/*
 * Copyright 2014 Open Networking Laboratory
 *
 * 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.onosproject.net.intent;


import java.util.Collections;
import java.util.List;

/**
 * Service for application submitting or withdrawing their intents.
 */
public interface IntentService {
    /**
     * Submits an intent into the system.
     * <p>
     * This is an asynchronous request meaning that any compiling or
     * installation activities may be done at later time.
     * </p>
     * @param intent intent to be submitted
     */
    void submit(Intent intent);

    /**
     * Withdraws an intent from the system.
     * <p>
     * This is an asynchronous request meaning that the environment may be
     * affected at later time.
     * </p>
     * @param intent intent to be withdrawn
     */
    void withdraw(Intent intent);

    /**
     * Fetches an intent based on its key.
     *
     * @param key key of the intent
     * @return intent object if the key is found, null otherwise
     */
    public Intent getIntent(Key key);

    /**
     * Returns an iterable of intents currently in the system.
     *
     * @return set of intents
     */
    Iterable<Intent> getIntents();

    /**
     * Returns the number of intents currently in the system.
     *
     * @return number of intents
     */
    long getIntentCount();

    /**
     * Retrieves the state of an intent by its identifier.
     *
     * @param intentKey intent identifier
     * @return the intent state or null if one with the given identifier is not
     * found
     */
    IntentState getIntentState(Key intentKey);

    /**
     * Returns the list of the installable events associated with the specified
     * top-level intent.
     *
     * @param intentKey top-level intent identifier
     * @return compiled installable intents
     */
    List<Intent> getInstallableIntents(Key intentKey);

    // TODO remove defaults
    default boolean isLocal(Key intentKey) {
        return true;
    }

    /**
     * Returns the list of intent requests pending processing.
     *
     * @return intents pending processing
     */
    default Iterable<Intent> getPending() {
        return Collections.emptyList();
    }

    /**
     * Adds the specified listener for intent events.
     *
     * @param listener listener to be added
     */
    void addListener(IntentListener listener);

    /**
     * Removes the specified listener for intent events.
     *
     * @param listener listener to be removed
     */
    void removeListener(IntentListener listener);
}