import SwiftUI

struct LoginView: View {
    @EnvironmentObject var store: ConnectionStore
    @StateObject private var vm = LoginViewModel()
    @State private var appeared = false

    private var connection: NASConnection? { store.savedConnection }

    var body: some View {
        ZStack {
            AppTheme.background.ignoresSafeArea()

            VStack(spacing: 0) {
                Spacer()

                // ── Brand + logo ──────────────────────────
                VStack(spacing: 20) {
                    brandMark
                        .opacity(appeared ? 1 : 0)
                        .offset(y: appeared ? 0 : 10)
                        .animation(.spring(response: 0.44, dampingFraction: 0.82).delay(0.06), value: appeared)

                    logoView
                        .scaleEffect(appeared ? 1 : 0.88)
                        .opacity(appeared ? 1 : 0)
                        .animation(.spring(response: 0.48, dampingFraction: 0.74).delay(0.12), value: appeared)
                }

                Spacer().frame(height: 32)

                // ── Session context ───────────────────────
                if let conn = connection {
                    VStack(spacing: 4) {
                        Text(conn.username)
                            .font(.system(size: 17, weight: .semibold))
                            .foregroundStyle(AppTheme.ink)
                        Text(conn.displayName)
                            .font(.system(size: 14, weight: .regular))
                            .foregroundStyle(AppTheme.inkTertiary)
                    }
                    .opacity(appeared ? 1 : 0)
                    .offset(y: appeared ? 0 : 6)
                    .animation(.spring(response: 0.4, dampingFraction: 0.8).delay(0.18), value: appeared)
                }

                Spacer().frame(height: 40)

                // ── Auth ──────────────────────────────────
                VStack(spacing: 14) {
                    Button(action: { vm.authenticateWithFaceID() }) {
                        HStack(spacing: 9) {
                            if vm.isAuthenticating {
                                ProgressView()
                                    .tint(AppTheme.inkInverse)
                                    .scaleEffect(0.85)
                            } else {
                                Image(systemName: "faceid")
                                    .font(.system(size: 18, weight: .medium))
                                Text("Sign in with Face ID")
                                    .font(.system(size: 15, weight: .semibold))
                            }
                        }
                    }
                    .buttonStyle(PrimaryButtonStyle())
                    .padding(.horizontal, AppTheme.hPad)
                    .disabled(vm.isAuthenticating)
                    .opacity(appeared ? 1 : 0)
                    .animation(.spring(response: 0.4, dampingFraction: 0.8).delay(0.24), value: appeared)

                    if let error = vm.authError {
                        HStack(spacing: 5) {
                            Image(systemName: "exclamationmark.circle")
                                .font(.system(size: 12, weight: .regular))
                            Text(error)
                                .font(AppTheme.caption())
                        }
                        .foregroundStyle(AppTheme.destructive)
                        .transition(.asymmetric(
                            insertion: .opacity.combined(with: .move(edge: .top)),
                            removal: .opacity
                        ))
                    }
                }
                .animation(.spring(response: 0.3, dampingFraction: 0.85), value: vm.authError != nil)

                Spacer()

                // ── Switch user ───────────────────────────
                Button(action: { store.signOut() }) {
                    Text("Switch User")
                        .font(.system(size: 13, weight: .regular))
                        .foregroundStyle(AppTheme.inkTertiary)
                }
                .buttonStyle(ScaleButtonStyle())
                .padding(.bottom, 52)
                .opacity(appeared ? 1 : 0)
                .animation(.spring(response: 0.4, dampingFraction: 0.8).delay(0.32), value: appeared)
            }
        }
        .onAppear {
            vm.onAuthenticated = { store.isSessionActive = true }
            appeared = true
        }
    }

    // MARK: — Brand mark

    private var brandMark: some View {
        Text("kisani.")
            .font(.system(size: 13, weight: .medium, design: .monospaced))
            .foregroundStyle(AppTheme.inkTertiary)
            .kerning(1.2)
    }

    // MARK: — Logo

    private var logoView: some View {
        ZStack {
            RoundedRectangle(cornerRadius: 24, style: .continuous)
                .stroke(AppTheme.inkQuaternary, lineWidth: 0.5)
                .frame(width: 92, height: 92)

            Image("ugreen_logo")
                .resizable()
                .scaledToFit()
                .frame(width: 90, height: 90)
                .clipShape(RoundedRectangle(cornerRadius: 22, style: .continuous))
        }
        .shadow(color: .black.opacity(0.12), radius: 20, x: 0, y: 6)
    }
}