import SwiftUI

/// Startseite: Kennzahlen des Servers und die letzten Bewegungen.
///
/// Bewusst ohne Diagramme - die Kennzahl selbst ist die Antwort, und jede
/// fuehrt per Tipp dorthin, wo man etwas tun kann.
struct OverviewView: View {
    @EnvironmentObject private var session: Session
    @EnvironmentObject private var display: DisplaySettings

    @State private var stats: DashboardStats?
    @State private var letzte: [Movement] = []
    @State private var busy = true
    @State private var error: String?
    @State private var manageShown = false

    private let spalten = [GridItem(.flexible()), GridItem(.flexible())]

    var body: some View {
        NavigationStack {
            List {
                if let error {
                    Section { Text(error).foregroundStyle(.red).font(.callout) }
                }

                Section {
                    LazyVGrid(columns: spalten, spacing: 12) {
                        NavigationLink { ProductListView() } label: {
                            StatTile(title: "Artikel mit Bestand",
                                     value: stats.map { String($0.productsInStock) } ?? "–",
                                     detail: stats.map { "von \($0.productsTotal)" } ?? "",
                                     systemImage: "shippingbox", tint: .accentColor)
                        }
                        NavigationLink { ShoppingListView() } label: {
                            StatTile(title: "Einzukaufen",
                                     value: stats.map { String($0.shoppingItems) } ?? "–",
                                     detail: "unter Mindestbestand",
                                     systemImage: "cart",
                                     tint: (stats?.shoppingItems ?? 0) > 0 ? .orange : .secondary)
                        }
                        NavigationLink { ExpiringView() } label: {
                            StatTile(title: "Läuft bald ab",
                                     value: stats.map { String($0.expiringSoon) } ?? "–",
                                     detail: "Chargen",
                                     systemImage: "clock",
                                     tint: (stats?.expiringSoon ?? 0) > 0 ? .orange : .secondary)
                        }
                        NavigationLink { ExpiringView() } label: {
                            StatTile(title: "Abgelaufen",
                                     value: stats.map { String($0.expired) } ?? "–",
                                     detail: "Chargen",
                                     systemImage: "exclamationmark.triangle",
                                     tint: (stats?.expired ?? 0) > 0 ? .red : .secondary)
                        }
                    }
                    .buttonStyle(.plain)
                    .listRowInsets(EdgeInsets(top: 8, leading: 8, bottom: 8, trailing: 8))
                }

                Section {
                    ForEach(letzte) { movement in
                        MovementRow(movement: movement)
                    }
                    if letzte.isEmpty && !busy {
                        Text("Noch keine Bewegungen.").foregroundStyle(.secondary)
                    }
                    NavigationLink("Ganzen Verlauf ansehen") { HistoryView() }
                } header: {
                    Text("Letzte Bewegungen")
                }
            }
            .navigationTitle(session.activeProfile?.name ?? "Vorrania")
            .toolbar {
                ToolbarItem(placement: .topBarTrailing) {
                    ServerMenu(manageShown: $manageShown)
                }
            }
            .sheet(isPresented: $manageShown) { ServerListView() }
            .refreshable { await load() }
            .task(id: session.activeProfileID) { await load() }
        }
    }

    private func load() async {
        busy = true
        defer { busy = false }
        do {
            stats = try await APIClient.shared.dashboardStats()
            letzte = try await APIClient.shared.movements(limit: 10)
            error = nil
        } catch {
            self.error = error.localizedDescription
        }
    }
}

/// Eine Kennzahl als Kachel.
struct StatTile: View {
    let title: String
    let value: String
    let detail: String
    let systemImage: String
    let tint: Color

    var body: some View {
        VStack(alignment: .leading, spacing: 6) {
            HStack(spacing: 6) {
                Image(systemName: systemImage).font(.caption).foregroundStyle(tint)
                Text(title).font(.caption).foregroundStyle(.secondary)
                    .lineLimit(1).minimumScaleFactor(0.8)
            }
            Text(value).font(.title).bold().foregroundStyle(tint)
            if !detail.isEmpty {
                Text(detail).font(.caption2).foregroundStyle(.tertiary)
                    .lineLimit(1).minimumScaleFactor(0.8)
            }
        }
        .frame(maxWidth: .infinity, alignment: .leading)
        .padding(12)
        .background(Color(.secondarySystemBackground))
        .clipShape(RoundedRectangle(cornerRadius: 12))
    }
}