import SwiftUI
import UIKit

extension View {
    /// Puts a Done button above the keyboard.
    ///
    /// The numeric fields (Settings → Average fuel economy and Typical
    /// fill-up, and the Worth the Drive fill-up box in the station list) use
    /// `.decimalPad`, which has NO Return key. Without this there is no way to
    /// dismiss the keyboard once such a field is tapped, and a
    /// `TextField(value:format:)` only commits the typed value when editing
    /// ends — so the number never stuck either.
    ///
    /// Apply ONCE per screen, to the list or form containing the fields: the
    /// keyboard toolbar belongs to the focused field, so a single attachment
    /// covers every field inside it. Attaching it to each field would show
    /// several Done buttons at once.
    ///
    /// - Parameter action: clears the screen's focus state. Prefer this where a
    ///   `@FocusState` exists; the default resigns the current first responder,
    ///   which works for fields inside subviews that have no focus binding.
    func keyboardDoneButton(action: (() -> Void)? = nil) -> some View {
        toolbar {
            ToolbarItemGroup(placement: .keyboard) {
                Spacer()
                Button("Done") {
                    if let action {
                        action()
                    } else {
                        UIApplication.shared.sendAction(
                            #selector(UIResponder.resignFirstResponder),
                            to: nil,
                            from: nil,
                            for: nil
                        )
                    }
                }
            }
        }
    }
}