import SwiftUI

struct StatsView: View {
    let weekPlans: [WeekPlan]
    let allDishes: [Dish]
    let allTags: [Tag]
    let language: AppLanguage

    @Environment(\.dismiss) private var dismiss

    var body: some View {
        NavigationStack {
            ScrollView {
                VStack(spacing: 24) {
                    summaryGrid
                    topDishesSection
                    tagBreakdownSection
                }
                .padding(.horizontal, 16)
                .padding(.vertical, 20)
            }
            .background(Color.mealMoodBackground.ignoresSafeArea())
            .onAppear { AnalyticsService.logStatsViewed() }
            .navigationTitle("stats_title")
            .navigationBarTitleDisplayMode(.inline)
            .toolbar {
                ToolbarItem(placement: .navigationBarTrailing) {
                    Button("tag_selector_done") { dismiss() }
                }
            }
        }
    }

    // MARK: - Summary grid

    private var summaryGrid: some View {
        VStack(spacing: 12) {
            HStack(spacing: 12) {
                StatCard(
                    icon: "flame.fill",
                    iconColor: .mealMoodCoral,
                    value: "\(streak)",
                    label: "stats_streak_label"
                )
                StatCard(
                    icon: "calendar",
                    iconColor: .mealMoodMint,
                    value: "\(weeksWithAnyDish)",
                    label: "stats_weeks_planned_label"
                )
            }
            HStack(spacing: 12) {
                StatCard(
                    icon: "checkmark.circle.fill",
                    iconColor: .mealMoodSuccess,
                    value: "\(completeWeeks)",
                    label: "stats_complete_weeks_label"
                )
                StatCard(
                    icon: "chart.bar.fill",
                    iconColor: .mealMoodWarning,
                    value: completionRateText,
                    label: "stats_completion_rate_label"
                )
            }
        }
    }

    // MARK: - Top dishes

    private var topDishesSection: some View {
        VStack(alignment: .leading, spacing: 12) {
            Text("stats_top_dishes_title")
                .font(.mealMoodH3)
                .foregroundColor(.mealMoodTextPrimary)

            if topDishes.isEmpty {
                Text("stats_no_data")
                    .font(.mealMoodBody)
                    .foregroundColor(.mealMoodTextSecondary)
                    .frame(maxWidth: .infinity, alignment: .center)
                    .padding(.vertical, 16)
            } else {
                VStack(spacing: 0) {
                    ForEach(Array(topDishes.enumerated()), id: \.element.dish.id) { index, entry in
                        TopDishRow(
                            rank: index + 1,
                            dishName: entry.dish.name,
                            count: entry.count,
                            maxCount: topDishes.first?.count ?? 1
                        )
                        if index < topDishes.count - 1 {
                            Divider().padding(.leading, 44)
                        }
                    }
                }
                .background(Color.mealMoodSurface)
                .clipShape(RoundedRectangle(cornerRadius: 12))
            }
        }
    }

    // MARK: - Tag breakdown

    private var tagBreakdownSection: some View {
        VStack(alignment: .leading, spacing: 12) {
            Text("stats_tags_title")
                .font(.mealMoodH3)
                .foregroundColor(.mealMoodTextPrimary)

            if tagUsage.isEmpty {
                Text("stats_no_data")
                    .font(.mealMoodBody)
                    .foregroundColor(.mealMoodTextSecondary)
                    .frame(maxWidth: .infinity, alignment: .center)
                    .padding(.vertical, 16)
            } else {
                VStack(spacing: 10) {
                    ForEach(tagUsage, id: \.tag.id) { entry in
                        TagBarRow(tagName: entry.tag.localizedName(language: language), tagColor: entry.tag.color, count: entry.count, maxCount: tagUsage.first?.count ?? 1)
                    }
                }
                .padding(14)
                .background(Color.mealMoodSurface)
                .clipShape(RoundedRectangle(cornerRadius: 12))
            }
        }
    }

    // MARK: - Computed stats

    private var plannedWeeks: [WeekPlan] {
        weekPlans.filter { plan in plan.slotList.contains { $0.dishId != nil } }
    }

    private var weeksWithAnyDish: Int { plannedWeeks.count }

    private var completeWeeks: Int {
        weekPlans.filter { plan in
            !plan.slotList.isEmpty && plan.slotList.allSatisfy { $0.dishId != nil || $0.isEatingOut || $0.isSkipped }
        }.count
    }

    private var completionRateText: String {
        guard weeksWithAnyDish > 0 else { return "—" }
        let rate = Int(Double(completeWeeks) / Double(weeksWithAnyDish) * 100)
        return "\(rate)%"
    }

    private var streak: Int {
        let sorted = plannedWeeks
            .map { $0.weekStartDate.startOfWeek() }
            .sorted(by: >)
        guard !sorted.isEmpty else { return 0 }
        let calendar = Calendar.current
        var count = 1
        var previous = sorted[0]
        for date in sorted.dropFirst() {
            let diff = calendar.dateComponents([.day], from: date, to: previous).day ?? 0
            if diff <= 7 {
                count += 1
                previous = date
            } else {
                break
            }
        }
        return count
    }

    private var dishUsage: [UUID: Int] {
        var counts: [UUID: Int] = [:]
        for plan in weekPlans {
            for slot in plan.slotList {
                if let id = slot.dishId { counts[id, default: 0] += 1 }
                if let id = slot.secondaryDishId { counts[id, default: 0] += 1 }
            }
        }
        return counts
    }

    private struct DishEntry { let dish: Dish; let count: Int }

    private var topDishes: [DishEntry] {
        let usage = dishUsage
        let dishMap = Dictionary(allDishes.map { ($0.id, $0) }, uniquingKeysWith: { first, _ in first })
        return usage
            .compactMap { id, count in dishMap[id].map { DishEntry(dish: $0, count: count) } }
            .sorted { $0.count > $1.count }
            .prefix(8)
            .map { $0 }
    }

    private struct TagEntry { let tag: Tag; let count: Int }

    private var tagUsage: [TagEntry] {
        let dishMap = Dictionary(allDishes.map { ($0.id, $0) }, uniquingKeysWith: { first, _ in first })
        let tagMap = Dictionary(allTags.map { ($0.id, $0) }, uniquingKeysWith: { first, _ in first })
        var counts: [UUID: Int] = [:]
        for plan in weekPlans {
            for slot in plan.slotList {
                for dishId in [slot.dishId, slot.secondaryDishId].compactMap({ $0 }) {
                    guard let dish = dishMap[dishId] else { continue }
                    for tagId in dish.tagIds { counts[tagId, default: 0] += 1 }
                }
            }
        }
        return counts
            .compactMap { id, count in tagMap[id].map { TagEntry(tag: $0, count: count) } }
            .sorted { $0.count > $1.count }
            .prefix(6)
            .map { $0 }
    }
}

// MARK: - Sub-views

private struct StatCard: View {
    let icon: String
    let iconColor: Color
    let value: String
    let label: LocalizedStringKey

    var body: some View {
        VStack(spacing: 8) {
            Image(systemName: icon)
                .font(.system(size: 24))
                .foregroundColor(iconColor)
            Text(value)
                .font(.mealMoodH2)
                .foregroundColor(.mealMoodTextPrimary)
            Text(label)
                .font(.mealMoodCaption)
                .foregroundColor(.mealMoodTextSecondary)
                .multilineTextAlignment(.center)
        }
        .frame(maxWidth: .infinity)
        .padding(.vertical, 18)
        .background(Color.mealMoodSurface)
        .clipShape(RoundedRectangle(cornerRadius: 14))
    }
}

private struct TopDishRow: View {
    let rank: Int
    let dishName: String
    let count: Int
    let maxCount: Int

    var body: some View {
        HStack(spacing: 12) {
            Text("\(rank)")
                .font(.mealMoodCaption)
                .foregroundColor(.mealMoodTextSecondary)
                .frame(width: 20, alignment: .center)

            VStack(alignment: .leading, spacing: 4) {
                Text(dishName)
                    .font(.mealMoodBody)
                    .foregroundColor(.mealMoodTextPrimary)
                    .lineLimit(1)

                GeometryReader { geo in
                    RoundedRectangle(cornerRadius: 3)
                        .fill(Color.mealMoodCoral.opacity(0.25))
                        .frame(width: geo.size.width, height: 4)
                        .overlay(alignment: .leading) {
                            RoundedRectangle(cornerRadius: 3)
                                .fill(Color.mealMoodCoral)
                                .frame(width: geo.size.width * CGFloat(count) / CGFloat(maxCount), height: 4)
                        }
                }
                .frame(height: 4)
            }

            Text("\(count)×")
                .font(.mealMoodCaption)
                .foregroundColor(.mealMoodTextSecondary)
                .frame(width: 28, alignment: .trailing)
        }
        .padding(.horizontal, 14)
        .padding(.vertical, 12)
    }
}

private struct TagBarRow: View {
    let tagName: String
    let tagColor: String
    let count: Int
    let maxCount: Int

    var body: some View {
        HStack(spacing: 10) {
            Circle()
                .fill(Color(hex: tagColor))
                .frame(width: 10, height: 10)

            Text(tagName)
                .font(.mealMoodSmall)
                .foregroundColor(.mealMoodTextPrimary)
                .frame(width: 90, alignment: .leading)
                .lineLimit(1)

            GeometryReader { geo in
                RoundedRectangle(cornerRadius: 3)
                    .fill(Color(hex: tagColor).opacity(0.2))
                    .frame(width: geo.size.width, height: 8)
                    .overlay(alignment: .leading) {
                        RoundedRectangle(cornerRadius: 3)
                            .fill(Color(hex: tagColor))
                            .frame(width: geo.size.width * CGFloat(count) / CGFloat(maxCount), height: 8)
                    }
            }
            .frame(height: 8)

            Text("\(count)")
                .font(.mealMoodCaption)
                .foregroundColor(.mealMoodTextSecondary)
                .frame(width: 28, alignment: .trailing)
        }
    }
}