import WidgetKit
import SwiftUI

// MARK: - App Group shared storage
//
// Auth flow:
// 1. Main app logs in → gets session cookie from gateway
// 2. Main app stores cookie value in App Group UserDefaults
// 3. Widget reads cookie from App Group UserDefaults
// 4. Widget makes API calls with that cookie
//
// Data stored in App Group:
// - "widget_sessionCookie": String (the session=xxx cookie value)
// - "widget_totalCalories": Double (fallback cache)
// - "widget_calorieGoal": Double (fallback cache)
// - "widget_lastUpdate": Date (when cache was last written)

private let appGroup = "group.com.quadjourney.platform"
private let gatewayURL = "https://dash.quadjourney.com"

private var sharedDefaults: UserDefaults {
    UserDefaults(suiteName: appGroup) ?? .standard
}

// MARK: - Timeline Entry

struct CalorieEntry: TimelineEntry {
    let date: Date
    let totalCalories: Double
    let calorieGoal: Double

    var progress: Double {
        guard calorieGoal > 0 else { return 0 }
        return min(max(totalCalories / calorieGoal, 0), 1.0)
    }

    var remaining: Double {
        max(calorieGoal - totalCalories, 0)
    }

    static let placeholder = CalorieEntry(date: .now, totalCalories: 845, calorieGoal: 2000)
}

// MARK: - Timeline Provider

struct CalorieProvider: TimelineProvider {
    func placeholder(in context: Context) -> CalorieEntry {
        .placeholder
    }

    func getSnapshot(in context: Context, completion: @escaping (CalorieEntry) -> Void) {
        if context.isPreview {
            completion(.placeholder)
            return
        }
        // Return cached data for snapshot
        completion(readCachedEntry())
    }

    func getTimeline(in context: Context, completion: @escaping (Timeline<CalorieEntry>) -> Void) {
        Task {
            let entry: CalorieEntry

            // Try fetching fresh data from API
            if let fresh = await fetchFromAPI() {
                entry = fresh
                // Cache for fallback
                sharedDefaults.set(fresh.totalCalories, forKey: "widget_totalCalories")
                sharedDefaults.set(fresh.calorieGoal, forKey: "widget_calorieGoal")
                sharedDefaults.set(Date(), forKey: "widget_lastUpdate")
            } else {
                // Network failed — use cached data
                entry = readCachedEntry()
            }

            // Refresh every 15 minutes (WidgetKit may throttle to ~every hour)
            let nextUpdate = Calendar.current.date(byAdding: .minute, value: 15, to: .now)!
            let timeline = Timeline(entries: [entry], policy: .after(nextUpdate))
            completion(timeline)
        }
    }

    // MARK: - API Fetch

    private func fetchFromAPI() async -> CalorieEntry? {
        guard let cookie = sharedDefaults.string(forKey: "widget_sessionCookie"),
              !cookie.isEmpty else {
            return nil // No auth — user hasn't logged in yet
        }

        let today = formatDate(.now)

        async let totalsData = apiGet("/api/fitness/entries/totals?date=\(today)", cookie: cookie)
        async let goalData = apiGet("/api/fitness/goals/for-date?date=\(today)", cookie: cookie)

        guard let totals = await totalsData,
              let goal = await goalData else {
            return nil
        }

        let calories = totals["total_calories"] as? Double
            ?? (totals["total_calories"] as? Int).map(Double.init)
            ?? 0
        let goalCalories = goal["calories"] as? Double
            ?? (goal["calories"] as? Int).map(Double.init)
            ?? 2000

        return CalorieEntry(date: .now, totalCalories: calories, calorieGoal: goalCalories)
    }

    private func apiGet(_ path: String, cookie: String) async -> [String: Any]? {
        guard let url = URL(string: gatewayURL + path) else { return nil }
        var request = URLRequest(url: url)
        request.setValue("session=\(cookie)", forHTTPHeaderField: "Cookie")
        request.timeoutInterval = 10

        do {
            let (data, response) = try await URLSession.shared.data(for: request)
            guard let http = response as? HTTPURLResponse,
                  (200...299).contains(http.statusCode) else { return nil }
            return try JSONSerialization.jsonObject(with: data) as? [String: Any]
        } catch {
            return nil
        }
    }

    private func readCachedEntry() -> CalorieEntry {
        let calories = sharedDefaults.double(forKey: "widget_totalCalories")
        let goal = sharedDefaults.double(forKey: "widget_calorieGoal")
        return CalorieEntry(
            date: .now,
            totalCalories: calories,
            calorieGoal: goal > 0 ? goal : 2000
        )
    }

    private func formatDate(_ date: Date) -> String {
        let f = DateFormatter()
        f.dateFormat = "yyyy-MM-dd"
        return f.string(from: date)
    }
}

// MARK: - Widget Views

struct CalorieRingView: View {
    let entry: CalorieEntry
    let size: CGFloat
    let lineWidth: CGFloat

    private let ringColor = Color(red: 0.020, green: 0.588, blue: 0.412)

    var body: some View {
        ZStack {
            Circle()
                .stroke(ringColor.opacity(0.2), lineWidth: lineWidth)

            Circle()
                .trim(from: 0, to: entry.progress)
                .stroke(ringColor, style: StrokeStyle(lineWidth: lineWidth, lineCap: .round))
                .rotationEffect(.degrees(-90))

            VStack(spacing: 1) {
                Text("\(Int(entry.totalCalories))")
                    .font(.system(size: size * 0.22, weight: .bold, design: .rounded))
                    .foregroundStyle(.primary)
                Text("/ \(Int(entry.calorieGoal))")
                    .font(.system(size: size * 0.1, weight: .medium, design: .rounded))
                    .foregroundStyle(.secondary)
            }
        }
        .frame(width: size, height: size)
    }
}

struct SmallWidgetView: View {
    let entry: CalorieEntry

    var body: some View {
        VStack(spacing: 8) {
            CalorieRingView(entry: entry, size: 90, lineWidth: 8)

            Text("\(Int(entry.remaining)) left")
                .font(.caption2.weight(.medium))
                .foregroundStyle(.secondary)
        }
        .frame(maxWidth: .infinity, maxHeight: .infinity)
    }
}

struct MediumWidgetView: View {
    let entry: CalorieEntry

    var body: some View {
        HStack(spacing: 20) {
            CalorieRingView(entry: entry, size: 100, lineWidth: 9)

            VStack(alignment: .leading, spacing: 6) {
                Text("Calories")
                    .font(.headline)
                    .foregroundStyle(.primary)

                Text("\(Int(entry.totalCalories)) of \(Int(entry.calorieGoal))")
                    .font(.subheadline)
                    .foregroundStyle(.secondary)

                Text("\(Int(entry.remaining)) remaining")
                    .font(.caption)
                    .foregroundStyle(.tertiary)
            }
        }
        .frame(maxWidth: .infinity, maxHeight: .infinity)
    }
}

struct CircularWidgetView: View {
    let entry: CalorieEntry

    var body: some View {
        Gauge(value: entry.progress) {
            Text("\(Int(entry.totalCalories))")
                .font(.system(size: 12, weight: .bold, design: .rounded))
        }
        .gaugeStyle(.accessoryCircular)
        .tint(Color(red: 0.020, green: 0.588, blue: 0.412))
    }
}

struct InlineWidgetView: View {
    let entry: CalorieEntry

    var body: some View {
        Text("\(Int(entry.totalCalories)) / \(Int(entry.calorieGoal)) cal")
    }
}

struct RectangularWidgetView: View {
    let entry: CalorieEntry

    var body: some View {
        HStack(spacing: 8) {
            Gauge(value: entry.progress) {
                EmptyView()
            }
            .gaugeStyle(.accessoryLinear)
            .tint(Color(red: 0.020, green: 0.588, blue: 0.412))

            Text("\(Int(entry.totalCalories)) cal")
                .font(.system(size: 13, weight: .bold, design: .rounded))
        }
    }
}

// MARK: - Entry View (family-aware)

struct PlatformWidgetEntryView: View {
    @Environment(\.widgetFamily) var family
    let entry: CalorieEntry

    var body: some View {
        switch family {
        case .systemSmall:
            SmallWidgetView(entry: entry)
        case .systemMedium:
            MediumWidgetView(entry: entry)
        case .accessoryCircular:
            CircularWidgetView(entry: entry)
        case .accessoryInline:
            InlineWidgetView(entry: entry)
        case .accessoryRectangular:
            RectangularWidgetView(entry: entry)
        default:
            SmallWidgetView(entry: entry)
        }
    }
}

// MARK: - Widget Configuration

struct PlatformWidget: Widget {
    let kind: String = "PlatformWidget"

    var body: some WidgetConfiguration {
        StaticConfiguration(kind: kind, provider: CalorieProvider()) { entry in
            PlatformWidgetEntryView(entry: entry)
                .containerBackground(.fill.tertiary, for: .widget)
        }
        .configurationDisplayName("Calories")
        .description("Today's calorie progress ring.")
        .supportedFamilies([
            .systemSmall,
            .systemMedium,
            .accessoryCircular,
            .accessoryInline,
            .accessoryRectangular,
        ])
    }
}

#Preview(as: .systemSmall) {
    PlatformWidget()
} timeline: {
    CalorieEntry(date: .now, totalCalories: 845, calorieGoal: 2000)
}