Rename PKCE Mode to Method to be in line with spec

This also resulted in renaming the computed variable `method` to
`testMethodURLQueryParameterValue` because `Method.method` would have
been confusing. The new name also better reflects where the value is
meant to be used.

Author: mokagio

WordPressAuthenticator/GoogleSignIn/URL+GoogleSignIn.swift

@@ -10,7 +10,7 @@ extension URL {
         let queryItems = [
             ("client_id", clientId),
             ("code_challenge", pkce.codeCallenge),
-            ("code_challenge_method", pkce.mode.method),
+            ("code_challenge_method", pkce.method.urlQueryParameterValue),
             ("redirect_uri", redirectURI(from: clientId)),
             ("response_type", "code"),
             // TODO: We might want to add some of these or them configurable

WordPressAuthenticator/OAuth/ProofKeyForCodeExchange.swift

@@ -13,11 +13,11 @@
 // Note: The common abbreviation of "Proof Key for Code Exchange" is PKCE and is pronounced "pixy".
 struct ProofKeyForCodeExchange {
 
-    enum Mode {
+    enum Method {
         case s256
         case plain
 
-        var method: String {
+        var urlQueryParameterValue: String {
             switch self {
             case .plain: return "plain"
             case .s256: return "S256"
@@ -26,15 +26,15 @@ struct ProofKeyForCodeExchange {
     }
 
     let codeVerifier: String
-    let mode: Mode
+    let method: Method
 
-    init(codeVerifier: String, mode: Mode) {
+    init(codeVerifier: String, method: Method) {
         self.codeVerifier = codeVerifier
-        self.mode = mode
+        self.method = method
     }
 
     var codeCallenge: String {
-        switch mode {
+        switch method {
         case .s256:
             // TODO: code_challenge = BASE64URL-ENCODE(SHA256(ASCII(code_verifier)))
             fatalError()

WordPressAuthenticatorTests/GoogleSignIn/OAuthRequestBody+GoogleSignInTests.swift

@@ -4,7 +4,7 @@ import XCTest
 class OAuthRequestBodyGoogleSignInTests: XCTestCase {
 
     func testGoogleSignInTokenRequestBody() throws {
-        let pkce = ProofKeyForCodeExchange(codeVerifier: "test", mode: .plain)
+        let pkce = ProofKeyForCodeExchange(codeVerifier: "test", method: .plain)
         let body = OAuthTokenRequestBody.googleSignInRequestBody(
             clientId: "com.app.123-abc",
             authCode: "codeValue",

WordPressAuthenticatorTests/GoogleSignIn/URL+GoogleSignInTests.swift

@@ -4,7 +4,7 @@ import XCTest
 class URLGoogleSignInTests: XCTestCase {
 
     func testGoogleSignInAuthURL() throws {
-        let pkce = ProofKeyForCodeExchange(codeVerifier: "test", mode: .plain)
+        let pkce = ProofKeyForCodeExchange(codeVerifier: "test", method: .plain)
         let url = try URL.googleSignInAuthURL(
             clientId: "123-abc245def.apps.googleusercontent.com",
             pkce: pkce
@@ -24,7 +24,7 @@ class URLGoogleSignInTests: XCTestCase {
         assertQueryItems(
             for: url,
             includeItemNamed: "code_challenge_method",
-            withValue: pkce.mode.method
+            withValue: pkce.method.urlQueryParameterValue
         )
         assertQueryItems(
             for: url,

WordPressAuthenticatorTests/OAuth/ProofKeyForCodeExchangeTests.swift

@@ -5,7 +5,7 @@ class ProofKeyForCodeExchangeTests: XCTestCase {
 
     func testCodeChallengeInPlainModeIsTheSameAsCodeVerifier() {
         XCTAssertEqual(
-            ProofKeyForCodeExchange(codeVerifier: "abc", mode: .plain).codeCallenge,
+            ProofKeyForCodeExchange(codeVerifier: "abc", method: .plain).codeCallenge,
             "abc"
         )
     }
@@ -14,11 +14,11 @@ class ProofKeyForCodeExchangeTests: XCTestCase {
         // TODO:
     }
 
-    func testModePlainMethod() {
-        XCTAssertEqual(ProofKeyForCodeExchange.Mode.plain.method, "plain")
+    func testMethodURLQueryParameterValuePlain() {
+        XCTAssertEqual(ProofKeyForCodeExchange.Method.plain.urlQueryParameterValue, "plain")
     }
 
-    func testModeS256Method() {
-        XCTAssertEqual(ProofKeyForCodeExchange.Mode.s256.method, "S256")
+    func testMethodURLQueryParameterValueS256() {
+        XCTAssertEqual(ProofKeyForCodeExchange.Method.s256.urlQueryParameterValue, "S256")
     }
 }