//
//  LoginForm.swift
//  Login
//
//  Created by Javier Cicchelli on 01/12/2022.
//  Copyright © 2022 Röck+Cöde. All rights reserved.
//

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 {
        VStack(
            alignment: .leading,
            spacing: 16
        ) {
            TextField(
                NSLocalizedString(
                    "login.text_field.username.placeholder",
                    bundle: .module,
                    comment: "The placeholder for the username text field."
                ),
                text: $username
            )
            .textContentType(.username)
            .lineLimit(1)
            .autocapitalization(.none)
            .disableAutocorrection(true)
            .keyboardType(.default)
            .focused($focusedField, equals: .username)
            .onSubmit {
                onUsernameReturnPressed()
            }
            
            Divider()
            
            SecureField(
                NSLocalizedString(
                    "login.text_field.password.placeholder",
                    bundle: .module, 
                    comment: "The placeholder for the password text field."
                ),
                text: $password
            )
            .textContentType(.password)
            .lineLimit(1)
            .autocapitalization(.none)
            .disableAutocorrection(true)
            .keyboardType(.default)
            .focused($focusedField, equals: .password)
            .onSubmit {
                onPasswordReturnPressed()
            }
            
            if let errorMessage {
                Divider()
                
                Text(
                    NSLocalizedString(
                        errorMessage,
                        bundle: .module,
                        comment: "The error message received from the backend."
                    )
                )
                .foregroundColor(.secondary)
                .font(.body)
                .multilineTextAlignment(.center)
                .frame(maxWidth: .infinity)
                .padding(.horizontal, 24)
            }
        }
        .frame(maxWidth: .infinity, alignment: .leading)
        .padding(16)
        .background(Color.secondary.colorInvert())
        .cornerRadius(8)
        .onAppear {
            setClearButtonIfNeeded()
        }
        .onChange(of: focusedField) { _ in
            onTextFieldFocused()
        }
    }
}

// MARK: - Helpers

private extension LoginForm {
    func setClearButtonIfNeeded() {
        let textFieldAppearance = UITextField.appearance()
        guard textFieldAppearance.clearButtonMode != .whileEditing else { return }
        
        textFieldAppearance.clearButtonMode = .whileEditing
    }
    
    func onTextFieldFocused() {
        guard errorMessage != nil else { return }
        
        password = ""
        errorMessage = nil
    }
    
    func onUsernameReturnPressed() {
        guard !username.isEmpty else { return }
        
        if password.isEmpty {
            focusedField = .password
        } else {
            onReturn()
        }
    }
    
    func onPasswordReturnPressed() {
        guard !password.isEmpty else { return }
        
        if username.isEmpty {
            focusedField = .username
        } else {
            onReturn()
        }
    }
}

// MARK: - Enumerations

private extension LoginForm {
    enum Field: Hashable {
        case username
        case password
    }
}

// MARK: - Previews

struct LoginForm_Previews: PreviewProvider {
    static var previews: some View {
        LoginForm(
            username: .constant("Some username"),
            password: .constant("Some Password"),
            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..."),
            onReturn: {}
        )
        .previewDisplayName("Login form with some error message")
    }
}