Use dnssd framework on Darwin platforms (#8)

* Use dnssd framework on Darwin platforms

Add `DNSResolver` protocol with two implementations: one backed by c-ares and the other dnssd. Use `dnssd` implementation on Darwin platforms by default.

* Address review feedback

Author: yim-lee

Package.swift

@@ -28,7 +28,7 @@ let package = Package(
         .library(name: "AsyncDNSResolver", targets: ["AsyncDNSResolver"]),
     ],
     dependencies: [
-        .package(url: "https://github.com/apple/swift-log", .upToNextMajor(from: "1.0.0")),
+        .package(url: "https://github.com/apple/swift-nio", .upToNextMajor(from: "2.53.0")),
     ],
     targets: [
         .target(
@@ -47,7 +47,7 @@ let package = Package(
             name: "AsyncDNSResolver",
             dependencies: [
                 "CAsyncDNSResolver",
-                .product(name: "Logging", package: "swift-log"),
+                .product(name: "NIOCore", package: "swift-nio"),
             ]
         ),
 

Sources/AsyncDNSResolver/AsyncDNSResolver.swift

@@ -12,10 +12,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-import CAsyncDNSResolver
-
-// MARK: - Async DNS resolver errors
-
 extension AsyncDNSResolver {
     public struct Error: Swift.Error, CustomStringConvertible {
         enum Code: Equatable, CustomStringConvertible {
@@ -43,7 +39,7 @@ extension AsyncDNSResolver {
             case initError(String?)
             case cancelled(String?)
             case service(String?)
-            case other(code: Int32, String?)
+            case other(code: Int, String?)
 
             var description: String {
                 switch self {
@@ -107,61 +103,6 @@ extension AsyncDNSResolver {
             self.code = code
         }
 
-        init(code: Int32, _ description: String? = nil) {
-            switch code {
-            case ARES_ENODATA:
-                self = .noData(description)
-            case ARES_EFORMERR:
-                self = .invalidQuery(description)
-            case ARES_ESERVFAIL:
-                self = .serverFailure(description)
-            case ARES_ENOTFOUND:
-                self = .notFound(description)
-            case ARES_ENOTIMP:
-                self = .notImplemented(description)
-            case ARES_EREFUSED:
-                self = .serverRefused(description)
-            case ARES_EBADQUERY:
-                self = .badQuery(description)
-            case ARES_EBADNAME:
-                self = .badName(description)
-            case ARES_EBADFAMILY:
-                self = .badFamily(description)
-            case ARES_EBADRESP:
-                self = .badResponse(description)
-            case ARES_ECONNREFUSED:
-                self = .connectionRefused(description)
-            case ARES_ETIMEOUT:
-                self = .timeout(description)
-            case ARES_EOF:
-                self = .eof(description)
-            case ARES_EFILE:
-                self = .fileIO(description)
-            case ARES_ENOMEM:
-                self = .noMemory(description)
-            case ARES_EDESTRUCTION:
-                self = .destruction(description)
-            case ARES_EBADSTR:
-                self = .badString(description)
-            case ARES_EBADFLAGS:
-                self = .badFlags(description)
-            case ARES_ENONAME:
-                self = .noName(description)
-            case ARES_EBADHINTS:
-                self = .badHints(description)
-            case ARES_ENOTINITIALIZED:
-                self = .notInitialized(description)
-            case ARES_ELOADIPHLPAPI, ARES_EADDRGETNETWORKPARAMS:
-                self = .initError(description)
-            case ARES_ECANCELLED:
-                self = .cancelled(description)
-            case ARES_ESERVICE:
-                self = .service(description)
-            default:
-                self = .other(code: code, description)
-            }
-        }
-
         public var description: String {
             "\(self.code)"
         }
@@ -262,7 +203,7 @@ extension AsyncDNSResolver {
             .init(code: .service(description))
         }
 
-        public static func other(code: Int32, _ description: String? = nil) -> Error {
+        public static func other(code: Int, _ description: String? = nil) -> Error {
             .init(code: .other(code: code, description))
         }
     }

Sources/AsyncDNSResolver/Error.swift renamed to Sources/AsyncDNSResolver/Errors.swift

@@ -14,9 +14,9 @@
 
 import CAsyncDNSResolver
 
-// MARK: - Options for async DNS resolver
+// MARK: - Options for `CAresDNSResolver`
 
-extension AsyncDNSResolver {
+extension CAresDNSResolver {
     public struct Options {
         public static var `default`: Options {
             .init()
@@ -87,7 +87,7 @@ extension AsyncDNSResolver {
     }
 }
 
-extension AsyncDNSResolver.Options {
+extension CAresDNSResolver.Options {
     public struct Flags: OptionSet {
         public let rawValue: Int32
 
@@ -119,7 +119,7 @@ extension AsyncDNSResolver.Options {
     }
 }
 
-extension AsyncDNSResolver.Options {
+extension CAresDNSResolver.Options {
     var aresOptions: AresOptions {
         let aresOptions = AresOptions()
         aresOptions.setFlags(self.flags.rawValue)