const target = {
  name: 'onlyy~'
}
// 創(chuàng)建一個對target的代理
const proxy = new Proxy(target, {
  // ...各種handler，例如get，set...
  get(target, property, receiver){
    // 其它操作
    // ...
    return Reflect.get(target, property, receiver)
  }
})

export interface Target {
  [ReactiveFlags.SKIP]?: boolean
  [ReactiveFlags.IS_REACTIVE]?: boolean
  [ReactiveFlags.IS_READONLY]?: boolean
  [ReactiveFlags.IS_SHALLOW]?: boolean
  [ReactiveFlags.RAW]?: any
}
export const reactiveMap = new WeakMap<Target, any>()
export const shallowReactiveMap = new WeakMap<Target, any>()
export const readonlyMap = new WeakMap<Target, any>()
export const shallowReadonlyMap = new WeakMap<Target, any>()
const enum TargetType {
  INVALID = 0,
  COMMON = 1,
  COLLECTION = 2
}

// 各個標志枚舉
export const enum ReactiveFlags {
  SKIP = '__v_skip',
  IS_REACTIVE = '__v_isReactive',
  IS_READONLY = '__v_isReadonly',
  IS_SHALLOW = '__v_isShallow',
  RAW = '__v_raw'
}
// ...
export const reactiveMap = new WeakMap<Target, any>()
export const shallowReactiveMap = new WeakMap<Target, any>()
export const readonlyMap = new WeakMap<Target, any>()
export const shallowReadonlyMap = new WeakMap<Target, any>()
const enum TargetType {
  INVALID = 0,
  COMMON = 1,
  COLLECTION = 2
}

function targetTypeMap(rawType: string) {
  switch (rawType) {
    case 'Object':
    case 'Array':
      return TargetType.COMMON
    case 'Map':
    case 'Set':
    case 'WeakMap':
    case 'WeakSet':
      return TargetType.COLLECTION
    default:
      return TargetType.INVALID
  }
}
function getTargetType(value: Target) {
  return value[ReactiveFlags.SKIP] || !Object.isExtensible(value)
    ? TargetType.INVALID
    : targetTypeMap(toRawType(value))
}

/*
 * const count = ref(0)
 * const obj = reactive({
 *   count
 * })
 *
 * obj.count++
 * obj.count // -> 1
 * count.value // -> 1
 */

export function reactive<T extends object>(target: T): UnwrapNestedRefs<T>
export function reactive(target: object) {
  // if trying to observe a readonly proxy, return the readonly version.
  if (isReadonly(target)) {
    return target
  }
  return createReactiveObject(
    target,
    false,
    mutableHandlers,
    mutableCollectionHandlers,
    reactiveMap
  )
}

function createReactiveObject(
  target: Target,
  isReadonly: boolean,
  baseHandlers: ProxyHandler<any>,
  collectionHandlers: ProxyHandler<any>,
  proxyMap: WeakMap<Target, any>
) {
  if (!isObject(target)) {
    if (__DEV__) {
      console.warn(`value cannot be made reactive: ${String(target)}`)
    }
    return target
  }
  // target is already a Proxy, return it.
  // exception: calling readonly() on a reactive object
  if (
    target[ReactiveFlags.RAW] &&
    !(isReadonly && target[ReactiveFlags.IS_REACTIVE])
  ) {
    return target
  }
  // target already has corresponding Proxy
  const existingProxy = proxyMap.get(target)
  if (existingProxy) {
    return existingProxy
  }
  // only specific value types can be observed.
  const targetType = getTargetType(target)
  if (targetType === TargetType.INVALID) {
    return target
  }
  const proxy = new Proxy(
    target,
    targetType === TargetType.COLLECTION ? collectionHandlers : baseHandlers
  )
  proxyMap.set(target, proxy)
  return proxy
}

// shallowReactive
export function shallowReactive<T extends object>(
  target: T
): ShallowReactive<T> {
  return createReactiveObject(
    target,
    false,
    shallowReactiveHandlers,
    shallowCollectionHandlers,
    shallowReactiveMap
  )
}
// raedonly
// 注意readonly不是響應式的，而是一個原對象的只讀的拷貝
// 具體實現在對應的handlers里
export function readonly<T extends object>(
  target: T
): DeepReadonly<UnwrapNestedRefs<T>> {
  return createReactiveObject(
    target,
    true,
    readonlyHandlers,
    readonlyCollectionHandlers,
    readonlyMap
  )
}
// shallowReadonly
// 是響應式的
// 只有最外層是只讀的
export function shallowReadonly<T extends object>(target: T): Readonly<T> {
  return createReactiveObject(
    target,
    true,
    shallowReadonlyHandlers,
    shallowReadonlyCollectionHandlers,
    shallowReadonlyMap
  )
}

// reactive
export const mutableHandlers: ProxyHandler<object> = {
  get,
  set,
  deleteProperty,
  has,
  ownKeys
}

function createGetter(isReadonly = false, shallow = false) {
  return function get(target: Target, key: string | symbol, receiver: object) {
    // 以下幾個if分支判斷target是否已經是由這幾個API創(chuàng)建的代理對象，代理得到的proxy才具有這些key
    if (key === ReactiveFlags.IS_REACTIVE) {
      // 是否是響應式對象
      return !isReadonly
    } else if (key === ReactiveFlags.IS_READONLY) {
      // 是否是只讀對象
      return isReadonly
    } else if (key === ReactiveFlags.IS_SHALLOW) {
      // 是否是淺層的 響應式/只讀 對象
      return shallow
    } else if (
      // __v_raw 屬性對應 代理對象的目標對象
      // 當該屬性有值，且在相應的proxyMap中存在代理對象時，說明target已經是一個proxy了
      // __v_raw 屬性對應的值為target本身
      key === ReactiveFlags.RAW &&
      receiver ===
        (isReadonly
          ? shallow
            ? shallowReadonlyMap
            : readonlyMap
          : shallow
          ? shallowReactiveMap
          : reactiveMap
        ).get(target)
    ) {
      return target
    }
    const targetIsArray = isArray(target)
    // 對數組的幾個方法進行代理，在'includes', 'indexOf', 'lastIndexOf'等方法中進行track捕獲依賴
    if (!isReadonly && targetIsArray && hasOwn(arrayInstrumentations, key)) {
      return Reflect.get(arrayInstrumentations, key, receiver)
    }
    const res = Reflect.get(target, key, receiver)
    if (isSymbol(key) ? builtInSymbols.has(key) : isNonTrackableKeys(key)) {
      return res
    }
    // 如果不是readonly，則捕獲依賴，因此，readonly 為非響應式的
    if (!isReadonly) {
      track(target, TrackOpTypes.GET, key)
    }
    if (shallow) {
      return res
    }
    // 如果get到的值是一個Ref，會直接解包，無需再使用 .value 來獲取真正需要的值
    // 除非目標對象target是數組，或者當前的key是整數
    // 例如，obj[0]，即使是一個Ref也不會直接解包，使用的時候依然要 obj[0].value
    // shallow沒有走到這一步，因此也不會自動解包
    if (isRef(res)) {
      // ref unwrapping - skip unwrap for Array + integer key.
      return targetIsArray && isIntegerKey(key) ? res : res.value
    }
    // 當get到的值是對象時，根據是否是readonly來遞歸操作，需要防止對象循環(huán)引用
    // shallow沒有走到這一步，因此shallow是淺層的
    if (isObject(res)) {
      // Convert returned value into a proxy as well. we do the isObject check
      // here to avoid invalid value warning. Also need to lazy access readonly
      // and reactive here to avoid circular dependency.
      return isReadonly ? readonly(res) : reactive(res)
    }
    return res
  }
}

function createSetter(shallow = false) {
  return function set(
    target: object,
    key: string | symbol,
    value: unknown,
    receiver: object
  ): boolean {
    let oldValue = (target as any)[key]
    // 當前值是Readonly的Ref，而新值不是Ref時，不允許修改
    if (isReadonly(oldValue) && isRef(oldValue) && !isRef(value)) {
      return false
    }
    // 如果是深層的修改
    if (!shallow) {
      // 解出原本的非proxy值
      if (!isShallow(value) && !isReadonly(value)) {
        oldValue = toRaw(oldValue)
        value = toRaw(value)
      }
      // 目標對象非數組，當前key的值是Ref而新值不是Ref，則通過 .value 賦值
      // 在Ref內部觸發(fā)更新
      if (!isArray(target) && isRef(oldValue) && !isRef(value)) {
        oldValue.value = value
        return true
      }
    } else {
      // 淺層模式下，忽略對象是否是響應式的
      // in shallow mode, objects are set as-is regardless of reactive or not
    }
    // 然后是觸發(fā)更新的部分了
    // 判斷當前key是否已經存在于target上
    const hadKey =
      isArray(target) && isIntegerKey(key)
        ? Number(key) < target.length
        : hasOwn(target, key)
    const result = Reflect.set(target, key, value, receiver)
    // don't trigger if target is something up in the prototype chain of original
    // 如果是原型鏈上的字段則不會觸發(fā)更新
    if (target === toRaw(receiver)) {
      if (!hadKey) {
        // 當前的key已經存在，觸發(fā)新增的更新
        trigger(target, TriggerOpTypes.ADD, key, value)
      } else if (hasChanged(value, oldValue)) {
        // 當前key不存在，觸發(fā)修改的更新
        trigger(target, TriggerOpTypes.SET, key, value, oldValue)
      }
    }
    return result
  }
}

function deleteProperty(target: object, key: string | symbol): boolean {
  const hadKey = hasOwn(target, key)
  const oldValue = (target as any)[key]
  const result = Reflect.deleteProperty(target, key)
  // 刪除成功 且 target中原來有這個屬性時，觸發(fā)刪除的更新
  if (result && hadKey) {
    trigger(target, TriggerOpTypes.DELETE, key, undefined, oldValue)
  }
  return result
}

function has(target: object, key: string | symbol): boolean {
  const result = Reflect.has(target, key)
  if (!isSymbol(key) || !builtInSymbols.has(key)) {
    track(target, TrackOpTypes.HAS, key)
  }
  return result
}

function ownKeys(target: object): (string | symbol)[] {
  track(target, TrackOpTypes.ITERATE, isArray(target) ? 'length' : ITERATE_KEY)
  return Reflect.ownKeys(target)
}

const readonlyGet = /*#__PURE__*/ createGetter(true)
export const readonlyHandlers: ProxyHandler<object> = {
  get: readonlyGet,
  set(target, key) {
    if (__DEV__) {
      warn(
        `Set operation on key "${String(key)}" failed: target is readonly.`,
        target
      )
    }
    return true
  },
  deleteProperty(target, key) {
    if (__DEV__) {
      warn(
        `Delete operation on key "${String(key)}" failed: target is readonly.`,
        target
      )
    }
    return true
  }
}

const shallowGet = /*#__PURE__*/ createGetter(false, true)
const shallowSet = /*#__PURE__*/ createSetter(true)
export const shallowReactiveHandlers = /*#__PURE__*/ extend(
  {},
  mutableHandlers,
  {
    get: shallowGet,
    set: shallowSet
  }
)

const shallowReadonlyGet = /*#__PURE__*/ createGetter(true, true)
// Props handlers are special in the sense that it should not unwrap top-level
// refs (in order to allow refs to be explicitly passed down), but should
// retain the reactivity of the normal readonly object.
export const shallowReadonlyHandlers = /*#__PURE__*/ extend(
  {},
  readonlyHandlers,
  {
    get: shallowReadonlyGet
  }
)

export const mutableCollectionHandlers: ProxyHandler<CollectionTypes> = {
  get: /*#__PURE__*/ createInstrumentationGetter(false, false)
}
export const shallowCollectionHandlers: ProxyHandler<CollectionTypes> = {
  get: /*#__PURE__*/ createInstrumentationGetter(false, true)
}
export const readonlyCollectionHandlers: ProxyHandler<CollectionTypes> = {
  get: /*#__PURE__*/ createInstrumentationGetter(true, false)
}
export const shallowReadonlyCollectionHandlers: ProxyHandler<CollectionTypes> =
  {
    get: /*#__PURE__*/ createInstrumentationGetter(true, true)
  }

const [
  mutableInstrumentations,
  readonlyInstrumentations,
  shallowInstrumentations,
  shallowReadonlyInstrumentations
] = /* #__PURE__*/ createInstrumentations()
function createInstrumentationGetter(isReadonly: boolean, shallow: boolean) {
  const instrumentations = shallow
    ? isReadonly
      ? shallowReadonlyInstrumentations
      : shallowInstrumentations
    : isReadonly
    ? readonlyInstrumentations
    : mutableInstrumentations
  return (
    target: CollectionTypes,
    key: string | symbol,
    receiver: CollectionTypes
  ) => {
    if (key === ReactiveFlags.IS_REACTIVE) {
      return !isReadonly
    } else if (key === ReactiveFlags.IS_READONLY) {
      return isReadonly
    } else if (key === ReactiveFlags.RAW) {
      return target
    }
    return Reflect.get(
      hasOwn(instrumentations, key) && key in target
        ? instrumentations
        : target,
      key,
      receiver
    )
  }
}

function createInstrumentations() {
  // 對應reactive
  const mutableInstrumentations: Record<string, Function> = {
    get(this: MapTypes, key: unknown) {
      return get(this, key)
    },
    get size() {
      return size(this as unknown as IterableCollections)
    },
    has,
    add,
    set,
    delete: deleteEntry,
    clear,
    forEach: createForEach(false, false)
  }
  // 對應shallowReactive
  const shallowInstrumentations: Record<string, Function> = {
    get(this: MapTypes, key: unknown) {
      return get(this, key, false, true)
    },
    get size() {
      return size(this as unknown as IterableCollections)
    },
    has,
    add,
    set,
    delete: deleteEntry,
    clear,
    forEach: createForEach(false, true)
  }
  // 對應readonly
  const readonlyInstrumentations: Record<string, Function> = {
    get(this: MapTypes, key: unknown) {
      return get(this, key, true)
    },
    get size() {
      return size(this as unknown as IterableCollections, true)
    },
    has(this: MapTypes, key: unknown) {
      return has.call(this, key, true)
    },
    add: createReadonlyMethod(TriggerOpTypes.ADD),
    set: createReadonlyMethod(TriggerOpTypes.SET),
    delete: createReadonlyMethod(TriggerOpTypes.DELETE),
    clear: createReadonlyMethod(TriggerOpTypes.CLEAR),
    forEach: createForEach(true, false)
  }
  // 對應shallowReadonly
  const shallowReadonlyInstrumentations: Record<string, Function> = {
    get(this: MapTypes, key: unknown) {
      return get(this, key, true, true)
    },
    get size() {
      return size(this as unknown as IterableCollections, true)
    },
    has(this: MapTypes, key: unknown) {
      return has.call(this, key, true)
    },
    add: createReadonlyMethod(TriggerOpTypes.ADD),
    set: createReadonlyMethod(TriggerOpTypes.SET),
    delete: createReadonlyMethod(TriggerOpTypes.DELETE),
    clear: createReadonlyMethod(TriggerOpTypes.CLEAR),
    forEach: createForEach(true, true)
  }
  // 使用 createIterableMethod 給這些 Instrumentations 掛上幾個迭代器
  const iteratorMethods = ['keys', 'values', 'entries', Symbol.iterator]
  iteratorMethods.forEach(method => {
    mutableInstrumentations[method as string] = createIterableMethod(
      method,
      false,
      false
    )
    readonlyInstrumentations[method as string] = createIterableMethod(
      method,
      true,
      false
    )
    shallowInstrumentations[method as string] = createIterableMethod(
      method,
      false,
      true
    )
    shallowReadonlyInstrumentations[method as string] = createIterableMethod(
      method,
      true,
      true
    )
  })
  return [
    mutableInstrumentations,
    readonlyInstrumentations,
    shallowInstrumentations,
    shallowReadonlyInstrumentations
  ]
}

function get(
  target: MapTypes,
  key: unknown,
  isReadonly = false,
  isShallow = false
) {
  // #1772: readonly(reactive(Map)) should return readonly + reactive version
  // of the value
  target = (target as any)[ReactiveFlags.RAW]
  const rawTarget = toRaw(target)
  const rawKey = toRaw(key)
  if (!isReadonly) {
    if (key !== rawKey) {
      track(rawTarget, TrackOpTypes.GET, key)
    }
    track(rawTarget, TrackOpTypes.GET, rawKey)
  }
  const { has } = getProto(rawTarget)
  const wrap = isShallow ? toShallow : isReadonly ? toReadonly : toReactive
  if (has.call(rawTarget, key)) {
    return wrap(target.get(key))
  } else if (has.call(rawTarget, rawKey)) {
    return wrap(target.get(rawKey))
  } else if (target !== rawTarget) {
    // #3602 readonly(reactive(Map))
    // ensure that the nested reactive `Map` can do tracking for itself
    target.get(key)
  }
}
function has(this: CollectionTypes, key: unknown, isReadonly = false): boolean {
  const target = (this as any)[ReactiveFlags.RAW]
  const rawTarget = toRaw(target)
  const rawKey = toRaw(key)
  if (!isReadonly) {
    if (key !== rawKey) {
      track(rawTarget, TrackOpTypes.HAS, key)
    }
    track(rawTarget, TrackOpTypes.HAS, rawKey)
  }
  return key === rawKey
    ? target.has(key)
    : target.has(key) || target.has(rawKey)
}
function size(target: IterableCollections, isReadonly = false) {
  target = (target as any)[ReactiveFlags.RAW]
  !isReadonly && track(toRaw(target), TrackOpTypes.ITERATE, ITERATE_KEY)
  return Reflect.get(target, 'size', target)
}
function add(this: SetTypes, value: unknown) {
  value = toRaw(value)
  const target = toRaw(this)
  const proto = getProto(target)
  const hadKey = proto.has.call(target, value)
  if (!hadKey) {
    target.add(value)
    trigger(target, TriggerOpTypes.ADD, value, value)
  }
  return this
}
function set(this: MapTypes, key: unknown, value: unknown) {
  value = toRaw(value)
  const target = toRaw(this)
  const { has, get } = getProto(target)
  let hadKey = has.call(target, key)
  if (!hadKey) {
    key = toRaw(key)
    hadKey = has.call(target, key)
  } else if (__DEV__) {
    checkIdentityKeys(target, has, key)
  }
  const oldValue = get.call(target, key)
  target.set(key, value)
  if (!hadKey) {
    trigger(target, TriggerOpTypes.ADD, key, value)
  } else if (hasChanged(value, oldValue)) {
    trigger(target, TriggerOpTypes.SET, key, value, oldValue)
  }
  return this
}
function deleteEntry(this: CollectionTypes, key: unknown) {
  const target = toRaw(this)
  const { has, get } = getProto(target)
  let hadKey = has.call(target, key)
  if (!hadKey) {
    key = toRaw(key)
    hadKey = has.call(target, key)
  } else if (__DEV__) {
    checkIdentityKeys(target, has, key)
  }
  const oldValue = get ? get.call(target, key) : undefined
  // forward the operation before queueing reactions
  const result = target.delete(key)
  if (hadKey) {
    trigger(target, TriggerOpTypes.DELETE, key, undefined, oldValue)
  }
  return result
}
function clear(this: IterableCollections) {
  const target = toRaw(this)
  const hadItems = target.size !== 0
  const oldTarget = __DEV__
    ? isMap(target)
      ? new Map(target)
      : new Set(target)
    : undefined
  // forward the operation before queueing reactions
  const result = target.clear()
  if (hadItems) {
    trigger(target, TriggerOpTypes.CLEAR, undefined, undefined, oldTarget)
  }
  return result
}

function createIterableMethod(
  method: string | symbol,
  isReadonly: boolean,
  isShallow: boolean
) {
  return function (
    this: IterableCollections,
    ...args: unknown[]
  ): Iterable & Iterator {
    const target = (this as any)[ReactiveFlags.RAW]
    const rawTarget = toRaw(target)
    const targetIsMap = isMap(rawTarget)
    const isPair =
      method === 'entries' || (method === Symbol.iterator && targetIsMap)
    const isKeyOnly = method === 'keys' && targetIsMap
    const innerIterator = target[method](...args)
    const wrap = isShallow ? toShallow : isReadonly ? toReadonly : toReactive
    !isReadonly &&
      track(
        rawTarget,
        TrackOpTypes.ITERATE,
        isKeyOnly ? MAP_KEY_ITERATE_KEY : ITERATE_KEY
      )
    // return a wrapped iterator which returns observed versions of the
    // values emitted from the real iterator
    return {
      // iterator protocol
      next() {
        const { value, done } = innerIterator.next()
        return done
          ? { value, done }
          : {
              value: isPair ? [wrap(value[0]), wrap(value[1])] : wrap(value),
              done
            }
      },
      // iterable protocol
      [Symbol.iterator]() {
        return this
      }
    }
  }
}