alpha-wallet-ios/AlphaWallet/Core/MulticastDelegate.swift

//
//  MulticastDelegate.swift
//  MulticastDelegateDemo
//
//  Created by Joao Nunes on 28/12/15.
//  Copyright © 2015 Joao Nunes. All rights reserved.
//

import Foundation

/**
 *  `MulticastDelegate` lets you easily create a "multicast delegate" for a given protocol or class.
 */
open class MulticastDelegate<T> {

    /// The delegates hash table.
    private let delegates: NSHashTable<AnyObject>

    /**
     *  Use the property to check if no delegates are contained there.
     *
     *  - returns: `true` if there are no delegates at all, `false` if there is at least one.
     */
    public var isEmpty: Bool {
        return delegates.allObjects.isEmpty
    }

    /**
     *  Use this method to initialize a new `MulticastDelegate` specifying whether delegate references should be weak or
     *  strong.
     *
     *  - parameter strongReferences: Whether delegates should be strongly referenced, false by default.
     *
     *  - returns: A new `MulticastDelegate` instance
     */
    public init(strongReferences: Bool = false) {

        delegates = strongReferences ? NSHashTable<AnyObject>() : NSHashTable<AnyObject>.weakObjects()
    }

    /**
     *  Use this method to initialize a new `MulticastDelegate` specifying the storage options yourself.
     *
     *  - parameter options: The underlying storage options to use
     *
     *  - returns: A new `MulticastDelegate` instance
     */
    public init(options: NSPointerFunctions.Options) {

        delegates = NSHashTable<AnyObject>(options: options, capacity: 0)
    }

    /**
     *  Use this method to add a delelgate.
     *
     *  Alternatively, you can use the `+=` operator to add a delegate.
     *
     *  - parameter delegate:  The delegate to be added.
     */
    public func addDelegate(_ delegate: T) {

        delegates.add(delegate as AnyObject)
    }

    /**
     *  Use this method to remove a previously-added delegate.
     *
     *  Alternatively, you can use the `-=` operator to add a delegate.
     *
     *  - parameter delegate:  The delegate to be removed.
     */
    public func removeDelegate(_ delegate: T) {

        delegates.remove(delegate as AnyObject)
    }

    /**
     *  Use this method to invoke a closure on each delegate.
     *
     *  Alternatively, you can use the `|>` operator to invoke a given closure on each delegate.
     *
     *  - parameter invocation: The closure to be invoked on each delegate.
     */
    public func invokeDelegates(_ invocation: (T) -> ()) {

        for delegate in delegates.allObjects {
            invocation(delegate as! T)
        }
    }

    /**
     *  Use this method to determine if the multicast delegate contains a given delegate.
     *
     *  - parameter delegate:   The given delegate to check if it's contained
     *
     *  - returns: `true` if the delegate is found or `false` otherwise
     */
    public func containsDelegate(_ delegate: T) -> Bool {

        return delegates.contains(delegate as AnyObject)
    }
}

/**
 *  Use this operator to add a delegate.
 *
 *  This is a convenience operator for calling `addDelegate`.
 *
 *  - parameter left:   The multicast delegate
 *  - parameter right:  The delegate to be added
 */
public func +=<T>(left: MulticastDelegate<T>, right: T) {

    left.addDelegate(right)
}

/**
 *  Use this operator to remove a delegate.
 *
 *  This is a convenience operator for calling `removeDelegate`.
 *
 *  - parameter left:   The multicast delegate
 *  - parameter right:  The delegate to be removed
 */
public func -=<T>(left: MulticastDelegate<T>, right: T) {

    left.removeDelegate(right)
}

/**
 *  Use this operator invoke a closure on each delegate.
 *
 *  This is a convenience operator for calling `invokeDelegates`.
 *
 *  - parameter left:   The multicast delegate
 *  - parameter right:  The closure to be invoked on each delegate
 *
 *  - returns: The `MulticastDelegate` after all its delegates have been invoked
 */
precedencegroup MulticastPrecedence {
    associativity: left
    higherThan: TernaryPrecedence
}
infix operator |> : MulticastPrecedence
public func |><T>(left: MulticastDelegate<T>, right: (T) -> ()) {

    left.invokeDelegates(right)
}