import SwiftUI
import LabWiseKit

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

    var missingInfoCount: Int {
        chemicals.filter(\.isMissingKeyInfo).count
    }

    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"
        }
    }

    func deleteSelected(ids: Set<String>) async {
        for id in ids {
            guard let chemical = chemicals.first(where: { $0.id == id }) else { continue }
            do {
                try await client.delete(id: chemical.id)
                chemicals.removeAll { $0.id == id }
            } catch {
                errorMessage = "Failed to delete some items"
            }
        }
    }
}

struct InventoryView: View {
    @State private var viewModel = InventoryViewModel()
    @State private var addMode: AddMode?
    @State private var isSelectMode = false
    @State private var selectedIDs: Set<String> = []
    @State private var showSpreadsheet = false

    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 {
                    ScrollView {
                        ContentUnavailableView(
                            "No Chemicals",
                            systemImage: "flask",
                            description: Text("Add your first chemical using the + button.")
                        )
                    }
                    .refreshable {
                        await viewModel.loadChemicals()
                    }
                } else {
                    List {
                        if viewModel.missingInfoCount > 0 && !isSelectMode {
                            Section {
                                MissingInfoBanner(count: viewModel.missingInfoCount)
                            }
                            .listRowBackground(Color.orange.opacity(0.08))
                        }
                        ForEach(viewModel.chemicals) { chemical in
                            if isSelectMode {
                                Button {
                                    if selectedIDs.contains(chemical.id) {
                                        selectedIDs.remove(chemical.id)
                                    } else {
                                        selectedIDs.insert(chemical.id)
                                    }
                                } label: {
                                    HStack(spacing: 12) {
                                        Image(systemName: selectedIDs.contains(chemical.id) ? "checkmark.circle.fill" : "circle")
                                            .foregroundStyle(selectedIDs.contains(chemical.id) ? .blue : .secondary)
                                            .font(.title3)
                                            .animation(.easeInOut(duration: 0.15), value: selectedIDs.contains(chemical.id))
                                        ChemicalRowView(chemical: chemical)
                                    }
                                    .frame(maxWidth: .infinity, alignment: .leading)
                                    .contentShape(Rectangle())
                                }
                                .buttonStyle(.plain)
                            } else {
                                NavigationLink(destination: ChemicalDetailView(chemical: chemical)) {
                                    ChemicalRowView(chemical: chemical)
                                        .frame(maxWidth: .infinity, alignment: .leading) // 📍 Force it to fill the row
                                        .contentShape(Rectangle()) // 📍 Make the transparent space tappable
                                }
                                .simultaneousGesture(
                                    LongPressGesture(minimumDuration: 0.5).onEnded { _ in
                                        withAnimation {
                                            isSelectMode = true
                                            selectedIDs = [chemical.id]
                                        }
                                    }
                                )
                            }
                        }
                        .onDelete(perform: isSelectMode ? nil : { indexSet in
                            for index in indexSet {
                                let chemical = viewModel.chemicals[index]
                                Task { await viewModel.delete(chemical: chemical) }
                            }
                        })
                    }
                    .refreshable {
                        await viewModel.loadChemicals()
                    }
                }
            }
            .navigationTitle(isSelectMode ? "\(selectedIDs.count) Selected" : "Inventory")
            .toolbar {
                if isSelectMode {
                    ToolbarItem(placement: .topBarLeading) {
                        Button("Cancel") {
                            withAnimation {
                                isSelectMode = false
                                selectedIDs = []
                            }
                        }
                    }
                    ToolbarItem(placement: .topBarTrailing) {
                        Button(role: .destructive) {
                            Task {
                                await viewModel.deleteSelected(ids: selectedIDs)
                                withAnimation {
                                    isSelectMode = false
                                    selectedIDs = []
                                }
                            }
                        } label: {
                            Text("Delete (\(selectedIDs.count))")
                        }
                        .disabled(selectedIDs.isEmpty)
                    }
                } else {
                    ToolbarItem(placement: .topBarLeading) {
                        Button {
                            showSpreadsheet = true
                        } label: {
                            Image(systemName: "tablecells")
                        }
                    }
                    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()
        }
        .fullScreenCover(isPresented: $showSpreadsheet) {
            SpreadsheetView(chemicals: viewModel.chemicals) {
                showSpreadsheet = false
            }
        }
    }
}

// MARK: - Missing-info banner

/// Shown above the inventory list when one or more rows are missing required
/// fields (typically the result of a web spreadsheet import). Mirrors the
/// amber banner on the web inventory page.
private struct MissingInfoBanner: View {
    let count: Int

    var body: some View {
        HStack(alignment: .top, spacing: 10) {
            Image(systemName: "exclamationmark.triangle.fill")
                .foregroundStyle(.orange)
            VStack(alignment: .leading, spacing: 2) {
                Text("Missing Key Information")
                    .font(.subheadline.weight(.semibold))
                Text("\(count) \(count == 1 ? "item is" : "items are") missing required fields. Tap an item flagged with “Missing info” to see exactly which fields and edit them.")
                    .font(.caption)
                    .foregroundStyle(.secondary)
            }
        }
        .padding(.vertical, 4)
    }
}