import Foundation

@MainActor
@Observable
final class AIFreeUsageManager {
    static let shared = AIFreeUsageManager()
    static let maxFreeUses = 3

    private static let usedCountKey = "AIFreeUsageManager.usedCount"

    private(set) var usedCount: Int

    var remainingUses: Int {
        max(0, Self.maxFreeUses - usedCount)
    }

    var hasExhaustedFreeUses: Bool {
        usedCount >= Self.maxFreeUses
    }

    func canUseFreeLiveAI(hasEverPurchasedPremium: Bool) -> Bool {
        !hasEverPurchasedPremium && remainingUses > 0
    }

    private init() {
        usedCount = UserDefaults.standard.integer(forKey: Self.usedCountKey)
    }

    func recordUse(for tool: AIHistoryToolKind) {
        guard usedCount < Self.maxFreeUses else { return }
        usedCount += 1
        persistUsedCount()
    }

    /// Restores the free AI quota for users who have never purchased premium (e.g. sandbox transaction reset).
    func resetFreeUses() {
        usedCount = 0
        persistUsedCount()
    }

    /// Permanently removes free AI access after a purchase or refund.
    func forfeitFreeUses() {
        usedCount = Self.maxFreeUses
        persistUsedCount()
    }

    private func persistUsedCount() {
        UserDefaults.standard.set(usedCount, forKey: Self.usedCountKey)
    }
}