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node_modules/vue/src/server/render-context.js 3.47 KB
aaac7fed   liuqimichale   add
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  /* @flow */
  
  import { isUndef } from 'shared/util'
  
  type RenderState = {
    type: 'Element';
    rendered: number;
    total: number;
    children: Array<VNode>;
    endTag: string;
  } | {
    type: 'Fragment';
    rendered: number;
    total: number;
    children: Array<VNode>;
  } | {
    type: 'Component';
    prevActive: Component;
  } | {
    type: 'ComponentWithCache';
    buffer: Array<string>;
    bufferIndex: number;
    componentBuffer: Array<Set<Class<Component>>>;
    key: string;
  };
  
  export class RenderContext {
    userContext: ?Object;
    activeInstance: Component;
    renderStates: Array<RenderState>;
    write: (text: string, next: Function) => void;
    renderNode: (node: VNode, isRoot: boolean, context: RenderContext) => void;
    next: () => void;
    done: (err: ?Error) => void;
  
    modules: Array<(node: VNode) => ?string>;
    directives: Object;
    isUnaryTag: (tag: string) => boolean;
  
    cache: any;
    get: ?(key: string, cb: Function) => void;
    has: ?(key: string, cb: Function) => void;
  
    constructor (options: Object) {
      this.userContext = options.userContext
      this.activeInstance = options.activeInstance
      this.renderStates = []
  
      this.write = options.write
      this.done = options.done
      this.renderNode = options.renderNode
  
      this.isUnaryTag = options.isUnaryTag
      this.modules = options.modules
      this.directives = options.directives
  
      const cache = options.cache
      if (cache && (!cache.get || !cache.set)) {
        throw new Error('renderer cache must implement at least get & set.')
      }
      this.cache = cache
      this.get = cache && normalizeAsync(cache, 'get')
      this.has = cache && normalizeAsync(cache, 'has')
  
      this.next = this.next.bind(this)
    }
  
    next () {
      const lastState = this.renderStates[this.renderStates.length - 1]
      if (isUndef(lastState)) {
        return this.done()
      }
      switch (lastState.type) {
        case 'Element':
        case 'Fragment':
          const { children, total } = lastState
          const rendered = lastState.rendered++
          if (rendered < total) {
            this.renderNode(children[rendered], false, this)
          } else {
            this.renderStates.pop()
            if (lastState.type === 'Element') {
              this.write(lastState.endTag, this.next)
            } else {
              this.next()
            }
          }
          break
        case 'Component':
          this.renderStates.pop()
          this.activeInstance = lastState.prevActive
          this.next()
          break
        case 'ComponentWithCache':
          this.renderStates.pop()
          const { buffer, bufferIndex, componentBuffer, key } = lastState
          const result = {
            html: buffer[bufferIndex],
            components: componentBuffer[bufferIndex]
          }
          this.cache.set(key, result)
          if (bufferIndex === 0) {
            // this is a top-level cached component,
            // exit caching mode.
            this.write.caching = false
          } else {
            // parent component is also being cached,
            // merge self into parent's result
            buffer[bufferIndex - 1] += result.html
            const prev = componentBuffer[bufferIndex - 1]
            result.components.forEach(c => prev.add(c))
          }
          buffer.length = bufferIndex
          componentBuffer.length = bufferIndex
          this.next()
          break
      }
    }
  }
  
  function normalizeAsync (cache, method) {
    const fn = cache[method]
    if (isUndef(fn)) {
      return
    } else if (fn.length > 1) {
      return (key, cb) => fn.call(cache, key, cb)
    } else {
      return (key, cb) => cb(fn.call(cache, key))
    }
  }