import SwiftUI
import SwiftData

/// Weekly shopping list: aggregates the ingredients of the dishes planned for
/// the given week. Dish-derived lines reconcile automatically with the plan;
/// the user can check items off, add loose items, and generate ingredients
/// on-device for planned dishes that have none yet.
struct ShoppingListView: View {
    let weekStartDate: Date
    let plan: WeekPlan
    let settings: AppSettings

    @Environment(\.modelContext) private var context
    @Environment(\.dismiss) private var dismiss
    @Query private var allItems: [ShoppingItem]
    @Query private var allDishes: [Dish]

    @State private var newItemText: String = ""
    @State private var generatingDishId: UUID?
    @State private var showPaywall = false
    @State private var editingDish: Dish?

    private var items: [ShoppingItem] {
        allItems
            .filter { $0.weekStartDate == weekStartDate }
            .sorted { $0.sortOrder < $1.sortOrder }
    }

    /// Dishes planned this week, deduplicated, in slot order.
    private var plannedDishes: [Dish] {
        var seen = Set<UUID>()
        var result: [Dish] = []
        let sortedSlots = plan.slotList.sorted {
            ($0.dayOfWeek, $0.mealType) < ($1.dayOfWeek, $1.mealType)
        }
        for slot in sortedSlots {
            for dishId in [slot.dishId, slot.secondaryDishId].compactMap({ $0 }) {
                guard !seen.contains(dishId),
                      let dish = allDishes.first(where: { $0.id == dishId }) else { continue }
                seen.insert(dishId)
                result.append(dish)
            }
        }
        return result
    }

    private var dishesWithoutIngredients: [Dish] {
        plannedDishes.filter { $0.ingredients.isEmpty }
    }

    private var freeTextItems: [ShoppingItem] {
        items.filter { $0.dishId == nil }
    }

    private func items(for dish: Dish) -> [ShoppingItem] {
        items.filter { $0.dishId == dish.id }
    }

    var body: some View {
        NavigationStack {
            List {
                if items.isEmpty && dishesWithoutIngredients.isEmpty {
                    emptyState
                }

                ForEach(plannedDishes, id: \.id) { dish in
                    let dishItems = items(for: dish)
                    if !dishItems.isEmpty {
                        Section(dish.name) {
                            ForEach(dishItems, id: \.id) { item in
                                itemRow(item)
                            }
                        }
                    }
                }

                if !dishesWithoutIngredients.isEmpty {
                    Section("shopping_missing_ingredients") {
                        ForEach(dishesWithoutIngredients, id: \.id) { dish in
                            missingIngredientsRow(dish)
                        }
                    }
                }

                Section("shopping_other_items") {
                    ForEach(freeTextItems, id: \.id) { item in
                        itemRow(item)
                    }
                    HStack {
                        TextField("shopping_add_item_placeholder", text: $newItemText)
                            .onSubmit(addFreeTextItem)
                        Button(action: addFreeTextItem) {
                            Image(systemName: "plus.circle.fill")
                                .foregroundColor(.mealMoodCoral)
                        }
                        .disabled(newItemText.trimmingCharacters(in: .whitespaces).isEmpty)
                    }
                }
            }
            .navigationTitle("shopping_list_title")
            .navigationBarTitleDisplayMode(.inline)
            .toolbar {
                ToolbarItem(placement: .navigationBarLeading) {
                    Button("shopping_done") { dismiss() }
                }
                ToolbarItem(placement: .navigationBarTrailing) {
                    HStack(spacing: 12) {
                        ShareLink(item: exportText) {
                            Image(systemName: "square.and.arrow.up")
                        }
                        .disabled(items.allSatisfy(\.isChecked))

                        Button {
                            clearChecked()
                        } label: {
                            Image(systemName: "checkmark.circle.badge.xmark")
                        }
                        .disabled(!items.contains(where: \.isChecked))
                        .accessibilityLabel(Text("shopping_clear_checked"))
                    }
                }
            }
            .onAppear {
                ShoppingListService.reconcile(
                    context: context,
                    weekStartDate: weekStartDate,
                    plannedDishes: plannedDishes
                )
                AnalyticsService.logShoppingListOpened(
                    itemCount: items.count,
                    missingDishes: dishesWithoutIngredients.count
                )
            }
            .sheet(isPresented: $showPaywall) {
                PremiumView(settings: settings, source: "ingredient_generation")
            }
            .sheet(item: $editingDish, onDismiss: {
                // Pick up ingredients the user just added in the editor.
                ShoppingListService.reconcile(
                    context: context,
                    weekStartDate: weekStartDate,
                    plannedDishes: plannedDishes
                )
            }) { dish in
                DishFormView(dish: dish)
            }
        }
    }

    private var emptyState: some View {
        VStack(spacing: 8) {
            Image(systemName: "cart")
                .font(.system(size: 40))
                .foregroundColor(.mealMoodTextSecondary)
            Text("shopping_empty_title")
                .font(.mealMoodBodyBold)
                .foregroundColor(.mealMoodTextPrimary)
            Text("shopping_empty_message")
                .font(.mealMoodCaption)
                .foregroundColor(.mealMoodTextSecondary)
                .multilineTextAlignment(.center)
        }
        .frame(maxWidth: .infinity)
        .padding(.vertical, 24)
        .listRowBackground(Color.clear)
    }

    private func itemRow(_ item: ShoppingItem) -> some View {
        Button {
            item.isChecked.toggle()
            HapticManager.shared.selection()
        } label: {
            HStack {
                Image(systemName: item.isChecked ? "checkmark.circle.fill" : "circle")
                    .foregroundColor(item.isChecked ? .mealMoodCoral : .mealMoodTextSecondary)
                Text(item.title)
                    .strikethrough(item.isChecked)
                    .foregroundColor(item.isChecked ? .mealMoodTextSecondary : .mealMoodTextPrimary)
                Spacer()
            }
        }
        .buttonStyle(.plain)
        .swipeActions(edge: .trailing) {
            Button(role: .destructive) {
                context.delete(item)
            } label: {
                Label("shopping_delete", systemImage: "trash")
            }
        }
    }

    @ViewBuilder
    private func missingIngredientsRow(_ dish: Dish) -> some View {
        HStack {
            // Tapping the dish opens its editor — the only path to add
            // ingredients on devices without on-device generation.
            Button {
                editingDish = dish
            } label: {
                HStack(spacing: 6) {
                    Text(dish.name)
                        .foregroundColor(.mealMoodTextPrimary)
                    Image(systemName: "square.and.pencil")
                        .font(.system(size: 13))
                        .foregroundColor(.mealMoodTextSecondary)
                }
            }
            .buttonStyle(.borderless)

            Spacer()

            if IngredientGenerator.isAvailable {
                if generatingDishId == dish.id {
                    ProgressView()
                } else {
                    Button {
                        generate(for: dish)
                    } label: {
                        Label("shopping_generate", systemImage: "sparkles")
                            .font(.mealMoodSmall.weight(.semibold))
                            .foregroundColor(.mealMoodCoral)
                    }
                    .buttonStyle(.borderless)
                }
            }
        }
    }

    private func generate(for dish: Dish) {
        guard PremiumAccess.canGenerateIngredients(isPremium: settings.isPremium) else {
            showPaywall = true
            return
        }
        generatingDishId = dish.id
        Task {
            let lines = await IngredientGenerator.generate(
                dishName: dish.name,
                language: settings.languageEnum
            )
            await MainActor.run {
                generatingDishId = nil
                guard !lines.isEmpty else { return }
                dish.ingredients = lines
                PremiumAccess.recordIngredientGeneration()
                AnalyticsService.logIngredientsGenerated(
                    lineCount: lines.count,
                    source: "shopping_list"
                )
                ShoppingListService.reconcile(
                    context: context,
                    weekStartDate: weekStartDate,
                    plannedDishes: plannedDishes
                )
            }
        }
    }

    private func addFreeTextItem() {
        let title = newItemText.trimmingCharacters(in: .whitespacesAndNewlines)
        guard !title.isEmpty else { return }
        let order = (items.map(\.sortOrder).max() ?? -1) + 1
        context.insert(
            ShoppingItem(weekStartDate: weekStartDate, title: title, sortOrder: order)
        )
        newItemText = ""
        AnalyticsService.logShoppingItemAdded()
    }

    private func clearChecked() {
        for item in items where item.isChecked {
            context.delete(item)
        }
    }

    private var exportText: String {
        ShoppingListService.exportText(
            items: items,
            header: String(localized: "shopping_share_header")
        )
    }
}