import SwiftUI
import UIKit

extension View {
  /// Presents a bottom-anchored drawer: it fills to the screen's bottom edge
  /// (no gap), shows a dimmed backdrop, and can be dragged down to dismiss.
  func bottomDrawer<Content: View>(isPresented: Binding<Bool>,
                                   @ViewBuilder content: @escaping () -> Content) -> some View {
    BottomDrawerHost(host: self, isPresented: isPresented, content: content)
  }
}

/// One place for the drawers shown above every screen. Attaching them at the
/// root keeps them anchored to the window instead of to scrolled content.
@MainActor
final class DrawerCoordinator: ObservableObject {
  @Published var transaction: TransactionRecord?
  @Published var qr: AddressQR?
  @Published var settings = false
}

private struct BottomDrawerHost<Host: View, Content: View>: View {
  let host: Host
  @Binding var isPresented: Bool
  @ViewBuilder var content: () -> Content

  @State private var dragOffset: CGFloat = 0

  private var bottomInset: CGFloat {
    for scene in UIApplication.shared.connectedScenes {
      guard let windowScene = scene as? UIWindowScene else { continue }
      if let window = windowScene.keyWindow {
        return window.safeAreaInsets.bottom
      }
    }
    return 0
  }

  private var maxHeight: CGFloat {
    for scene in UIApplication.shared.connectedScenes {
      guard let windowScene = scene as? UIWindowScene else { continue }
      if let window = windowScene.keyWindow {
        return window.bounds.height * 0.92
      }
    }
    return 800
  }

  var body: some View {
    ZStack(alignment: .bottom) {
      host

      if isPresented {
        Color.black.opacity(0.5)
          .ignoresSafeArea()
          .onTapGesture { dismiss() }
          .transition(.opacity)

        VStack(spacing: 0) {
          Capsule()
            .fill(Theme.muted.opacity(0.55))
            .frame(width: 36, height: 5)
            .padding(.top, 8)

          content()
            .padding(.top, 14)
            .padding(.bottom, 16)
        }
        .frame(maxWidth: .infinity, alignment: .top)
        .frame(maxHeight: maxHeight)
        .background(Theme.surface)
        .clipShape(UnevenRoundedRectangle(topLeadingRadius: 20, topTrailingRadius: 20, style: .continuous))
        // Push the panel's background down to the physical screen edge without
        // taking the host content out of its safe area.
        .offset(y: dragOffset + bottomInset)
        .gesture(dismissDrag)
        .transition(.move(edge: .bottom))
      }
    }
    .animation(.spring(response: 0.32, dampingFraction: 0.86), value: isPresented)
  }

  private func dismiss() {
    isPresented = false
    dragOffset = 0
  }

  private var dismissDrag: some Gesture {
    DragGesture()
      .onChanged { value in
        dragOffset = max(0, value.translation.height)
      }
      .onEnded { value in
        if value.translation.height > 120 || value.predictedEndTranslation.height > 200 {
          dismiss()
        } else {
          dragOffset = 0
        }
      }
  }
}