구조 패턴

import Foundation
import CoreGraphics

// flyweight
protocol Monster {
    func createAtCurrentLocation(at location: CGPoint)
    func deleteAtCurrentLocation(at location: CGPoint)
    func recreateAtOtherLocation(at location: CGPoint)
    func attack()
}

// flyweight 구현체
class LowerLevelMonster: Monster {
    func createAtCurrentLocation(at: CGPoint) {
        // some code
    }

    func deleteAtCurrentLocation(at: CGPoint) {
        // some code
    }

    func recreateAtOtherLocation(at: CGPoint) {
        // some code
    }

    func attack() {
        // some code
    }
}

class MonsterClient {
    let monster: Monster
    var currentLocation: CGPoint
    init(monster: Monster, currentLocation: CGPoint) {
        self.monster = monster
        self.currentLocation = currentLocation
    }

    func createMonster(currentLocation: CGPoint) {
        monster.createAtCurrentLocation(at: currentLocation)
    }

    func recreateMonster(currentLocation: CGPoint, at location: CGPoint) {
        monster.deleteAtCurrentLocation(at: currentLocation)
        monster.recreateAtOtherLocation(at: location)
    }
}

// MARK: Factory: flyweight들을 관리하는 객체
class MonsterFactory {
    static let shared = MonsterFactory()
    private init() { }

    enum MonsterLevel {
        case lower
    }

    private var createdMonster = [MonsterLevel: Monster]()

    private func createMonster(_ level: MonsterLevel) -> Monster {
        switch level {
        case .lower:
            let lowerLevelMonster = LowerLevelMonster()
            createdMonster[level] = lowerLevelMonster

            return lowerLevelMonster
        }
    }

    func monster(level: MonsterLevel) -> Monster {
        if let monster = createdMonster[level] {
            return monster
        } else {
            let monster = createMonster(level)
            return monster
        }
    }
}

let lowerLevelMonster = MonsterFactory.shared.monster(level: .lower)
let lowerLevelMonsterClient = MonsterClient(monster: lowerLevelMonster, currentLocation: CGPoint(x: 10, y: 20))

lowerLevelMonsterClient.createMonster(currentLocation: CGPoint(x: 10, y: 20))
lowerLevelMonsterClient.recreateMonster(currentLocation: CGPoint(x: 10, y: 20), at: CGPoint(x: 100, y: 110))

// subject
protocol YouTubeDownloadSubject {
   func downloadYoutubeVideos() async -> [String]
}

final class RealSubject: YouTubeDownloadSubject {
    func downloadYoutubeVideos() async -> [String] {
        //Todo: 유튜브 서버에서 비디오를 다운로드해오는 부분을 구현한다.
    }
}

final class Proxy: YouTubeDownloadSubject {
        //진짜 요청을 받아서 처리하는 개체, 정말로 사용할때만 초기화하기 위하여 lazy키워드 사용
    private lazy var realSubject = RealSubject()
        //캐싱구현
    private var videoCache = [String]()
        //클라이언트 권한 받음
    private var client: Clinet

    init(_ client: Clinet) {
        self.client = client
    }

    func downloadYoutubeVideos() async -> [String] {
        //클라이언트 권한에 따라 제어를 할 수도 있다.
        guard client.auth == .owner else {
            print("유튜브 비디오를 다운로드할 권한이 없습니다.")
            return []
        }

        //비디오 캐시가 비어있으면 실제 realSubject에 데이터를 요청함.
        if videoCache.isEmpty {
            videoCache = await realSubject.downloadYoutubeVideos()
            return videoCache
        } else {
            //비디오 캐시에 데이터 있으면 그거 리턴해줌.
            return videoCache
        }
    }
}

let client = Clinet(.owner)
let proxy = Proxy(client)

//프로토콜 타입을 받습니다.
func loadYouTubeVideo(_ service: YouTubeDownloadSubject) {
    service.downloadYoutubeVideos()
}

loadYouTubeVideo(proxy)

import Foundation

// Component
protocol Military {
    var unitName: String { get set }
    func attack()
}

// Leafs
struct AirForce: Military {
    var unitName: String
    func attack() {
        print("\\(unitName) 공격 🔫")
    }
}

struct Navy: Military {
    var unitName: String
    func attack() {
        print("\\(unitName) 공격 🔫")
    }
}

struct Army: Military {
    var unitName: String
    func attack() {
        print("\\(unitName) 공격 🔫")
    }
}

// Composite
struct MilitaryGroup: Military {
    var unitName: String
    var group: [Military]

    func attack() {
        print("-----\\(unitName) 예하에 있는 부대에 공격 명령을 하달한다.-----")
        group.forEach { unit in
            unit.attack()
        }
    }
}

let navy627 = Navy(unitName: "해군 627대대")
let navy625 = Navy(unitName: "해군 625대대")
let army653 = Army(unitName: "육군 653대대")
let army669 = Army(unitName: "육군 669대대")
let airForce257 = AirForce(unitName: "공군 257대대")
let airForce239 = AirForce(unitName: "공군 239대대")

let navy1 = MilitaryGroup(unitName: "해군 1사단", group: [navy627, navy625])
let army1 = MilitaryGroup(unitName: "육군 1사단", group: [army653, army669])
let airForce1 = MilitaryGroup(unitName: "공군 1사단", group: [airForce257, airForce239])

let thirdROKArmy = MilitaryGroup(unitName: "3군 사령부", group: [navy1, army1, airForce1])

thirdROKArmy.attack()