import Foundation
import StoreKit

struct PaywallConfig: Codable, Sendable {
    struct PlanCopy: Codable, Sendable {
        let title: String
        let badge: String?
        let subtitleTemplate: String
        let trialSubtitleTemplate: String?
        let ctaTemplate: String

        init(
            title: String,
            badge: String? = nil,
            subtitleTemplate: String,
            trialSubtitleTemplate: String? = nil,
            ctaTemplate: String
        ) {
            self.title = title
            self.badge = badge
            self.subtitleTemplate = subtitleTemplate
            self.trialSubtitleTemplate = trialSubtitleTemplate
            self.ctaTemplate = ctaTemplate
        }
    }

    struct TrustItem: Codable, Sendable {
        let icon: String
        let title: String
        let subtitle: String
    }

    struct Footer: Codable, Sendable {
        let continueFree: String
        let manageSubscription: String
        let restorePurchase: String
        let privacyPolicy: String
        let termsOfService: String
        let support: String
    }

    struct URLs: Codable, Sendable {
        let privacy: String
        let terms: String
        let support: String
        let manageSubscriptions: String
    }

    struct Plans: Codable, Sendable {
        let monthly: PlanCopy
        let yearly: PlanCopy
        let lifetime: PlanCopy
    }

    struct DurationUnit: Codable, Sendable {
        let one: String
        let other: String
        let lowerOne: String
        let lowerOther: String
    }

    struct Duration: Codable, Sendable {
        let units: DurationUnits
        let countUnitTemplate: String
        let unknownFallback: String
    }

    struct DurationUnits: Codable, Sendable {
        let day: DurationUnit
        let week: DurationUnit
        let month: DurationUnit
        let year: DurationUnit
    }

    struct Trial: Codable, Sendable {
        let badgeTemplate: String
        let ctaTemplate: String
    }

    struct Messages: Codable, Sendable {
        let productNotFound: String
        let failedVerification: String
        let noPlansAvailable: String
        let plansLoadFailed: String
        let purchaseFailedTitle: String
        let restoreNotFoundTitle: String
        let restoreNotFoundMessage: String
        let pendingPurchaseTitle: String
        let pendingPurchaseMessage: String
        let alertOK: String
        let retry: String
        let retrying: String
        let periodFallback: String
    }

    struct Sidebar: Codable, Sendable {
        let unlockTitle: String
        let proTitle: String
        let unlockDescription: String
        let proDescription: String
        let upgradeAction: String
        let manageSubscriptionAction: String
        let lifetimeAction: String
    }

    let leftPanelTitle: String
    let rightTitle: String
    let rightSubtitle: String
    let features: [String]
    let trustItems: [TrustItem]
    let lifetimeTrustItem: TrustItem
    let plans: Plans
    let footer: Footer
    let urls: URLs
    let trial: Trial
    let duration: Duration
    let messages: Messages
    let sidebar: Sidebar
    let loadingPrice: String
    let loadingCTA: String
    let subscriptionDisclosureTemplate: String
    let trialDisclosureTemplate: String
    let lifetimeDisclosure: String
    let loadingDisclosure: String
}

extension PaywallConfig {
    func mergingMarketing(from remote: PaywallConfig) -> PaywallConfig {
        PaywallConfig(
            leftPanelTitle: remote.leftPanelTitle,
            rightTitle: remote.rightTitle,
            rightSubtitle: remote.rightSubtitle,
            features: remote.features,
            trustItems: remote.trustItems,
            lifetimeTrustItem: remote.lifetimeTrustItem,
            plans: remote.plans,
            footer: footer,
            urls: urls,
            trial: trial,
            duration: duration,
            messages: messages,
            sidebar: remote.sidebar,
            loadingPrice: loadingPrice,
            loadingCTA: loadingCTA,
            subscriptionDisclosureTemplate: subscriptionDisclosureTemplate,
            trialDisclosureTemplate: trialDisclosureTemplate,
            lifetimeDisclosure: lifetimeDisclosure,
            loadingDisclosure: loadingDisclosure
        )
    }

    static func loadBundled() -> PaywallConfig {
        guard let url = Bundle.main.url(forResource: "paywall", withExtension: "json"),
              let data = try? Data(contentsOf: url),
              let config = try? JSONDecoder().decode(PaywallConfig.self, from: data) else {
            fatalError("Missing or invalid paywall.json in app bundle.")
        }
        return config
    }

    func formatDuration(count: Int, unit: Product.SubscriptionPeriod.Unit, lowercase: Bool) -> String {
        guard count > 0 else {
            return duration.unknownFallback.replacingOccurrences(of: "{count}", with: "0")
        }

        let durationUnit: DurationUnit
        switch unit {
        case .day: durationUnit = duration.units.day
        case .week: durationUnit = duration.units.week
        case .month: durationUnit = duration.units.month
        case .year: durationUnit = duration.units.year
        @unknown default:
            return duration.unknownFallback.replacingOccurrences(of: "{count}", with: "\(count)")
        }

        let unitWord: String
        if count == 1 {
            unitWord = lowercase ? durationUnit.lowerOne : durationUnit.one
        } else {
            unitWord = lowercase ? durationUnit.lowerOther : durationUnit.other
        }

        if count == 1, lowercase {
            return unitWord
        }

        return duration.countUnitTemplate
            .replacingOccurrences(of: "{count}", with: "\(count)")
            .replacingOccurrences(of: "{unit}", with: unitWord)
    }

    func trialDurationDescription(from offer: Product.SubscriptionOffer, lowercase: Bool = false) -> String {
        let count = offer.period.value * offer.periodCount
        return formatDuration(count: count, unit: offer.period.unit, lowercase: lowercase)
    }

    func subscriptionPeriodDescription(from period: Product.SubscriptionPeriod) -> String {
        formatDuration(count: period.value, unit: period.unit, lowercase: true)
    }

    func trialBadgeText(from offer: Product.SubscriptionOffer) -> String {
        let duration = trialDurationDescription(from: offer)
        return trial.badgeTemplate.replacingOccurrences(of: "{duration}", with: duration)
    }

    func trialCTATitle(from offer: Product.SubscriptionOffer) -> String {
        let duration = trialDurationDescription(from: offer)
        return trial.ctaTemplate.replacingOccurrences(of: "{duration}", with: duration)
    }
}

extension PaywallConfig: Equatable {
    static func == (lhs: PaywallConfig, rhs: PaywallConfig) -> Bool {
        guard let lhsData = try? JSONEncoder().encode(lhs),
              let rhsData = try? JSONEncoder().encode(rhs) else {
            return false
        }
        return lhsData == rhsData
    }
}

extension Notification.Name {
    static let paywallConfigDidUpdate = Notification.Name("paywallConfigDidUpdate")
}