TheGunShoot.swift

class TheGunActivity: OnShootListener, OnReloadListener {
    
    func onShootSucceed(message: String) {
        print(message)
    }
    
    func onShootFailure(message: String) {
        print(message)
    }
    
    func onReloadSucceed(message: String) {
        print(message)
    }
    
}

protocol OnShootListener {
    func onShootSucceed(message: String)
    func onShootFailure(message: String)
}

protocol OnReloadListener {
    func onReloadSucceed(message: String)
}

struct GunSpecification {
    let projectilePerShoot: Int
    let maxProjectilePerReload: Int
    let color: String
    let type: String
}

protocol Gun {
    var projectile: Int {get set}
    var specification: GunSpecification {get set}
    var activity: TheGunActivity {get set}
    init(specification: GunSpecification, activity: TheGunActivity)
    
}

extension Gun {
    mutating func shoot() -> Bool {
        let isShootSucceed = projectile >= specification.projectilePerShoot
        if isShootSucceed {
            projectile -= specification.projectilePerShoot
            activity.onShootSucceed(message: "Dorrr!. \(projectile) left")
        } else {
            activity.onShootFailure(message: "Shoot failure. Please reload")
        }
        
        return isShootSucceed
    }
    
    mutating func reload() {
        projectile = specification.maxProjectilePerReload
        activity.onReloadSucceed(message: "Reload succeed")
    }
}

class Shootgun: Gun {
    var projectile: Int
    var specification: GunSpecification
    var activity: TheGunActivity
    
    required init(specification: GunSpecification, activity: TheGunActivity) {
        self.projectile = 0
        self.specification = specification
        self.activity = activity
    }
}

class Deagle: Gun {
    var projectile: Int
    var specification: GunSpecification
    var activity: TheGunActivity
    
    required init(specification: GunSpecification, activity: TheGunActivity) {
        self.projectile = 0
        self.specification = specification
        self.activity = activity
    }
}

class CurrentGun {
    private var gun: Gun? = nil
    
    func changeCurrentGun(gun: Gun) {
        self.gun = gun
        print("Weapon changed !")
    }
    
    func getSpecification() -> GunSpecification? {
        return gun?.specification ?? nil
    }
    
    func shoot() -> Bool {
        return gun?.shoot() ?? false
    }
    
    func reload() {
        gun?.reload()
    }
}

class TheGunShoot {
    
    private func testTheGun(gun: Gun) {
        let currentGun = CurrentGun()
        currentGun.changeCurrentGun(gun: gun)
        let specification = currentGun.getSpecification()
        
        guard let spec = specification else {
            print("You don't have a gun")
            return
        }
        
        print("Type : \(spec.type)")
        print("Color : \(spec.color)")
        print("Max Ammo : \(spec.maxProjectilePerReload)")
        print("Ammo per shoot : \(spec.projectilePerShoot)")
        
        currentGun.reload()
        for _ in 0 ... 4 {
            let isShootSucceed = currentGun.shoot()
            if !isShootSucceed {
                currentGun.reload()
            }
        }
    }
    
    func start() {
        let gunActivity = TheGunActivity()
        
        //shotgun is take out one projectiles per shoot
        let s12kSpec = GunSpecification(projectilePerShoot: 1 ,maxProjectilePerReload: 3,
                                        color: "Brown", type: "S12K")
        let shotgun: Gun = Shootgun(specification: s12kSpec, activity: gunActivity)
        
        //Deagle is take out two projectiles in one shoot
        let deagleSpec = GunSpecification(projectilePerShoot: 2 ,maxProjectilePerReload: 3,
                                          color: "Red", type: "Deagle")
        let deagle: Gun = Deagle(specification: deagleSpec, activity: gunActivity)
        
        testTheGun(gun: shotgun)
        testTheGun(gun: deagle)
    }
}

func execute() {
    let theGunShoot = TheGunShoot()
    theGunShoot.start()
}

execute()

/*
 PRINTED ->
 
 Weapon changed !
 Type : S12K
 Color : Brown
 Max Ammo : 3
 Ammo per shoot : 1
 Reload succeed
 Dorrr!. 2 left
 Dorrr!. 1 left
 Dorrr!. 0 left
 Shoot failure. Please reload
 Reload succeed
 Dorrr!. 2 left
 Weapon changed !
 Type : Deagle
 Color : Red
 Max Ammo : 3
 Ammo per shoot : 2
 Reload succeed
 Dorrr!. 1 left
 Shoot failure. Please reload
 Reload succeed
 Dorrr!. 1 left
 Shoot failure. Please reload
 Reload succeed
 Dorrr!. 1 left
 */