import SwiftUI
import LabWiseKit

@Observable
final class InventoryViewModel {
    var chemicals: [Chemical] = []
    var isLoading = false
    var errorMessage: String?

    private let client = ChemicalsClient()

    func loadChemicals() async {
        isLoading = true
        errorMessage = nil
        defer { isLoading = false }
        do {
            chemicals = try await client.list()
        } catch {
            errorMessage = "Failed to load chemicals"
        }
    }

    func delete(chemical: Chemical) async {
        do {
            try await client.delete(id: chemical.id)
            chemicals.removeAll { $0.id == chemical.id }
        } catch {
            errorMessage = "Failed to delete"
        }
    }
}

struct InventoryView: View {
    @State private var viewModel = InventoryViewModel()
    @State private var showAddSheet = false
    @State private var showScanSheet = false
    @State private var addMode: AddMode?

    enum AddMode: String, Identifiable {
        case manual, scan
        var id: String { rawValue }
    }

    var body: some View {
        NavigationStack {
            Group {
                if viewModel.isLoading && viewModel.chemicals.isEmpty {
                    ProgressView("Loading...")
                        .frame(maxWidth: .infinity, maxHeight: .infinity)
                } else if viewModel.chemicals.isEmpty {
                    ContentUnavailableView(
                        "No Chemicals",
                        systemImage: "flask",
                        description: Text("Add your first chemical using the + button.")
                    )
                } else {
                    List {
                        ForEach(viewModel.chemicals) { chemical in
                            NavigationLink(destination: ChemicalDetailView(chemical: chemical)) {
                                ChemicalRowView(chemical: chemical)
                            }
                        }
                        .onDelete { indexSet in
                            for index in indexSet {
                                let chemical = viewModel.chemicals[index]
                                Task { await viewModel.delete(chemical: chemical) }
                            }
                        }
                    }
                    .refreshable {
                        await viewModel.loadChemicals()
                    }
                }
            }
            .navigationTitle("Inventory")
            .toolbar {
                ToolbarItem(placement: .topBarTrailing) {
                    Menu {
                        Button {
                            addMode = .scan
                        } label: {
                            Label("Scan Label", systemImage: "camera.fill")
                        }
                        Button {
                            addMode = .manual
                        } label: {
                            Label("Manual Entry", systemImage: "square.and.pencil")
                        }
                    } label: {
                        Image(systemName: "plus")
                    }
                }
            }
            .alert("Error", isPresented: .constant(viewModel.errorMessage != nil)) {
                Button("OK") { viewModel.errorMessage = nil }
            } message: {
                Text(viewModel.errorMessage ?? "")
            }
        }
        .sheet(item: $addMode) { mode in
            switch mode {
            case .manual:
                AddChemicalView { saved in
                    addMode = nil
                    if saved {
                        Task { await viewModel.loadChemicals() }
                    }
                }
            case .scan:
                ScanView()
                    .onDisappear {
                        Task { await viewModel.loadChemicals() }
                    }
            }
        }
        .task {
            await viewModel.loadChemicals()
        }
    }
}