125 lines
4.4 KiB
Swift
125 lines
4.4 KiB
Swift
//
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// SaplingParameterDownloader.swift
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// ZcashLightClientKit
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//
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// Created by Francisco Gindre on 10/7/20.
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//
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import Foundation
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/**
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Helper class to handle the download of Sapling parameters
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*/
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public enum SaplingParameterDownloader {
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public enum Errors: Error {
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case invalidURL(url: String)
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case failed(error: Error)
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}
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/// Download a Spend parameter from default host and stores it at given URL
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/// - Parameters:
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/// - at: The destination URL for the download
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@discardableResult
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public static func downloadSpendParameter(_ at: URL) async throws -> URL {
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guard let url = URL(string: spendParamsURLString) else {
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throw Errors.invalidURL(url: spendParamsURLString)
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}
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return try await withCheckedThrowingContinuation { continuation in
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downloadFileWithRequest(URLRequest(url: url), at: at) { result in
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switch result {
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case .success(let outputResultURL):
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continuation.resume(returning: outputResultURL)
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case .failure(let outputResultError):
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continuation.resume(throwing: outputResultError)
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}
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}
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}
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}
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/// Download an Output parameter from default host and stores it at given URL
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/// - Parameters:
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/// - at: The destination URL for the download
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@discardableResult
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public static func downloadOutputParameter(_ at: URL) async throws -> URL {
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guard let url = URL(string: outputParamsURLString) else {
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throw Errors.invalidURL(url: outputParamsURLString)
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}
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return try await withCheckedThrowingContinuation { continuation in
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downloadFileWithRequest(URLRequest(url: url), at: at) { result in
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switch result {
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case .success(let outputResultURL):
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continuation.resume(returning: outputResultURL)
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case .failure(let outputResultError):
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continuation.resume(throwing: outputResultError)
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}
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}
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}
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}
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private static func downloadFileWithRequest(_ request: URLRequest, at destination: URL, result: @escaping (Result<URL, Error>) -> Void) {
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let task = URLSession.shared.downloadTask(with: request) { url, _, error in
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if let error = error {
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result(.failure(Errors.failed(error: error)))
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return
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} else if let localUrl = url {
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do {
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try FileManager.default.moveItem(at: localUrl, to: destination)
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result(.success(destination))
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} catch {
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result(.failure(error))
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}
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}
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}
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task.resume()
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}
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/// Downloads the parameters if not present and provides the resulting URLs for both parameters
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/// - Parameters:
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/// - spendURL: URL to check whether the parameter is already downloaded
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/// - outputURL: URL to check whether the parameter is already downloaded
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public static func downloadParamsIfnotPresent(
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spendURL: URL,
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outputURL: URL
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) async throws -> (spend: URL, output: URL) {
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do {
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async let spendResultURL = ensureSpendParameter(at: spendURL)
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async let outputResultURL = ensureOutputParameter(at: outputURL)
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let results = try await [spendResultURL, outputResultURL]
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return (spend: results[0], output: results[1])
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} catch {
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throw Errors.failed(error: error)
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}
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}
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static func ensureSpendParameter(at url: URL) async throws -> URL {
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if isFilePresent(url: url) {
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return url
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} else {
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return try await downloadSpendParameter(url)
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}
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}
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static func ensureOutputParameter(at url: URL) async throws -> URL {
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if isFilePresent(url: url) {
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return url
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} else {
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return try await downloadOutputParameter(url)
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}
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}
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static func isFilePresent(url: URL) -> Bool {
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(try? FileManager.default.attributesOfItem(atPath: url.path)) != nil
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}
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public static var spendParamsURLString: String {
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return ZcashSDK.cloudParameterURL + ZcashSDK.spendParamFilename
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}
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public static var outputParamsURLString: String {
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return ZcashSDK.cloudParameterURL + ZcashSDK.outputParamFilename
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}
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}
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