import FirebaseAnalytics

enum AnalyticsEvent {
    // Onboarding
    static let onboardingCompleted = "onboarding_completed"

    // Dishes
    static let dishAdded = "dish_added"
    static let dishDeleted = "dish_deleted"

    // Planner
    static let mealAssigned = "meal_assigned"
    static let mealCleared = "meal_cleared"
    static let weekReset = "week_reset"
    static let weekPlanShared = "week_plan_shared"

    // Premium
    static let premiumUpgradeTapped = "premium_upgrade_tapped"
    static let premiumPurchased = "premium_purchased"
    static let premiumPurchaseFailed = "premium_purchase_failed"
    static let premiumRestored = "premium_restored"

    // Planner
    static let autoAssignUsed = "auto_assign_used"
    static let weekCopiedPrevious = "week_copied_previous"

    // Shopping list (2.0)
    static let shoppingListOpened = "shopping_list_opened"
    static let shoppingItemAdded = "shopping_item_added"
    static let ingredientsGenerated = "ingredients_generated"

    // Onboarding
    static let onboardingStepViewed = "onboarding_step_viewed"

    // Settings
    static let iCloudSyncToggled = "icloud_sync_toggled"
    static let notificationsToggled = "notifications_toggled"
    static let languageChanged = "language_changed"

    // Stats
    static let statsViewed = "stats_viewed"

    // Feedback loop
    static let weekRated = "week_rated"

    // Conversion funnel (1.1.5)
    static let paywallViewed = "paywall_viewed"
    static let paywallDismissed = "paywall_dismissed"
    static let dishLimitHit = "dish_limit_hit"
    static let weekLimitHit = "week_limit_hit"
    static let freeTrialStarted = "free_trial_started"
}

enum AnalyticsService {
    /// UI tests drive the app against the production Firebase project, so every
    /// run would otherwise land in GA4 as a real user: a full onboarding funnel,
    /// a paywall view, the lot. It already happened — the step 5/6 events
    /// recorded under 2.0 were test runs, not users.
    static let launchArgumentDisablingAnalytics = "UITEST_DISABLE_ANALYTICS"

    static let isDisabled: Bool =
        ProcessInfo.processInfo.arguments.contains(launchArgumentDisablingAnalytics)

    /// Silences Firebase's own automatic events (first_open, session_start,
    /// screen_view), which no-oping `logEvent` alone would not catch.
    /// Call once, right after `FirebaseApp.configure()`.
    ///
    /// Always sets the flag, never just when disabling: Firebase persists this
    /// across launches, so a single test run would otherwise leave analytics off
    /// for good on that install.
    static func applyCollectionPolicy() {
        Analytics.setAnalyticsCollectionEnabled(!isDisabled)
    }

    static func logEvent(_ name: String, parameters: [String: Any]? = nil) {
        guard !isDisabled else { return }
        Analytics.logEvent(name, parameters: parameters)
    }

    static func logScreenView(_ screenName: String) {
        guard !isDisabled else { return }
        Analytics.logEvent(AnalyticsEventScreenView, parameters: [
            AnalyticsParameterScreenName: screenName,
            AnalyticsParameterScreenClass: screenName
        ])
    }

    // MARK: - Convenience methods

    static func logDishAdded(tagCount: Int, source: String = "editor") {
        logEvent(AnalyticsEvent.dishAdded, parameters: [
            "tag_count": tagCount,
            "source": source
        ])
    }

    static func logDishDeleted() {
        logEvent(AnalyticsEvent.dishDeleted)
    }

    static func logMealAssigned() {
        logEvent(AnalyticsEvent.mealAssigned)
    }

    static func logMealCleared() {
        logEvent(AnalyticsEvent.mealCleared)
    }

    static func logWeekReset() {
        logEvent(AnalyticsEvent.weekReset)
    }

    static func logWeekPlanShared(format: String) {
        logEvent(AnalyticsEvent.weekPlanShared, parameters: ["format": format])
    }

    static func logPremiumUpgradeTapped(source: String) {
        logEvent(AnalyticsEvent.premiumUpgradeTapped, parameters: ["source": source])
    }

    static func logPremiumPurchased(environment: String = "unknown") {
        logEvent(AnalyticsEvent.premiumPurchased, parameters: ["environment": environment])
    }

    /// Why a tapped upgrade never became a purchase. Without this a user who
    /// changed their mind and a user whose purchase broke look identical — both
    /// are just a `premium_upgrade_tapped` with nothing after it.
    ///
    /// `reason` is one of: `cancelled`, `pending`, `unverified`, `error`.
    static func logPremiumPurchaseFailed(reason: String, productId: String, detail: String? = nil) {
        var parameters: [String: Any] = ["reason": reason, "product_id": productId]
        if let detail {
            // GA4 drops string params over 100 chars.
            parameters["detail"] = String(detail.prefix(100))
        }
        logEvent(AnalyticsEvent.premiumPurchaseFailed, parameters: parameters)
    }

    static func logPremiumRestored() {
        logEvent(AnalyticsEvent.premiumRestored)
    }

    static func logOnboardingCompleted(dishCount: Int) {
        logEvent(AnalyticsEvent.onboardingCompleted, parameters: ["dish_count": dishCount])
    }

    // Human-readable names for each onboarding step, indexed by step number.
    // Keep in sync with the OnboardingView step order.
    private static let onboardingStepNames = [
        "0_welcome", "1_meal_windows", "2_weekends",
        "3_calendar", "4_first_dishes", "5_week_ready", "6_paywall"
    ]

    static func logOnboardingStepViewed(step: Int) {
        // GA4 text custom dimensions do not capture numeric params (they show as
        // "(not set)"). Log the step as a String so the drop-off is queryable.
        let name = step >= 0 && step < onboardingStepNames.count ? onboardingStepNames[step] : "\(step)"
        logEvent(AnalyticsEvent.onboardingStepViewed, parameters: [
            "step": "\(step)",
            "step_name": name
        ])
    }

    static func logAutoAssignUsed(filledSlots: Int, unfilledSlots: Int) {
        logEvent(AnalyticsEvent.autoAssignUsed, parameters: [
            "filled_slots": filledSlots,
            "unfilled_slots": unfilledSlots
        ])
    }

    static func logWeekCopiedPrevious(copiedSlots: Int, source: String) {
        logEvent(AnalyticsEvent.weekCopiedPrevious, parameters: [
            "copied_slots": copiedSlots,
            "source": source
        ])
    }

    static func logShoppingListOpened(itemCount: Int, missingDishes: Int) {
        logEvent(AnalyticsEvent.shoppingListOpened, parameters: [
            "item_count": itemCount,
            "missing_dishes": missingDishes
        ])
    }

    static func logShoppingItemAdded() {
        logEvent(AnalyticsEvent.shoppingItemAdded)
    }

    static func logIngredientsGenerated(lineCount: Int, source: String) {
        logEvent(AnalyticsEvent.ingredientsGenerated, parameters: [
            "line_count": lineCount,
            "source": source
        ])
    }

    static func logICloudSyncToggled(enabled: Bool) {
        logEvent(AnalyticsEvent.iCloudSyncToggled, parameters: ["enabled": enabled])
    }

    static func logNotificationsToggled(enabled: Bool) {
        logEvent(AnalyticsEvent.notificationsToggled, parameters: ["enabled": enabled])
    }

    static func logStatsViewed() {
        logEvent(AnalyticsEvent.statsViewed)
    }

    static func logWeekRated(rating: Int) {
        let value = rating == 1 ? "liked" : rating == -1 ? "disliked" : "cleared"
        logEvent(AnalyticsEvent.weekRated, parameters: ["rating": value])
    }

    static func logPaywallViewed(source: String) {
        logEvent(AnalyticsEvent.paywallViewed, parameters: ["source": source])
    }

    static func logPaywallDismissed(source: String, secondsOnScreen: Int, didConvert: Bool) {
        logEvent(AnalyticsEvent.paywallDismissed, parameters: [
            "source": source,
            "seconds_on_screen": secondsOnScreen,
            "did_convert": didConvert
        ])
    }

    static func logDishLimitHit() {
        logEvent(AnalyticsEvent.dishLimitHit)
    }

    static func logWeekLimitHit() {
        logEvent(AnalyticsEvent.weekLimitHit)
    }

    static func logFreeTrialStarted(plan: String) {
        logEvent(AnalyticsEvent.freeTrialStarted, parameters: ["plan": plan])
    }
}