import Foundation

// Sample1: 分解して再構築
struct Person {
    let name: String
    let isValid: Bool = true
}

let names: [String] = ["jolly", "joester"]

// ①初期状態
//var persons: [Person] = []
//for name in names {
//    let person = Person(name: name)
//    if person.isValid {
//        persons.append(person)
//    }
//}

// ②関心の分離
//var possiblePersons: [Person] = []
//for name in names {
//    let person = Person(name: name)
//}
//
//var persons: [Person] = []
//for person in persons {
//    if person.isValid {
//        persons.append(person)
//    }
//}

// ③mapとfiltreを使う
//let possiblePersons = names.map(Person.init)
//let persons = possiblePersons.filter { $0.isValid }

let persons = names
    .map(Person.init)
    .filter { $0.isValid }


// Sample2:
// ①初期状態
//func login(username: String, password: String, completion: (String?, Error?) -> Void) {
//
//}
//
//login(username: "jolly", password: "joester") {
//    (token, error) in
//    if let token = token {
//        // success
//    } else if let error = error {
//        // failure
//    }
//}

// ②ラベルをつける
//func login(username: String, password: String, completion: (_ token: String?, Error?) -> Void) {
//
//}
//
//login(username: "jolly", password: "joester") {
//    (token, error) in
//    if let token = token {
//        // success
//    } else if let error = error {
//        // failure
//    }
//}

// ③Tokenを型にする
struct Token {
    let string: String
}

//func login(username: String, password: String, completion: (Token?, Error?) -> Void) {
//}
//
//login(username: "jolly", password: "joester") { (token, error) in
//    if let token = token {
//        // success
//    } else if let error = error {
//        // failure
//    }
//}

// ④username AND passwordを型にする
struct Credential {
    var username: String
    var password: String
}

let credential = Credential(username: "jolly", password: "joester")

//func login(credential: Credential, completion: (Token?, Error?) -> Void) {
//
//}
//
//login(credential: credential) { (token, error) in
//    if let token = token {
//        // success
//    } else if let error = error {
//        // failure
//    }
//}

// ⑤token OR errorを型にする
enum Result<Value> {
    case success(Value)
    case failure(Error)
}

func login(credential: Credential, completion: (Result<Token>) -> Void) {

}

login(credential: credential) { result in
    switch result {
    case .success(let token):
        // success
        print("success")
    case .failure(let error):
        // failure
        print("failure")
    }
}