//
//  TransactionObserver.swift
//  Toki Trainer
//
//  Created by Madeline Pace on 12/18/23.
//

import CoreData
import StoreKit

@MainActor
final class TransactionObserver: ObservableObject {

    var updates: Task<Void, Never>? = nil

    @Published var donationHearts: Int = 0
    @Published var hasDonated = false


    init() {
        updates = newTransactionListenerTask()
        donationHearts = UserDefaults.standard.integer(forKey: K.UserDefaults.donationHearts)
        hasDonated = UserDefaults.standard.bool(forKey: K.UserDefaults.hasDonated)
    }

    deinit {
        updates?.cancel()
    }

    func addDonationHearts(_ amount: Int) {
        if hasDonated == false {
            hasDonated = true
            UserDefaults.standard.set(hasDonated, forKey: K.UserDefaults.hasDonated)
        }

        DispatchQueue.main.async {
            self.donationHearts += amount
        }
        UserDefaults.standard.set(donationHearts, forKey: K.UserDefaults.donationHearts)
    }

    private func newTransactionListenerTask() -> Task<Void, Never> {
        Task(priority: .background) {
            for await verificationResult in Transaction.updates {
                await self.handle(updatedTransaction: verificationResult)
            }
        }
    }

    private func handle(updatedTransaction verificationResult: VerificationResult<Transaction>) async {
        guard case .verified(let transaction) = verificationResult else {
            return
        }

        switch transaction.productType {
        case Product.ProductType.consumable:
            processConsumable(transaction.productID)
        case Product.ProductType.nonRenewable, Product.ProductType.autoRenewable:
            processSubscription(transaction.productID)
        default:
            return
        }

        print("Finishing transaction")
        await transaction.finish()
    }

    func processConsumable(_ productID: String) {
        print("Consumable ID: \(productID)")
        switch productID {
        case K.ConsumableTransactions.TierOne:
            self.addDonationHearts(100)
        case K.ConsumableTransactions.TierTwo:
            self.addDonationHearts(500)
        case K.ConsumableTransactions.TierThree:
            self.addDonationHearts(1000)
        case K.ConsumableTransactions.TierFour:
            self.addDonationHearts(2000)
        default:
            return
        }
    }

    func processSubscription(_ productID: String) {
        print("Subscription ID: \(productID)")
        switch productID {
        case K.MonthlyTransactions.TierOne:
            self.addDonationHearts(100)
        case K.MonthlyTransactions.TierTwo:
            self.addDonationHearts(500)
        case K.MonthlyTransactions.TierThree:
            self.addDonationHearts(1000)
        default:
            return
        }
    }
}