//
//  LoginView.swift
//  BeReal
//
//  Created by Javier Cicchelli on 30/11/2022.
//  Copyright © 2022 Röck+Cöde. All rights reserved.
//

import SwiftUI

public struct LoginView: View {
    
    // MARK: States

    @State private var containerTopPadding: CGFloat = 0
    
    // MARK: Initialisers
    
    public init() {}
    
    // MARK: Body
    
    public var body: some View {
        ScrollView(
            .vertical,
            showsIndicators: false
        ) {
            LoginContainer()
                .padding(.horizontal, 24)
                .padding(.top, containerTopPadding)
        }
        .background(Color.red)
        .overlay(ViewHeightGeometry())
        .onPreferenceChange(ViewHeightPreferenceKey.self) { height in
            containerTopPadding = height * 0.1
        }
    }
    
}

// MARK: - Views

fileprivate extension LoginView {
    struct LoginContainer: View {
        
        // MARK: States
        
        @State private var isAuthenticating: Bool = false
        @State private var username: String = ""
        @State private var password: String = ""
        @State private var errorMessage: String?

        // MARK: Body
        
        var body: some View {
            VStack(spacing: 32) {
                Text("login.title.text", bundle: .module)
                    .font(.largeTitle)
                    .fontWeight(.bold)
                    .foregroundColor(.primary)
  
                LoginForm(
                    username: $username,
                    password: $password,
                    errorMessage: $errorMessage
                ) {
                    // TODO: login with the username and password.
                }

                Button {
                    // TODO: login with the username and password.
                } label: {
                    Label {
                        Text("login.button.log_in.text", bundle: .module)
                            .fontWeight(.semibold)
                    } icon: {
                        if isAuthenticating {
                            ProgressView()
                        } else {
                            EmptyView()
                        }
                    }
                    .labelStyle(LogInLabelStyle())
                }
                .tint(.orange)
                .buttonStyle(.borderedProminent)
                .buttonBorderShape(.roundedRectangle(radius: 8))
                .controlSize(.large)
                .disabled(isLoginDisabled)
            }
        }
    }
    
    struct ViewHeightGeometry: View {
        var body: some View {
            GeometryReader { proxy in
                Color.clear.preference(
                    key: ViewHeightPreferenceKey.self,
                    value: proxy.size.height + proxy.safeAreaInsets.top + proxy.safeAreaInsets.bottom
                )
            }
        }
    }
}

// MARK: - Label styles

private extension LoginView.LoginContainer {
    struct LogInLabelStyle: LabelStyle {
        func makeBody(configuration: Configuration) -> some View {
            HStack(spacing: 8) {
                Spacer()
                
                configuration.title
                    .font(.body)
                    .foregroundColor(.primary)
                
                configuration.icon
                    .tint(.primary)
                
                Spacer()
            }
        }
    }
}

// MARK: - Helpers

private extension LoginView.LoginContainer {
    var isLoginDisabled: Bool {
        username.isEmpty || password.isEmpty
    }
}

// MARK: - Preference keys

struct ViewHeightPreferenceKey: PreferenceKey {
    static var defaultValue: CGFloat = 0
    
    static func reduce(value: inout CGFloat, nextValue: () -> CGFloat) {
        value = nextValue()
    }
}

// MARK: - Previews

struct LoginView_Previews: PreviewProvider {
    static var previews: some View {
        LoginView()
    }
}