// ── Feature Flag Client ───────────────────────────────────────
// Polls platform-service /flags/poll for feature flags.
// Flags cached in memory, re-polled every 5 minutes.
// Consumers call FeatureFlagService.shared.isEnabled("flag_key").

import Foundation

@MainActor
final class FeatureFlagService: ObservableObject {
    static let shared = FeatureFlagService()

    @Published private(set) var flags: [String: Bool] = [:]
    private var pollTimer: Timer?
    private let pollIntervalSec: TimeInterval = 5 * 60 // 5 minutes
    private let productId = "chronomind"

    private var baseURL: String {
        Bundle.main.object(forInfoDictionaryKey: "PLATFORM_SERVICE_URL") as? String
            ?? "https://api.chronomind.app"
    }

    private init() {}

    // MARK: - Public API

    func start(userId: String? = nil) {
        Task { await fetchFlags(userId: userId) }
        pollTimer?.invalidate()
        pollTimer = Timer.scheduledTimer(withTimeInterval: pollIntervalSec, repeats: true) { [weak self] _ in
            guard let self else { return }
            Task { @MainActor in await self.fetchFlags(userId: userId) }
        }
    }

    func stop() {
        pollTimer?.invalidate()
        pollTimer = nil
    }

    func isEnabled(_ key: String) -> Bool {
        flags[key] == true
    }

    // MARK: - Fetch

    private func fetchFlags(userId: String? = nil) async {
        var components = URLComponents(string: "\(baseURL)/api/flags/poll")
        var queryItems: [URLQueryItem] = [.init(name: "platform", value: "ios")]
        if let userId { queryItems.append(.init(name: "userId", value: userId)) }
        components?.queryItems = queryItems

        guard let url = components?.url else { return }

        var request = URLRequest(url: url)
        request.setValue(productId, forHTTPHeaderField: "X-Product-Id")
        request.timeoutInterval = 10

        do {
            let (data, response) = try await URLSession.shared.data(for: request)
            guard let http = response as? HTTPURLResponse, http.statusCode == 200 else { return }

            struct FlagsResponse: Codable {
                let flags: [String: Bool]
            }
            let parsed = try JSONDecoder().decode(FlagsResponse.self, from: data)
            flags = parsed.flags
        } catch {
            // Keep existing flags on error
        }
    }
}