import SwiftUI

struct CheckInView: 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 scannedItem: Item?
    @State private var suggestion: LookupResult.Suggestion?
    @State private var suggestedGroupId: Int?
    @State private var suggestedGroupName: String?
    @State private var suggestedCategoryId: Int?
    @State private var suggestedCategoryName: String?
    @State private var unknownCode: String?
    @State private var manualCodeShown = false
    @State private var manualCode = ""
    @State private var units: [Unit] = []
    @State private var locations: [StorageLocation] = []

    var body: some View {
        // Kamera bewusst nur als Feld oben statt bildschirmfuellend - der
        // Sucher ueber die ganze Flaeche wirkte erschlagend.
        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) }

                if let suggestion {
                    suggestionCard(suggestion)
                } else if let unknownCode {
                    unknownCard(unknownCode)
                }

                VStack(spacing: 10) {
                    Button {
                        paused = true
                        manualCodeShown = true
                    } label: {
                        Label("EAN manuell", systemImage: "keyboard")
                            .frame(maxWidth: .infinity)
                    }
                    .buttonStyle(.borderedProminent)

                    NavigationLink {
                        ProductFormView(prefillBarcode: nil, groupId: nil) { created in
                            product = created
                        }
                    } label: {
                        Label("Artikel anlegen", systemImage: "plus")
                            .frame(maxWidth: .infinity)
                    }
                    .buttonStyle(.bordered)
                }
                .padding(.horizontal)
            }
            .padding(.vertical)
        }
        .navigationTitle("Einlagern")
        .navigationBarTitleDisplayMode(.inline)
        .toolbar {
            ToolbarItem(placement: .topBarLeading) {
                Button("Fertig") { dismiss() }
            }
            ToolbarItem(placement: .topBarTrailing) { TorchButton(isOn: $torchOn, locked: $torchLocked) }
        }
        .task {
            units = (try? await APIClient.shared.units()) ?? []
            locations = (try? await APIClient.shared.locations()) ?? []
        }
        .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(item: $product) { item in
            NavigationStack {
                CheckInFormView(product: item, units: units, locations: locations) { message in
                    status = message
                    product = nil
                    paused = false
                }
            }
        }
        .sheet(item: $scannedItem, onDismiss: { paused = false }) { it in
            NavigationStack { ItemEditView(item: it) }
        }
    }

    // MARK: - Bausteine

    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)
    }

    /// Sagt vor dem Anlegen, welche Gruppe der Artikel bekommt und warum.
    @ViewBuilder
    private func groupNote() -> some View {
        if let kategorie = suggestedCategoryName {
            noteRow(symbol: "square.grid.2x2",
                    title: "Wird der Kategorie „\(kategorie)“ zugeordnet",
                    detail: "Aus der Produkt-Datenbank vorgeschlagen – im Formular änderbar.")
        }
        if let name = suggestedGroupName {
            noteRow(symbol: "tag",
                    title: "Wird der Gruppe „\(name)“ zugeordnet",
                    detail: "Dieser EAN-Code ist dort hinterlegt.")
        }
    }

    private func noteRow(symbol: String, title: String, detail: String) -> some View {
        HStack(alignment: .top, spacing: 6) {
            Image(systemName: symbol)
            VStack(alignment: .leading, spacing: 1) {
                Text(title).font(.caption).bold()
                Text(detail).font(.caption2).foregroundStyle(.secondary)
            }
        }
        .padding(8)
        .frame(maxWidth: .infinity, alignment: .leading)
        .background(Color.accentColor.opacity(0.15))
        .clipShape(RoundedRectangle(cornerRadius: 8))
    }

    private func suggestionCard(_ item: LookupResult.Suggestion) -> some View {
        VStack(alignment: .leading, spacing: 8) {
            Text(item.name).font(.headline)
            Text([item.brand, item.quantityText].compactMap { $0 }.joined(separator: " · "))
                .font(.caption).foregroundStyle(.secondary)
            Text("In einer Produkt-Datenbank gefunden, noch nicht im Katalog.")
                .font(.caption2).foregroundStyle(.secondary)
            groupNote()
            NavigationLink {
                ProductFormView(prefillBarcode: item.barcode, groupId: suggestedGroupId,
                                categoryId: suggestedCategoryId, suggestion: item) { created in
                    suggestion = nil
                    product = created
                }
            } label: {
                Label("Anlegen & einlagern", systemImage: "plus.circle.fill")
                    .frame(maxWidth: .infinity)
            }
            .buttonStyle(.borderedProminent)
        }
        .padding()
        .background(.thinMaterial)
        .clipShape(RoundedRectangle(cornerRadius: 12))
        .padding(.horizontal)
    }

    private func unknownCard(_ code: String) -> some View {
        VStack(alignment: .leading, spacing: 8) {
            Text("Unbekannter Code \(code)").font(.headline)
            Text("Weder im Katalog noch in Open Food / Products Facts.")
                .font(.caption).foregroundStyle(.secondary)
            groupNote()
            NavigationLink {
                ProductFormView(prefillBarcode: code, groupId: suggestedGroupId,
                                categoryId: suggestedCategoryId) { created in
                    unknownCode = nil
                    product = created
                }
            } label: {
                Label("Artikel anlegen", systemImage: "plus")
                    .frame(maxWidth: .infinity)
            }
            .buttonStyle(.borderedProminent)
        }
        .padding()
        .background(.thinMaterial)
        .clipShape(RoundedRectangle(cornerRadius: 12))
        .padding(.horizontal)
    }

    // MARK: - Logik

    private func resolve(_ code: String) async {
        paused = true
        error = nil
        status = nil
        suggestion = nil
        unknownCode = nil
        do {
            // Einzelstück-QR (…/i/<UID>) → direkt das Stück öffnen statt Barcode-Suche.
            if let r = code.range(of: "/i/") {
                let uid = String(code[r.upperBound...])
                    .trimmingCharacters(in: CharacterSet(charactersIn: "/ "))
                    .uppercased()
                if !uid.isEmpty, let item = try? await APIClient.shared.itemByUid(uid: uid) {
                    scannedItem = item
                    return
                }
            }
            let result = try await APIClient.shared.lookup(barcode: code)
            suggestedGroupId = result.groupId
            suggestedGroupName = result.groupName
            suggestedCategoryId = result.categoryId
            suggestedCategoryName = result.categoryName
            if let existing = result.existingProduct {
                product = existing
            } else if let hint = result.suggestion {
                suggestion = hint
            } else {
                unknownCode = code
            }
        } catch {
            self.error = error.localizedDescription
            paused = false
        }
    }
}