// TypeScript 5.x

// 基础联合类型
let value: string | number

value = 'hello' // ✅
value = 42 // ✅
// value = true;  // ❌ boolean 不在联合类型中

// 函数参数使用联合类型
function formatId(id: string | number): string {
  return `ID: ${id}`
}

formatId(123) // "ID: 123"
formatId('abc') // "ID: abc"

function getLength(value: string | number) {
  // ❌ 错误：number 没有 length 属性
  // return value.length;

  // ✅ toString() 是共有方法
  return value.toString().length
}

// 需要类型收窄才能访问特定类型的成员
function getLength2(value: string | number): number {
  if (typeof value === 'string') {
    return value.length // ✅ 这里 value 是 string
  }
  return value.toString().length // 这里 value 是 number
}

function process(value: string | number | boolean) {
  if (typeof value === 'string') {
    // value: string
    console.log(value.toUpperCase())
  } else if (typeof value === 'number') {
    // value: number
    console.log(value.toFixed(2))
  } else {
    // value: boolean
    console.log(value ? 'yes' : 'no')
  }
}

class Dog {
  bark() {
    console.log('Woof!')
  }
}

class Cat {
  meow() {
    console.log('Meow!')
  }
}

function speak(animal: Dog | Cat) {
  if (animal instanceof Dog) {
    animal.bark() // animal: Dog
  } else {
    animal.meow() // animal: Cat
  }
}

interface Fish {
  swim(): void
}

interface Bird {
  fly(): void
}

function move(animal: Fish | Bird) {
  if ('swim' in animal) {
    animal.swim() // animal: Fish
  } else {
    animal.fly() // animal: Bird
  }
}

function printMessage(message: string | null | undefined) {
  if (message) {
    // message: string（排除了 null、undefined 和空字符串）
    console.log(message.toUpperCase())
  } else {
    console.log('No message')
  }
}

// 定义带有 kind 属性的类型
interface Circle {
  kind: 'circle'
  radius: number
}

interface Rectangle {
  kind: 'rectangle'
  width: number
  height: number
}

interface Triangle {
  kind: 'triangle'
  base: number
  height: number
}

type Shape = Circle | Rectangle | Triangle

// 根据 kind 属性收窄类型
function getArea(shape: Shape): number {
  switch (shape.kind) {
    case 'circle':
      return Math.PI * shape.radius ** 2
    case 'rectangle':
      return shape.width * shape.height
    case 'triangle':
      return (shape.base * shape.height) / 2
  }
}

// 使用
const circle: Circle = { kind: 'circle', radius: 10 }
console.log(getArea(circle)) // 314.159...

type Shape = Circle | Rectangle | Triangle

function getArea(shape: Shape): number {
  switch (shape.kind) {
    case 'circle':
      return Math.PI * shape.radius ** 2
    case 'rectangle':
      return shape.width * shape.height
    case 'triangle':
      return (shape.base * shape.height) / 2
    default:
      // 穷尽检查：如果所有情况都处理了，shape 是 never
      const _exhaustiveCheck: never = shape
      return _exhaustiveCheck
  }
}

// 如果新增类型但忘记处理，TypeScript 会报错
interface Square {
  kind: 'square'
  size: number
}

type Shape2 = Circle | Rectangle | Triangle | Square

function getArea2(shape: Shape2): number {
  switch (shape.kind) {
    case 'circle':
      return Math.PI * shape.radius ** 2
    case 'rectangle':
      return shape.width * shape.height
    case 'triangle':
      return (shape.base * shape.height) / 2
    // 缺少 'square' 的处理
    default:
      // ❌ 错误：类型 Square 不能赋值给类型 never
      const _exhaustiveCheck: never = shape
      return _exhaustiveCheck
  }
}

interface Person {
  name: string
  age: number
}

interface Employee {
  employeeId: string
  department: string
}

// 交叉类型：同时具有 Person 和 Employee 的所有属性
type Worker = Person & Employee

const worker: Worker = {
  name: '张三',
  age: 30,
  employeeId: 'E001',
  department: '技术部',
}

// 基础类型交叉（通常得到 never）
type T1 = string & number // never（不存在既是字符串又是数字的值）

// 对象类型交叉（合并属性）
type A = { a: string }
type B = { b: number }
type AB = A & B // { a: string; b: number }

// 相同属性名的交叉
type X = { prop: string }
type Y = { prop: number }
type XY = X & Y // { prop: never }（string & number = never）

// 相同属性名但类型兼容时可以交叉
type P = { name: string }
type Q = { name: 'hello' } // 字面量类型
type PQ = P & Q // { name: "hello" }

// 时间戳混入
interface Timestamped {
  createdAt: Date
  updatedAt: Date
}

// ID 混入
interface Identifiable {
  id: string
}

// 基础用户
interface BaseUser {
  name: string
  email: string
}

// 完整用户 = 基础用户 + 混入
type User = BaseUser & Identifiable & Timestamped

const user: User = {
  id: 'u123',
  name: '张三',
  email: 'zhangsan@example.com',
  createdAt: new Date(),
  updatedAt: new Date(),
}

type LogFn = (message: string) => void
type ErrorFn = (error: Error) => void

// 函数交叉 = 函数重载
type Logger = LogFn & ErrorFn

const logger: Logger = (input: string | Error) => {
  if (typeof input === 'string') {
    console.log(input)
  } else {
    console.error(input.message)
  }
}

logger('info message')
logger(new Error('error message'))

// 联合类型：或 (A | B)
// 值可以是 A 或 B 其中之一
type StringOrNumber = string | number
let a: StringOrNumber = 'hello' // ✅
let b: StringOrNumber = 42 // ✅

// 交叉类型：且 (A & B)
// 值必须同时满足 A 和 B
type Named = { name: string }
type Aged = { age: number }
type Person = Named & Aged

const person: Person = {
  name: '张三', // 必须有
  age: 25, // 必须有
}

// 联合类型接受的值范围更广（或）
type T1 = { a: string } | { b: number }
const v1: T1 = { a: 'hello' } // ✅ 只需满足其一
const v2: T1 = { b: 42 } // ✅

// 交叉类型接受的值范围更窄（且）
type T2 = { a: string } & { b: number }
const v3: T2 = { a: 'hello', b: 42 } // ✅ 必须同时满足
// const v4: T2 = { a: 'hello' };  // ❌ 缺少 b

// API 响应可能是成功或失败
interface SuccessResponse<T> {
  status: 'success'
  data: T
}

interface ErrorResponse {
  status: 'error'
  error: string
  code: number
}

type ApiResponse<T> = SuccessResponse<T> | ErrorResponse

function handleResponse<T>(response: ApiResponse<T>) {
  if (response.status === 'success') {
    // response: SuccessResponse<T>
    console.log('Data:', response.data)
  } else {
    // response: ErrorResponse
    console.error(`Error ${response.code}: ${response.error}`)
  }
}

interface AddTodoAction {
  type: 'ADD_TODO'
  payload: { text: string }
}

interface RemoveTodoAction {
  type: 'REMOVE_TODO'
  payload: { id: number }
}

interface ToggleTodoAction {
  type: 'TOGGLE_TODO'
  payload: { id: number }
}

type TodoAction = AddTodoAction | RemoveTodoAction | ToggleTodoAction

function todoReducer(state: Todo[], action: TodoAction): Todo[] {
  switch (action.type) {
    case 'ADD_TODO':
      return [
        ...state,
        { id: Date.now(), text: action.payload.text, done: false },
      ]
    case 'REMOVE_TODO':
      return state.filter((todo) => todo.id !== action.payload.id)
    case 'TOGGLE_TODO':
      return state.map((todo) =>
        todo.id === action.payload.id ? { ...todo, done: !todo.done } : todo
      )
  }
}

// 基础配置
interface BaseConfig {
  name: string
  version: string
}

// 开发配置
interface DevConfig {
  debug: true
  hotReload: boolean
}

// 生产配置
interface ProdConfig {
  debug: false
  minify: boolean
  sourceMaps: boolean
}

// 完整配置 = 基础 + (开发 | 生产)
type AppConfig = BaseConfig & (DevConfig | ProdConfig)

const devConfig: AppConfig = {
  name: 'MyApp',
  version: '1.0.0',
  debug: true,
  hotReload: true,
}

const prodConfig: AppConfig = {
  name: 'MyApp',
  version: '1.0.0',
  debug: false,
  minify: true,
  sourceMaps: false,
}

// (string | number)[] - 数组，元素可以是 string 或 number
const arr1: (string | number)[] = [1, 'hello', 2, 'world']

// string[] | number[] - 要么全是 string，要么全是 number
const arr2: string[] | number[] = [1, 2, 3] // ✅
const arr3: string[] | number[] = ['a', 'b', 'c'] // ✅
// const arr4: string[] | number[] = [1, 'a'];  // ❌ 混合不行

type Animal = { type: 'dog'; bark(): void } | { type: 'cat'; meow(): void }

// 使用 Extract 提取
type Dog = Extract<Animal, { type: 'dog' }>
// { type: 'dog'; bark(): void }

// 使用 Exclude 排除
type NotDog = Exclude<Animal, { type: 'dog' }>
// { type: 'cat'; meow(): void }

// 属性类型冲突会得到 never
type A = { x: string }
type B = { x: number }
type C = A & B // { x: never }

// 解决方案：使用 Omit 排除冲突属性
type D = Omit<A, 'x'> & B // { x: number }