loggersoft.kotlin.utils.event.Signal.kt Maven / Gradle / Ivy

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/*
 * Copyright (C) 2018 Alexander Kornilov ([email protected])
 *
 * 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 loggersoft.kotlin.utils.event

/**
 * A receiver of the event.
 */
typealias Receiver = (sender: S, event: E) -> Unit

/**
 * Represents interface for subscription on an event.
 *
 * @author Alexander Kornilov ([email protected]).
 */
interface Subscription {

    /**
     * Subscribes [receiver] on signal.
     * Optional parameter [subscriber] is used to [unsubscribe].
     * @return [subscriber]
     */
    fun subscribe(subscriber: Any, receiver: Receiver): Any

    /**
     * Subscribes [receiver] on signal without possibility to [unsubscribe].
     */
    fun subscribe(receiver: Receiver) {
        subscribe(receiver, receiver)
    }

    /**
     * Unsubscribe [subscriber] from event.
     */
    fun unsubscribe(subscriber: Any): Boolean

    /**
     * Operator equivalent of [subscribe] without possibility to [unsubscribe].
     */
    operator fun plusAssign(receiver: Receiver)
            = subscribe(receiver)

    /**
     * Operator equivalent of [unsubscribe]
     */
    operator fun minusAssign(subscriber: Any) {
        unsubscribe(subscriber)
    }

    /**
     * Operator equivalent of [subscribe] with possibility to [unsubscribe].
     */
    operator fun set(index: Any, receiver: Receiver) {
        subscribe(index, receiver)
    }
}

/**
 * Represents interface of a signal for using inside sender object.
 *
 * @author Alexander Kornilov ([email protected]).
 */
interface Signal {

    /**
     * Sender object of signal.
     */
    val sender: S

    /**
     * Reference to subscription object: the public part of [Signal] interface.
     */
    val subscription: Subscription

    /**
     * Unmodified list of receivers.
     */
    val receivers: Collection>

    /**
     * Checks [subscriber] for presence in subscribers list.
     */
    fun hasSubscriber(subscriber: Any): Boolean

    /**
     * Unsubscribe all subscribers.
     */
    fun unsubscribeAll()

    /**
     * Emits signal for all receivers with specified [event].
     */
    fun emit(event: E)

    /**
     * Operator equivalent of [hasSubscriber].
     */
    operator fun contains(subscriber: Any): Boolean
            = hasSubscriber(subscriber)
}