/* @flow */
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import type Watcher from './watcher'
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import { remove } from '../util/index'
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import config from '../config'
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let uid = 0
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/**
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* A dep is an observable that can have multiple
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* directives subscribing to it.
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*/
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export default class Dep {
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static target: ?Watcher;
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id: number;
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subs: Array<Watcher>;
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constructor () {
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this.id = uid++
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this.subs = []
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}
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addSub (sub: Watcher) {
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this.subs.push(sub)
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}
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removeSub (sub: Watcher) {
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remove(this.subs, sub)
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}
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depend () {
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if (Dep.target) {
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Dep.target.addDep(this)
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}
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}
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notify () {
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// stabilize the subscriber list first
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const subs = this.subs.slice()
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if (process.env.NODE_ENV !== 'production' && !config.async) {
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// subs aren't sorted in scheduler if not running async
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// we need to sort them now to make sure they fire in correct
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// order
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subs.sort((a, b) => a.id - b.id)
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}
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for (let i = 0, l = subs.length; i < l; i++) {
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subs[i].update()
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}
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}
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}
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// The current target watcher being evaluated.
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// This is globally unique because only one watcher
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// can be evaluated at a time.
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Dep.target = null
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const targetStack = []
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export function pushTarget (target: ?Watcher) {
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targetStack.push(target)
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Dep.target = target
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}
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export function popTarget () {
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targetStack.pop()
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Dep.target = targetStack[targetStack.length - 1]
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}
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