Merge pull request #4647 from b-onc/feat/username-verification

Feature: Check username validity on text field return

Wikipedia/Code/WMFAccountCreationViewController.storyboard

@@ -71,6 +71,7 @@
                                                         <connections>
                                                             <action selector="textFieldDidBeginEditing:" destination="LsX-JK-bT6" eventType="editingDidBegin" id="VM3-mK-wNB"/>
                                                             <action selector="textFieldDidChange:" destination="LsX-JK-bT6" eventType="editingChanged" id="Eys-MQ-tYh"/>
+                                                            <action selector="textFieldDidEndEditing:reason:" destination="LsX-JK-bT6" eventType="editingDidEnd" id="2Bj-vl-8sb"/>
                                                             <outlet property="delegate" destination="LsX-JK-bT6" id="QIw-fL-bzL"/>
                                                         </connections>
                                                     </textField>

Wikipedia/Code/WMFAccountCreationViewController.swift

@@ -285,6 +285,28 @@ class WMFAccountCreationViewController: WMFScrollViewController, WMFCaptchaViewC
         default: break
         }
     }
+
+    @IBAction func textFieldDidEndEditing(_ textField: UITextField, reason: UITextField.DidEndEditingReason) {
+        guard textField === usernameField, reason == .committed, let username = textField.text else { return }
+        let siteURL = dataStore.primarySiteURL!
+        // We can check for username validity in the background
+        Task {
+            accountCreator.checkUsername(username, siteURL: siteURL) { canCreate in
+                if !canCreate {
+                    Task {
+                        await MainActor.run {
+                            self.usernameAlertLabel.text = WMFAccountCreatorError.usernameUnavailable.localizedDescription
+                            self.usernameAlertLabel.isHidden = false
+                            self.usernameField.textColor = self.theme.colors.error
+                        }
+                    }
+                }
+            } failure: { error in
+                // TODO: What to do if this request fails?
+            }
+
+        }
+    }
 
     fileprivate func createAccount() {
         WMFAlertManager.sharedInstance.showAlert(WMFLocalizedString("account-creation-saving", value:"Saving...", comment:"Alert shown when user saves account creation form. {{Identical|Saving}}"), sticky: true, canBeDismissedByUser: false, dismissPreviousAlerts: true, tapCallBack: nil)

Wikipedia/Code/WMFAccountCreator.swift

@@ -33,6 +33,73 @@ public struct WMFAccountCreatorResult {
 }
 
 public class WMFAccountCreator: Fetcher {
+
+    struct CheckUsernameAPIResponse: Codable {
+        struct Query: Codable {
+            struct User: Codable {
+                struct CanCreateError: Codable {
+                    let message: String
+                    let params: [String]
+                    let type: String
+                    let code: String
+                }
+
+                enum CodingKeys: String, CodingKey {
+                    case userId = "userid"
+                    case name
+                    case missing
+                    case canCreate = "cancreate"
+                    case canCreateError = "cancreateerror"
+                }
+
+                let userId: Int?
+                let name: String
+                let missing: Bool?
+                let canCreate: Bool?
+                let canCreateError: [CanCreateError]?
+            }
+
+            let users: [User]
+        }
+
+        enum CodingKeys: String, CodingKey {
+            case batchComplete = "batchcomplete"
+            case query
+        }
+
+        let batchComplete: Bool
+        let query: Query
+    }
+
+    public func checkUsername(
+        _ username: String,
+        siteURL: URL,
+        success: @escaping (Bool) -> Void,
+        failure: @escaping WMFErrorHandler
+    ) {
+        let parameters: [String: String] = [
+            "action": "query",
+            "list": "users",
+            "ususers": username,
+            "usprop": "cancreate",
+            "formatversion": "2",
+            "format": "json"
+        ]
+
+        performDecodableMediaWikiAPIGET(
+            for: siteURL,
+            with: parameters
+        ) { (result: Result<CheckUsernameAPIResponse, Error>) in
+            switch result {
+            case .failure(let error):
+                failure(error)
+            case .success(let apiResponse):
+                let usernameAvailable = apiResponse.query.users.first?.canCreate ?? false
+                success(usernameAvailable)
+            }
+        }
+    }
+
     public func createAccount(username: String, password: String, retypePassword: String, email: String?, captchaID: String?, captchaWord: String?, siteURL: URL, success: @escaping WMFAccountCreatorResultBlock, failure: @escaping WMFErrorHandler) {
         var parameters: [String: String] = [
             "action": "createaccount",