import SwiftUI

struct CheckOutView: View {
    @Environment(\.dismiss) private var dismiss

    @State private var paused = false
    @State private var torchOn = false
    @State private var torchLocked = false
    @State private var status: String?
    @State private var error: String?
    @State private var product: Product?
    @State private var units: [Unit] = []
    @State private var manualCodeShown = false
    @State private var manualCode = ""
    @State private var searchShown = false

    var body: some View {
        // Kamera als Feld oben, siehe CheckInView.
        ScrollView {
            VStack(spacing: 14) {
                ScannerView(onCode: { code in Task { await resolve(code) } },
                            isPaused: $paused, torchOn: $torchOn, torchLocked: $torchLocked)
                    .aspectRatio(4.0 / 3.0, contentMode: .fit)
                    .clipShape(RoundedRectangle(cornerRadius: 16))
                    .padding(.horizontal)

                Text("Barcode vor die Kamera halten")
                    .font(.caption).foregroundStyle(.secondary)

                if let status { banner(status, color: .green) }
                if let error { banner(error, color: .red) }

                VStack(spacing: 10) {
                    Button {
                        paused = true
                        searchShown = true
                    } label: {
                        Label("Artikel suchen", systemImage: "magnifyingglass")
                            .frame(maxWidth: .infinity)
                    }
                    .buttonStyle(.borderedProminent)

                    Button {
                        paused = true
                        manualCodeShown = true
                    } label: {
                        Label("EAN manuell", systemImage: "keyboard")
                            .frame(maxWidth: .infinity)
                    }
                    .buttonStyle(.bordered)
                }
                .padding(.horizontal)
            }
            .padding(.vertical)
        }
        .navigationTitle("Auslagern")
        .navigationBarTitleDisplayMode(.inline)
        .toolbar {
            ToolbarItem(placement: .topBarLeading) { Button("Fertig") { dismiss() } }
            ToolbarItem(placement: .topBarTrailing) { TorchButton(isOn: $torchOn, locked: $torchLocked) }
        }
        .task { units = (try? await APIClient.shared.units()) ?? [] }
        .alert("EAN eingeben", isPresented: $manualCodeShown) {
            TextField("z.B. 8076809572569", text: $manualCode)
                .keyboardType(.numberPad)
            Button("Suchen") {
                let code = manualCode
                manualCode = ""
                Task { await resolve(code) }
            }
            Button("Abbrechen", role: .cancel) { paused = false }
        }
        .sheet(isPresented: $searchShown) {
            NavigationStack {
                ProductSearchView { picked in
                    searchShown = false
                    product = picked
                }
            }
        }
        .sheet(item: $product) { item in
            NavigationStack {
                CheckOutFormView(product: item, units: units) { message in
                    status = message
                    product = nil
                    paused = false
                }
            }
        }
    }

    private func banner(_ text: String, color: Color) -> some View {
        Text(text)
            .font(.callout)
            .padding(10)
            .frame(maxWidth: .infinity, alignment: .leading)
            .background(color.opacity(0.9))
            .foregroundStyle(.white)
            .clipShape(RoundedRectangle(cornerRadius: 10))
            .padding(.horizontal)
    }

    private func resolve(_ code: String) async {
        paused = true
        error = nil
        status = nil
        do {
            let result = try await APIClient.shared.lookup(barcode: code)
            if let existing = result.existingProduct {
                product = existing
            } else {
                error = "Kein bekanntes Produkt zu diesem Code im Lager."
                paused = false
            }
        } catch {
            self.error = error.localizedDescription
            paused = false
        }
    }
}

/// Auslagern: Menge, Einheit und optional eine bestimmte Charge (sonst FEFO).
struct CheckOutFormView: View {
    let product: Product
    let units: [Unit]
    var onDone: (String) -> Void

    @Environment(\.dismiss) private var dismiss
    @EnvironmentObject private var display: DisplaySettings

    @State private var quantity = "1"
    @State private var unit = ""
    @State private var lots: [Lot] = []
    @State private var lotId: Int?
    @State private var busy = false
    @State private var error: String?

    private var unitOptions: [UnitOption] {
        var options = units
            .filter { $0.kind == product.kind }
            .map { UnitOption(value: $0.name, label: $0.name) }
        if let size = product.packageSize, size > 0 {
            // Angezeigt wird "Glas"/"Dose", geschickt wird "package".
            options.append(UnitOption(value: UnitOption.packageValue,
                                      label: product.packageLabel ?? "Packung"))
        }
        return options
    }

    var body: some View {
        Form {
            Section {
                VStack(alignment: .leading) {
                    Text(product.name).font(.headline)
                    Text("Verfügbar: \(format(product.stockInArticleUnits)) \(product.articleUnitLabel)")
                        .font(.caption).foregroundStyle(.secondary)
                }
            }

            Section("Charge") {
                Picker("Charge", selection: $lotId) {
                    Text("Automatisch (zuerst ablaufende)").tag(Int?.none)
                    ForEach(lots) { lot in
                        Text(label(for: lot)).tag(Int?.some(lot.id))
                    }
                }
            }

            Section("Menge") {
                QuantityField(label: "Menge", text: $quantity)
                Picker("Einheit", selection: $unit) {
                    ForEach(unitOptions) { Text($0.label).tag($0.value) }
                }
            }

            if let error {
                Section { Text(error).foregroundStyle(.red).font(.callout) }
            }

            Section {
                Button(busy ? "Speichern…" : "Auslagern") { Task { await submit() } }
                    .disabled(busy)
            }
        }
        .navigationTitle("Auslagern")
        .navigationBarTitleDisplayMode(.inline)
        .toolbar {
            ToolbarItem(placement: .topBarLeading) { Button("Abbrechen") { dismiss() } }
        }
        .task {
            unit = (product.packageSize ?? 0) > 0 ? UnitOption.packageValue : product.unitName
            lots = (try? await APIClient.shared.lots(productId: product.id)) ?? []
        }
    }

    private func label(for lot: Lot) -> String {
        let amount = format(lot.quantity / product.articleUnitFactor)
        return "\(display.formatBestBefore(lot.bestBefore, precision: lot.bestBeforePrecision)) · \(amount) \(product.articleUnitLabel)"
    }

    private func format(_ value: Double) -> String {
        value == value.rounded() ? String(Int(value)) : String(format: "%.2f", value)
    }

    private func submit() async {
        error = nil
        guard let amount = Double(quantity.replacingOccurrences(of: ",", with: ".")), amount > 0 else {
            error = "Bitte eine Menge größer 0 angeben."
            return
        }
        busy = true
        defer { busy = false }
        do {
            let response = try await APIClient.shared.checkOut(
                CheckOutRequest(productId: product.id, quantity: amount, unit: unit, lotId: lotId)
            )
            let total = response.productStock / product.articleUnitFactor
            onDone("Ausgelagert\nNeuer Bestand: \(format(total)) \(display.articleUnit(product, count: total))")
            dismiss()
        } catch {
            self.error = error.localizedDescription
        }
    }
}