code style (#9)

motivation: nicer code

changes
* rename Result to ResultType since swift is getting formal Result soon
* use Handler instead of T for generics in CodableLambda which is more readable
* simpler bytes->String decoding

Sources/SwiftAwsLambda/Lambda+Codable.swift

@@ -27,7 +27,7 @@ extension Lambda {
     /// Run a Lambda defined by implementing the `LambdaCodableHandler` protocol, having `In` and `Out` are `Decodable` and `Encodable` respectively.
     ///
     /// - note: This is a blocking operation that will run forever, as it's lifecycle is managed by the AWS Lambda Runtime Engine.
-    public static func run<T>(_ handler: T) where T: LambdaCodableHandler {
+    public static func run<Handler>(_ handler: Handler) where Handler: LambdaCodableHandler {
         self.run(handler as LambdaHandler)
     }
 
@@ -37,13 +37,13 @@ extension Lambda {
     }
 
     // for testing
-    internal static func run<T>(handler: T, maxTimes: Int = 0) -> LambdaLifecycleResult where T: LambdaCodableHandler {
+    internal static func run<Handler>(handler: Handler, maxTimes: Int = 0) -> LambdaLifecycleResult where Handler: LambdaCodableHandler {
         return self.run(handler: handler as LambdaHandler, maxTimes: maxTimes)
     }
 }
 
 /// A result type for a Lambda that returns a generic `Out`, having `Out` extend `Encodable`.
-public typealias LambdaCodableResult<Out> = Result<Out, String>
+public typealias LambdaCodableResult<Out> = ResultType<Out, String>
 
 /// A callback for a Lambda that returns a `LambdaCodableResult<Out>` result type, having `Out` extend `Encodable`.
 public typealias LambdaCodableCallback<Out> = (LambdaCodableResult<Out>) -> Void

Sources/SwiftAwsLambda/Lambda+String.swift

@@ -40,7 +40,7 @@ extension Lambda {
 }
 
 /// A result type for a Lambda that returns a `String`.
-public typealias LambdaStringResult = Result<String, String>
+public typealias LambdaStringResult = ResultType<String, String>
 
 /// A callback for a Lambda that returns a `LambdaStringResult` result type.
 public typealias LambdaStringCallback = (LambdaStringResult) -> Void
@@ -53,13 +53,10 @@ public protocol LambdaStringHandler: LambdaHandler {
     func handle(context: LambdaContext, payload: String, callback: @escaping LambdaStringCallback)
 }
 
-/// Default implementation of `String` -> `[UInt8]` encoding and `[UInt8]` -> `String' decoding 
+/// Default implementation of `String` -> `[UInt8]` encoding and `[UInt8]` -> `String' decoding
 public extension LambdaStringHandler {
     func handle(context: LambdaContext, payload: [UInt8], callback: @escaping LambdaCallback) {
-        guard let payloadAsString = String(bytes: payload, encoding: .utf8) else {
-            return callback(.failure("failed casting payload to String"))
-        }
-        self.handle(context: context, payload: payloadAsString, callback: { result in
+        self.handle(context: context, payload: String(decoding: payload, as: UTF8.self), callback: { result in
             switch result {
             case let .success(string):
                 return callback(.success([UInt8](string.utf8)))

Sources/SwiftAwsLambda/Lambda.swift

@@ -139,7 +139,7 @@ public enum Lambda {
 }
 
 /// A result type for a Lambda that returns a `[UInt8]`.
-public typealias LambdaResult = Result<[UInt8], String>
+public typealias LambdaResult = ResultType<[UInt8], String>
 
 public typealias LambdaCallback = (LambdaResult) -> Void
 
@@ -169,7 +169,7 @@ public struct LambdaContext {
     }
 }
 
-internal typealias LambdaLifecycleResult = Result<Int, Error>
+internal typealias LambdaLifecycleResult = ResultType<Int, Error>
 
 private struct LambdaClosureWrapper: LambdaHandler {
     private let closure: LambdaClosure

Sources/SwiftAwsLambda/LambdaRunner.swift

@@ -63,7 +63,7 @@ internal final class LambdaRunner {
     }
 }
 
-internal typealias LambdaRunResult = Result<(), Error>
+internal typealias LambdaRunResult = ResultType<(), Error>
 
 private extension LambdaHandler {
     func handle(context: LambdaContext, payload: [UInt8], promise: EventLoopPromise<LambdaResult>) {

Sources/SwiftAwsLambda/LambdaRuntimeClient.swift

@@ -76,8 +76,8 @@ internal class LambdaRuntimeClient {
     }
 }
 
-internal typealias RequestWorkResult = Result<(LambdaContext, [UInt8]), LambdaRuntimeClientError>
-internal typealias PostResultsResult = Result<(), LambdaRuntimeClientError>
+internal typealias RequestWorkResult = ResultType<(LambdaContext, [UInt8]), LambdaRuntimeClientError>
+internal typealias PostResultsResult = ResultType<(), LambdaRuntimeClientError>
 
 internal enum LambdaRuntimeClientError: Error {
     case badStatusCode(HTTPResponseStatus)

Sources/SwiftAwsLambda/Utils.swift

@@ -16,7 +16,7 @@ import Dispatch
 import NIO
 
 /// Genric result type, that is used throught the library.
-public enum Result<Value, Error> {
+public enum ResultType<Value, Error> {
     case success(Value)
     case failure(Error)
 }

Tests/SwiftAwsLambdaTests/MockLambdaServer.swift

@@ -189,7 +189,7 @@ internal protocol LambdaServerBehavior {
     func processError(requestId: String, error: ErrorResponse) -> ProcessErrorResult
 }
 
-internal typealias GetWorkResult = Result<(String, String), GetWorkError>
+internal typealias GetWorkResult = ResultType<(String, String), GetWorkError>
 
 internal enum GetWorkError: Int {
     case badRequest = 400
@@ -209,7 +209,7 @@ internal enum ProcessResponseError: Int {
     case internalServerError = 500
 }
 
-internal typealias ProcessErrorResult = Result<(), ProcessError>
+internal typealias ProcessErrorResult = ResultType<(), ProcessError>
 
 internal enum ProcessError: Int, Error {
     case invalidErrorShape = 299