From a3a44a90b061b5154d9dbcb307409051a39d397d Mon Sep 17 00:00:00 2001
From: Javier Cicchelli <javier@rock-n-code.com>
Date: Fri, 2 Dec 2022 18:16:51 +0100
Subject: [PATCH] Implemented focus and handling of the return key presses in
 the LoginForm view apart from overall UI improvements.

---
 BeReal/Login/Components/LoginForm.swift | 91 +++++++++++++++++++------
 1 file changed, 72 insertions(+), 19 deletions(-)

diff --git a/BeReal/Login/Components/LoginForm.swift b/BeReal/Login/Components/LoginForm.swift
index 024f080..bce0dfe 100644
--- a/BeReal/Login/Components/LoginForm.swift
+++ b/BeReal/Login/Components/LoginForm.swift
@@ -10,12 +10,20 @@ import SwiftUI
 
 struct LoginForm: View {
     
+    // MARK: States
+    
+    @FocusState private var focusedField: Field?
+    
     // MARK: Bindings
     
     @Binding var username: String
     @Binding var password: String
     @Binding var errorMessage: String?
     
+    // MARK: Properties
+    
+    let onReturn: () -> Void
+    
     // MARK: Body
     
     var body: some View {
@@ -23,25 +31,33 @@ struct LoginForm: View {
             alignment: .leading,
             spacing: 16
         ) {
-            TextField(
-                "Username",
-                text: $username
-            )
-            .textContentType(.username)
-            .autocapitalization(.none)
-            .disableAutocorrection(true)
-            .keyboardType(.default)
+            TextField("Username", text: $username) { isBeginEditing in
+                guard isBeginEditing, errorMessage != nil else { return }
+                
+                errorMessage = nil
+            }
+                .textContentType(.username)
+                .lineLimit(1)
+                .autocapitalization(.none)
+                .disableAutocorrection(true)
+                .keyboardType(.default)
+                .focused($focusedField, equals: .username)
+                .onSubmit {
+                    onUsernameReturnPressed()
+                }
             
             Divider()
             
-            SecureField(
-                "Password",
-                text: $password
-            )
-            .textContentType(.password)
-            .autocapitalization(.none)
-            .disableAutocorrection(true)
-            .keyboardType(.default)
+            SecureField("Password", text: $password)
+                .textContentType(.password)
+                .lineLimit(1)
+                .autocapitalization(.none)
+                .disableAutocorrection(true)
+                .keyboardType(.default)
+                .focused($focusedField, equals: .password)
+                .onSubmit {
+                    onPasswordReturnPressed()
+                }
             
             if let errorMessage {
                 Divider()
@@ -53,7 +69,7 @@ struct LoginForm: View {
         }
         .frame(maxWidth: .infinity, alignment: .leading)
         .padding(16)
-        .background(Color.white)
+        .background(Color.primary.colorInvert())
         .cornerRadius(8)
         .onAppear {
             setClearButtonIfNeeded()
@@ -69,6 +85,41 @@ private extension LoginForm {
         
         UITextField.appearance().clearButtonMode = .whileEditing
     }
+    
+    func onUsernameReturnPressed() {
+        guard !username.isEmpty else {
+            focusedField = .username
+            return
+        }
+        
+        if password.isEmpty {
+            focusedField = .password
+        } else {
+            onReturn()
+        }
+    }
+    
+    func onPasswordReturnPressed() {
+        guard !password.isEmpty else {
+            focusedField = .password
+            return
+        }
+        
+        if username.isEmpty {
+            focusedField = .username
+        } else {
+            onReturn()
+        }
+    }
+}
+
+// MARK: - Enumerations
+
+private extension LoginForm {
+    enum Field: Hashable {
+        case username
+        case password
+    }
 }
 
 // MARK: - Previews
@@ -78,14 +129,16 @@ struct LoginForm_Previews: PreviewProvider {
         LoginForm(
             username: .constant("Some username"),
             password: .constant("Some Password"),
-            errorMessage: .constant(nil)
+            errorMessage: .constant(nil),
+            onReturn: {}
         )
         .previewDisplayName("Login form with no error message")
         
         LoginForm(
             username: .constant("Some username"),
             password: .constant("Some Password"),
-            errorMessage: .constant("Some error goes in here...")
+            errorMessage: .constant("Some error goes in here..."),
+            onReturn: {}
         )
         .previewDisplayName("Login form with some error message")
     }