import Foundation

protocol HasSquare {
    func getSquare() -> Double
}

protocol HasPerimeter {
    func getPerimeter() -> Double
}

protocol DefaultShape: HasSquare, HasPerimeter { }

class Triangle: HasPerimeter {
    public var a: Double?
    private var b: Double?
    private var c: Double?
    private var perimeter: Double?

    init() {}

    init(a: Double) {
        self.a = a
        self.b = a
        self.c = a
        self.perimeter = 3*a
    }

    init(a: Double, b: Double, c: Double) {
        self.a = a
        self.b = b
        self.c = c
        self.perimeter = a + b + c
    }

    func change(a: Double) {
        self.a = a
        if let b = self.b,
           let c = self.c {
            self.perimeter = a + b + c
        } else {
            self.perimeter = -1
        }
    }

    func change(b: Double) {
        self.b = b
        guard let a = self.a,
              let c = self.c else {
            self.perimeter = -1
            return
        }
        self.perimeter = a + b + c
    }

    func change(c: Double) {
        self.c = c
        self.perimeter = self.a! + self.b! + self.c! //так делать нельзя
    }

    func getPerimeter() -> Double {
        return perimeter ?? -1 //стандарное значение
    }

}



var myTriangle: Triangle = Triangle()
myTriangle.change(a: 3)
myTriangle.change(b: 4)
myTriangle.change(c: 5)
print(myTriangle.getPerimeter())

class Circle: DefaultShape {
    var a: Double
    private let r:Double

    init(radius: Double) {
        self.r = radius
        self.a = 10
    }

    func getSquare() -> Double {
        return Double.pi * r * r
    }

    func getPerimeter() -> Double {
        return 2 * Double.pi * r
    }
}

var circle = Circle(radius: 5)

class Rectangle: DefaultShape {
    private var a: Double
    private var b: Double

    init(_ a: Double, _ b: Double) {
        self.a = a
        self.b = b
    }

    func getSquare() -> Double {
        return a * b
    }

    func getPerimeter() -> Double {
        return 2 * (a + b)
    }
}

class Square: Rectangle {
    init(_ a: Double) {
        super.init(a, a)
    }
}

let pam: Any? = String(40)
if let unwrappedPam = pam as? String {
    print(unwrappedPam)
}


let square: DefaultShape = Square(10)
if let squareToo = square as? Rectangle {
    print(squareToo.getPerimeter())
}
print(square.getSquare())


func reverse(string: String) -> String {
    return String(string.reversed())
}

//let myFunc: (_ string: String) -> String

class PairDouble {
    var a: Double
    var b: Double

    init(a: Double, b: Double) {
        self.a = a
        self.b = b
    }
}

func reverse(pair: PairDouble) {
    let temp = pair.a
    pair.a = pair.b
    pair.b = temp
}

var myPair = PairDouble(a: 1, b: 2)
reverse(pair: myPair)
print("\(myPair.a), \(myPair.b)")

func getPiInCompletion (a _: Int, completion: (_ pi: Double, _ cosPi: Double) -> ()) {
    let pi = Double.pi
    let cosPi = cos(pi)
    completion(pi, cosPi)
}

getPiInCompletion(a: 10) { pi, _ in
    print("pi * pi = \(pi * pi)")
}