todos/App/Sources/Views/ContentView.swift

import SwiftData
import SwiftUI

/// The main content view of the app.
///
/// This view serves as the primary interface for managing todo tasks.
struct ContentView: View {

    // MARK: Properties

    /// The horizontal size class of the environment.
    @Environment(\.horizontalSizeClass)
    private var horizontalSizeClass

    /// The view model managing the state and logic for this view.
    @State
    private var viewModel = ViewModel()

    // MARK: Body

    /// The content and behavior of the view.
    ///
    /// Displays a navigation split view with:
    /// - Sidebar: List of todo task groups
    /// - Detail: List of todo task related to a selected todo task group
    /// - A floating action button for adding new tasks
    ///
    /// The view presents a sheet to allow users to create new todo tasks.
    var body: some View {
        NavigationSplitView {
            TaskGroupListView($viewModel.group)
                .newTaskButton(show: viewModel.showNewTaskButtonInSidebar(when: horizontalSizeClass)) {
                    viewModel.showNewTask()
                }
        } detail: {
            if let group = viewModel.group {
                TaskListView(group: group)
                    .id(group)
                    .newTaskButton(show: viewModel.showNewTaskButtonInDetails) {
                        viewModel.showNewTask()
                    }
            }
            else {
                ContentUnavailableView(
                    "view.content.content-unavailable.title",
                    systemImage: "sidebar.left",
                    description: Text("view.content.content-unavailable.description")
                )
            }
        }
        .sheet(isPresented: $viewModel.newTaskShown) {
            NavigationStack {
                NewTaskView()
            }            
        }
    }

}

// MARK: - Previews

#Preview {
    ContentView()
}