import SwiftUI
import CoreImage

/// QR-Code als Bild (CoreImage). Inhalt ist der Link auf das Einzelstück, damit
/// ein Scan – auch mit der Systemkamera – die App/Weboberfläche öffnet.
enum QRImage {
    static func make(_ text: String, scale: CGFloat = 8) -> UIImage? {
        guard let data = text.data(using: .utf8),
              let filter = CIFilter(name: "CIQRCodeGenerator") else { return nil }
        filter.setValue(data, forKey: "inputMessage")
        filter.setValue("M", forKey: "inputCorrectionLevel")
        guard let ci = filter.outputImage?
            .transformed(by: CGAffineTransform(scaleX: scale, y: scale)) else { return nil }
        let context = CIContext()
        guard let cg = context.createCGImage(ci, from: ci.extent) else { return nil }
        return UIImage(cgImage: cg)
    }
}

func qrLink(forUid uid: String) -> String {
    let base = Session.shared.baseURL?.absoluteString
        .trimmingCharacters(in: CharacterSet(charactersIn: "/")) ?? ""
    return base.isEmpty ? uid : "\(base)/i/\(uid)"
}

private func dateToString(_ d: Date) -> String {
    let f = DateFormatter(); f.dateFormat = "yyyy-MM-dd"; return f.string(from: d)
}
private func stringToDate(_ s: String) -> Date? {
    let f = DateFormatter(); f.dateFormat = "yyyy-MM-dd"; return f.date(from: s)
}

// MARK: - Liste (in der Produkt-Detailansicht)

/// Einzelstücke eines Gegenstands: Liste mit Anlegen; jedes Stück öffnet die
/// Detail-/Bearbeiten-Ansicht.
struct ProductItemsSection: View {
    let product: Product
    var onChanged: () async -> Void

    @State private var items: [Item] = []
    @State private var showAdd = false

    var body: some View {
        Section("Einzelstücke (\(items.count))") {
            ForEach(items) { it in
                NavigationLink {
                    ItemEditView(item: it) { Task { await refresh() } }
                } label: {
                    VStack(alignment: .leading, spacing: 2) {
                        Text(it.uid).font(.body.monospaced()).bold()
                        Text(untertitel(it)).font(.caption).foregroundStyle(.secondary)
                    }
                }
            }
            if items.isEmpty {
                Text("Noch keine Einzelstücke.").foregroundStyle(.secondary)
            }
            Button { showAdd = true } label: {
                Label("Einzelstücke anlegen", systemImage: "plus")
            }
        }
        .task(id: product.id) { await reload() }
        .sheet(isPresented: $showAdd) {
            NavigationStack {
                ItemAddSheet(productId: product.id) { await refresh() }
            }
        }
    }

    private func untertitel(_ it: Item) -> String {
        [it.locationName, it.acquiredOn.map { "gekauft \($0)" }, it.shopName]
            .compactMap { $0 }.joined(separator: " · ")
    }
    private func reload() async {
        items = (try? await APIClient.shared.items(productId: product.id)) ?? []
    }
    private func refresh() async { await reload(); await onChanged() }
}

// MARK: - Detail / Bearbeiten (auch Ziel eines Scans)

struct ItemEditView: View {
    let item: Item
    var onChanged: (() -> Void)? = nil

    @Environment(\.dismiss) private var dismiss

    @State private var locations: [StorageLocation] = []
    @State private var shops: [ShopItem] = []
    @State private var photo: Data?
    @State private var locationId: Int?
    @State private var shopId: Int?
    @State private var hasAcquired = false
    @State private var acquired = Date()
    @State private var hasWarranty = false
    @State private var warranty = Date()
    @State private var note = ""
    @State private var busy = false
    @State private var error: String?
    @State private var showRemove = false
    @State private var reason = "broken"
    @State private var removeNote = ""

    var body: some View {
        Form {
            Section {
                if let photo, let ui = UIImage(data: photo) {
                    Image(uiImage: ui)
                        .resizable().scaledToFit()
                        .frame(maxWidth: .infinity).frame(maxHeight: 220)
                        .clipShape(RoundedRectangle(cornerRadius: 8))
                }
                if let name = item.productName {
                    LabeledContent("Artikel", value: name)
                }
                if let brand = item.productBrand, !brand.isEmpty {
                    LabeledContent("Marke", value: brand)
                }
                LabeledContent("UID", value: item.uid)
            }

            Section {
                Picker("Lagerort", selection: $locationId) {
                    Text("– ohne –").tag(Int?.none)
                    ForEach(locations) { l in Text(l.name).tag(Int?.some(l.id)) }
                }
                Picker("Gekauft bei", selection: $shopId) {
                    Text("– unbekannt –").tag(Int?.none)
                    ForEach(shops) { s in Text(s.name).tag(Int?.some(s.id)) }
                }
                Toggle("Kaufdatum", isOn: $hasAcquired)
                if hasAcquired { DatePicker("Gekauft am", selection: $acquired, displayedComponents: .date) }
                Toggle("Garantie", isOn: $hasWarranty)
                if hasWarranty { DatePicker("Garantie bis", selection: $warranty, displayedComponents: .date) }
                LabeledField(label: "Notiz", text: $note)
            }

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

            Section {
                Button(busy ? "Speichern…" : "Speichern") { Task { await save() } }.disabled(busy)
                Button("Entfernen (mit Grund)", role: .destructive) { showRemove = true }
            }
        }
        .navigationTitle("Einzelstück")
        .navigationBarTitleDisplayMode(.inline)
        .toolbar { ToolbarItem(placement: .topBarLeading) { Button("Fertig") { dismiss() } } }
        .task { await load() }
        .sheet(isPresented: $showRemove) {
            NavigationStack { removeSheet }
        }
    }

    private var removeSheet: some View {
        Form {
            Picker("Grund", selection: $reason) {
                ForEach(RemovalReasons.all, id: \.value) { Text($0.label).tag($0.value) }
            }
            LabeledField(label: "Notiz", text: $removeNote)
            Section {
                Button("Entfernen", role: .destructive) { Task { await remove() } }
            }
        }
        .navigationTitle("Entfernen")
        .navigationBarTitleDisplayMode(.inline)
        .toolbar { ToolbarItem(placement: .topBarLeading) { Button("Abbrechen") { showRemove = false } } }
    }

    private func load() async {
        locations = (try? await APIClient.shared.locations()) ?? []
        shops = (try? await APIClient.shared.shops()) ?? []
        photo = try? await APIClient.shared.productImage(id: item.productId)
        locationId = item.locationId
        shopId = item.shopId
        note = item.note ?? ""
        if let s = item.acquiredOn, let d = stringToDate(s) { acquired = d; hasAcquired = true }
        if let s = item.warrantyUntil, let d = stringToDate(s) { warranty = d; hasWarranty = true }
    }

    private func save() async {
        busy = true; defer { busy = false }; error = nil
        do {
            _ = try await APIClient.shared.updateItem(id: item.id, ItemUpdateRequest(
                locationId: locationId, shopId: shopId,
                acquiredOn: hasAcquired ? dateToString(acquired) : nil,
                warrantyUntil: hasWarranty ? dateToString(warranty) : nil,
                note: note.isEmpty ? nil : note))
            onChanged?()
            dismiss()
        } catch { self.error = error.localizedDescription }
    }

    private func remove() async {
        do {
            try await APIClient.shared.removeItem(id: item.id, ItemRemoveRequest(
                reason: reason, note: removeNote.isEmpty ? nil : removeNote))
            showRemove = false
            onChanged?()
            dismiss()
        } catch { self.error = error.localizedDescription; showRemove = false }
    }
}

// MARK: - Anlegen

struct ItemAddSheet: View {
    let productId: Int
    var onDone: () async -> Void

    @Environment(\.dismiss) private var dismiss

    @State private var count = 1
    @State private var locations: [StorageLocation] = []
    @State private var shops: [ShopItem] = []
    @State private var locationId: Int?
    @State private var shopId: Int?
    @State private var hasAcquired = false
    @State private var acquired = Date()
    @State private var hasWarranty = false
    @State private var warranty = Date()
    @State private var note = ""
    @State private var busy = false
    @State private var error: String?

    var body: some View {
        Form {
            Section {
                Stepper("Anzahl: \(count)", value: $count, in: 1...200)
                Picker("Lagerort", selection: $locationId) {
                    Text("– ohne –").tag(Int?.none)
                    ForEach(locations) { l in Text(l.name).tag(Int?.some(l.id)) }
                }
                Picker("Gekauft bei", selection: $shopId) {
                    Text("– unbekannt –").tag(Int?.none)
                    ForEach(shops) { s in Text(s.name).tag(Int?.some(s.id)) }
                }
                Toggle("Kaufdatum", isOn: $hasAcquired)
                if hasAcquired { DatePicker("Gekauft am", selection: $acquired, displayedComponents: .date) }
                Toggle("Garantie", isOn: $hasWarranty)
                if hasWarranty { DatePicker("Garantie bis", selection: $warranty, displayedComponents: .date) }
                LabeledField(label: "Notiz", text: $note)
            } footer: {
                Text("Gemeinsame Startwerte – danach je Stück änderbar. Jedes Stück bekommt eine eigene UID + QR.")
            }
            if let error { Section { Text(error).foregroundStyle(.red).font(.callout) } }
            Section {
                Button(busy ? "Anlegen…" : "Anlegen") { Task { await create() } }.disabled(busy)
            }
        }
        .navigationTitle("Einzelstücke anlegen")
        .navigationBarTitleDisplayMode(.inline)
        .toolbar { ToolbarItem(placement: .topBarLeading) { Button("Abbrechen") { dismiss() } } }
        .task {
            locations = (try? await APIClient.shared.locations()) ?? []
            shops = (try? await APIClient.shared.shops()) ?? []
        }
    }

    private func create() async {
        busy = true; defer { busy = false }; error = nil
        do {
            _ = try await APIClient.shared.createItems(productId: productId, ItemCreateRequest(
                count: count, locationId: locationId, shopId: shopId,
                acquiredOn: hasAcquired ? dateToString(acquired) : nil,
                warrantyUntil: hasWarranty ? dateToString(warranty) : nil,
                note: note.isEmpty ? nil : note))
            await onDone()
            dismiss()
        } catch { self.error = error.localizedDescription }
    }
}