey;
import org.springframework.webflow.execution.repository.support.AbstractFlowExecutionRepository;
import org.springframework.webflow.execution.repository.support.CompositeFlowExecutionKey;

/**
 * Base class for repositories that take flow execution snapshots using a {@link FlowExecutionSnapshotFactory}.
 * 
 * @author Keith Donald
 */
public abstract class AbstractSnapshottingFlowExecutionRepository extends AbstractFlowExecutionRepository {

	/**
	 * The factory to use to take flow execution snapshots.
	 */
	private FlowExecutionSnapshotFactory snapshotFactory;

	/**
	 * Creates a new snapshotting flow execution repository.
	 * @param conversationManager the conversation manager
	 * @param snapshotFactory the execution snapshot factory
	 */
	public AbstractSnapshottingFlowExecutionRepository(ConversationManager conversationManager,
			FlowExecutionSnapshotFactory snapshotFactory) {
		super(conversationManager);
		Assert.notNull(snapshotFactory, "The flow execution snapshot factory is required");
		this.snapshotFactory = snapshotFactory;
	}

	/**
	 * Returns the configured flow execution snapshot factory.
	 * @return the snapshot factory
	 */
	public FlowExecutionSnapshotFactory getSnapshotFactory() {
		return snapshotFactory;
	}

	/**
	 * Returns the snapshotId portion of the flow execution key.
	 * @param key the execution key
	 */
	protected Serializable getSnapshotId(FlowExecutionKey key) {
		return ((CompositeFlowExecutionKey) key).getSnapshotId();
	}

	/**
	 * Take a new flow execution snapshot.
	 * @param flowExecution the execution to snapshot
	 * @return the snapshot
	 */
	protected FlowExecutionSnapshot snapshot(FlowExecution flowExecution) {
		return snapshotFactory.createSnapshot(flowExecution);
	}

	/**
	 * Restore a flow execution from a snapshot.
	 * @param snapshot the snapshot
	 * @param key the flow execution snapshot key
	 * @param conversation the governing conversation
	 * @return the restored flow execution
	 */
	@SuppressWarnings("unchecked")
	protected FlowExecution restoreFlowExecution(FlowExecutionSnapshot snapshot, FlowExecutionKey key,
			Conversation conversation) {
		MutableAttributeMap<Object> conversationScope = (MutableAttributeMap<Object>) conversation
				.getAttribute("scope");
		String flowId = (String) conversation.getAttribute("name");
		return snapshotFactory.restoreExecution(snapshot, flowId, key, conversationScope, this);
	}

	/**
	 * Puts the value of conversation scope in the conversation object.
	 * @param flowExecution the flow execution holding a reference to conversation scope
	 * @param conversation the conversation where conversation scope is stored
	 */
	protected void putConversationScope(FlowExecution flowExecution, Conversation conversation) {
		conversation.putAttribute("scope", flowExecution.getConversationScope());
	}
}