#40: Add the login screen from EI.

- Remove SSO and replace fallback with OIDC.

ElementX/Sources/Other/SwiftUI/ErrorHandling/AlertInfo.swift

@@ -0,0 +1,89 @@
+// 
+// Copyright 2021 New Vector Ltd
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+import SwiftUI
+
+/// A type that describes an alert to be shown to the user.
+///
+/// The alert info can be added to the view state bindings and used as an alert's `item`:
+/// ```
+/// MyView
+///     .alert(item: $viewModel.alertInfo) { $0.alert }
+/// ```
+struct AlertInfo<T: Hashable>: Identifiable {
+    /// An identifier that can be used to distinguish one error from another.
+    let id: T
+    /// The alert's title.
+    let title: String
+    /// The alert's message (optional).
+    var message: String?
+    /// The alert's primary button title and action. Defaults to an Ok button with no action.
+    var primaryButton: (title: String, action: (() -> Void)?) = (ElementL10n.ok, nil)
+    /// The alert's secondary button title and action.
+    var secondaryButton: (title: String, action: (() -> Void)?)?
+}
+
+extension AlertInfo {
+    /// Initialises the type with the title from an `Error`'s localised description along with the default Ok button.
+    ///
+    /// Currently this initialiser creates an alert for every error, however in the future it may be updated to filter
+    /// out some specific errors such as cancellation and networking issues that create too much noise or are
+    /// indicated to the user using other mechanisms.
+    init(error: Error) where T == String {
+        self.init(id: error.localizedDescription,
+                  title: error.localizedDescription)
+    }
+    
+    /// Initialises the type with a generic title and message for an unknown error along with the default Ok button.
+    /// - Parameters:
+    ///   - id: An ID that identifies the error.
+    ///   - error: The Error that occurred.
+    init(id: T) {
+        self.id = id
+        title = ElementL10n.dialogTitleError
+        message = ElementL10n.unknownError
+    }
+}
+
+extension AlertInfo {
+    private var messageText: Text? {
+        guard let message = message else { return nil }
+        return Text(message)
+    }
+    
+    /// Returns a SwiftUI `Alert` created from this alert info, using default button
+    /// styles for both primary and (if set) secondary buttons.
+    var alert: Alert {
+        if let secondaryButton = secondaryButton {
+            return Alert(title: Text(title),
+                         message: messageText,
+                         primaryButton: alertButton(for: primaryButton),
+                         secondaryButton: alertButton(for: secondaryButton))
+        } else {
+            return Alert(title: Text(title),
+                         message: messageText,
+                         dismissButton: alertButton(for: primaryButton))
+        }
+    }
+    
+    private func alertButton(for buttonParameters: (title: String, action: (() -> Void)?)) -> Alert.Button {
+        guard let action = buttonParameters.action else {
+            return .default(Text(buttonParameters.title))
+        }
+        
+        return .default(Text(buttonParameters.title), action: action)
+    }
+}