106 lines
4.0 KiB
Swift
106 lines
4.0 KiB
Swift
import Foundation
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/// Fiat prices for the two tickers the wallet supports, fetched from a public
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/// price API. Cached briefly in memory and in UserDefaults so screens do not
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/// refetch on every refresh, and so the currency conversion shows up instantly
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/// on a cold start.
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final class PriceService {
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static let shared = PriceService()
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struct Prices: Codable {
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var xrp: Double?
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var xmr: Double?
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var currency: String
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var fetchedAt: Date?
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}
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private static let cacheLifetime: TimeInterval = 60
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private static let defaultsKey = "koins.prices"
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private var memory: Prices?
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private var inFlight: Task<Prices, Never>?
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private init() {
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if let data = UserDefaults.standard.data(forKey: Self.defaultsKey),
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let saved = try? JSONDecoder().decode(Prices.self, from: data) {
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memory = saved
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}
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}
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func prices(currency: String) async -> Prices {
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if let memory,
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memory.currency == currency,
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let fetchedAt = memory.fetchedAt,
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Date().timeIntervalSince(fetchedAt) < Self.cacheLifetime {
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return memory
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}
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if let inFlight { return await inFlight.value }
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let task = Task<Prices, Never> { [weak self] in
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guard let self else { return Prices(currency: currency, fetchedAt: nil) }
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let fetched = await self.fetch(currency: currency)
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self.memory = fetched
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if let data = try? JSONEncoder().encode(fetched) {
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UserDefaults.standard.set(data, forKey: Self.defaultsKey)
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}
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return fetched
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}
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inFlight = task
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let result = await task.value
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inFlight = nil
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return result
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}
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private func fetch(currency: String) async -> Prices {
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if let prices = try? await fromCoinGecko(currency: currency) { return prices }
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return (try? await fromKraken(currency: currency)) ?? Prices(currency: currency, fetchedAt: nil)
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}
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private func fromCoinGecko(currency: String) async throws -> Prices {
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let code = currency.lowercased()
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guard let url = URL(string: "https://api.coingecko.com/api/v3/simple/price?ids=monero,ripple&vs_currencies=\(code)") else {
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throw XRPError.network("Invalid price endpoint")
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}
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let (data, response) = try await URLSession.shared.data(from: url)
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guard let http = response as? HTTPURLResponse, (200..<300).contains(http.statusCode) else {
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throw XRPError.network("CoinGecko request failed")
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}
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let json = try JSONSerialization.jsonObject(with: data) as? [String: Any] ?? [:]
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return Prices(
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xrp: (json["ripple"] as? [String: Any]).flatMap { ($0[code] as? NSNumber)?.doubleValue },
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xmr: (json["monero"] as? [String: Any]).flatMap { ($0[code] as? NSNumber)?.doubleValue },
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currency: currency,
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fetchedAt: Date())
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}
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/// Kraken only lists USD and EUR for both assets; anything else just yields
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/// no price rather than a wrong one.
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private func fromKraken(currency: String) async throws -> Prices {
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let supported: [String: (xrp: String, xmr: String)] = [
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"USD": ("XXRPZUSD", "XXMRZUSD"),
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"EUR": ("XXRPZEUR", "XXMRZEUR"),
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]
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guard let pairs = supported[currency] else {
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throw XRPError.network("Kraken has no \(currency) pairs")
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}
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guard let url = URL(string: "https://api.kraken.com/0/public/Ticker?pair=\(pairs.xrp),\(pairs.xmr)") else {
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throw XRPError.network("Invalid price endpoint")
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}
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let (data, response) = try await URLSession.shared.data(from: url)
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guard let http = response as? HTTPURLResponse, (200..<300).contains(http.statusCode) else {
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throw XRPError.network("Kraken request failed")
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}
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let json = try JSONSerialization.jsonObject(with: data) as? [String: Any] ?? [:]
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let result = json["result"] as? [String: Any] ?? [:]
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func lastTrade(_ key: String) -> Double? {
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(result[key] as? [String: Any])
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.flatMap { entry in (entry["c"] as? [Any])?.first }
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.flatMap { ($0 as? String).flatMap(Double.init) }
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}
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return Prices(xrp: lastTrade(pairs.xrp),
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xmr: lastTrade(pairs.xmr),
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currency: currency,
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fetchedAt: Date())
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}
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} |