Add support for AppSync events. (#187)

motivation: Support AWS AppSync events
changes: add Codable models for AppSync events

Sources/AWSLambdaEvents/AppSync.swift

@@ -0,0 +1,169 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftAWSLambdaRuntime open source project
+//
+// Copyright (c) 2017-2020 Apple Inc. and the SwiftAWSLambdaRuntime project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftAWSLambdaRuntime project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+// https://docs.aws.amazon.com/appsync/latest/devguide/resolver-context-reference.html
+public enum AppSync {
+    public struct Event: Decodable {
+        public let arguments: [String: ArgumentValue]
+
+        public enum ArgumentValue: Codable {
+            case string(String)
+            case dictionary([String: String])
+
+            public init(from decoder: Decoder) throws {
+                let container = try decoder.singleValueContainer()
+                if let strValue = try? container.decode(String.self) {
+                    self = .string(strValue)
+                } else if let dictionaryValue = try? container.decode([String: String].self) {
+                    self = .dictionary(dictionaryValue)
+                } else {
+                    throw DecodingError.dataCorruptedError(in: container, debugDescription: """
+                    Unexpected AppSync argument.
+                    Expected a String or a Dictionary.
+                    """)
+                }
+            }
+
+            public func encode(to encoder: Encoder) throws {
+                var container = encoder.singleValueContainer()
+                switch self {
+                case .dictionary(let array):
+                    try container.encode(array)
+                case .string(let str):
+                    try container.encode(str)
+                }
+            }
+        }
+
+        public let request: Request
+        public struct Request: Decodable {
+            let headers: HTTPHeaders
+        }
+
+        public let source: [String: String]?
+        public let stash: [String: String]?
+
+        public let info: Info
+        public struct Info: Codable {
+            public var selectionSetList: [String]
+            public var selectionSetGraphQL: String
+            public var parentTypeName: String
+            public var fieldName: String
+            public var variables: [String: String]
+        }
+
+        public let identity: Identity?
+        public enum Identity: Codable {
+            case iam(IAMIdentity)
+            case cognitoUserPools(CognitoUserPoolIdentity)
+
+            public struct IAMIdentity: Codable {
+                public let accountId: String
+                public let cognitoIdentityPoolId: String
+                public let cognitoIdentityId: String
+                public let sourceIp: [String]
+                public let username: String?
+                public let userArn: String
+                public let cognitoIdentityAuthType: String
+                public let cognitoIdentityAuthProvider: String
+            }
+
+            public struct CognitoUserPoolIdentity: Codable {
+                public let defaultAuthStrategy: String
+                public let issuer: String
+                public let sourceIp: [String]
+                public let sub: String
+                public let username: String?
+
+                public struct Claims {
+                    let sub: String
+                    let emailVerified: Bool
+                    let iss: String
+                    let phoneNumberVerified: Bool
+                    let cognitoUsername: String
+                    let aud: String
+                    let eventId: String
+                    let tokenUse: String
+                    let authTime: Int
+                    let phoneNumber: String?
+                    let exp: Int
+                    let iat: Int
+                    let email: String?
+
+                    enum CodingKeys: String, CodingKey {
+                        case sub
+                        case emailVerified = "email_verified"
+                        case iss
+                        case phoneNumberVerified = "phone_number_verified"
+                        case cognitoUsername = "cognito:username"
+                        case aud
+                        case eventId = "event_id"
+                        case tokenUse = "token_use"
+                        case authTime = "auth_time"
+                        case phoneNumber = "phone_number"
+                        case exp
+                        case iat
+                        case email
+                    }
+                }
+            }
+
+            public init(from decoder: Decoder) throws {
+                let container = try decoder.singleValueContainer()
+                if let iamIdentity = try? container.decode(IAMIdentity.self) {
+                    self = .iam(iamIdentity)
+                } else if let cognitoIdentity = try? container.decode(CognitoUserPoolIdentity.self) {
+                    self = .cognitoUserPools(cognitoIdentity)
+                } else {
+                    throw DecodingError.dataCorruptedError(in: container, debugDescription: """
+                    Unexpected Identity argument.
+                    Expected a IAM Identity or a Cognito User Pool Identity.
+                    """)
+                }
+            }
+
+            public func encode(to encoder: Encoder) throws {
+                var container = encoder.singleValueContainer()
+                switch self {
+                case .iam(let iamIdentity):
+                    try container.encode(iamIdentity)
+                case .cognitoUserPools(let cognitoUserPool):
+                    try container.encode(cognitoUserPool)
+                }
+            }
+        }
+    }
+}
+
+public extension AppSync {
+    enum Response<ResultType: Encodable>: Encodable {
+        public func encode(to encoder: Encoder) throws {
+            var container = encoder.singleValueContainer()
+            switch self {
+            case .array(let array):
+                try container.encode(array)
+            case .object(let object):
+                try container.encode(object)
+            case .dictionary(let dictionary):
+                try container.encode(dictionary)
+            }
+        }
+
+        case object(ResultType)
+        case array([ResultType])
+        case dictionary([String: ResultType])
+    }
+
+    typealias JSONStringResponse = Response<String>
+}