feat: region resolver via bundle (#479)

Author: wooj2

AWSClientRuntime/Sources/Config/Bundle.swift

@@ -0,0 +1,18 @@
+//
+// Copyright Amazon.com Inc. or its affiliates.
+// All Rights Reserved.
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+        
+#if os(iOS) || os(watchOS) || os(tvOS)
+import Foundation.NSBundle
+public typealias Bundle = Foundation.Bundle
+#else
+public struct Bundle {
+    func object(forInfoDictionaryKey key: String) -> Any? {
+        return nil
+    }
+    public static var main: Bundle = Bundle()
+}
+#endif

AWSClientRuntime/Sources/Config/BundleConfiguration.swift

@@ -0,0 +1,28 @@
+//
+// Copyright Amazon.com Inc. or its affiliates.
+// All Rights Reserved.
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+
+// Adapted from: https://nshipster.com/xcconfig/
+struct BundleConfiguration {
+    enum Error: Swift.Error {
+        case missingKey, invalidValue
+    }
+
+    static func value<T>(bundle: Bundle, for key: String) throws -> T where T: LosslessStringConvertible {
+        guard let object = bundle.object(forInfoDictionaryKey: key) else {
+            throw Error.missingKey
+        }
+        switch object {
+        case let value as T:
+            return value
+        case let string as String:
+            guard let value = T(string) else { fallthrough }
+            return value
+        default:
+            throw Error.invalidValue
+        }
+    }
+}

AWSClientRuntime/Sources/Regions/BundleRegionProvider.swift

@@ -0,0 +1,45 @@
+//
+// Copyright Amazon.com Inc. or its affiliates.
+// All Rights Reserved.
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+import AwsCommonRuntimeKit
+import ClientRuntime
+
+public struct BundleRegionProvider: RegionProvider {
+    private let logger: SwiftLogger
+    private let bundle: Bundle
+    private let regionKey: String
+    private let maxSizeRegion = 20
+
+    public init(bundle: Bundle = Bundle.main, regionKey: String = "AWS_REGION") {
+        self.logger = SwiftLogger(label: "BundleRegionProvider")
+        self.bundle = bundle
+        self.regionKey = regionKey
+    }
+    
+    public func resolveRegion() -> Future<String?> {
+        let future = Future<String?>()
+        #if os(iOS) || os(watchOS) || os(tvOS)
+        guard let region = region() else {
+            future.fulfill(nil)
+        }
+        return region.count > maxSizeRegion
+            ? future.fulfill(region.prefix(maxSizeRegion))
+            : future.fulfill(region)
+        #else
+        future.fulfill(nil)
+        #endif
+        return future
+    }
+
+    func region() -> String? {
+        do {
+            return try BundleConfiguration.value(bundle: self.bundle, for: regionKey)
+        } catch {
+            logger.debug("\(error)")
+        }
+        return nil
+    }
+}

AWSClientRuntime/Sources/Regions/DefaultRegionResolver.swift

@@ -11,8 +11,7 @@ public struct DefaultRegionResolver: RegionResolver {
     public let providers: [RegionProvider]
     let logger: SwiftLogger
 
-    public init(providers: [RegionProvider] = [EnvironmentRegionProvider(), ProfileRegionProvider(), IMDSRegionProvider()]) {
-        // TODO: add more region resolvers i.e. System Properties, etc
+    public init(providers: [RegionProvider] = [BundleRegionProvider(), EnvironmentRegionProvider(), ProfileRegionProvider(), IMDSRegionProvider()]) {
         self.providers = providers
         self.logger = SwiftLogger(label: "DefaultRegionProvider")
     }