import SwiftUI

struct TaskDetailScreen: View {
    let task: WorkTask
    var showCompleteButton = false
    var showAcceptButton = false

    @EnvironmentObject var appState: AppState
    @Environment(\.dismiss) var dismiss

    @State private var details: TaskDetails?
    @State private var isLoading = true
    @State private var error: String?

    // Beacon
    @State private var beaconDetected = false
    @State private var bluetoothOff = false
    @State private var autoCompleting = false
    @State private var showAutoCompleteDialog = false
    @State private var showAcceptAlert = false
    @State private var showCompleteAlert = false
    @State private var beaconScanner: BeaconScanner?
    @State private var showingMyTasks = false
    @State private var showingChat = false

    var body: some View {
        ZStack(alignment: .bottomTrailing) {
            Group {
                if isLoading {
                    ProgressView()
                } else if let error = error {
                    errorView(error)
                } else if let details = details {
                    contentView(details)
                }
            }
            .frame(maxWidth: .infinity, maxHeight: .infinity)

            Button { showingMyTasks = true } label: {
                Image(systemName: "checkmark.circle.fill")
                    .font(.title3)
                    .padding(12)
                    .background(Color.payfritGreen)
                    .foregroundColor(.white)
                    .clipShape(Circle())
                    .shadow(radius: 4)
            }
            .padding(.trailing, 16)
            .padding(.bottom, 80)
        }
        .navigationTitle(task.title)
        .toolbarBackground(task.color, for: .navigationBar)
        .toolbarBackground(.visible, for: .navigationBar)
        .toolbarColorScheme(.dark, for: .navigationBar)
        .alert("Accept Task?", isPresented: $showAcceptAlert) {
            Button("Cancel", role: .cancel) { }
            Button("Accept") { acceptTask() }
        } message: {
            Text("Claim this task and add it to your tasks?")
        }
        .alert("Complete Task?", isPresented: $showCompleteAlert) {
            Button("Cancel", role: .cancel) { }
            Button("Complete") { completeTask() }
        } message: {
            Text("Mark this task as completed?")
        }
        .sheet(isPresented: $showAutoCompleteDialog) {
            AutoCompleteCountdownView(taskId: task.taskId) { result in
                showAutoCompleteDialog = false
                if result == "success" {
                    dismiss()
                } else if result == "cancelled" || result == "error" {
                    autoCompleting = false
                    beaconDetected = false
                    beaconScanner?.resetSamples()
                    beaconScanner?.startScanning()
                }
            }
        }
        .navigationDestination(isPresented: $showingMyTasks) {
            MyTasksScreen()
        }
        .navigationDestination(isPresented: $showingChat) {
            ChatScreen(taskId: task.taskId, userType: "worker",
                       otherPartyName: details?.customerFullName)
        }
        .task { await loadDetails() }
        .onDisappear { beaconScanner?.dispose() }
    }

    // MARK: - Content

    @ViewBuilder
    private func contentView(_ details: TaskDetails) -> some View {
        ScrollView {
            VStack(spacing: 16) {
                customerSection(details)
                if task.isChat {
                    chatButton(details)
                }
                locationSection(details)

                if !details.tableMembers.isEmpty {
                    tableMembersSection(details)
                }

                if !details.mainItems.isEmpty {
                    orderItemsSection(details)
                }

                if !details.orderRemarks.isEmpty {
                    remarksSection(details)
                }

                Spacer().frame(height: 80)
            }
            .padding(16)
        }
        .safeAreaInset(edge: .bottom) {
            if showAcceptButton || showCompleteButton {
                bottomBar
            }
        }
    }

    // MARK: - Customer

    private func customerSection(_ d: TaskDetails) -> some View {
        HStack(spacing: 16) {
            // Avatar
            ZStack {
                Circle()
                    .fill(task.color.opacity(0.2))
                    .frame(width: 64, height: 64)

                if !d.customerPhotoUrl.isEmpty, let url = URL(string: d.customerPhotoUrl) {
                    AsyncImage(url: url) { image in
                        image.resizable().scaledToFill()
                    } placeholder: {
                        initialsView(d)
                    }
                    .frame(width: 64, height: 64)
                    .clipShape(Circle())
                } else {
                    initialsView(d)
                }
            }

            VStack(alignment: .leading, spacing: 4) {
                Text(d.customerFullName)
                    .font(.title3.bold())
                if !d.customerPhone.isEmpty {
                    Text(d.customerPhone)
                        .font(.subheadline)
                        .foregroundColor(.secondary)
                }
            }

            Spacer()

            if !d.customerPhone.isEmpty {
                Button { callCustomer(d.customerPhone) } label: {
                    Image(systemName: "phone.fill")
                        .foregroundColor(.green)
                        .font(.title2)
                }
            }
        }
        .padding(16)
        .background(Color(.secondarySystemGroupedBackground))
        .cornerRadius(12)
    }

    private func initialsView(_ d: TaskDetails) -> some View {
        let f = d.customerFirstName.isEmpty ? "" : String(d.customerFirstName.prefix(1)).uppercased()
        let l = d.customerLastName.isEmpty ? "" : String(d.customerLastName.prefix(1)).uppercased()
        let text = "\(f)\(l)".isEmpty ? "?" : "\(f)\(l)"
        return Text(text)
            .font(.title2.bold())
            .foregroundColor(task.color)
    }

    // MARK: - Chat Button

    @ViewBuilder
    private func chatButton(_ d: TaskDetails) -> some View {
        Button { showingChat = true } label: {
            HStack(spacing: 12) {
                ZStack {
                    RoundedRectangle(cornerRadius: 12)
                        .fill(Color.payfritGreen.opacity(0.1))
                        .frame(width: 48, height: 48)
                    Image(systemName: "bubble.left.and.bubble.right.fill")
                        .foregroundColor(.payfritGreen)
                        .font(.title2)
                }

                VStack(alignment: .leading, spacing: 2) {
                    Text("Chat with Customer")
                        .font(.callout.weight(.medium))
                        .foregroundColor(.primary)
                    Text(d.customerFullName)
                        .font(.caption)
                        .foregroundColor(.secondary)
                }

                Spacer()

                Image(systemName: "chevron.right")
                    .foregroundColor(.secondary)
                    .font(.caption)
            }
            .padding(16)
            .background(Color(.secondarySystemGroupedBackground))
            .cornerRadius(12)
        }
    }

    // MARK: - Location

    private func locationSection(_ d: TaskDetails) -> some View {
        HStack(spacing: 16) {
            ZStack {
                RoundedRectangle(cornerRadius: 12)
                    .fill(Color.payfritGreen.opacity(0.1))
                    .frame(width: 48, height: 48)
                Image(systemName: d.isDelivery ? "bicycle" : "table.furniture")
                    .foregroundColor(.payfritGreen)
                    .font(.title2)
            }

            VStack(alignment: .leading, spacing: 4) {
                Text(d.isDelivery ? "Delivery" : "Table Service")
                    .font(.caption)
                    .foregroundColor(.secondary)
                Text(d.locationDisplay)
                    .font(.callout.weight(.medium))
            }

            Spacer()

            if d.isDelivery && d.deliveryLat != 0 {
                Button { openMaps(d) } label: {
                    Image(systemName: "arrow.triangle.turn.up.right.diamond.fill")
                        .foregroundColor(.payfritGreen)
                }
            }

            if !d.isDelivery && !d.beaconUUID.isEmpty && showCompleteButton {
                beaconIndicator
            }
        }
        .padding(16)
        .background(Color(.secondarySystemGroupedBackground))
        .cornerRadius(12)
    }

    @ViewBuilder
    private var beaconIndicator: some View {
        if autoCompleting {
            ProgressView()
        } else if bluetoothOff {
            Image(systemName: "antenna.radiowaves.left.and.right.slash")
                .foregroundColor(.payfritGreen)
        } else if beaconDetected {
            Image(systemName: "antenna.radiowaves.left.and.right")
                .foregroundColor(.green)
        } else {
            Image(systemName: "antenna.radiowaves.left.and.right")
                .foregroundColor(.payfritGreen)
                .opacity(0.7)
        }
    }

    // MARK: - Table Members

    private func tableMembersSection(_ d: TaskDetails) -> some View {
        VStack(alignment: .leading, spacing: 12) {
            HStack {
                Image(systemName: "person.3.fill")
                    .foregroundColor(.secondary)
                Text("Table Members (\(d.tableMembers.count))")
                    .font(.subheadline.weight(.semibold))
            }

            FlowLayout(spacing: 8) {
                ForEach(d.tableMembers) { member in
                    HStack(spacing: 6) {
                        Circle()
                            .fill(member.isHost ? Color.yellow.opacity(0.3) : Color(.systemGray4))
                            .frame(width: 28, height: 28)
                            .overlay(
                                Text(member.initials)
                                    .font(.caption2)
                            )
                        Text(member.fullName)
                            .font(.subheadline)
                    }
                    .padding(.horizontal, 10)
                    .padding(.vertical, 6)
                    .background(member.isHost ? Color.yellow.opacity(0.1) : Color(.systemGray6))
                    .cornerRadius(16)
                    .overlay(
                        RoundedRectangle(cornerRadius: 16)
                            .stroke(member.isHost ? Color.yellow : Color.clear, lineWidth: 1)
                    )
                }
            }
        }
        .padding(16)
        .background(Color(.secondarySystemGroupedBackground))
        .cornerRadius(12)
    }

    // MARK: - Order Items

    private func orderItemsSection(_ d: TaskDetails) -> some View {
        VStack(alignment: .leading, spacing: 12) {
            HStack {
                Image(systemName: "list.bullet.rectangle.portrait")
                    .foregroundColor(.secondary)
                Text("Order Items (\(d.mainItems.count))")
                    .font(.subheadline.weight(.semibold))
            }

            ForEach(d.mainItems) { item in
                orderItemRow(item, details: d)
            }
        }
        .padding(16)
        .background(Color(.secondarySystemGroupedBackground))
        .cornerRadius(12)
    }

    private func orderItemRow(_ item: OrderLineItem, details d: TaskDetails) -> some View {
        let modifiers = d.modifiers(for: item.lineItemId)

        return HStack(alignment: .top, spacing: 12) {
            // Item image placeholder
            RoundedRectangle(cornerRadius: 8)
                .fill(Color(.systemGray5))
                .frame(width: 56, height: 56)
                .overlay(
                    Image(systemName: "fork.knife")
                        .foregroundColor(.secondary)
                )

            VStack(alignment: .leading, spacing: 4) {
                HStack(spacing: 8) {
                    Text("\(item.quantity)x")
                        .font(.caption.bold())
                        .foregroundColor(.white)
                        .padding(.horizontal, 8)
                        .padding(.vertical, 2)
                        .background(task.color)
                        .cornerRadius(4)

                    Text(item.itemName)
                        .font(.callout.weight(.semibold))
                }

                ForEach(modifiers) { mod in
                    let children = d.lineItems.filter { $0.parentLineItemId == mod.lineItemId }
                    if !children.isEmpty {
                        ForEach(children) { child in
                            Text("- \(mod.itemName): \(child.itemName)")
                                .font(.caption)
                                .foregroundColor(.secondary)
                        }
                    } else {
                        Text("- \(mod.itemName)")
                            .font(.caption)
                            .foregroundColor(.secondary)
                    }
                }

                if !item.remark.isEmpty {
                    Text("\"\(item.remark)\"")
                        .font(.caption)
                        .foregroundColor(.payfritGreen)
                        .italic()
                }
            }
        }
        .padding(.bottom, 8)
    }

    // MARK: - Remarks

    private func remarksSection(_ d: TaskDetails) -> some View {
        HStack(alignment: .top, spacing: 12) {
            Image(systemName: "note.text")
                .foregroundColor(.yellow)
            VStack(alignment: .leading, spacing: 4) {
                Text("Order Notes")
                    .font(.caption.weight(.semibold))
                    .foregroundColor(.yellow)
                Text(d.orderRemarks)
                    .font(.callout)
            }
            Spacer()
        }
        .padding(16)
        .background(Color.yellow.opacity(0.1))
        .cornerRadius(12)
    }

    // MARK: - Bottom Bar

    private var bottomBar: some View {
        HStack {
            if showAcceptButton {
                Button { showAcceptAlert = true } label: {
                    Label("Accept Task", systemImage: "plus.circle.fill")
                        .frame(maxWidth: .infinity)
                        .padding(.vertical, 14)
                }
                .buttonStyle(.borderedProminent)
                .tint(.payfritGreen)
            }

            if showCompleteButton {
                Button { showCompleteAlert = true } label: {
                    Label("Complete Task", systemImage: "checkmark.circle.fill")
                        .frame(maxWidth: .infinity)
                        .padding(.vertical, 14)
                }
                .buttonStyle(.borderedProminent)
                .tint(.green)
            }
        }
        .padding(.horizontal)
        .padding(.vertical, 12)
        .background(.ultraThinMaterial)
    }

    // MARK: - Error

    private func errorView(_ message: String) -> some View {
        VStack(spacing: 16) {
            Image(systemName: "exclamationmark.circle")
                .font(.system(size: 48))
                .foregroundColor(.red)
            Text(message)
                .multilineTextAlignment(.center)
            Button("Retry") { Task { await loadDetails() } }
                .buttonStyle(.borderedProminent)
        }
        .padding()
    }

    // MARK: - Actions

    private func loadDetails() async {
        isLoading = true
        error = nil
        do {
            let d = try await APIService.shared.getTaskDetails(taskId: task.taskId)
            details = d
            isLoading = false

            if showCompleteButton && !d.beaconUUID.isEmpty {
                startBeaconScanning(d.beaconUUID)
            }
        } catch {
            self.error = error.localizedDescription
            isLoading = false
        }
    }

    private func startBeaconScanning(_ uuid: String) {
        let scanner = BeaconScanner(
            targetUUID: uuid,
            onBeaconDetected: { [self] _ in
                if !beaconDetected && !autoCompleting {
                    beaconDetected = true
                    autoCompleting = true
                    beaconScanner?.stopScanning()
                    showAutoCompleteDialog = true
                }
            },
            onBluetoothOff: { bluetoothOff = true },
            onPermissionDenied: { self.error = "Bluetooth permission is required for auto-complete. Please enable it in Settings." }
        )
        beaconScanner = scanner
        scanner.startScanning()
    }

    private func acceptTask() {
        Task {
            do {
                try await APIService.shared.acceptTask(taskId: task.taskId)
                if task.isChat {
                    showingChat = true
                } else {
                    dismiss()
                }
            } catch {
                self.error = error.localizedDescription
            }
        }
    }

    private func completeTask() {
        Task {
            do {
                try await APIService.shared.completeTask(taskId: task.taskId)
                dismiss()
            } catch {
                self.error = error.localizedDescription
            }
        }
    }

    private func callCustomer(_ phone: String) {
        guard let url = URL(string: "tel:\(phone)") else { return }
        #if os(iOS)
        UIApplication.shared.open(url)
        #endif
    }

    private func openMaps(_ d: TaskDetails) {
        guard d.deliveryLat != 0, d.deliveryLng != 0 else { return }
        let urlStr = "https://www.google.com/maps/dir/?api=1&destination=\(d.deliveryLat),\(d.deliveryLng)"
        guard let url = URL(string: urlStr) else { return }
        #if os(iOS)
        UIApplication.shared.open(url)
        #endif
    }
}

// MARK: - Auto-Complete Countdown

struct AutoCompleteCountdownView: View {
    let taskId: Int
    let onResult: (String) -> Void

    @State private var countdown = 3
    @State private var completing = false
    @State private var message = "Auto-completing in"

    var body: some View {
        VStack(spacing: 24) {
            Image(systemName: completing ? "checkmark.circle.fill" : "timer")
                .font(.system(size: 48))
                .foregroundColor(completing ? .green : .payfritGreen)

            Text(completing ? "Task Completed!" : "Auto-Complete")
                .font(.title2.bold())

            Text(completing ? message : "\(message) \(countdown)...")
                .font(.body)

            if !completing {
                Button("Cancel") { onResult("cancelled") }
                    .buttonStyle(.bordered)
            }
        }
        .padding(32)
        .presentationDetents([.height(280)])
        .task { await startCountdown() }
    }

    private func startCountdown() async {
        for i in stride(from: 3, through: 1, by: -1) {
            countdown = i
            try? await Task.sleep(nanoseconds: 1_000_000_000)
        }

        completing = true
        message = "Completing task..."

        do {
            try await APIService.shared.completeTask(taskId: taskId)
            message = "Closing this window now"
            try? await Task.sleep(nanoseconds: 1_000_000_000)
            onResult("success")
        } catch {
            onResult("error")
        }
    }
}

// MARK: - Flow Layout (for table members)

struct FlowLayout: Layout {
    var spacing: CGFloat = 8

    func sizeThatFits(proposal: ProposedViewSize, subviews: Subviews, cache: inout ()) -> CGSize {
        let result = arrangeSubviews(proposal: proposal, subviews: subviews)
        return result.size
    }

    func placeSubviews(in bounds: CGRect, proposal: ProposedViewSize, subviews: Subviews, cache: inout ()) {
        let result = arrangeSubviews(proposal: proposal, subviews: subviews)
        for (index, position) in result.positions.enumerated() {
            subviews[index].place(at: CGPoint(x: bounds.minX + position.x, y: bounds.minY + position.y),
                                   proposal: .unspecified)
        }
    }

    private func arrangeSubviews(proposal: ProposedViewSize, subviews: Subviews) -> (positions: [CGPoint], size: CGSize) {
        let maxWidth = proposal.width ?? .infinity
        var positions: [CGPoint] = []
        var currentX: CGFloat = 0
        var currentY: CGFloat = 0
        var lineHeight: CGFloat = 0
        var totalWidth: CGFloat = 0

        for subview in subviews {
            let size = subview.sizeThatFits(.unspecified)
            if currentX + size.width > maxWidth && currentX > 0 {
                currentX = 0
                currentY += lineHeight + spacing
                lineHeight = 0
            }
            positions.append(CGPoint(x: currentX, y: currentY))
            lineHeight = max(lineHeight, size.height)
            currentX += size.width + spacing
            totalWidth = max(totalWidth, currentX)
        }

        return (positions, CGSize(width: totalWidth, height: currentY + lineHeight))
    }
}