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250 lines (201 loc) · 8.16 KB
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private struct _Decoder: Decoder {
fileprivate let node: JSValue
init(referencing node: JSValue, userInfo: [CodingUserInfoKey: Any], codingPath: [CodingKey] = []) {
self.node = node
self.userInfo = userInfo
self.codingPath = codingPath
}
let codingPath: [CodingKey]
let userInfo: [CodingUserInfoKey: Any]
func container<Key>(keyedBy _: Key.Type) throws -> KeyedDecodingContainer<Key> where Key: CodingKey {
guard let ref = node.object else { throw _typeMismatch(at: codingPath, JSObject.self, reality: node) }
return KeyedDecodingContainer(_KeyedDecodingContainer(decoder: self, ref: ref))
}
func unkeyedContainer() throws -> UnkeyedDecodingContainer {
guard let ref = node.object else { throw _typeMismatch(at: codingPath, JSObject.self, reality: node) }
return _UnkeyedDecodingContainer(decoder: self, ref: ref)
}
func singleValueContainer() throws -> SingleValueDecodingContainer {
self
}
func decoder(referencing node: JSValue, with key: CodingKey) -> _Decoder {
_Decoder(referencing: node, userInfo: userInfo, codingPath: codingPath + [key])
}
func superDecoder(referencing node: JSValue) -> _Decoder {
_Decoder(referencing: node, userInfo: userInfo, codingPath: codingPath.dropLast())
}
}
private enum Object {
static let ref = JSObject.global.Object.function!
static func keys(_ object: JSObject) -> [String] {
let keys = ref.keys!(object).array!
return keys.map { $0.string! }
}
}
private func _keyNotFound(at codingPath: [CodingKey], _ key: CodingKey) -> DecodingError {
let description = "No value associated with key \(key) (\"\(key.stringValue)\")."
let context = DecodingError.Context(codingPath: codingPath, debugDescription: description)
return .keyNotFound(key, context)
}
private func _typeMismatch(at codingPath: [CodingKey], _ type: Any.Type, reality: Any) -> DecodingError {
let description = "Expected to decode \(type) but found \(reality) instead."
let context = DecodingError.Context(codingPath: codingPath, debugDescription: description)
return .typeMismatch(type, context)
}
struct _JSCodingKey: CodingKey {
var stringValue: String
var intValue: Int?
init?(stringValue: String) {
self.stringValue = stringValue
intValue = nil
}
init?(intValue: Int) {
stringValue = "\(intValue)"
self.intValue = intValue
}
init(index: Int) {
stringValue = "Index \(index)"
intValue = index
}
static let `super` = _JSCodingKey(stringValue: "super")!
}
private struct _KeyedDecodingContainer<Key: CodingKey>: KeyedDecodingContainerProtocol {
private let decoder: _Decoder
private let ref: JSObject
var codingPath: [CodingKey] { return decoder.codingPath }
var allKeys: [Key] {
Object.keys(ref).compactMap(Key.init(stringValue:))
}
init(decoder: _Decoder, ref: JSObject) {
self.decoder = decoder
self.ref = ref
}
func _decode(forKey key: CodingKey) throws -> JSValue {
let result = ref[key.stringValue]
guard !result.isUndefined else {
throw _keyNotFound(at: codingPath, key)
}
return result
}
func _throwTypeMismatchIfNil<T>(forKey key: CodingKey, _ transform: (JSValue) -> T?) throws -> T {
let jsValue = try _decode(forKey: key)
guard let value = transform(jsValue) else {
throw _typeMismatch(at: codingPath, T.self, reality: jsValue)
}
return value
}
func contains(_ key: Key) -> Bool {
!ref[key.stringValue].isUndefined
}
func decodeNil(forKey key: Key) throws -> Bool {
try _decode(forKey: key).isNull
}
func decode<T>(_: T.Type, forKey key: Key) throws -> T where T: ConstructibleFromJSValue & Decodable {
return try _throwTypeMismatchIfNil(forKey: key) { T.construct(from: $0) }
}
func decode<T>(_: T.Type, forKey key: Key) throws -> T where T: Decodable {
return try T(from: _decoder(forKey: key))
}
func nestedContainer<NestedKey>(keyedBy _: NestedKey.Type, forKey key: Key) throws -> KeyedDecodingContainer<NestedKey> where NestedKey: CodingKey {
try _decoder(forKey: key).container(keyedBy: NestedKey.self)
}
func nestedUnkeyedContainer(forKey key: Key) throws -> UnkeyedDecodingContainer {
try _decoder(forKey: key).unkeyedContainer()
}
func superDecoder() throws -> Decoder {
try _decoder(forKey: _JSCodingKey.super)
}
func superDecoder(forKey key: Key) throws -> Decoder {
try _decoder(forKey: key)
}
func _decoder(forKey key: CodingKey) throws -> Decoder {
let value = try _decode(forKey: key)
return decoder.decoder(referencing: value, with: key)
}
}
private struct _UnkeyedDecodingContainer: UnkeyedDecodingContainer {
var codingPath: [CodingKey] { decoder.codingPath }
let count: Int?
var isAtEnd: Bool { currentIndex >= count ?? 0 }
var currentIndex: Int = 0
private var currentKey: CodingKey { return _JSCodingKey(index: currentIndex) }
let decoder: _Decoder
let ref: JSObject
init(decoder: _Decoder, ref: JSObject) {
self.decoder = decoder
count = ref.length.number.map(Int.init)
self.ref = ref
}
mutating func _currentValue() -> JSValue {
defer { currentIndex += 1 }
return ref[currentIndex]
}
mutating func _throwTypeMismatchIfNil<T>(_ transform: (JSValue) -> T?) throws -> T {
let value = _currentValue()
guard let jsValue = transform(value) else {
throw _typeMismatch(at: codingPath, T.self, reality: value)
}
return jsValue
}
mutating func decodeNil() throws -> Bool {
return _currentValue().isNull
}
mutating func decode<T>(_: T.Type) throws -> T where T: ConstructibleFromJSValue & Decodable {
try _throwTypeMismatchIfNil { T.construct(from: $0) }
}
mutating func decode<T>(_: T.Type) throws -> T where T: Decodable {
return try T(from: _decoder())
}
mutating func nestedContainer<NestedKey>(keyedBy _: NestedKey.Type) throws -> KeyedDecodingContainer<NestedKey> where NestedKey: CodingKey {
return try _decoder().container(keyedBy: NestedKey.self)
}
mutating func nestedUnkeyedContainer() throws -> UnkeyedDecodingContainer {
return try _decoder().unkeyedContainer()
}
mutating func superDecoder() throws -> Decoder {
_decoder()
}
mutating func _decoder() -> Decoder {
decoder.decoder(referencing: _currentValue(), with: currentKey)
}
}
extension _Decoder: SingleValueDecodingContainer {
func _throwTypeMismatchIfNil<T>(_ transform: (JSValue) -> T?) throws -> T {
guard let jsValue = transform(node) else {
throw _typeMismatch(at: codingPath, T.self, reality: node)
}
return jsValue
}
func decodeNil() -> Bool {
node.isNull
}
func decode<T>(_: T.Type) throws -> T where T: ConstructibleFromJSValue & Decodable {
try _throwTypeMismatchIfNil { T.construct(from: $0) }
}
func decode<T>(_ type: T.Type) throws -> T where T: Decodable {
let primitive = { (node: JSValue) -> T? in
guard let constructibleType = type as? ConstructibleFromJSValue.Type else {
return nil
}
return constructibleType.construct(from: node) as? T
}
return try primitive(node) ?? type.init(from: self)
}
}
/// `JSValueDecoder` facilitates the decoding of JavaScript value into semantic `Decodable` types.
public class JSValueDecoder {
/// Initializes a new `JSValueDecoder`.
public init() {}
/// Decodes a top-level value of the given type from the given JavaScript value representation.
///
/// - Parameter T: The type of the value to decode.
/// - Parameter value: The `JSValue` to decode from.
public func decode<T>(
_: T.Type = T.self,
from value: JSValue,
userInfo: [CodingUserInfoKey: Any] = [:]
) throws -> T where T: Decodable {
let decoder = _Decoder(referencing: value, userInfo: userInfo)
return try T(from: decoder)
}
}