//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//

//===----------------------------------------------------------------------===//
// Plist Encoder
//===----------------------------------------------------------------------===//

/// `PropertyListEncoder` facilitates the encoding of `Encodable` values into property lists.
open class PropertyListEncoder {

    // MARK: - Options

    /// The output format to write the property list data in. Defaults to `.binary`.
    open var outputFormat: PropertyListSerialization.PropertyListFormat = .binary

    /// Contextual user-provided information for use during encoding.
    open var userInfo: [CodingUserInfoKey : Any] = [:]

    /// Options set on the top-level encoder to pass down the encoding hierarchy.
    fileprivate struct _Options {
        let outputFormat: PropertyListSerialization.PropertyListFormat
        let userInfo: [CodingUserInfoKey : Any]
    }

    /// The options set on the top-level encoder.
    fileprivate var options: _Options {
        return _Options(outputFormat: outputFormat, userInfo: userInfo)
    }

    // MARK: - Constructing a Property List Encoder

    /// Initializes `self` with default strategies.
    public init() {}

    // MARK: - Encoding Values

    /// Encodes the given top-level value and returns its property list representation.
    ///
    /// - parameter value: The value to encode.
    /// - returns: A new `Data` value containing the encoded property list data.
    /// - throws: `EncodingError.invalidValue` if a non-conforming floating-point value is encountered during encoding, and the encoding strategy is `.throw`.
    /// - throws: An error if any value throws an error during encoding.
    open func encode<Value : Encodable>(_ value: Value) throws -> Data {
        let encoder = _PlistEncoder(options: self.options)
        try value.encode(to: encoder)

        guard encoder.storage.count > 0 else {
            throw EncodingError.invalidValue(value,
                                             EncodingError.Context(codingPath: [],
                                                                   debugDescription: "Top-level \(Value.self) did not encode any values."))
        }

        let topLevel = encoder.storage.popContainer()
        if topLevel is NSNumber {
            throw EncodingError.invalidValue(value,
                                             EncodingError.Context(codingPath: [],
                                                                   debugDescription: "Top-level \(Value.self) encoded as number property list fragment."))
        } else if topLevel is NSString {
            throw EncodingError.invalidValue(value,
                                             EncodingError.Context(codingPath: [],
                                                                   debugDescription: "Top-level \(Value.self) encoded as string property list fragment."))
        } else if topLevel is NSDate {
            throw EncodingError.invalidValue(value,
                                             EncodingError.Context(codingPath: [],
                                                                   debugDescription: "Top-level \(Value.self) encoded as date property list fragment."))
        }

        do {
            return try PropertyListSerialization.data(fromPropertyList: topLevel, format: self.outputFormat, options: 0)
        } catch {
            throw EncodingError.invalidValue(value, EncodingError.Context(codingPath: [], debugDescription: "Unable to encode the given top-level value as a property list", underlyingError: error))
        }
    }
}

// MARK: - _PlistEncoder

fileprivate class _PlistEncoder : Encoder {
    // MARK: Properties

    /// The encoder's storage.
    fileprivate var storage: _PlistEncodingStorage

    /// Options set on the top-level encoder.
    fileprivate let options: PropertyListEncoder._Options

    /// The path to the current point in encoding.
    fileprivate(set) public var codingPath: [CodingKey?]

    /// Contextual user-provided information for use during encoding.
    public var userInfo: [CodingUserInfoKey : Any] {
        return self.options.userInfo
    }

    // MARK: - Initialization

    /// Initializes `self` with the given top-level encoder options.
    fileprivate init(options: PropertyListEncoder._Options, codingPath: [CodingKey?] = []) {
        self.options = options
        self.storage = _PlistEncodingStorage()
        self.codingPath = codingPath
    }

    // MARK: - Coding Path Operations

    /// Performs the given closure with the given key pushed onto the end of the current coding path.
    ///
    /// - parameter key: The key to push. May be nil for unkeyed containers.
    /// - parameter work: The work to perform with the key in the path.
    fileprivate func with<T>(pushedKey key: CodingKey?, _ work: () throws -> T) rethrows -> T {
        self.codingPath.append(key)
        let ret: T = try work()
        self.codingPath.removeLast()
        return ret
    }

    /// Returns whether a new element can be encoded at this coding path.
    ///
    /// `true` if an element has not yet been encoded at this coding path; `false` otherwise.
    fileprivate var canEncodeNewValue: Bool {
        // Every time a new value gets encoded, the key it's encoded for is pushed onto the coding path (even if it's a nil key from an unkeyed container).
        // At the same time, every time a container is requested, a new value gets pushed onto the storage stack.
        // If there are more values on the storage stack than on the coding path, it means the value is requesting more than one container, which violates the precondition.
        //
        // This means that anytime something that can request a new container goes onto the stack, we MUST push a key onto the coding path.
        // Things which will not request containers do not need to have the coding path extended for them (but it doesn't matter if it is, because they will not reach here).
        return self.storage.count == self.codingPath.count
    }

    // MARK: - Encoder Methods
    public func container<Key>(keyedBy: Key.Type) -> KeyedEncodingContainer<Key> {
        // If an existing keyed container was already requested, return that one.
        let topContainer: NSMutableDictionary
        if self.canEncodeNewValue {
            // We haven't yet pushed a container at this level; do so here.
            topContainer = self.storage.pushKeyedContainer()
        } else {
            guard let container = self.storage.containers.last as? NSMutableDictionary else {
                preconditionFailure("Attempt to push new keyed encoding container when already previously encoded at this path.")
            }

            topContainer = container
        }

        let container = _PlistKeyedEncodingContainer<Key>(referencing: self, codingPath: self.codingPath, wrapping: topContainer)
        return KeyedEncodingContainer(container)
    }

    public func unkeyedContainer() -> UnkeyedEncodingContainer {
        // If an existing unkeyed container was already requested, return that one.
        let topContainer: NSMutableArray
        if self.canEncodeNewValue {
            // We haven't yet pushed a container at this level; do so here.
            topContainer = self.storage.pushUnkeyedContainer()
        } else {
            guard let container = self.storage.containers.last as? NSMutableArray else {
                preconditionFailure("Attempt to push new unkeyed encoding container when already previously encoded at this path.")
            }

            topContainer = container
        }

        return _PlistUnkeyedEncodingContainer(referencing: self, codingPath: self.codingPath, wrapping: topContainer)
    }

    public func singleValueContainer() -> SingleValueEncodingContainer {
        return self
    }
}

// MARK: - Encoding Storage and Containers

fileprivate struct _PlistEncodingStorage {
    // MARK: Properties

    /// The container stack.
    /// Elements may be any one of the plist types (NSNumber, NSString, NSDate, NSArray, NSDictionary).
    private(set) fileprivate var containers: [NSObject] = []

    // MARK: - Initialization

    /// Initializes `self` with no containers.
    fileprivate init() {}

    // MARK: - Modifying the Stack

    fileprivate var count: Int {
        return self.containers.count
    }

    fileprivate mutating func pushKeyedContainer() -> NSMutableDictionary {
        let dictionary = NSMutableDictionary()
        self.containers.append(dictionary)
        return dictionary
    }

    fileprivate mutating func pushUnkeyedContainer() -> NSMutableArray {
        let array = NSMutableArray()
        self.containers.append(array)
        return array
    }

    fileprivate mutating func push(container: NSObject) {
        self.containers.append(container)
    }

    fileprivate mutating func popContainer() -> NSObject {
        precondition(self.containers.count > 0, "Empty container stack.")
        return self.containers.popLast()!
    }
}

// MARK: - Encoding Containers

fileprivate struct _PlistKeyedEncodingContainer<K : CodingKey> : KeyedEncodingContainerProtocol {
    typealias Key = K

    // MARK: Properties

    /// A reference to the encoder we're writing to.
    private let encoder: _PlistEncoder

    /// A reference to the container we're writing to.
    private let container: NSMutableDictionary

    /// The path of coding keys taken to get to this point in encoding.
    private(set) public var codingPath: [CodingKey?]

    // MARK: - Initialization

    /// Initializes `self` with the given references.
    fileprivate init(referencing encoder: _PlistEncoder, codingPath: [CodingKey?], wrapping container: NSMutableDictionary) {
        self.encoder = encoder
        self.codingPath = codingPath
        self.container = container
    }

    // MARK: - Coding Path Operations

    /// Performs the given closure with the given key pushed onto the end of the current coding path.
    ///
    /// - parameter key: The key to push. May be nil for unkeyed containers.
    /// - parameter work: The work to perform with the key in the path.
    fileprivate mutating func with<T>(pushedKey key: CodingKey?, _ work: () throws -> T) rethrows -> T {
        self.codingPath.append(key)
        let ret: T = try work()
        self.codingPath.removeLast()
        return ret
    }

    // MARK: - KeyedEncodingContainerProtocol Methods

    public mutating func encodeNil(forKey key: Key)               throws { self.container[key.stringValue] = _plistNullNSString }
    public mutating func encode(_ value: Bool, forKey key: Key)   throws { self.container[key.stringValue] = self.encoder.box(value) }
    public mutating func encode(_ value: Int, forKey key: Key)    throws { self.container[key.stringValue] = self.encoder.box(value) }
    public mutating func encode(_ value: Int8, forKey key: Key)   throws { self.container[key.stringValue] = self.encoder.box(value) }
    public mutating func encode(_ value: Int16, forKey key: Key)  throws { self.container[key.stringValue] = self.encoder.box(value) }
    public mutating func encode(_ value: Int32, forKey key: Key)  throws { self.container[key.stringValue] = self.encoder.box(value) }
    public mutating func encode(_ value: Int64, forKey key: Key)  throws { self.container[key.stringValue] = self.encoder.box(value) }
    public mutating func encode(_ value: UInt, forKey key: Key)   throws { self.container[key.stringValue] = self.encoder.box(value) }
    public mutating func encode(_ value: UInt8, forKey key: Key)  throws { self.container[key.stringValue] = self.encoder.box(value) }
    public mutating func encode(_ value: UInt16, forKey key: Key) throws { self.container[key.stringValue] = self.encoder.box(value) }
    public mutating func encode(_ value: UInt32, forKey key: Key) throws { self.container[key.stringValue] = self.encoder.box(value) }
    public mutating func encode(_ value: UInt64, forKey key: Key) throws { self.container[key.stringValue] = self.encoder.box(value) }
    public mutating func encode(_ value: String, forKey key: Key) throws { self.container[key.stringValue] = self.encoder.box(value) }
    public mutating func encode(_ value: Float, forKey key: Key)  throws { self.container[key.stringValue] = self.encoder.box(value) }
    public mutating func encode(_ value: Double, forKey key: Key) throws { self.container[key.stringValue] = self.encoder.box(value) }

    public mutating func encode<T : Encodable>(_ value: T, forKey key: Key) throws {
        try self.encoder.with(pushedKey: key) {
            self.container[key.stringValue] = try self.encoder.box(value)
        }
    }

    public mutating func nestedContainer<NestedKey>(keyedBy keyType: NestedKey.Type, forKey key: Key) -> KeyedEncodingContainer<NestedKey> {
        let dictionary = NSMutableDictionary()
        self.container[key.stringValue] = dictionary

        return self.with(pushedKey: key) {
            let container = _PlistKeyedEncodingContainer<NestedKey>(referencing: self.encoder, codingPath: self.codingPath, wrapping: dictionary)
            return KeyedEncodingContainer(container)
        }
    }

    public mutating func nestedUnkeyedContainer(forKey key: Key) -> UnkeyedEncodingContainer {
        let array = NSMutableArray()
        self.container[key.stringValue] = array

        return self.with(pushedKey: key) {
            return _PlistUnkeyedEncodingContainer(referencing: self.encoder, codingPath: self.codingPath, wrapping: array)
        }
    }

    public mutating func superEncoder() -> Encoder {
        return _PlistReferencingEncoder(referencing: self.encoder, at: _PlistSuperKey.super, wrapping: self.container)
    }

    public mutating func superEncoder(forKey key: Key) -> Encoder {
        return _PlistReferencingEncoder(referencing: self.encoder, at: key, wrapping: self.container)
    }
}

fileprivate struct _PlistUnkeyedEncodingContainer : UnkeyedEncodingContainer {
    // MARK: Properties

    /// A reference to the encoder we're writing to.
    private let encoder: _PlistEncoder

    /// A reference to the container we're writing to.
    private let container: NSMutableArray

    /// The path of coding keys taken to get to this point in encoding.
    private(set) public var codingPath: [CodingKey?]

    // MARK: - Initialization

    /// Initializes `self` with the given references.
    fileprivate init(referencing encoder: _PlistEncoder, codingPath: [CodingKey?], wrapping container: NSMutableArray) {
        self.encoder = encoder
        self.codingPath = codingPath
        self.container = container
    }

    // MARK: - Coding Path Operations

    /// Performs the given closure with the given key pushed onto the end of the current coding path.
    ///
    /// - parameter key: The key to push. May be nil for unkeyed containers.
    /// - parameter work: The work to perform with the key in the path.
    fileprivate mutating func with<T>(pushedKey key: CodingKey?, _ work: () throws -> T) rethrows -> T {
        self.codingPath.append(key)
        let ret: T = try work()
        self.codingPath.removeLast()
        return ret
    }

    // MARK: - UnkeyedEncodingContainer Methods

    public mutating func encodeNil()             throws { self.container.add(_plistNullNSString) }
    public mutating func encode(_ value: Bool)   throws { self.container.add(self.encoder.box(value)) }
    public mutating func encode(_ value: Int)    throws { self.container.add(self.encoder.box(value)) }
    public mutating func encode(_ value: Int8)   throws { self.container.add(self.encoder.box(value)) }
    public mutating func encode(_ value: Int16)  throws { self.container.add(self.encoder.box(value)) }
    public mutating func encode(_ value: Int32)  throws { self.container.add(self.encoder.box(value)) }
    public mutating func encode(_ value: Int64)  throws { self.container.add(self.encoder.box(value)) }
    public mutating func encode(_ value: UInt)   throws { self.container.add(self.encoder.box(value)) }
    public mutating func encode(_ value: UInt8)  throws { self.container.add(self.encoder.box(value)) }
    public mutating func encode(_ value: UInt16) throws { self.container.add(self.encoder.box(value)) }
    public mutating func encode(_ value: UInt32) throws { self.container.add(self.encoder.box(value)) }
    public mutating func encode(_ value: UInt64) throws { self.container.add(self.encoder.box(value)) }
    public mutating func encode(_ value: Float)  throws { self.container.add(self.encoder.box(value)) }
    public mutating func encode(_ value: Double) throws { self.container.add(self.encoder.box(value)) }
    public mutating func encode(_ value: String) throws { self.container.add(self.encoder.box(value)) }

    public mutating func encode<T : Encodable>(_ value: T) throws {
        try self.encoder.with(pushedKey: nil) {
            self.container.add(try self.encoder.box(value))
        }
    }

    public mutating func nestedContainer<NestedKey>(keyedBy keyType: NestedKey.Type) -> KeyedEncodingContainer<NestedKey> {
        let dictionary = NSMutableDictionary()
        self.container.add(dictionary)

        return self.with(pushedKey: nil) {
            let container = _PlistKeyedEncodingContainer<NestedKey>(referencing: self.encoder, codingPath: self.codingPath, wrapping: dictionary)
            return KeyedEncodingContainer(container)
        }
    }

    public mutating func nestedUnkeyedContainer() -> UnkeyedEncodingContainer {
        let array = NSMutableArray()
        self.container.add(array)

        return self.with(pushedKey: nil) {
            return _PlistUnkeyedEncodingContainer(referencing: self.encoder, codingPath: self.codingPath, wrapping: array)
        }
    }

    public mutating func superEncoder() -> Encoder {
        return _PlistReferencingEncoder(referencing: self.encoder, at: self.container.count, wrapping: self.container)
    }
}

extension _PlistEncoder : SingleValueEncodingContainer {
    // MARK: - SingleValueEncodingContainer Methods

    private func assertCanEncodeNewValue() {
        precondition(self.canEncodeNewValue, "Attempt to encode value through single value container when previously value already encoded.")
    }

    public func encodeNil() throws {
        assertCanEncodeNewValue()
        self.storage.push(container: _plistNullNSString)
    }

    public func encode(_ value: Bool) throws {
        assertCanEncodeNewValue()
        self.storage.push(container: box(value))
    }

    public func encode(_ value: Int) throws {
        assertCanEncodeNewValue()
        self.storage.push(container: box(value))
    }

    public func encode(_ value: Int8) throws {
        assertCanEncodeNewValue()
        self.storage.push(container: box(value))
    }

    public func encode(_ value: Int16) throws {
        assertCanEncodeNewValue()
        self.storage.push(container: box(value))
    }

    public func encode(_ value: Int32) throws {
        assertCanEncodeNewValue()
        self.storage.push(container: box(value))
    }

    public func encode(_ value: Int64) throws {
        assertCanEncodeNewValue()
        self.storage.push(container: box(value))
    }

    public func encode(_ value: UInt) throws {
        assertCanEncodeNewValue()
        self.storage.push(container: box(value))
    }

    public func encode(_ value: UInt8) throws {
        assertCanEncodeNewValue()
        self.storage.push(container: box(value))
    }

    public func encode(_ value: UInt16) throws {
        assertCanEncodeNewValue()
        self.storage.push(container: box(value))
    }

    public func encode(_ value: UInt32) throws {
        assertCanEncodeNewValue()
        self.storage.push(container: box(value))
    }

    public func encode(_ value: UInt64) throws {
        assertCanEncodeNewValue()
        self.storage.push(container: box(value))
    }

    public func encode(_ value: String) throws {
        assertCanEncodeNewValue()
        self.storage.push(container: box(value))
    }

    public func encode(_ value: Float) throws {
        assertCanEncodeNewValue()
        self.storage.push(container: box(value))
    }

    public func encode(_ value: Double) throws {
        assertCanEncodeNewValue()
        self.storage.push(container: box(value))
    }

    public func encode<T : Encodable>(_ value: T) throws {
        assertCanEncodeNewValue()
        try self.storage.push(container: box(value))
    }
}

// MARK: - Concrete Value Representations

extension _PlistEncoder {

    /// Returns the given value boxed in a container appropriate for pushing onto the container stack.
    fileprivate func box(_ value: Bool)   -> NSObject { return NSNumber(value: value) }
    fileprivate func box(_ value: Int)    -> NSObject { return NSNumber(value: value) }
    fileprivate func box(_ value: Int8)   -> NSObject { return NSNumber(value: value) }
    fileprivate func box(_ value: Int16)  -> NSObject { return NSNumber(value: value) }
    fileprivate func box(_ value: Int32)  -> NSObject { return NSNumber(value: value) }
    fileprivate func box(_ value: Int64)  -> NSObject { return NSNumber(value: value) }
    fileprivate func box(_ value: UInt)   -> NSObject { return NSNumber(value: value) }
    fileprivate func box(_ value: UInt8)  -> NSObject { return NSNumber(value: value) }
    fileprivate func box(_ value: UInt16) -> NSObject { return NSNumber(value: value) }
    fileprivate func box(_ value: UInt32) -> NSObject { return NSNumber(value: value) }
    fileprivate func box(_ value: UInt64) -> NSObject { return NSNumber(value: value) }
    fileprivate func box(_ value: Float)  -> NSObject { return NSNumber(value: value) }
    fileprivate func box(_ value: Double) -> NSObject { return NSNumber(value: value) }
    fileprivate func box(_ value: String) -> NSObject { return NSString(string: value) }
    fileprivate func box(_ value: Data)   -> NSObject { return NSData(data: value) }

    fileprivate func box<T : Encodable>(_ value: T) throws -> NSObject {
        if T.self == Date.self {
            // PropertyListSerialization handles Date directly.
            return NSDate(timeIntervalSinceReferenceDate: (value as! Date).timeIntervalSinceReferenceDate)
        } else if T.self == Data.self {
            // PropertyListSerialization handles Data directly.
            return NSData(data: (value as! Data))
        }

        // The value should request a container from the _PlistEncoder.
        let currentTopContainer = self.storage.containers.last
        try value.encode(to: self)

        // The top container should be a new container.
        guard self.storage.containers.last! !== currentTopContainer else {
            // If the value didn't request a container at all, encode the default container instead.
            return NSDictionary()
        }

        return self.storage.popContainer()
    }
}

// MARK: - _PlistReferencingEncoder

/// _PlistReferencingEncoder is a special subclass of _PlistEncoder which has its own storage, but references the contents of a different encoder.
/// It's used in superEncoder(), which returns a new encoder for encoding a superclass -- the lifetime of the encoder should not escape the scope it's created in, but it doesn't necessarily know when it's done being used (to write to the original container).
fileprivate class _PlistReferencingEncoder : _PlistEncoder {
    // MARK: Reference types.

    /// The type of container we're referencing.
    private enum Reference {
        /// Referencing a specific index in an array container.
        case array(NSMutableArray, Int)

        /// Referencing a specific key in a dictionary container.
        case dictionary(NSMutableDictionary, String)
    }

    // MARK: - Properties

    /// The encoder we're referencing.
    private let encoder: _PlistEncoder

    /// The container reference itself.
    private let reference: Reference

    // MARK: - Initialization

    /// Initializes `self` by referencing the given array container in the given encoder.
    fileprivate init(referencing encoder: _PlistEncoder, at index: Int, wrapping array: NSMutableArray) {
        self.encoder = encoder
        self.reference = .array(array, index)
        super.init(options: encoder.options, codingPath: encoder.codingPath)

        self.codingPath.append(nil)
    }

    /// Initializes `self` by referencing the given dictionary container in the given encoder.
    fileprivate init(referencing encoder: _PlistEncoder, at key: CodingKey, wrapping dictionary: NSMutableDictionary) {
        self.encoder = encoder
        self.reference = .dictionary(dictionary, key.stringValue)
        super.init(options: encoder.options, codingPath: encoder.codingPath)

        self.codingPath.append(key)
    }

    // MARK: - Coding Path Operations

    fileprivate override var canEncodeNewValue: Bool {
        // With a regular encoder, the storage and coding path grow together.
        // A referencing encoder, however, inherits its parents coding path, as well as the key it was created for.
        // We have to take this into account.
        return self.storage.count == self.codingPath.count - self.encoder.codingPath.count - 1
    }

    // MARK: - Deinitialization

    // Finalizes `self` by writing the contents of our storage to the referenced encoder's storage.
    deinit {
        let value: Any
        switch self.storage.count {
        case 0: value = NSDictionary()
        case 1: value = self.storage.popContainer()
        default: fatalError("Referencing encoder deallocated with multiple containers on stack.")
        }

        switch self.reference {
        case .array(let array, let index):
            array.insert(value, at: index)

        case .dictionary(let dictionary, let key):
            dictionary[NSString(string: key)] = value
        }
    }
}

//===----------------------------------------------------------------------===//
// Plist Decoder
//===----------------------------------------------------------------------===//

/// `PropertyListDecoder` facilitates the decoding of property list values into semantic `Decodable` types.
open class PropertyListDecoder {
    // MARK: Options

    /// Contextual user-provided information for use during decoding.
    open var userInfo: [CodingUserInfoKey : Any] = [:]

    /// Options set on the top-level encoder to pass down the decoding hierarchy.
    fileprivate struct _Options {
        let userInfo: [CodingUserInfoKey : Any]
    }

    /// The options set on the top-level decoder.
    fileprivate var options: _Options {
        return _Options(userInfo: userInfo)
    }

    // MARK: - Constructing a Property List Decoder

    /// Initializes `self` with default strategies.
    public init() {}

    // MARK: - Decoding Values

    /// Decodes a top-level value of the given type from the given property list representation.
    ///
    /// - parameter type: The type of the value to decode.
    /// - parameter data: The data to decode from.
    /// - returns: A value of the requested type.
    /// - throws: `DecodingError.dataCorrupted` if values requested from the payload are corrupted, or if the given data is not a valid property list.
    /// - throws: An error if any value throws an error during decoding.
    open func decode<T : Decodable>(_ type: T.Type, from data: Data) throws -> T {
        var format: PropertyListSerialization.PropertyListFormat = .binary
        return try decode(T.self, from: data, format: &format)
    }

    /// Decodes a top-level value of the given type from the given property list representation.
    ///
    /// - parameter type: The type of the value to decode.
    /// - parameter data: The data to decode from.
    /// - parameter format: The parsed property list format.
    /// - returns: A value of the requested type along with the detected format of the property list.
    /// - throws: `DecodingError.dataCorrupted` if values requested from the payload are corrupted, or if the given data is not a valid property list.
    /// - throws: An error if any value throws an error during decoding.
    open func decode<T : Decodable>(_ type: T.Type, from data: Data, format: inout PropertyListSerialization.PropertyListFormat) throws -> T {
        let topLevel: Any
        do {
            topLevel = try PropertyListSerialization.propertyList(from: data, options: [], format: &format)
        } catch {
            throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: [], debugDescription: "The given data was not a valid property list.", underlyingError: error))
        }
        let decoder = _PlistDecoder(referencing: topLevel, options: self.options)
        return try T(from: decoder)
    }
}

// MARK: - _PlistDecoder

fileprivate class _PlistDecoder : Decoder {
    // MARK: Properties

    /// The decoder's storage.
    fileprivate var storage: _PlistDecodingStorage

    /// Options set on the top-level decoder.
    fileprivate let options: PropertyListDecoder._Options

    /// The path to the current point in encoding.
    fileprivate(set) public var codingPath: [CodingKey?]

    /// Contextual user-provided information for use during encoding.
    public var userInfo: [CodingUserInfoKey : Any] {
        return self.options.userInfo
    }

    // MARK: - Initialization

    /// Initializes `self` with the given top-level container and options.
    fileprivate init(referencing container: Any, at codingPath: [CodingKey?] = [], options: PropertyListDecoder._Options) {
        self.storage = _PlistDecodingStorage()
        self.storage.push(container: container)
        self.codingPath = codingPath
        self.options = options
    }

    // MARK: - Coding Path Operations

    /// Performs the given closure with the given key pushed onto the end of the current coding path.
    ///
    /// - parameter key: The key to push. May be nil for unkeyed containers.
    /// - parameter work: The work to perform with the key in the path.
    fileprivate func with<T>(pushedKey key: CodingKey?, _ work: () throws -> T) rethrows -> T {
        self.codingPath.append(key)
        let ret: T = try work()
        self.codingPath.removeLast()
        return ret
    }

    // MARK: - Decoder Methods

    public func container<Key>(keyedBy type: Key.Type) throws -> KeyedDecodingContainer<Key> {
        guard !(self.storage.topContainer is NSNull) else {
            throw DecodingError.valueNotFound(KeyedDecodingContainer<Key>.self,
                                              DecodingError.Context(codingPath: self.codingPath,
                                                      debugDescription: "Cannot get keyed decoding container -- found null value instead."))
        }

        guard let topContainer = self.storage.topContainer as? [String : Any] else {
            throw DecodingError._typeMismatch(at: self.codingPath, expectation: [String : Any].self, reality: self.storage.topContainer)
        }

        let container = _PlistKeyedDecodingContainer<Key>(referencing: self, wrapping: topContainer)
        return KeyedDecodingContainer(container)
    }

    public func unkeyedContainer() throws -> UnkeyedDecodingContainer {
        guard !(self.storage.topContainer is NSNull) else {
            throw DecodingError.valueNotFound(UnkeyedDecodingContainer.self,
                                              DecodingError.Context(codingPath: self.codingPath,
                                                      debugDescription: "Cannot get unkeyed decoding container -- found null value instead."))
        }

        guard let topContainer = self.storage.topContainer as? [Any] else {
            throw DecodingError._typeMismatch(at: self.codingPath, expectation: [Any].self, reality: self.storage.topContainer)
        }

        return _PlistUnkeyedDecodingContainer(referencing: self, wrapping: topContainer)
    }

    public func singleValueContainer() throws -> SingleValueDecodingContainer {
        return self
    }
}

// MARK: - Decoding Storage

fileprivate struct _PlistDecodingStorage {
    // MARK: Properties

    /// The container stack.
    /// Elements may be any one of the plist types (NSNumber, Date, String, Array, [String : Any]).
    private(set) fileprivate var containers: [Any] = []

    // MARK: - Initialization

    /// Initializes `self` with no containers.
    fileprivate init() {}

    // MARK: - Modifying the Stack

    fileprivate var count: Int {
        return self.containers.count
    }

    fileprivate var topContainer: Any {
        precondition(self.containers.count > 0, "Empty container stack.")
        return self.containers.last!
    }

    fileprivate mutating func push(container: Any) {
        self.containers.append(container)
    }

    fileprivate mutating func popContainer() {
        precondition(self.containers.count > 0, "Empty container stack.")
        self.containers.removeLast()
    }
}

// MARK: Decoding Containers

fileprivate struct _PlistKeyedDecodingContainer<K : CodingKey> : KeyedDecodingContainerProtocol {
    typealias Key = K

    // MARK: Properties

    /// A reference to the decoder we're reading from.
    private let decoder: _PlistDecoder

    /// A reference to the container we're reading from.
    private let container: [String : Any]

    /// The path of coding keys taken to get to this point in decoding.
    private(set) public var codingPath: [CodingKey?]

    // MARK: - Initialization

    /// Initializes `self` by referencing the given decoder and container.
    fileprivate init(referencing decoder: _PlistDecoder, wrapping container: [String : Any]) {
        self.decoder = decoder
        self.container = container
        self.codingPath = decoder.codingPath
    }

    // MARK: - KeyedDecodingContainerProtocol Methods

    public var allKeys: [Key] {
        return self.container.keys.flatMap { Key(stringValue: $0) }
    }

    public func contains(_ key: Key) -> Bool {
        return self.container[key.stringValue] != nil
    }

    public func decodeNil(forKey key: Key) throws -> Bool {
        guard let entry = self.container[key.stringValue] else {
            throw DecodingError.keyNotFound(key, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "No value associated with key \(key) (\"\(key.stringValue)\")."))
        }

        guard let value = entry as? String else {
            return false
        }

        return value == _plistNull
    }

    public func decode(_ type: Bool.Type, forKey key: Key) throws -> Bool {
        guard let entry = self.container[key.stringValue] else {
            throw DecodingError.keyNotFound(key, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "No value associated with key \(key) (\"\(key.stringValue)\")."))
        }

        return try self.decoder.with(pushedKey: key) {
            guard let value = try self.decoder.unbox(entry, as: Bool.self) else {
                throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "Expected \(type) value but found null instead."))
            }

            return value
        }
    }

    public func decode(_ type: Int.Type, forKey key: Key) throws -> Int {
        guard let entry = self.container[key.stringValue] else {
            throw DecodingError.keyNotFound(key, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "No value associated with key \(key) (\"\(key.stringValue)\")."))
        }

        return try self.decoder.with(pushedKey: key) {
            guard let value = try self.decoder.unbox(entry, as: Int.self) else {
                throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "Expected \(type) value but found null instead."))
            }

            return value
        }
    }

    public func decode(_ type: Int8.Type, forKey key: Key) throws -> Int8 {
        guard let entry = self.container[key.stringValue] else {
            throw DecodingError.keyNotFound(key, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "No value associated with key \(key) (\"\(key.stringValue)\")."))
        }

        return try self.decoder.with(pushedKey: key) {
            guard let value = try self.decoder.unbox(entry, as: Int8.self) else {
                throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "Expected \(type) value but found null instead."))
            }

            return value
        }
    }

    public func decode(_ type: Int16.Type, forKey key: Key) throws -> Int16 {
        guard let entry = self.container[key.stringValue] else {
            throw DecodingError.keyNotFound(key, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "No value associated with key \(key) (\"\(key.stringValue)\")."))
        }

        return try self.decoder.with(pushedKey: key) {
            guard let value = try self.decoder.unbox(entry, as: Int16.self) else {
                throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "Expected \(type) value but found null instead."))
            }

            return value
        }
    }

    public func decode(_ type: Int32.Type, forKey key: Key) throws -> Int32 {
        guard let entry = self.container[key.stringValue] else {
            throw DecodingError.keyNotFound(key, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "No value associated with key \(key) (\"\(key.stringValue)\")."))
        }

        return try self.decoder.with(pushedKey: key) {
            guard let value = try self.decoder.unbox(entry, as: Int32.self) else {
                throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "Expected \(type) value but found null instead."))
            }

            return value
        }
    }

    public func decode(_ type: Int64.Type, forKey key: Key) throws -> Int64 {
        guard let entry = self.container[key.stringValue] else {
            throw DecodingError.keyNotFound(key, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "No value associated with key \(key) (\"\(key.stringValue)\")."))
        }

        return try self.decoder.with(pushedKey: key) {
            guard let value = try self.decoder.unbox(entry, as: Int64.self) else {
                throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "Expected \(type) value but found null instead."))
            }

            return value
        }
    }

    public func decode(_ type: UInt.Type, forKey key: Key) throws -> UInt {
        guard let entry = self.container[key.stringValue] else {
            throw DecodingError.keyNotFound(key, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "No value associated with key \(key) (\"\(key.stringValue)\")."))
        }

        return try self.decoder.with(pushedKey: key) {
            guard let value = try self.decoder.unbox(entry, as: UInt.self) else {
                throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "Expected \(type) value but found null instead."))
            }

            return value
        }
    }

    public func decode(_ type: UInt8.Type, forKey key: Key) throws -> UInt8 {
        guard let entry = self.container[key.stringValue] else {
            throw DecodingError.keyNotFound(key, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "No value associated with key \(key) (\"\(key.stringValue)\")."))
        }

        return try self.decoder.with(pushedKey: key) {
            guard let value = try self.decoder.unbox(entry, as: UInt8.self) else {
                throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "Expected \(type) value but found null instead."))
            }

            return value
        }
    }

    public func decode(_ type: UInt16.Type, forKey key: Key) throws -> UInt16 {
        guard let entry = self.container[key.stringValue] else {
            throw DecodingError.keyNotFound(key, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "No value associated with key \(key) (\"\(key.stringValue)\")."))
        }

        return try self.decoder.with(pushedKey: key) {
            guard let value = try self.decoder.unbox(entry, as: UInt16.self) else {
                throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "Expected \(type) value but found null instead."))
            }

            return value
        }
    }

    public func decode(_ type: UInt32.Type, forKey key: Key) throws -> UInt32 {
        guard let entry = self.container[key.stringValue] else {
            throw DecodingError.keyNotFound(key, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "No value associated with key \(key) (\"\(key.stringValue)\")."))
        }

        return try self.decoder.with(pushedKey: key) {
            guard let value = try self.decoder.unbox(entry, as: UInt32.self) else {
                throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "Expected \(type) value but found null instead."))
            }

            return value
        }
    }

    public func decode(_ type: UInt64.Type, forKey key: Key) throws -> UInt64 {
        guard let entry = self.container[key.stringValue] else {
            throw DecodingError.keyNotFound(key, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "No value associated with key \(key) (\"\(key.stringValue)\")."))
        }

        return try self.decoder.with(pushedKey: key) {
            guard let value = try self.decoder.unbox(entry, as: UInt64.self) else {
                throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "Expected \(type) value but found null instead."))
            }

            return value
        }
    }

    public func decode(_ type: Float.Type, forKey key: Key) throws -> Float {
        guard let entry = self.container[key.stringValue] else {
            throw DecodingError.keyNotFound(key, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "No value associated with key \(key) (\"\(key.stringValue)\")."))
        }

        return try self.decoder.with(pushedKey: key) {
            guard let value = try self.decoder.unbox(entry, as: Float.self) else {
                throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "Expected \(type) value but found null instead."))
            }

            return value
        }
    }

    public func decode(_ type: Double.Type, forKey key: Key) throws -> Double {
        guard let entry = self.container[key.stringValue] else {
            throw DecodingError.keyNotFound(key, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "No value associated with key \(key) (\"\(key.stringValue)\")."))
        }

        return try self.decoder.with(pushedKey: key) {
            guard let value = try self.decoder.unbox(entry, as: Double.self) else {
                throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "Expected \(type) value but found null instead."))
            }

            return value
        }
    }

    public func decode(_ type: String.Type, forKey key: Key) throws -> String {
        guard let entry = self.container[key.stringValue] else {
            throw DecodingError.keyNotFound(key, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "No value associated with key \(key) (\"\(key.stringValue)\")."))
        }

        return try self.decoder.with(pushedKey: key) {
            guard let value = try self.decoder.unbox(entry, as: String.self) else {
                throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "Expected \(type) value but found null instead."))
            }

            return value
        }
    }

    public func decode<T : Decodable>(_ type: T.Type, forKey key: Key) throws -> T {
        guard let entry = self.container[key.stringValue] else {
            throw DecodingError.keyNotFound(key, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "No value associated with key \(key) (\"\(key.stringValue)\")."))
        }

        return try self.decoder.with(pushedKey: key) {
            guard let value = try self.decoder.unbox(entry, as: T.self) else {
                throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "Expected \(type) value but found null instead."))
            }

            return value
        }
    }

    public func nestedContainer<NestedKey>(keyedBy type: NestedKey.Type, forKey key: Key) throws -> KeyedDecodingContainer<NestedKey> {
        return try self.decoder.with(pushedKey: key) {
            guard let value = self.container[key.stringValue] else {
                throw DecodingError.valueNotFound(KeyedDecodingContainer<NestedKey>.self,
                                                  DecodingError.Context(codingPath: self.codingPath,
                                                          debugDescription: "Cannot get nested keyed container -- no value found for key \"\(key.stringValue)\""))
            }

            guard let dictionary = value as? [String : Any] else {
                throw DecodingError._typeMismatch(at: self.codingPath, expectation: [String : Any].self, reality: value)
            }

            let container = _PlistKeyedDecodingContainer<NestedKey>(referencing: self.decoder, wrapping: dictionary)
            return KeyedDecodingContainer(container)
        }
    }

    public func nestedUnkeyedContainer(forKey key: Key) throws -> UnkeyedDecodingContainer {
        return try self.decoder.with(pushedKey: key) {
            guard let value = self.container[key.stringValue] else {
                throw DecodingError.valueNotFound(UnkeyedDecodingContainer.self,
                                                  DecodingError.Context(codingPath: self.codingPath,
                                                          debugDescription: "Cannot get nested unkeyed container -- no value found for key \"\(key.stringValue)\""))
            }

            guard let array = value as? [Any] else {
                throw DecodingError._typeMismatch(at: self.codingPath, expectation: [Any].self, reality: value)
            }

            return _PlistUnkeyedDecodingContainer(referencing: self.decoder, wrapping: array)
        }
    }

    private func _superDecoder(forKey key: CodingKey) throws -> Decoder {
        return self.decoder.with(pushedKey: key) {
            let value: Any = self.container[key.stringValue] ?? NSNull()
            return _PlistDecoder(referencing: value, at: self.decoder.codingPath, options: self.decoder.options)
        }
    }

    public func superDecoder() throws -> Decoder {
        return try _superDecoder(forKey: _PlistSuperKey.super)
    }

    public func superDecoder(forKey key: Key) throws -> Decoder {
        return try _superDecoder(forKey: key)
    }
}

fileprivate struct _PlistUnkeyedDecodingContainer : UnkeyedDecodingContainer {
    // MARK: Properties

    /// A reference to the decoder we're reading from.
    private let decoder: _PlistDecoder

    /// A reference to the container we're reading from.
    private let container: [Any]

    /// The path of coding keys taken to get to this point in decoding.
    private(set) public var codingPath: [CodingKey?]

    /// The index of the element we're about to decode.
    private var currentIndex: Int

    // MARK: - Initialization

    /// Initializes `self` by referencing the given decoder and container.
    fileprivate init(referencing decoder: _PlistDecoder, wrapping container: [Any]) {
        self.decoder = decoder
        self.container = container
        self.codingPath = decoder.codingPath
        self.currentIndex = 0
    }

    // MARK: - UnkeyedDecodingContainer Methods

    public var count: Int? {
        return self.container.count
    }

    public var isAtEnd: Bool {
        return self.currentIndex >= self.count!
    }

    public mutating func decodeNil() throws -> Bool {
        guard !self.isAtEnd else {
            throw DecodingError.valueNotFound(Any?.self, DecodingError.Context(codingPath: self.decoder.codingPath + [nil], debugDescription: "Unkeyed container is at end."))
        }

        if self.container[self.currentIndex] is NSNull {
            self.currentIndex += 1
            return true
        } else {
            return false
        }
    }

    public mutating func decode(_ type: Bool.Type) throws -> Bool {
        guard !self.isAtEnd else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [nil], debugDescription: "Unkeyed container is at end."))
        }

        return try self.decoder.with(pushedKey: nil) {
            guard let decoded = try self.decoder.unbox(self.container[self.currentIndex], as: Bool.self) else {
                throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [nil], debugDescription: "Expected \(type) but found null instead."))
            }

            self.currentIndex += 1
            return decoded
        }
    }

    public mutating func decode(_ type: Int.Type) throws -> Int {
        guard !self.isAtEnd else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [nil], debugDescription: "Unkeyed container is at end."))
        }

        return try self.decoder.with(pushedKey: nil) {
            guard let decoded = try self.decoder.unbox(self.container[self.currentIndex], as: Int.self) else {
                throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [nil], debugDescription: "Expected \(type) but found null instead."))
            }

            self.currentIndex += 1
            return decoded
        }
    }

    public mutating func decode(_ type: Int8.Type) throws -> Int8 {
        guard !self.isAtEnd else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [nil], debugDescription: "Unkeyed container is at end."))
        }

        return try self.decoder.with(pushedKey: nil) {
            guard let decoded = try self.decoder.unbox(self.container[self.currentIndex], as: Int8.self) else {
                throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [nil], debugDescription: "Expected \(type) but found null instead."))
            }

            self.currentIndex += 1
            return decoded
        }
    }

    public mutating func decode(_ type: Int16.Type) throws -> Int16 {
        guard !self.isAtEnd else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [nil], debugDescription: "Unkeyed container is at end."))
        }

        return try self.decoder.with(pushedKey: nil) {
            guard let decoded = try self.decoder.unbox(self.container[self.currentIndex], as: Int16.self) else {
                throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [nil], debugDescription: "Expected \(type) but found null instead."))
            }

            self.currentIndex += 1
            return decoded
        }
    }

    public mutating func decode(_ type: Int32.Type) throws -> Int32 {
        guard !self.isAtEnd else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [nil], debugDescription: "Unkeyed container is at end."))
        }

        return try self.decoder.with(pushedKey: nil) {
            guard let decoded = try self.decoder.unbox(self.container[self.currentIndex], as: Int32.self) else {
                throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [nil], debugDescription: "Expected \(type) but found null instead."))
            }

            self.currentIndex += 1
            return decoded
        }
    }

    public mutating func decode(_ type: Int64.Type) throws -> Int64 {
        guard !self.isAtEnd else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [nil], debugDescription: "Unkeyed container is at end."))
        }

        return try self.decoder.with(pushedKey: nil) {
            guard let decoded = try self.decoder.unbox(self.container[self.currentIndex], as: Int64.self) else {
                throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [nil], debugDescription: "Expected \(type) but found null instead."))
            }

            self.currentIndex += 1
            return decoded
        }
    }

    public mutating func decode(_ type: UInt.Type) throws -> UInt {
        guard !self.isAtEnd else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [nil], debugDescription: "Unkeyed container is at end."))
        }

        return try self.decoder.with(pushedKey: nil) {
            guard let decoded = try self.decoder.unbox(self.container[self.currentIndex], as: UInt.self) else {
                throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [nil], debugDescription: "Expected \(type) but found null instead."))
            }

            self.currentIndex += 1
            return decoded
        }
    }

    public mutating func decode(_ type: UInt8.Type) throws -> UInt8 {
        guard !self.isAtEnd else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [nil], debugDescription: "Unkeyed container is at end."))
        }

        return try self.decoder.with(pushedKey: nil) {
            guard let decoded = try self.decoder.unbox(self.container[self.currentIndex], as: UInt8.self) else {
                throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [nil], debugDescription: "Expected \(type) but found null instead."))
            }

            self.currentIndex += 1
            return decoded
        }
    }

    public mutating func decode(_ type: UInt16.Type) throws -> UInt16 {
        guard !self.isAtEnd else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [nil], debugDescription: "Unkeyed container is at end."))
        }

        return try self.decoder.with(pushedKey: nil) {
            guard let decoded = try self.decoder.unbox(self.container[self.currentIndex], as: UInt16.self) else {
                throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [nil], debugDescription: "Expected \(type) but found null instead."))
            }

            self.currentIndex += 1
            return decoded
        }
    }

    public mutating func decode(_ type: UInt32.Type) throws -> UInt32 {
        guard !self.isAtEnd else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [nil], debugDescription: "Unkeyed container is at end."))
        }

        return try self.decoder.with(pushedKey: nil) {
            guard let decoded = try self.decoder.unbox(self.container[self.currentIndex], as: UInt32.self) else {
                throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [nil], debugDescription: "Expected \(type) but found null instead."))
            }

            self.currentIndex += 1
            return decoded
        }
    }

    public mutating func decode(_ type: UInt64.Type) throws -> UInt64 {
        guard !self.isAtEnd else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [nil], debugDescription: "Unkeyed container is at end."))
        }

        return try self.decoder.with(pushedKey: nil) {
            guard let decoded = try self.decoder.unbox(self.container[self.currentIndex], as: UInt64.self) else {
                throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [nil], debugDescription: "Expected \(type) but found null instead."))
            }

            self.currentIndex += 1
            return decoded
        }
    }

    public mutating func decode(_ type: Float.Type) throws -> Float {
        guard !self.isAtEnd else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [nil], debugDescription: "Unkeyed container is at end."))
        }

        return try self.decoder.with(pushedKey: nil) {
            guard let decoded = try self.decoder.unbox(self.container[self.currentIndex], as: Float.self) else {
                throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [nil], debugDescription: "Expected \(type) but found null instead."))
            }

            self.currentIndex += 1
            return decoded
        }
    }

    public mutating func decode(_ type: Double.Type) throws -> Double {
        guard !self.isAtEnd else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [nil], debugDescription: "Unkeyed container is at end."))
        }

        return try self.decoder.with(pushedKey: nil) {
            guard let decoded = try self.decoder.unbox(self.container[self.currentIndex], as: Double.self) else {
                throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [nil], debugDescription: "Expected \(type) but found null instead."))
            }

            self.currentIndex += 1
            return decoded
        }
    }

    public mutating func decode(_ type: String.Type) throws -> String {
        guard !self.isAtEnd else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [nil], debugDescription: "Unkeyed container is at end."))
        }

        return try self.decoder.with(pushedKey: nil) {
            guard let decoded = try self.decoder.unbox(self.container[self.currentIndex], as: String.self) else {
                throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [nil], debugDescription: "Expected \(type) but found null instead."))
            }

            self.currentIndex += 1
            return decoded
        }
    }

    public mutating func decode<T : Decodable>(_ type: T.Type) throws -> T {
        guard !self.isAtEnd else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [nil], debugDescription: "Unkeyed container is at end."))
        }

        return try self.decoder.with(pushedKey: nil) {
            guard let decoded = try self.decoder.unbox(self.container[self.currentIndex], as: T.self) else {
                throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [nil], debugDescription: "Expected \(type) but found null instead."))
            }

            self.currentIndex += 1
            return decoded
        }
    }

    public mutating func nestedContainer<NestedKey>(keyedBy type: NestedKey.Type) throws -> KeyedDecodingContainer<NestedKey> {
        return try self.decoder.with(pushedKey: nil) {
            guard !self.isAtEnd else {
                throw DecodingError.valueNotFound(KeyedDecodingContainer<NestedKey>.self,
                                                  DecodingError.Context(codingPath: self.codingPath,
                                                          debugDescription: "Cannot get nested keyed container -- unkeyed container is at end."))
            }

            let value = self.container[self.currentIndex]
            guard !(value is NSNull) else {
                throw DecodingError.valueNotFound(KeyedDecodingContainer<NestedKey>.self,
                                                  DecodingError.Context(codingPath: self.codingPath,
                                                          debugDescription: "Cannot get keyed decoding container -- found null value instead."))
            }

            guard let dictionary = value as? [String : Any] else {
                throw DecodingError._typeMismatch(at: self.codingPath, expectation: [String : Any].self, reality: value)
            }

            self.currentIndex += 1
            let container = _PlistKeyedDecodingContainer<NestedKey>(referencing: self.decoder, wrapping: dictionary)
            return KeyedDecodingContainer(container)
        }
    }

    public mutating func nestedUnkeyedContainer() throws -> UnkeyedDecodingContainer {
        return try self.decoder.with(pushedKey: nil) {
            guard !self.isAtEnd else {
                throw DecodingError.valueNotFound(UnkeyedDecodingContainer.self,
                                                  DecodingError.Context(codingPath: self.codingPath,
                                                          debugDescription: "Cannot get nested unkeyed container -- unkeyed container is at end."))
            }

            let value = self.container[self.currentIndex]
            guard !(value is NSNull) else {
                throw DecodingError.valueNotFound(UnkeyedDecodingContainer.self,
                                                  DecodingError.Context(codingPath: self.codingPath,
                                                          debugDescription: "Cannot get keyed decoding container -- found null value instead."))
            }

            guard let array = value as? [Any] else {
                throw DecodingError._typeMismatch(at: self.codingPath, expectation: [Any].self, reality: value)
            }

            self.currentIndex += 1
            return _PlistUnkeyedDecodingContainer(referencing: self.decoder, wrapping: array)
        }
    }

    public mutating func superDecoder() throws -> Decoder {
        return try self.decoder.with(pushedKey: nil) {
            guard !self.isAtEnd else {
                throw DecodingError.valueNotFound(Decoder.self, DecodingError.Context(codingPath: self.codingPath,
                                                                        debugDescription: "Cannot get superDecoder() -- unkeyed container is at end."))
            }

            let value = self.container[self.currentIndex]
            self.currentIndex += 1
            return _PlistDecoder(referencing: value, at: self.decoder.codingPath, options: self.decoder.options)
        }
    }
}

extension _PlistDecoder : SingleValueDecodingContainer {
    // MARK: SingleValueDecodingContainer Methods

    private func expectNonNull<T>(_ type: T.Type) throws {
        guard !self.decodeNil() else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.codingPath, debugDescription: "Expected \(type) but found null value instead."))
        }
    }

    public func decodeNil() -> Bool {
        guard let string = self.storage.topContainer as? String else {
            return false
        }

        return string == _plistNull
    }

    public func decode(_ type: Bool.Type) throws -> Bool {
        try expectNonNull(Bool.self)
        return try self.unbox(self.storage.topContainer, as: Bool.self)!
    }

    public func decode(_ type: Int.Type) throws -> Int {
        try expectNonNull(Int.self)
        return try self.unbox(self.storage.topContainer, as: Int.self)!
    }

    public func decode(_ type: Int8.Type) throws -> Int8 {
        try expectNonNull(Int8.self)
        return try self.unbox(self.storage.topContainer, as: Int8.self)!
    }

    public func decode(_ type: Int16.Type) throws -> Int16 {
        try expectNonNull(Int16.self)
        return try self.unbox(self.storage.topContainer, as: Int16.self)!
    }

    public func decode(_ type: Int32.Type) throws -> Int32 {
        try expectNonNull(Int32.self)
        return try self.unbox(self.storage.topContainer, as: Int32.self)!
    }

    public func decode(_ type: Int64.Type) throws -> Int64 {
        try expectNonNull(Int64.self)
        return try self.unbox(self.storage.topContainer, as: Int64.self)!
    }

    public func decode(_ type: UInt.Type) throws -> UInt {
        try expectNonNull(UInt.self)
        return try self.unbox(self.storage.topContainer, as: UInt.self)!
    }

    public func decode(_ type: UInt8.Type) throws -> UInt8 {
        try expectNonNull(UInt8.self)
        return try self.unbox(self.storage.topContainer, as: UInt8.self)!
    }

    public func decode(_ type: UInt16.Type) throws -> UInt16 {
        try expectNonNull(UInt16.self)
        return try self.unbox(self.storage.topContainer, as: UInt16.self)!
    }

    public func decode(_ type: UInt32.Type) throws -> UInt32 {
        try expectNonNull(UInt32.self)
        return try self.unbox(self.storage.topContainer, as: UInt32.self)!
    }

    public func decode(_ type: UInt64.Type) throws -> UInt64 {
        try expectNonNull(UInt64.self)
        return try self.unbox(self.storage.topContainer, as: UInt64.self)!
    }

    public func decode(_ type: Float.Type) throws -> Float {
        try expectNonNull(Float.self)
        return try self.unbox(self.storage.topContainer, as: Float.self)!
    }

    public func decode(_ type: Double.Type) throws -> Double {
        try expectNonNull(Double.self)
        return try self.unbox(self.storage.topContainer, as: Double.self)!
    }

    public func decode(_ type: String.Type) throws -> String {
        try expectNonNull(String.self)
        return try self.unbox(self.storage.topContainer, as: String.self)!
    }

    public func decode<T : Decodable>(_ type: T.Type) throws -> T {
        try expectNonNull(T.self)
        return try self.unbox(self.storage.topContainer, as: T.self)!
    }
}

// MARK: - Concrete Value Representations

extension _PlistDecoder {
    /// Returns the given value unboxed from a container.
    fileprivate func unbox(_ value: Any, as type: Bool.Type) throws -> Bool? {
        if let string = value as? String, string == _plistNull { return nil }

        if let number = value as? NSNumber {
            // TODO: Add a flag to coerce non-boolean numbers into Bools?
            if number === kCFBooleanTrue as NSNumber {
                return true
            } else if number === kCFBooleanFalse as NSNumber {
                return false
            }

        /* FIXME: If swift-corelibs-foundation doesn't change to use NSNumber, this code path will need to be included and tested:
        } else if let bool = value as? Bool {
            return bool
        */

        }

        throw DecodingError._typeMismatch(at: self.codingPath, expectation: type, reality: value)
    }

    fileprivate func unbox(_ value: Any, as type: Int.Type) throws -> Int? {
        if let string = value as? String, string == _plistNull { return nil }

        guard let number = value as? NSNumber else {
            throw DecodingError._typeMismatch(at: self.codingPath, expectation: type, reality: value)
        }

        let int = number.intValue
        guard NSNumber(value: int) == number else {
            throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: self.codingPath, debugDescription: "Parsed property list number <\(number)> does not fit in \(type)."))
        }

        return int
    }

    fileprivate func unbox(_ value: Any, as type: Int8.Type) throws -> Int8? {
        if let string = value as? String, string == _plistNull { return nil }

        guard let number = value as? NSNumber else {
            throw DecodingError._typeMismatch(at: self.codingPath, expectation: type, reality: value)
        }

        let int8 = number.int8Value
        guard NSNumber(value: int8) == number else {
            throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: self.codingPath, debugDescription: "Parsed property list number <\(number)> does not fit in \(type)."))
        }

        return int8
    }

    fileprivate func unbox(_ value: Any, as type: Int16.Type) throws -> Int16? {
        if let string = value as? String, string == _plistNull { return nil }

        guard let number = value as? NSNumber else {
            throw DecodingError._typeMismatch(at: self.codingPath, expectation: type, reality: value)
        }

        let int16 = number.int16Value
        guard NSNumber(value: int16) == number else {
            throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: self.codingPath, debugDescription: "Parsed property list number <\(number)> does not fit in \(type)."))
        }

        return int16
    }

    fileprivate func unbox(_ value: Any, as type: Int32.Type) throws -> Int32? {
        if let string = value as? String, string == _plistNull { return nil }

        guard let number = value as? NSNumber else {
            throw DecodingError._typeMismatch(at: self.codingPath, expectation: type, reality: value)
        }

        let int32 = number.int32Value
        guard NSNumber(value: int32) == number else {
            throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: self.codingPath, debugDescription: "Parsed property list number <\(number)> does not fit in \(type)."))
        }

        return int32
    }

    fileprivate func unbox(_ value: Any, as type: Int64.Type) throws -> Int64? {
        if let string = value as? String, string == _plistNull { return nil }

        guard let number = value as? NSNumber else {
            throw DecodingError._typeMismatch(at: self.codingPath, expectation: type, reality: value)
        }

        let int64 = number.int64Value
        guard NSNumber(value: int64) == number else {
            throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: self.codingPath, debugDescription: "Parsed property list number <\(number)> does not fit in \(type)."))
        }

        return int64
    }

    fileprivate func unbox(_ value: Any, as type: UInt.Type) throws -> UInt? {
        if let string = value as? String, string == _plistNull { return nil }

        guard let number = value as? NSNumber else {
            throw DecodingError._typeMismatch(at: self.codingPath, expectation: type, reality: value)
        }

        let uint = number.uintValue
        guard NSNumber(value: uint) == number else {
            throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: self.codingPath, debugDescription: "Parsed property list number <\(number)> does not fit in \(type)."))
        }

        return uint
    }

    fileprivate func unbox(_ value: Any, as type: UInt8.Type) throws -> UInt8? {
        if let string = value as? String, string == _plistNull { return nil }

        guard let number = value as? NSNumber else {
            throw DecodingError._typeMismatch(at: self.codingPath, expectation: type, reality: value)
        }

        let uint8 = number.uint8Value
        guard NSNumber(value: uint8) == number else {
            throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: self.codingPath, debugDescription: "Parsed property list number <\(number)> does not fit in \(type)."))
        }

        return uint8
    }

    fileprivate func unbox(_ value: Any, as type: UInt16.Type) throws -> UInt16? {
        if let string = value as? String, string == _plistNull { return nil }

        guard let number = value as? NSNumber else {
            throw DecodingError._typeMismatch(at: self.codingPath, expectation: type, reality: value)
        }

        let uint16 = number.uint16Value
        guard NSNumber(value: uint16) == number else {
            throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: self.codingPath, debugDescription: "Parsed property list number <\(number)> does not fit in \(type)."))
        }

        return uint16
    }

    fileprivate func unbox(_ value: Any, as type: UInt32.Type) throws -> UInt32? {
        if let string = value as? String, string == _plistNull { return nil }

        guard let number = value as? NSNumber else {
            throw DecodingError._typeMismatch(at: self.codingPath, expectation: type, reality: value)
        }

        let uint32 = number.uint32Value
        guard NSNumber(value: uint32) == number else {
            throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: self.codingPath, debugDescription: "Parsed property list number <\(number)> does not fit in \(type)."))
        }

        return uint32
    }

    fileprivate func unbox(_ value: Any, as type: UInt64.Type) throws -> UInt64? {
        if let string = value as? String, string == _plistNull { return nil }

        guard let number = value as? NSNumber else {
            throw DecodingError._typeMismatch(at: self.codingPath, expectation: type, reality: value)
        }

        let uint64 = number.uint64Value
        guard NSNumber(value: uint64) == number else {
            throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: self.codingPath, debugDescription: "Parsed property list number <\(number)> does not fit in \(type)."))
        }

        return uint64
    }

    fileprivate func unbox(_ value: Any, as type: Float.Type) throws -> Float? {
        if let string = value as? String, string == _plistNull { return nil }

        guard let number = value as? NSNumber else {
            throw DecodingError._typeMismatch(at: self.codingPath, expectation: type, reality: value)
        }

        let float = number.floatValue
        guard NSNumber(value: float) == number else {
            throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: self.codingPath, debugDescription: "Parsed property list number <\(number)> does not fit in \(type)."))
        }

        return float
    }

    fileprivate func unbox(_ value: Any, as type: Double.Type) throws -> Double? {
        if let string = value as? String, string == _plistNull { return nil }

        guard let number = value as? NSNumber else {
            throw DecodingError._typeMismatch(at: self.codingPath, expectation: type, reality: value)
        }

        let double = number.doubleValue
        guard NSNumber(value: double) == number else {
            throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: self.codingPath, debugDescription: "Parsed property list number <\(number)> does not fit in \(type)."))
        }

        return double
    }

    fileprivate func unbox(_ value: Any, as type: String.Type) throws -> String? {
        guard let string = value as? String else {
            throw DecodingError._typeMismatch(at: self.codingPath, expectation: type, reality: value)
        }

        return string == _plistNull ? nil : string
    }

    fileprivate func unbox(_ value: Any, as type: Date.Type) throws -> Date? {
        if let string = value as? String, string == _plistNull { return nil }

        guard let date = value as? Date else {
            throw DecodingError._typeMismatch(at: self.codingPath, expectation: type, reality: value)
        }

        return date
    }

    fileprivate func unbox(_ value: Any, as type: Data.Type) throws -> Data? {
        if let string = value as? String, string == _plistNull { return nil }

        guard let data = value as? Data else {
            throw DecodingError._typeMismatch(at: self.codingPath, expectation: type, reality: value)
        }

        return data
    }

    fileprivate func unbox<T : Decodable>(_ value: Any, as type: T.Type) throws -> T? {
        let decoded: T
        if T.self == Date.self {
            guard let date = try self.unbox(value, as: Date.self) else { return nil }
            decoded = date as! T
        } else if T.self == Data.self {
            guard let data = try self.unbox(value, as: Data.self) else { return nil }
            decoded = data as! T
        } else {
            self.storage.push(container: value)
            decoded = try T(from: self)
            self.storage.popContainer()
        }

        return decoded
    }
}

//===----------------------------------------------------------------------===//
// Shared Plist Null Representation
//===----------------------------------------------------------------------===//

// Since plists do not support null values by default, we will encode them as "$null".
fileprivate let _plistNull = "$null"
fileprivate let _plistNullNSString = NSString(string: _plistNull)

//===----------------------------------------------------------------------===//
// Shared Super Key
//===----------------------------------------------------------------------===//

fileprivate enum _PlistSuperKey : String, CodingKey {
    case `super`
}