The Joy of Server Side Swift Development

The Joy Of Server Side
Swift Development

In 1943 Konrad Zuse invented
Plankalkül

1950s
...
- Fortran(concept)
- Fortran II
- ALGOL 58(IAL)
- LISP(implementation)
...

1950s
58 Programming languages

1960s
...
- ALGOL 60
- COBOL 61(implementation)
- FORTRAN IV
- APL(concept)
- Simula(concept) - SNOBOL - CPL - SNOBOL3
- ALGOL 68(concept)
- BASIC
...

1960s

1970s
...
- Pascal
- Smalltalk
- C
- Prolog
- Structured Query language ( SQL)
- Bourne Shell(sh)
- Modula-2
- AWK
...

1970s

1980s
...
- Ada 80(MIL-STD-1815)
- GW-BASIC
- Turbo Pascal
- Objective-C
- C++
- Eiffel
- Erlang
...

1980s

1990s
...
- AMOS BASIC
- Haskell
- Python
- Visual Basic
- Brainfuck
- Borland Delphi
- Java
- PHP
- Ruby
- JavaScript
- Standard C++
...

1990s

2000s
...
- ActionScript
- C#
- D
- Scala
- Groovy
- F#
- Clojure
- Go
...

2000s

2010s
...
- Rust
- Elm
- Kotlin
- Elixir
- Hack
- C++14
...

2010s

Do we really need another
programming language?

Who Am I?
@giordanoscalzo
https://github.com/gscalzo
A developer

Officially, only Linux is
Supported

Server side development
without a web framework?

Perfect: github.github.com/PerfectlySoft/Perfect (8829)
Vapor: github.com/vapor/vapor (6763)
Kitura: github.com/IBM-Swift/Kitura (4578)
Swifton: github.com/necolt/Swifton (2016)
Zewo: github.com/Zewo/Zewo (1358)
Blackfish: github.com/elliottminns/blackfish (932)
Slimane: github.com/noppoMan/Slimane (61)
Tailor: github.com/brownleej/tailor (55)
Kunugi: github.com/novi/Kunugi (35)
Quark: github.com/QuarkX/Quark (33)

"Perfect is a complete and
powerful toolbox,
framework, and application
server for Linux, iOS, and
macOS"

They got money
(Even without React.js!)

Open-source-ish, but
enterprise-ish...

Sean Stephens
Chief Executive Officer

let server = HTTPServer()
var routes = Routes()
routes.add(method: .get, uri: "/", handler: {
request, response in
response.setHeader(.contentType, value: "text/html")
response.appendBody(string:
"<html><title>Hello, world!</title><body>Hello, world!</body></html>")
response.completed()
}
)
server.addRoutes(routes)
server.serverPort = 8181
server.documentRoot = "./webroot"
configureServer(server)
do {
try server.start()
} catch PerfectError.networkError(let err, let msg) {
print("Network error thrown: (err) (msg)")
}

4 Laravel inspired
4 Easy to setup
4 Fantastic Command Line Tool

let drop = Droplet()
drop.get("/") { request in
return try drop.view.make("welcome.html")
}
drop.get("plaintext") { request in
return "Hello, World!"
}
drop.serve()

4 Backed by IBM
4 Express.js-like
4 Perfectly integrated in IBM cloud solution BlueMix

import Kitura
let router = Router()
router.get("/") {
request, response, next in
response.send("Hello, World!")
next()
}
Kitura.addHTTPServer(onPort: 8080, with: router)
Kitura.run()

You can write Basic in
Swift...

You can write Haskell-ish
in Swift...

MrDrizzle Server Requirements:
4 Convert from Wunderground Models to MrDrizzle
Model
4 Refresh cache every hour

mkdir MrDrizzleServer
cd MrDrizzleServer
swift package init --type executable

Swift Package Manager
import PackageDescription
let package = Package(
name: "MrDrizzleServer",
dependencies: [
.Package(url: "https://github.com/vapor/vapor.git", majorVersion: 1, minor: 0)
]
)

Let's make it run
// main.swift
import Foundation
import HTTP
import Vapor
let wheaterUndergroundKey = "KEY"
let wheaterUndergroundDomain = "api.wunderground.com"
drop.get("/hello") { _ in
return "Hello World"
}
drop.run()

$ swift build
> Cloning https://github.com/vapor/vapor.git
> HEAD is now at 453f7cf Merge pull request #628
> Resolved version: 1.0.3
> Cloning https://github.com/vapor/crypto.git
> HEAD is now at 0aaa68b Merge pull request #15
> Resolved version: 1.0.1
> Cloning https://github.com/vapor/core.git
....
....
> Compile Swift Module 'TypeSafeRouting' (3 sources)
> Compile Swift Module 'Vapor' (83 sources)
> Compile Swift Module 'MrDrizzleServer' (1 sources)
> Linking ./.build/debug/MrDrizzleServer
$ .build/debug/MrDrizzleServer

> Could not load localization files
> No cipher key was set, using blank key.
> Chacha20 cipher requires an initialization
> No command supplied, defaulting to serve
> No preparations.
> No servers.json configuration found.
> Starting server at 0.0.0.0:8080

$ swift package generate-xcodeproj
> generated: ./MrDrizzleServer.xcodeproj

This version:
drop.get("/hello") { _ in
return "Hello World"
}

Is equivalent to:
func handler(request: Request) throws -> ResponseRepresentable {
return Response(status: .ok, body: "Hello, World")
}
drop.get("/hello", handler: handler)
because:
extension Swift.String: ResponseRepresentable {
public func makeResponse() -> Response {
return Response(body: self.bytes)
}
}

The list of the stations:
struct StationInfo {
let name: String
let stationId: String
let lat: Float
let lon: Float
}
let stationsInfo = [
StationInfo(name: "Chelsea",
stationId: "ILONDON330",
lat: 51.479633, lon:-0.180277),
StationInfo(name: "Westminster",
stationId: "ILONDON120",
lat: 51.65343, lon:-0.183732)
//...
]

Let's define a schema for
our models

Model schema in pseudocode
object Stations {
Array of Station stations
}
object Station {
string id
float lat
float lon
string name
Array of HourlyMeasure measures
}
object HourlyMeasure {
int32 hour
float temp_f
float temp_c
}

syntax = "proto3";
message Stations {
repeated Station stations = 1;
}
message Station {
string id = 1;
float lat = 2;
float lon = 3;
string name = 4;
repeated HourlyMeasure measures = 5;
}
message HourlyMeasure {
int32 hour = 1;
float temp_f = 2;
float temp_c = 3;
}

Given this:
syntax = "proto3";
message Stations {
repeated Station stations = 1;
}
message Station {
string id = 1;
float lat = 2;
float lon = 3;
string name = 4;
repeated HourlyMeasure measures = 5;
}
message HourlyMeasure {
int32 hour = 1;
float temp_f = 2;
float temp_c = 3;
}

/*
* DO NOT EDIT.
*
* Generated by the protocol buffer compiler.
* Source: mrdrizzle.proto
*
*/
public struct Stations: ProtobufGeneratedMessage {
public var swiftClassName: String {return "Stations"}
public var protoMessageName: String {return "Stations"}
public var protoPackageName: String {return ""}
//...
}
public struct Station: ProtobufGeneratedMessage {
public var swiftClassName: String {return "Station"}
public var protoMessageName: String {return "Station"}
//...
}
public struct HourlyMeasure: ProtobufGeneratedMessage {
public var swiftClassName: String {return "HourlyMeasure"}
public var protoMessageName: String {return "HourlyMeasure"}
//...
}

We extend these structs to
instantiate from the
wunderground JSON

Wheater Underground JSON:
{
"response": {
"version": "0.1",
},
"hourly_forecast": [
{
"FCTTIME": {
"hour": "22",
"mday": "19",
"mday_padded": "19",
"yday": "292",
"isdst": "1",
"age": "",
"UTCDATE": ""
},
"temp": {
"english": "52",
"metric": "11"
},
"condition": "Clear",
"icon": "clear",
"metric": "-9999"
},
...

extension Station {
init?(stationInfo: StationInfo, json: JSON) {
guard let hourly_forecast =
json["hourly_forecast"]?.array as? [JSON]
else {
return nil
}
let measures = hourly_forecast.flatMap {
HourlyMeasure(json: $0)
}
self.init(lat: stationInfo.lat,
lon: stationInfo.lon,
name: stationInfo.name,
measures: measures)
}
}

extension HourlyMeasure {
init?(json: JSON) {
guard let fctTime = json["FCTTIME"]?.object,
let hour = fctTime["hour"]?.string,
let temp = json["temp"]?.object,
let tempF = temp["english"]?.string,
let tempC = temp["metric"]?.string
else {
return nil
}
self.init(hour: Int32(hour),
tempF: Float(tempF),
tempC: Float(tempC))
}
}

Retrieving from
Wunderground Server

extension Station {
init?(stationInfo: StationInfo, client: ClientProtocol.Type) {
let url = "http://(wheaterUndergroundDomain)/api/" +
"(wheaterUndergroundKey)/hourly/q/pws:" +
"(stationInfo.stationId).json"
guard let response = try? client.get(url),
case .data(let bytes) = response.body,
let json = try? JSON(bytes: bytes)
else {
return nil
}
self.init(stationInfo: stationInfo, json: json)
}
}

We cannot use URLSession :-(
class WeatherService {
private let refreshQueue = DispatchQueue(label: "com.mrdrizzle.refresh")
private(set) var stations = Stations()
init(stationsInfo: [StationInfo], client: ClientProtocol.Type) {
refresh(stationsInfo: stationsInfo, client: client)
}
private func refresh(stationsInfo: [StationInfo], client: ClientProtocol.Type) {
stations = stations.refreshed(given: stationsInfo, client: client)
refreshQueue.asyncAfter(deadline: .now() + 3600) { [weak self] in
self?.refresh(stationsInfo: stationsInfo, client: client)
}
}
}

private extension Stations {
func refreshed(given stationsInfo: [StationInfo],
client: ClientProtocol.Type) -> Stations {
return Stations(stations: stationsInfo.flatMap {
Station(stationInfo: $0, client: client)
})
}
}

//main.swift
let stationsInfo = [
StationInfo(name: "Chelsea", stationId: "ILONDON330", lat: 51.479633, lon:-0.180277),
StationInfo(name: "Westminster", stationId: "ILONDON120", lat: 51.65343, lon:-0.183732)
//...
]
let weatherService = WeatherService(stationsInfo: stationsInfo, client: drop.client)
drop.get("/api/weather") { _ in
let stations = weatherService.stations
guard let data = try? stations.serializeProtobuf(),
let bytes = try? data.makeBytes()
else {
throw Abort.serverError
}
return Response(status: .ok, body: .data(bytes))
}
drop.run()

Networking classes from
https://talk.objc.io/
episodes/S01E01-
networking

struct Resource<A> {
let url: URL
let parse: (Data) -> A?
}
for example:
let url = URL(string: "http://mrdrizzle.com:8080/hello")!
let helloResource = Resource<String>(url: url, parse: { data in
return String(data: data, encoding: .utf8)
})

class ApiService {
func load<A>(resource: Resource<A>, completion: @escaping (A?) -> ()) {
URLSession.shared.dataTask(with: resource.url) { data, response, error in
guard let httpResponse = response as? HTTPURLResponse,
httpResponse.statusCode == 200,
let data = data
else {
completion(nil)
return
}
completion(resource.parse(data))
}.resume()
}
}

let helloResource = Resource<String>(url: url) { data in
return String(data: data, encoding: .utf8)
}
ApiService().load(resource: helloResource) {
guard let hello = $0 else {
print("ERROR - Hello")
return
}
print(hello)
}

let stationResources = Resource<Stations>(url: url) { data in
return try? Stations(protobuf: data)
}
ApiService().load(resource: stationResources) {
guard let stations = $0 else {
print("ERROR - Stations")
return
}
print(stations)
}

A Deep Learning Functional
Reactive Chatbot!

Diagram of a Facebook
Messenger ChatBot

import PackageDescription
let package = Package(
name: "UncleLucio",
dependencies: [
.Package(url: "https://github.com/vapor/vapor.git", majorVersion: 1, minor: 0)
]
)

// main.swift
import Foundation
import Vapor
import HTTP
let PAGE_ACCESS_TOKEN = "STUFF"
let fbURL = "https://graph.facebook.com/v2.6/me/messages?access_token=" +
PAGE_ACCESS_TOKEN
let uncleLucio = UncleLucio(jokesDB: JokesDB())

// main.swift
drop.get("fbwebhook") { request in
guard let token = request.data["hub.verify_token"]?.string,
let response = request.data["hub.challenge"]?.string
else {
throw Abort.badRequest
}
if token == "UNCLELUCIO_VERIFICATION_TOKEN" {
return response // Response(status: .ok, text: response)
} else {
return "Error, invalid token"//Response(status: .ok, text: "Error, invalid token")
}
}

// main.swift
drop.post("fbwebhook") { request in
request.log()
guard let jsonBody = request.json,
let chatMessage = ChatMessage(message: jsonBody)
else {
throw Abort.badRequest
}
let replyMessage = uncleLucio.message(after: chatMessage)
return try drop.client.post(fbURL,
headers: ["Content-Type": "application/json; charset=utf-8"],
body: replyMessage.toJSON())
}
drop.run()

// ChatMessage.swift
import Foundation
import Vapor
import HTTP
struct ChatMessage {
let sender: String
let recipient: String
let text: String?
}

Payload send by Facebook callback
{
"object": "page",
"entry": [
{
"id": "1677732245875632",
"time": 1476209402183,
"messaging": [
{
"sender": {
"id": "1243544059050238"
},
"recipient": {
"id": "1677732245875632"
},
"timestamp": 1476209402090,
"message": {
"mid": "mid.1476209402075:82aff934133d72d746",
"seq": 17,
"text": "Knock knock"
}
}
]
}
]
}

extension ChatMessage {
init?(message: JSON) {
guard let entry = message["entry"]?.array?.first as? JSON
else {
return nil
}
guard let messaging = entry["messaging"]?.array?.first as? JSON
else {
return nil
}
guard let senderWrapper = messaging["sender"]?.object,
let sender = senderWrapper["id"]?.string
else {
return nil
}
self.sender = sender
guard let recipientWrapper = messaging["recipient"]?.object,
let recipient = recipientWrapper["id"]?.string
else {
return nil
}
self.recipient = recipient
guard let message = messaging["message"]?.object
else {
return nil
}
self.text = message["text"]?.string
}
}

extension ChatMessage {
func toJSON() throws -> JSON {
return try JSON(node: [
"sender": try JSON(node: [
"id": sender
]),
"recipient": try JSON(node: [
"id": recipient
]),
"message": try JSON(node: [
"text": text
]),
])
}
}

// UncleLucio.swift
class UncleLucio {
private let jokesDB: JokesDB
private var sessions = [String: State]()
init(jokesDB: JokesDB) {
self.jokesDB = jokesDB
}
func message(after chatMessage: ChatMessage) -> ChatMessage {
//...
return replyMessage
}
}

// UncleLucio.swift
func message(after chatMessage: ChatMessage) -> ChatMessage {
let state = sessions[chatMessage.sender] ?? StartState(joke: jokesDB.randomJoke())
let (text, newState) = state.nextState(when: chatMessage.text ?? "pota")
if newState is Done {
sessions.removeValue(forKey: chatMessage.sender)
} else {
sessions[chatMessage.sender] = newState
}
let replyMessage = ChatMessage(sender: chatMessage.recipient,
recipient: chatMessage.sender,
text: text)
return replyMessage
}

// UncleLucio.swift
protocol State {
func nextState(when message: String) -> (String, State)
}

// UncleLucio.swift
struct StartState: State {
let joke: Joke
func nextState(when message: String) -> (String, State) {
if message.lowercased().contains("joke") {
return ("Knock Knock", WaitingForReplyState(joke: joke))
}
return ("pota", self)
}
}

struct WaitingForReplyState: State {
let joke: Joke
let text = message.lowercased()
if text.contains("who's there") ||
text.contains("who is there") {
return ("(joke.subject)!", WaitingForSubjectReplyState(joke: joke))
}
return ("pota", StartState(joke: joke))
}
}

struct WaitingForSubjectReplyState: State {
let joke: Joke
let text = message.lowercased()
if text.contains("(joke.subject.lowercased()) who") {
return ("(joke.punchline)nahahah", Done())
}
return ("pota", StartState(joke: joke))
}
}

struct Done: State {
return ("pota", Done())
}
}

func testInStart_ReceivingGarbage_SaysSlogan_GoesStart() {
let state = StartState(joke: joke())
let (text, nextState) = state.nextState(when: "foobar")
XCTAssertEqual(text, "pota")
XCTAssertTrue(nextState is StartState)
}

func testWaitingForSubjectReply_ReceivingReply_SaysPunchline_GoesDone() {
let state = WaitingForSubjectReplyState(joke: joke())
let (text, nextState) = state.nextState(when: "(joke().subject) who")
XCTAssertEqual(text, "(joke().punchline)nahahah")
XCTAssertTrue(nextState is Done)
}

class JokesDB {
private let jokes: [Joke] = [
("Harry", "Harry up and let me in!"),
("Wanda", "Wanda hang out with me right now?"),
("Olive", "Olive you and I don’t care who knows it!"),
("Ho-ho", "You know, your Santa impression could use a little work."),
("Hanna", "...Hanna partridge in a pear tree!"),
("Mary and Abbey", "Mary Christmas and Abbey New Year!"),
("Irish", "Irish you a Merry Christmas!"),
("Yule log", "Yule log the door after you let me in, won’t you?"),
("Ya", "I’m excited to see you too!"),
("Sherlock", "Sherlock your door shut tight!"),
("Scold", "Scold outside—let me in!"),
("Robin", "Robin you! Hand over your cash!"),
("Needle", "Needle little help gettin’ in the door."),
("Nana", "Nana your business who’s there."),
("Luke", "Luke through the keyhole to see!"),
("Isabelle", "Isabelle working, or should I keep knocking?"),
].map {
Joke(subject: $0.0,
punchline: $0.1)
}
func randomJoke() -> Joke {
return jokes.randomItem()
}
}

extension Array {
func randomItem() -> Element {
let index = Int(arc4random_uniform(UInt32(self.count)))
return self[index]
}
}

https://github.com/gscalzo/UncleLucio

A reason for using Swift in
Server...

"Everything in Its Right
Place" (cit.)

The Joy of Server Side Swift Development

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