import Foundation

//Variables and Constants

// Constants (immutable)

let pi: Double = 3.14159
let greeting: String = "Hello, Swift!"

// Variables (mutable)

var age: Int = 25
var name: String = "John Doe"
var temperature: Float = 36.6

print(greeting)
print("Name: \(name), Age: \(age)")
print("Temperature: \(temperature)°C, Pi: \(pi)")

//Control Flow

// if-else statement

if age > 18 {
    print("\(name) is an adult.")
} else {
    print("\(name) is not an adult.")
}

// switch statement

let grade: String = "B"

switch grade {
case "A":
    print("Excellent!")
case "B":
    print("Good job!")
case "C":
    print("Well done!")
case "D":
    print("You passed!")
case "F":
    print("Better try again!")
default:
    print("Invalid grade")
}

// for loop

for i in 1...5 {
    print("Iteration \(i)")
}

// while loop

var countdown = 5
while countdown > 0 {
    print("Countdown: \(countdown)")
    countdown -= 1
}

//Functions

func greet(person: String) -> String {
    return "Hello, \(person)!"
}

let greetingMessage = greet(person: "Alice")
print(greetingMessage)

func calculateArea(radius: Double) -> Double {
    return pi * radius * radius
}

let area = calculateArea(radius: 5.0)
print("Area of the circle: \(area)")

//Data Types in Swift

// Array

var numbers: [Int] = [1, 2, 3, 4, 5]
print("Numbers: \(numbers)")

// Dictionary

var capitals: [String: String] = [
    "France": "Paris",
    "Japan": "Tokyo",
    "USA": "Washington, D.C."
]
print("Capitals: \(capitals)")

// Set

var uniqueNumbers: Set<Int> = [1, 2, 3, 3, 2, 1]
print("Unique Numbers: \(uniqueNumbers)")

// Tuple

let http404Error = (404, "Not Found")
print("Error Code: \(http404Error.0), Message: \(http404Error.1)")

// Optional

var optionalString: String? = "Hello"
print(optionalString ?? "No value")

//Classes and Structures

// Class

class Person {
    var firstName: String
    var lastName: String
    var age: Int
    
    init(firstName: String, lastName: String, age: Int) {
        self.firstName = firstName
        self.lastName = lastName
        self.age = age
    }
    
    func fullName() -> String {
        return "\(firstName) \(lastName)"
    }
}

let person = Person(firstName: "John", lastName: "Doe", age: 30)
print("Person: \(person.fullName()), Age: \(person.age)")

// Structure

struct Rectangle {
    var width: Double
    var height: Double
    
    func area() -> Double {
        return width * height
    }
}

let rectangle = Rectangle(width: 10.0, height: 5.0)
print("Rectangle area: \(rectangle.area())")