import SwiftUI

/// A view modifier that adds a floating action button for creating new tasks.
///
/// This modifier overlays a glass-effect button in the bottom-trailing corner of the view.
/// The button can be conditionally shown or hidden with smooth animations.
struct NewTaskButtonModifier: ViewModifier {

    // MARK: Properties

    /// Whether the floating button should be displayed.
    let showButton: Bool

    /// The action to perform when the button is tapped.
    let action: () -> Void

    // MARK: Functions

    /// Applies the floating action button to the content view.
    ///
    /// When `showButton` is true, overlays a blue glass-effect button with a plus icon
    /// in the bottom-trailing corner. The button animates in/out with opacity and scale transitions,
    /// and includes a spring animation when pressed.
    ///
    /// - Parameter content: The view to which the button will be added.
    /// - Returns: The modified view with the floating button overlay.
    func body(content: Content) -> some View {
        ZStack(alignment: .bottomTrailing) {
            content

            if showButton {
                Button(action: action) {
                    Image(systemName: "plus")
                        .frame(width: 48, height: 48)
                        .foregroundStyle(.white)
                }
                .glassEffect(.regular.tint(.blue.opacity(0.8)).interactive())
                .padding(.trailing, 20)
            }
        }
        .animation(
            .spring(response: 0.4, dampingFraction: 0.8),
            value: showButton
        )
    }

}

// MARK: - View Extension

extension View {

    /// Adds a floating action button for creating new tasks.
    ///
    /// This convenience method applies the ``NewTaskButtonModifier`` to show a glass-effect
    /// button in the bottom-trailing corner of the view.
    ///
    /// - Parameters:
    ///   - show: Whether the floating button should be displayed.
    ///   - action: The action to perform when the button is tapped.
    /// - Returns: The modified view with the floating button overlay.
    func newTaskButton(
        show: Bool,
        action: @escaping () -> Void
    ) -> some View {
        modifier(
            NewTaskButtonModifier(
                showButton: show,
                action: action
            )
        )
    }

}
// MARK: - Previews

#Preview("New Task Button") {
    @Previewable
    @State
    var showButton = true

    VStack {
        Spacer()
        Toggle(
            "Show Button",
            isOn: $showButton
        )
        Spacer()
    }
    .padding(.horizontal)
    .frame(
        maxWidth: .infinity,
        maxHeight: .infinity
    )
    .newTaskButton(show: showButton) {
        // On action closure.
    }
}