Bridging.swift

//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2016 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See http://swift.org/LICENSE.txt for license information
// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//

import CoreFoundation

// Support protocols for casting
public protocol _ObjectBridgeable {
    func _bridgeToAnyObject() -> AnyObject
}

public protocol _StructBridgeable {
    func _bridgeToAny() -> Any
}

/// - Note: This is a similar interface to the _ObjectiveCBridgeable protocol
public protocol _ObjectTypeBridgeable : _ObjectBridgeable {
    associatedtype _ObjectType : AnyObject
    
    func _bridgeToObjectiveC() -> _ObjectType
    
    static func _forceBridgeFromObjectiveC(_ source: _ObjectType, result: inout Self?)
    
    @discardableResult
    static func _conditionallyBridgeFromObjectiveC(_ source: _ObjectType, result: inout Self?) -> Bool
    
    static func _unconditionallyBridgeFromObjectiveC(_ source: _ObjectType?) -> Self
}

/// - Note: This does not exist currently on Darwin but it is the inverse correlation to the bridge types such that a 
/// reference type can be converted via a callout to a conversion method.
public protocol _StructTypeBridgeable : _StructBridgeable {
    associatedtype _StructType
    
    func _bridgeToSwift() -> _StructType
}

// Default adoption of the type specific variants to the Any variant
extension _ObjectTypeBridgeable {
    public func _bridgeToAnyObject() -> AnyObject {
        return _bridgeToObjectiveC()
    }
}

extension _StructTypeBridgeable {
    public func _bridgeToAny() -> Any {
        return _bridgeToSwift()
    }
}

// slated for removal, these are the swift-corelibs-only variant of the _ObjectiveCBridgeable
internal protocol _CFBridgeable {
    associatedtype CFType
    var _cfObject: CFType { get }
}

internal protocol _SwiftBridgeable {
    associatedtype SwiftType
    var _swiftObject: SwiftType { get }
}

internal protocol _NSBridgeable {
    associatedtype NSType
    var _nsObject: NSType { get }
}


/// - Note: This is an internal boxing value for containing abstract structures
internal final class _SwiftValue : NSObject, NSCopying {
    internal private(set) var value: Any
    
    static func fetch(_ object: AnyObject?) -> Any? {
        if let obj = object {
            return fetch(nonOptional: obj)
        }
        return nil
    }
    
    static func fetch(nonOptional object: AnyObject) -> Any {
        if object === kCFBooleanTrue {
            return true
        } else if object === kCFBooleanFalse {
            return false
        } else if let container = object as? _SwiftValue {
            return container.value
        } else if let val = object as? _StructBridgeable {
            return val._bridgeToAny()
        } else {
            return object
        }
    }
    
    static func store(_ value: Any?) -> NSObject? {
        if let val = value {
            return store(val)
        }
        return nil
    }
    
    static func store(_ value: Any) -> NSObject {
        if let val = value as? NSObject {
            return val
        } else if let val = value as? _ObjectBridgeable {
            return val._bridgeToAnyObject() as! NSObject
        } else {
            return _SwiftValue(value)
        }
    }
    
    init(_ value: Any) {
        self.value = value
    }
    
    override var hash: Int {
        if let hashable = value as? AnyHashable {
            return hashable.hashValue
        }
        return ObjectIdentifier(self).hashValue
    }
    
    override func isEqual(_ value: Any?) -> Bool {
        switch value {
        case let other as _SwiftValue:
            guard let left = other.value as? AnyHashable,
                let right = self.value as? AnyHashable else { return self === other }
            
            return left == right
        case let other as AnyHashable:
            guard let hashable = self.value as? AnyHashable else { return false }
            return other == hashable
        default:
            return false
        }
    }
    
    public func copy(with zone: NSZone?) -> Any {
        return _SwiftValue(value)
    }
}