SideStore/SideStoreApp/Sources/SideStoreAppKit/Operations/DownloadAppOperation.swift

//
//  DownloadAppOperation.swift
//  AltStore
//
//  Created by Riley Testut on 6/10/19.
//  Copyright © 2019 Riley Testut. All rights reserved.
//

import Foundation
import RoxasUIKit

import AltSign
import SideKit
import SideStoreCore
import Shared
import os.log

private extension DownloadAppOperation {
    struct DependencyError: ALTLocalizedError {
        let dependency: Dependency
        let error: Error

        var failure: String? {
            String(format: NSLocalizedString("Could not download “%@”.", comment: ""), dependency.preferredFilename)
        }

        var underlyingError: Error? {
            error
        }
    }
}

@objc(DownloadAppOperation)
final class DownloadAppOperation: ResultOperation<ALTApplication> {
    let app: AppProtocol
    let context: AppOperationContext

    private let bundleIdentifier: String
    private var sourceURL: URL?
    private let destinationURL: URL

    private let session = URLSession(configuration: .default)
    private let temporaryDirectory = FileManager.default.uniqueTemporaryURL()

    init(app: AppProtocol, destinationURL: URL, context: AppOperationContext) {
        self.app = app
        self.context = context

        bundleIdentifier = app.bundleIdentifier
        sourceURL = app.url
        self.destinationURL = destinationURL

        super.init()

        // App = 3, Dependencies = 1
        progress.totalUnitCount = 4
    }

    override func main() {
        super.main()

        if let error = context.error {
            finish(.failure(error))
            return
        }

        os_log("Downloading App: %@", type: .info , bundleIdentifier)

        guard let sourceURL = sourceURL else { return finish(.failure(OperationError.appNotFound)) }

        downloadApp(from: sourceURL) { result in
            do {
                let application = try result.get()

                if self.context.bundleIdentifier == StoreApp.dolphinAppID, self.context.bundleIdentifier != application.bundleIdentifier {
                    if var infoPlist = NSDictionary(contentsOf: application.bundle.infoPlistURL) as? [String: Any] {
                        // Manually update the app's bundle identifier to match the one specified in the source.
                        // This allows people who previously installed the app to still update and refresh normally.
                        infoPlist[kCFBundleIdentifierKey as String] = StoreApp.dolphinAppID
                        (infoPlist as NSDictionary).write(to: application.bundle.infoPlistURL, atomically: true)
                    }
                }

                self.downloadDependencies(for: application) { result in
                    do {
                        _ = try result.get()

                        try FileManager.default.copyItem(at: application.fileURL, to: self.destinationURL, shouldReplace: true)

                        guard let copiedApplication = ALTApplication(fileURL: self.destinationURL) else { throw OperationError.invalidApp }
                        self.finish(.success(copiedApplication))

                        self.progress.completedUnitCount += 1
                    } catch {
                        self.finish(.failure(error))
                    }
                }
            } catch {
                self.finish(.failure(error))
            }
        }
    }

    override func finish(_ result: Result<ALTApplication, Error>) {
        do {
            try FileManager.default.removeItem(at: temporaryDirectory)
        } catch {
			os_log("Failed to remove DownloadAppOperation temporary directory: %@. %@", type: .error , temporaryDirectory.absoluteString, error.localizedDescription)
        }

        super.finish(result)
    }
}

private extension DownloadAppOperation {
    func downloadApp(from sourceURL: URL, completionHandler: @escaping (Result<ALTApplication, Error>) -> Void) {
        func finishOperation(_ result: Result<URL, Error>) {
            do {
                let fileURL = try result.get()

                var isDirectory: ObjCBool = false
                guard FileManager.default.fileExists(atPath: fileURL.path, isDirectory: &isDirectory) else { throw OperationError.appNotFound }

                try FileManager.default.createDirectory(at: temporaryDirectory, withIntermediateDirectories: true, attributes: nil)

                let appBundleURL: URL

                if isDirectory.boolValue {
                    // Directory, so assuming this is .app bundle.
                    guard Bundle(url: fileURL) != nil else { throw OperationError.invalidApp }

                    appBundleURL = temporaryDirectory.appendingPathComponent(fileURL.lastPathComponent)
                    try FileManager.default.copyItem(at: fileURL, to: appBundleURL)
                } else {
                    // File, so assuming this is a .ipa file.
                    appBundleURL = try FileManager.default.unzipAppBundle(at: fileURL, toDirectory: temporaryDirectory)
                }

                guard let application = ALTApplication(fileURL: appBundleURL) else { throw OperationError.invalidApp }
                completionHandler(.success(application))
            } catch {
                completionHandler(.failure(error))
            }
        }

        if sourceURL.isFileURL {
            finishOperation(.success(sourceURL))

            progress.completedUnitCount += 3
        } else {
            let downloadTask = session.downloadTask(with: sourceURL) { fileURL, response, error in
                do {
                    let (fileURL, _) = try Result((fileURL, response), error).get()
                    finishOperation(.success(fileURL))

                    try? FileManager.default.removeItem(at: fileURL)
                } catch {
                    finishOperation(.failure(error))
                }
            }
            progress.addChild(downloadTask.progress, withPendingUnitCount: 3)

            downloadTask.resume()
        }
    }
}

private extension DownloadAppOperation {
    struct AltStorePlist: Decodable {
        private enum CodingKeys: String, CodingKey {
            case dependencies = "ALTDependencies"
        }

        var dependencies: [Dependency]
    }

    struct Dependency: Decodable {
        var downloadURL: URL
        var path: String?

        var preferredFilename: String {
            let preferredFilename = path.map { ($0 as NSString).lastPathComponent } ?? downloadURL.lastPathComponent
            return preferredFilename
        }

        init(from decoder: Decoder) throws {
            enum CodingKeys: String, CodingKey {
                case downloadURL
                case path
            }

            let container = try decoder.container(keyedBy: CodingKeys.self)

            let urlString = try container.decode(String.self, forKey: .downloadURL)
            let path = try container.decodeIfPresent(String.self, forKey: .path)

            guard let downloadURL = URL(string: urlString) else {
                throw DecodingError.dataCorruptedError(forKey: .downloadURL, in: container, debugDescription: "downloadURL is not a valid URL.")
            }

            self.downloadURL = downloadURL
            self.path = path
        }
    }

    func downloadDependencies(for application: ALTApplication, completionHandler: @escaping (Result<Set<URL>, Error>) -> Void) {
        guard FileManager.default.fileExists(atPath: application.bundle.altstorePlistURL.path) else {
            return completionHandler(.success([]))
        }

        do {
            let data = try Data(contentsOf: application.bundle.altstorePlistURL)

            let altstorePlist = try PropertyListDecoder().decode(AltStorePlist.self, from: data)

            var dependencyURLs = Set<URL>()
            var dependencyError: DependencyError?

            let dispatchGroup = DispatchGroup()
            let progress = Progress(totalUnitCount: Int64(altstorePlist.dependencies.count), parent: self.progress, pendingUnitCount: 1)

            for dependency in altstorePlist.dependencies {
                dispatchGroup.enter()

                download(dependency, for: application, progress: progress) { result in
                    switch result {
                    case let .failure(error): dependencyError = error
                    case let .success(fileURL): dependencyURLs.insert(fileURL)
                    }

                    dispatchGroup.leave()
                }
            }

            dispatchGroup.notify(qos: .userInitiated, queue: .global()) {
                if let dependencyError = dependencyError {
                    completionHandler(.failure(dependencyError))
                } else {
                    completionHandler(.success(dependencyURLs))
                }
            }
        } catch let error as DecodingError {
            let nsError = (error as NSError).withLocalizedFailure(String(format: NSLocalizedString("Could not download dependencies for %@.", comment: ""), application.name))
            completionHandler(.failure(nsError))
        } catch {
            completionHandler(.failure(error))
        }
    }

    func download(_ dependency: Dependency, for application: ALTApplication, progress: Progress, completionHandler: @escaping (Result<URL, DependencyError>) -> Void) {
        let downloadTask = session.downloadTask(with: dependency.downloadURL) { fileURL, response, error in
            do {
                let (fileURL, _) = try Result((fileURL, response), error).get()
                defer { try? FileManager.default.removeItem(at: fileURL) }

                let path = dependency.path ?? dependency.preferredFilename
                let destinationURL = application.fileURL.appendingPathComponent(path)

                let directoryURL = destinationURL.deletingLastPathComponent()
                if !FileManager.default.fileExists(atPath: directoryURL.path) {
                    try FileManager.default.createDirectory(at: directoryURL, withIntermediateDirectories: true)
                }

                try FileManager.default.copyItem(at: fileURL, to: destinationURL, shouldReplace: true)

                completionHandler(.success(destinationURL))
            } catch {
                completionHandler(.failure(DependencyError(dependency: dependency, error: error)))
            }
        }
        progress.addChild(downloadTask.progress, withPendingUnitCount: 1)

        downloadTask.resume()
    }
}