/*

    Copyright (C) 2016 Apple Inc. All Rights Reserved.

    See LICENSE.txt for this sample’s licensing information

    Abstract:

    A class tha mimics asynchronous calls to send payments to a server.

*/

import Foundation

public class PaymentProvider {

    // MARK: Properties

    public var mostRecentPayment: Payment? {

        let paymentHistory = loadPaymentHistory()

        return paymentHistory.last

    }

    // MARK: Intialization

    public init() {}

    // MARK: Payment methods

    public func canSend(_ payment: Payment, completion: (_ success: Bool, _ error: NSError?) -> Void) {

        /*

            For the purposes of this sample, we don't have a server-side component.

            Instead we just accept any payment.

        */

        completion(true, nil)

    }

    public func send(_ payment: Payment, completion: (_ success: Bool, _ sentPayment: Payment?, _ error: NSError?) -> Void) {

        /*

            For the purposes of this sample, we don't have a server-side component.

            Instead we're just storing payment locally.

        */

        // Create a new `Payment` that includes the current date as the date it was made.

        let datedPayment = Payment(contact: payment.contact, amount: payment.amount, currencyCode: payment.currencyCode, date: Date())

        // Add the dated payment to the payment history and save it.

        var paymentHistory = loadPaymentHistory()

        paymentHistory.append(datedPayment)

        save(paymentHistory)

        // Call the completion handler.

        completion(true, datedPayment, nil)

    }

    // MARK: Convenience

    public func validate(_ currencyCode: String) -> String? {

        if currencyCode == "USD" || currencyCode == "AMBIGUOUS_DOLLAR" {

            return "USD"

        }

        else {

            return nil

        }

    }

    public func loadPaymentHistory() -> [Payment] {

        var paymentHistory = [Payment]()

        // Parse payments from the shared `NSUserDefaults`.

        let defaults = makeUserDefaults()

        if let paymentsDictionaries = defaults.object(forKey: "paymentHistory") as? [[String: AnyObject]] {

            paymentHistory = paymentsDictionaries.flatMap { Payment(dictionaryRepresentation: $0) }

        }

        return paymentHistory

    }

    private func save(_ payments: [Payment]) {

        // Make sure the number of payments isn't too large

        let paymentsToSave = payments.suffix(50)

        /*

            Convert the payments to an array of dictionaries that can be saved in

            user defaults.

        */

        let paymentsDictionaries: [[String: Any]] = paymentsToSave.map { $0.dictionaryRepresentation }

        // Save the payments to shared `NSUserDefaults`.

        let defaults = makeUserDefaults()

        defaults.set(paymentsDictionaries as AnyObject, forKey: "paymentHistory")

    }

    private func makeUserDefaults() -> UserDefaults {

        guard let defaults = UserDefaults(suiteName: "group.com.example.apple-samplecode.Payments") else { fatalError("Unable to make shared NSUserDefaults object") }

        return defaults

    }

}