Download AppStore high res app screens

appstore-screens-Package.swift

// swift-tools-version:4.0
// The swift-tools-version declares the minimum version of Swift required to build this package.

import PackageDescription

let package = Package(
    name: "appstore-screens",
    dependencies: [
        // Dependencies declare other packages that this package depends on.
        // .package(url: /* package url */, from: "1.0.0"),
        .package(url: "https://github.com/tid-kijyun/Kanna.git", from: "4.0.0"),
        .package(url: "https://github.com/Alamofire/Alamofire.git", from: "4.0.0")
    ],
    targets: [
        // Targets are the basic building blocks of a package. A target can define a module or a test suite.
        // Targets can depend on other targets in this package, and on products in packages which this package depends on.
        .target(
            name: "appstore-screens",
            dependencies: ["Kanna", "Alamofire"]),
    ]
)

appstore-screens.swift

import Foundation
import Kanna
import Alamofire

guard let url = URL(string: CommandLine.arguments[1]) else {
    print("You should pass as argument an App Store URL."); exit(0)
}

Alamofire.request(url).responseString(queue: nil, encoding: .utf8) { response in
    guard let html = response.result.value else {
        print("No response."); exit(0)
    }
    guard let doc = try? HTML(html: html, encoding: .utf8) else {
        print("Response isn't HTML."); exit(0)
    }

    var index = 0
    var downloaded: [String] = []

    let elements = doc.css("picture.we-artwork--screenshot-platform-iphone")
    for item in elements {
        guard let srcset = item.css("source").first?["srcset"] else {
            continue
        }
        let srcsets = srcset.split(separator: ",")
        guard let x3image = srcsets.last else { //x3
            continue
        }
        let screenPath = x3image[x3image.startIndex..<x3image.index(x3image.endIndex, offsetBy: -3)]
        guard let screenURL = URL(string: String(screenPath)) else {
            fatalError("AppStore screenshot URL is invalid: \(screenPath)")
        }
        index += 1
        let filename = screenURL.deletingPathExtension().lastPathComponent + String(index) + "." + screenURL.pathExtension

        print("Start download:", filename)
        let destination: DownloadRequest.DownloadFileDestination = { tempURL, response in
            let documentsURL = URL(fileURLWithPath: FileManager.default.currentDirectoryPath)
            let fileURL = documentsURL.appendingPathComponent(filename)
            print("Saved at:", fileURL)
            return (fileURL, [.removePreviousFile, .createIntermediateDirectories])
        }
        Alamofire.download(screenURL, to: destination).response { response in
            if let error = response.error {
                print("Download of \"\(filename)\" failed with:", error)
            }
            else {
                print("Download of \"\(filename)\" has completed with no error")
            }

            // Resize
            let task = Process()
            task.launchPath = "/usr/local/bin/nconvert"
            task.arguments = ["-out", "jpeg", "-ratio", "-resize", "321", "0", filename]
            task.launch()
            task.waitUntilExit()
            if task.terminationStatus != 0 {
                print("Resize using `nconvert` as failed.")
                exit(0)
            }

            downloaded.append(screenURL.lastPathComponent)
            if downloaded.count == index {
                print("Finished.")
                exit(0)
            }
        }
    }
}

RunLoop.main.run()

Usage:

./appstore-screens "https://itunes.apple.com/pt/app/ampme/id986905979?mt=8"

Command dependency: NConvert for image resize.