import Foundation
import CoreData

/// Decides when to ask for an App Store rating: after a "positive moment"
/// (a saved check-in), only once the habit is established (≥2 distinct months
/// of snapshots) and at most once per app version. Apple additionally caps
/// the system prompt at 3 displays per year, so over-calling is safe.
///
/// Call sites own the actual prompt via SwiftUI's `\.requestReview` — this
/// service only answers "should we ask now?" and records that we did.
@MainActor
enum ReviewRequestService {
    private static let lastVersionKey = "reviewRequest.lastVersion"

    /// Returns true at most once per app version, and only when the user has
    /// snapshots in 2+ distinct months (they've seen the app deliver value).
    /// Marks the version as asked when returning true.
    static func shouldRequestAfterCheckIn() -> Bool {
        guard distinctSnapshotMonths() >= 2 else { return false }

        let version = Bundle.main.object(forInfoDictionaryKey: "CFBundleShortVersionString") as? String ?? "unknown"
        let defaults = UserDefaults.standard
        guard defaults.string(forKey: lastVersionKey) != version else { return false }

        defaults.set(version, forKey: lastVersionKey)
        return true
    }

    private static func distinctSnapshotMonths() -> Int {
        let request = NSFetchRequest<Snapshot>(entityName: "Snapshot")
        guard let snapshots = try? CoreDataStack.shared.viewContext.fetch(request) else { return 0 }
        let calendar = Calendar.current
        let months = Set(snapshots.map { snapshot in
            calendar.dateComponents([.year, .month], from: snapshot.date)
        })
        return months.count
    }
}