import SwiftUI

/// Nur ansehen: Barcode → Artikel, Einzelstück-QR → genau dieses Stück,
/// Lagerort-QR → Liste aller Artikel an diesem Ort. Kein Ein-/Auslagern.
struct LookupScanView: View {
    @Environment(\.dismiss) private var dismiss
    @EnvironmentObject private var display: DisplaySettings

    @State private var paused = false
    @State private var torchOn = false
    @State private var torchLocked = false
    @State private var error: String?
    @State private var item: Item?
    @State private var product: Product?
    @State private var contents: LocationContents?

    var body: some View {
        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, Einzelstück- oder Lagerort-QR scannen – nur ansehen")
                    .font(.caption).foregroundStyle(.secondary)
                    .multilineTextAlignment(.center)

                if let error {
                    Text(error).font(.callout).foregroundStyle(.red)
                        .frame(maxWidth: .infinity, alignment: .leading)
                        .padding(.horizontal)
                }
            }
            .padding(.vertical)
        }
        .navigationTitle("Nachschlagen")
        .navigationBarTitleDisplayMode(.inline)
        .toolbar {
            ToolbarItem(placement: .topBarLeading) { Button("Fertig") { dismiss() } }
            ToolbarItem(placement: .topBarTrailing) { TorchButton(isOn: $torchOn, locked: $torchLocked) }
        }
        .sheet(item: $item, onDismiss: { paused = false }) { it in
            NavigationStack { ItemEditView(item: it) }
        }
        .sheet(item: $product, onDismiss: { paused = false }) { p in
            NavigationStack { ProductDetailView(product: p) }
                .environmentObject(display)
        }
        .sheet(item: $contents, onDismiss: { paused = false }) { c in
            NavigationStack { LocationContentsView(contents: c) }
                .environmentObject(display)
        }
    }

    private func resolve(_ code: String) async {
        paused = true
        error = nil
        // Einzelstück-QR (…/i/<UID>)?
        if let r = code.range(of: "/i/") {
            let uid = String(code[r.upperBound...])
                .trimmingCharacters(in: CharacterSet(charactersIn: "/ ")).uppercased()
            if !uid.isEmpty, let found = try? await APIClient.shared.itemByUid(uid: uid) {
                item = found
                return
            }
        }
        // Lagerort-QR (…/l/<Code>)? → alles zeigen, was dort (inkl. Unterorte) liegt.
        if let r = code.range(of: "/l/") {
            let loc = String(code[r.upperBound...])
                .trimmingCharacters(in: CharacterSet(charactersIn: "/ ")).uppercased()
            if !loc.isEmpty {
                do {
                    contents = try await APIClient.shared.locationContents(code: loc)
                } catch {
                    self.error = "Lagerort nicht gefunden: \(loc)"
                    paused = false
                }
                return
            }
        }
        // Sonst als Barcode auflösen.
        do {
            let result = try await APIClient.shared.lookup(barcode: code)
            if let existing = result.existingProduct {
                product = existing
            } else {
                error = "Nicht im Katalog: \(code)"
                paused = false
            }
        } catch {
            self.error = error.localizedDescription
            paused = false
        }
    }
}

/// Liste aller Artikel eines gescannten Lagerorts (inkl. Unterorte).
struct LocationContentsView: View {
    let contents: LocationContents
    @EnvironmentObject private var display: DisplaySettings

    var body: some View {
        List {
            if contents.products.isEmpty {
                Text("Hier ist nichts eingelagert.").foregroundStyle(.secondary)
            } else {
                Section {
                    ForEach(contents.products) { e in
                        NavigationLink {
                            ProductLoaderView(productId: e.productId).environmentObject(display)
                        } label: {
                            HStack {
                                VStack(alignment: .leading, spacing: 2) {
                                    Text(e.name)
                                    if let brand = e.brand, !brand.isEmpty {
                                        Text(brand).font(.caption).foregroundStyle(.secondary)
                                    }
                                }
                                Spacer()
                                Text("\(mengeText(e.stock)) \(e.unitLabel)")
                                    .foregroundStyle(.secondary)
                            }
                        }
                    }
                } footer: {
                    Text("Bestand inkl. der Unterorte. Tippen öffnet den Artikel.")
                }
            }
        }
        .navigationTitle(contents.locationName)
        .navigationBarTitleDisplayMode(.inline)
    }

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

/// Lädt einen Artikel per ID nach und zeigt dann seine Detailansicht.
struct ProductLoaderView: View {
    let productId: Int
    @EnvironmentObject private var display: DisplaySettings
    @State private var product: Product?
    @State private var error: String?

    var body: some View {
        Group {
            if let product {
                ProductDetailView(product: product).environmentObject(display)
            } else if let error {
                Text(error).foregroundStyle(.red).padding()
            } else {
                ProgressView()
            }
        }
        .task {
            do { product = try await APIClient.shared.product(id: productId) }
            catch { self.error = error.localizedDescription }
        }
    }
}