var greeting = "Hello, Swift!"

// 基本屬性
print(greeting.count)         // 13 字元數
print(greeting.isEmpty)       // false 是否為空
print(greeting.uppercased())  // 全大寫
print(greeting.lowercased())  // 全小寫

// 包含 / 開頭 / 結尾 檢查
print(greeting.contains("Swift"))      // true
print(greeting.hasPrefix("Hello"))     // true
print(greeting.hasSuffix("!"))         // true

// 字串替換
let newGreeting = greeting.replacingOccurrences(of: "Hello", with: "你好")
print(newGreeting)  // 你好, Swift!

// 分割字串
let csv = "蘋果,香蕉,葡萄,西瓜"
let fruits = csv.split(separator: ",")
print(fruits)  // ["蘋果", "香蕉", "葡萄", "西瓜"]

// 去除空白
let padded = "  Hello  "
print(padded.trimmingCharacters(in: .whitespaces))

// Swift 完整支援 Unicode
let emoji = "Swift 🐦 很棒！"
print(emoji)
print("字元數：\(emoji.count)")

// 遍歷每個字元
for char in "SWIFT" {
    print(char, terminator: "-")
}
print()

// 中文字串
let chineseText = "學習程式設計，改變世界"
print(chineseText.count)  // 11

// 字串比較
let str1 = "apple"
let str2 = "apple"
print(str1 == str2)   // true
print(str1 < "banana")  // true (字母順序)

// 基本 if-else
let temperature = 28

if temperature >= 35 {
    print("天氣很熱，注意防曬！")
} else if temperature >= 25 {
    print("天氣溫暖舒適 ☀️")
} else if temperature >= 15 {
    print("天氣有些涼，帶件外套")
} else {
    print("天氣寒冷，多穿點！")
}

// 成績評分系統
let score = 78

let grade: String
if score >= 90 {
    grade = "A（優秀）"
} else if score >= 80 {
    grade = "B（良好）"
} else if score >= 70 {
    grade = "C（普通）"
} else if score >= 60 {
    grade = "D（及格）"
} else {
    grade = "F（不及格）"
}

print("分數：\(score) → 等級：\(grade)")

// if let 同時解包多個 optional（Swift 5.7+）
var firstName: String? = "Tim"
var lastName: String? = "Cook"

if let first = firstName, let last = lastName {
    print("全名：\(first) \(last)")
}

// guard let 早退模式
func processAge(_ ageStr: String) {
    guard let age = Int(ageStr), age >= 0 else {
        print("無效的年齡輸入：\(ageStr)")
        return
    }
    
    if age >= 18 {
        print("年齡 \(age)：成年人")
    } else {
        print("年齡 \(age)：未成年")
    }
}

processAge("25")
processAge("16")
processAge("abc")

let day = 3

switch day {
case 1:
    print("星期一 💼")
case 2:
    print("星期二")
case 3:
    print("星期三")
case 4, 5:                    // 多個值共用
    print("星期四或五 🎉")
case 6, 7:
    print("週末！😎")
default:
    print("無效日期")
}

// 範圍匹配
let score = 85
switch score {
case 90...100:
    print("優秀 🏆")
case 80..<90:
    print("良好 ⭐")
case 70..<80:
    print("普通")
case 60..<70:
    print("及格")
default:
    print("不及格 😢")
}

// 元組匹配
let point = (2, 0)

switch point {
case (0, 0):
    print("原點")
case (_, 0):
    print("X 軸上，x = \(point.0)")
case (0, _):
    print("Y 軸上，y = \(point.1)")
case (-2...2, -2...2):
    print("在中央區域")
default:
    print("其他位置")
}

// where 條件
let number = 42
switch number {
case let n where n < 0:
    print("\(n) 是負數")
case let n where n % 2 == 0:
    print("\(n) 是偶數")
case let n where n % 2 != 0:
    print("\(n) 是奇數")
default:
    break
}

// 數字範圍
print("=== 1到5 ===")
for i in 1...5 {
    print(i, terminator: " ")
}
print()

// 遍歷陣列
let planets = ["水星", "金星", "地球", "火星"]
for planet in planets {
    print("行星：\(planet)")
}

// 帶索引遍歷
for (index, planet) in planets.enumerated() {
    print("\(index + 1). \(planet)")
}

// stride - 自訂步長
print("\n偶數：", terminator: "")
for i in stride(from: 0, to: 11, by: 2) {
    print(i, terminator: " ")
}

print("\n倒數：", terminator: "")
for i in stride(from: 10, through: 0, by: -2) {
    print(i, terminator: " ")
}

// while - 先判斷再執行
var countdown = 5
print("發射倒計時：")
while countdown > 0 {
    print("\(countdown)...")
    countdown -= 1
}
print("🚀 發射！")

// repeat-while - 至少執行一次（類似 do-while）
var password = ""
var attempts = 0
repeat {
    attempts += 1
    password = attempts == 3 ? "swift123" : "wrong"
    print("第 \(attempts) 次嘗試")
} while password != "swift123"
print("✅ 登入成功！")

// break 和 continue
print("\n跳過 3 的倍數：", terminator: "")
for i in 1...10 {
    if i % 3 == 0 { continue }  // 跳過
    print(i, terminator: " ")
}

// 建立陣列
var fruits = ["蘋果", "香蕉", "葡萄"]
var numbers: [Int] = [1, 2, 3, 4, 5]
var emptyArray: [String] = []

// 存取元素
print(fruits[0])          // 蘋果
print(fruits.first!)      // 蘋果
print(fruits.last!)       // 葡萄
print(fruits.count)       // 3

// 修改陣列
fruits.append("西瓜")              // 加到末尾
fruits.insert("草莓", at: 1)       // 插入特定位置
fruits.remove(at: 0)               // 刪除索引 0
fruits[0] = "鳳梨"                 // 修改元素

print(fruits)

// 常用屬性
print("是否為空：\(fruits.isEmpty)")
print("包含西瓜：\(fruits.contains("西瓜"))")

let scores = [45, 82, 61, 93, 55, 78, 88]

// map - 轉換每個元素
let doubled = scores.map { $0 * 2 }
print("加倍：\(doubled)")

// filter - 過濾元素
let passing = scores.filter { $0 >= 60 }
print("及格的：\(passing)")

// reduce - 聚合計算
let total = scores.reduce(0) { $0 + $1 }
let average = Double(total) / Double(scores.count)
print("總分：\(total)")
print("平均：\(String(format: "%.1f", average))")

// sorted
let sorted = scores.sorted()
let sortedDesc = scores.sorted(by: >)
print("升序：\(sorted)")
print("降序：\(sortedDesc)")

// 鏈式操作：過濾及格成績，轉為等級
let grades = scores
    .filter { $0 >= 60 }
    .map { score -> String in
        switch score {
        case 90...100: return "A"
        case 80..<90: return "B"
        case 70..<80: return "C"
        default: return "D"
        }
    }
print("等級：\(grades)")

// 基本函式
func greet(name: String) -> String {
    return "你好，\(name)！"
}
print(greet(name: "小明"))

// 多個參數
func add(_ a: Int, _ b: Int) -> Int {
    return a + b
}
print(add(3, 5))

// 預設參數值
func createProfile(name: String, age: Int = 18, role: String = "用戶") -> String {
    return "\(name)（\(age)歲）- \(role)"
}
print(createProfile(name: "Alice"))
print(createProfile(name: "Bob", age: 25, role: "管理員"))

// 回傳多個值（使用元組）
func minMax(_ array: [Int]) -> (min: Int, max: Int) {
    return (array.min()!, array.max()!)
}
let result = minMax([5, 3, 8, 1, 9, 2])
print("最小：\(result.min)，最大：\(result.max)")

// 可變參數
func sum(_ numbers: Int...) -> Int {
    return numbers.reduce(0, +)
}
print(sum(1, 2, 3, 4, 5))

// 外部標籤 內部標籤: 型別
func move(from startPoint: String, to endPoint: String) {
    print("從 \(startPoint) 移動到 \(endPoint)")
}
// 呼叫時使用外部標籤
move(from: "台北", to: "高雄")

// 使用 _ 省略外部標籤
func multiply(_ x: Int, by y: Int) -> Int {
    return x * y
}
print(multiply(6, by: 7))

// @discardableResult - 可以忽略回傳值
@discardableResult
func saveToDatabase(data: String) -> Bool {
    print("儲存：\(data)")
    return true
}
saveToDatabase(data: "用戶資料")

// 完整閉包語法
let fullClosure = { (x: Int, y: Int) -> Int in
    return x + y
}

// 省略型別（推斷）
let shortClosure = { (x: Int, y: Int) in x + y }

// 使用 $0, $1 簡寫參數
let minimal = { $0 + $1 }

print(fullClosure(3, 4))    // 7
print(shortClosure(3, 4))   // 7
print(minimal(3, 4))        // 7

// 尾隨閉包（最後一個參數是閉包）
let numbers = [5, 2, 8, 1, 9]

// 標準寫法
let sorted1 = numbers.sorted(by: { (a, b) -> Bool in return a < b })

// 尾隨閉包
let sorted2 = numbers.sorted { $0 < $1 }

print(sorted2)  // [1, 2, 5, 8, 9]

// 實際應用：非同步回調
func fetchData(completion: (String) -> Void) {
    let data = "來自伺服器的資料"
    completion(data)
}

fetchData { data in
    print("收到：\(data)")
}

// 閉包可以捕獲並修改外部變數
func makeCounter() -> () -> Int {
    var count = 0
    return {
        count += 1
        return count
    }
}

let counter1 = makeCounter()
let counter2 = makeCounter()

print(counter1())  // 1
print(counter1())  // 2
print(counter1())  // 3
print(counter2())  // 1（獨立計數器）
print(counter2())  // 2

struct Player {
    var name: String
    var health: Int
    var level: Int
    
    // 計算屬性
    var isAlive: Bool {
        return health > 0
    }
    
    var description: String {
        return "\(name) (等級\(level), 血量\(health))"
    }
    
    // Mutating 方法（修改 struct 需加 mutating）
    mutating func takeDamage(_ damage: Int) {
        health = max(0, health - damage)
        print("\(name) 受到 \(damage) 點傷害，剩餘血量：\(health)")
    }
    
    mutating func levelUp() {
        level += 1
        health = min(100, health + 20)
        print("\(name) 升級到 \(level) 級！")
    }
}

var hero = Player(name: "英雄", health: 100, level: 1)
print(hero.description)
hero.takeDamage(30)
hero.levelUp()
print("存活中：\(hero.isAlive)")

// 基礎類別
class Animal {
    var name: String
    var sound: String
    
    init(name: String, sound: String) {
        self.name = name
        self.sound = sound
    }
    
    func speak() {
        print("\(name) 說：\(sound)!")
    }
    
    deinit {
        // 物件被銷毀時呼叫
        print("\(name) 離開了")
    }
}

// 繼承
class Dog: Animal {
    var breed: String
    
    init(name: String, breed: String) {
        self.breed = breed
        super.init(name: name, sound: "汪汪")
    }
    
    // 覆寫父類別方法
    override func speak() {
        print("🐕 \(name)（\(breed)）：\(sound)！搖尾巴中...")
    }
    
    func fetch() {
        print("\(name) 去撿球了！🎾")
    }
}

let animal = Animal(name: "動物", sound: "...")
let dog = Dog(name: "小黑", breed: "柴犬")

animal.speak()
dog.speak()
dog.fetch()

// 型別檢查
print(dog is Animal)  // true（繼承關係）
print(dog is Dog)     // true

// 定義協定
protocol Drawable {
    var color: String { get }
    func draw()
    func area() -> Double
}

protocol Resizable {
    mutating func resize(by factor: Double)
}

// 結構體遵守多個協定
struct Circle: Drawable, Resizable {
    var radius: Double
    var color: String
    
    func draw() {
        print("畫一個 \(color) 的圓形，半徑 \(radius)")
    }
    
    func area() -> Double {
        return Double.pi * radius * radius
    }
    
    mutating func resize(by factor: Double) {
        radius *= factor
    }
}

struct Rectangle: Drawable {
    var width: Double
    var height: Double
    var color: String
    
    func draw() {
        print("畫一個 \(color) 的矩形 \(width) × \(height)")
    }
    
    func area() -> Double {
        return width * height
    }
}

// 協定型別使用
var shapes: [any Drawable] = [
    Circle(radius: 5.0, color: "紅色"),
    Rectangle(width: 4.0, height: 3.0, color: "藍色")
]

for shape in shapes {
    shape.draw()
    print("  面積：\(String(format: "%.2f", shape.area()))")
}

import Foundation

// 定義非同步函式
func fetchUserName(id: Int) async throws -> String {
    // 模擬網路延遲
    try await Task.sleep(nanoseconds: 1_000_000_000)
    
    let users = [1: "Alice", 2: "Bob", 3: "Charlie"]
    guard let name = users[id] else {
        throw URLError(.badURL)
    }
    return name
}

// 並發執行多個非同步任務
func fetchMultipleUsers() async {
    async let user1 = fetchUserName(id: 1)
    async let user2 = fetchUserName(id: 2)
    
    // 等待兩個任務都完成
    do {
        let (name1, name2) = try await (user1, user2)
        print("用戶 1：\(name1)")
        print("用戶 2：\(name2)")
    } catch {
        print("錯誤：\(error)")
    }
}

// Task - 啟動非同步任務
Task {
    await fetchMultipleUsers()
}

// Actor - 執行緒安全的共享狀態
actor BankAccount {
    private var balance: Double = 0
    
    func deposit(_ amount: Double) {
        balance += amount
        print("存入 \(amount)，餘額：\(balance)")
    }
    
    func withdraw(_ amount: Double) -> Bool {
        guard balance >= amount else {
            print("餘額不足！")
            return false
        }
        balance -= amount
        print("提款 \(amount)，餘額：\(balance)")
        return true
    }
}

// 使用 Actor
Task {
    let account = BankAccount()
    await account.deposit(1000)
    await account.withdraw(300)
    await account.withdraw(800) // 餘額不足
}

// 建立字典
var scores: [String: Int] = ["Alice": 95, "Bob": 82, "Charlie": 78]
var capitals = ["台灣": "台北", "日本": "東京", "美國": "華盛頓"]

// 讀取（返回 Optional）
if let aliceScore = scores["Alice"] {
    print("Alice 的分數：\(aliceScore)")
}

// 使用 ?? 提供預設值
let davidScore = scores["David"] ?? 0
print("David 的分數：\(davidScore)")

// 新增 / 修改
scores["David"] = 90
scores["Alice"] = 98  // 修改

// 刪除
scores.removeValue(forKey: "Bob")
scores["Charlie"] = nil  // 另一種刪除方式

print("字典：\(scores)")
print("人數：\(scores.count)")

// 遍歷字典
for (name, score) in scores.sorted(by: { $0.value > $1.value }) {
    print("\(name): \(score) 分")
}

// 取出所有鍵 / 值
print("所有人：\(Array(scores.keys))")
print("所有分數：\(Array(scores.values))")

// 建立 Set（需明確型別標注）
var fruits: Set = ["蘋果", "香蕉", "葡萄", "蘋果"]
// 重複的「蘋果」只會存一個
print(fruits)
print("元素數量：\(fruits.count)")

// 集合運算
let setA: Set = [1, 2, 3, 4, 5]
let setB: Set = [3, 4, 5, 6, 7]

print("聯集：\(setA.union(setB).sorted())")
print("交集：\(setA.intersection(setB).sorted())")
print("差集：\(setA.subtracting(setB).sorted())")
print("對稱差集：\(setA.symmetricDifference(setB).sorted())")

// 子集 / 超集 判斷
let setC: Set = [3, 4]
print("setC 是 setA 的子集：\(setC.isSubset(of: setA))")
print("setA 是 setC 的超集：\(setA.isSuperset(of: setC))")

// 陣列去重
let arr = [1, 2, 2, 3, 3, 3, 4]
let unique = Array(Set(arr)).sorted()
print("去重後：\(unique)")

// Optional 宣告
var name: String? = "Swift"
var age: Int? = nil

// 1. 可選鏈 Optional Chaining
let count = name?.count  // 若 name 為 nil 則返回 nil
print(count ?? 0)

// 2. if let 安全解包
if let unwrappedName = name {
    print("名字：\(unwrappedName)")
}

// 3. guard let 早退
func printAge(_ age: Int?) {
    guard let age = age else {
        print("年齡不明")
        return
    }
    print("年齡：\(age)")
}
printAge(25)
printAge(nil)

// 4. ?? 空合運算子
let displayAge = age ?? 18
print("顯示年齡：\(displayAge)")

// 5. 可選鏈連鎖
struct Address { var city: String? }
struct Person { var address: Address? }

let person = Person(address: Address(city: "台北"))
let city = person.address?.city ?? "未知城市"
print("城市：\(city)")

// 6. 強制解包（謹慎使用！）
let safeValue: String? = "確定有值"
print(safeValue!)  // 確定有值時才用 !

// 基本列舉
enum Direction {
    case north, south, east, west
}

let dir = Direction.north
print(dir)

// 帶原始值的列舉
enum Planet: Int {
    case mercury = 1, venus, earth, mars
    
    var description: String {
        switch self {
        case .earth: return "我們的家鄉 🌍"
        case .mars:  return "未來的移民地 🔴"
        default:     return "神秘星球"
        }
    }
}

let earth = Planet.earth
print("\(earth)：\(earth.description)")
print("地球是第 \(earth.rawValue) 顆行星")

// 帶關聯值的列舉（Swift 最強大的特性之一）
enum PaymentMethod {
    case cash(amount: Double)
    case creditCard(number: String, expiry: String)
    case applePay(phoneLastFour: String)
}

let payment = PaymentMethod.creditCard(number: "1234", expiry: "12/26")

switch payment {
case .cash(let amount):
    print("現金：\(amount) 元")
case .creditCard(let num, let exp):
    print("信用卡：\(num)，到期：\(exp)")
case .applePay(let phone):
    print("Apple Pay：\(phone)")
}

// 泛型函式
func swap(_ a: inout T, _ b: inout T) {
    let temp = a
    a = b
    b = temp
}

var x = 10, y = 20
swap(&x, &y)
print("x=\(x), y=\(y)")

var str1 = "Hello", str2 = "World"
swap(&str1, &str2)
print("\(str1) \(str2)")

// 泛型型別（Stack 堆疊）
struct Stack {
    private var items: [Element] = []
    
    mutating func push(_ item: Element) {
        items.append(item)
    }
    
    mutating func pop() -> Element? {
        return items.popLast()
    }
    
    var top: Element? {
        return items.last
    }
    
    var isEmpty: Bool { items.isEmpty }
    var count: Int { items.count }
}

var stack = Stack()
stack.push(1)
stack.push(2)
stack.push(3)
print("堆疊頂端：\(stack.top!)")
print("彈出：\(stack.pop()!)")
print("剩餘：\(stack.count) 個")

// 型別約束
func findMax(_ array: [T]) -> T? {
    return array.max()
}

print(findMax([3, 1, 4, 1, 5, 9])!)
print(findMax(["banana", "apple", "cherry"])!)

// 定義錯誤型別
enum LoginError: Error {
    case emptyUsername
    case emptyPassword
    case invalidCredentials
    case accountLocked(reason: String)
}

// 會拋出錯誤的函式
func login(username: String, password: String) throws -> String {
    guard !username.isEmpty else { throw LoginError.emptyUsername }
    guard !password.isEmpty else { throw LoginError.emptyPassword }
    
    if username == "admin" && password == "swift123" {
        return "歡迎回來，\(username)！"
    } else if username == "blocked" {
        throw LoginError.accountLocked(reason: "多次輸入錯誤密碼")
    } else {
        throw LoginError.invalidCredentials
    }
}

// do-try-catch 處理錯誤
func attemptLogin(_ user: String, _ pass: String) {
    do {
        let message = try login(username: user, password: pass)
        print("✅ \(message)")
    } catch LoginError.emptyUsername {
        print("❌ 請輸入用戶名")
    } catch LoginError.emptyPassword {
        print("❌ 請輸入密碼")
    } catch LoginError.invalidCredentials {
        print("❌ 用戶名或密碼錯誤")
    } catch LoginError.accountLocked(let reason) {
        print("🔒 帳號已鎖定：\(reason)")
    } catch {
        print("未知錯誤：\(error)")
    }
}

attemptLogin("admin", "swift123")
attemptLogin("", "pass")
attemptLogin("admin", "wrong")
attemptLogin("blocked", "pass")

// defer - 確保執行清理工作
func readFile(name: String) throws {
    print("📂 開啟檔案：\(name)")
    defer {
        print("📁 關閉檔案：\(name)")  // 一定會執行
    }
    
    // 模擬讀取
    print("📖 讀取內容...")
    if name == "secret.txt" {
        throw LoginError.invalidCredentials
    }
    print("✅ 讀取完成")
}

try? readFile(name: "data.txt")
print("---")
try? readFile(name: "secret.txt")