runtime/bridge/Handler.js

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

/**
 * @fileOverview
 * Task handler for communication between javascript and native.
 */

const handlerMap = {
  createBody: 'callCreateBody',
  addElement: 'callAddElement',
  removeElement: 'callRemoveElement',
  moveElement: 'callMoveElement',
  updateAttrs: 'callUpdateAttrs',
  updateStyle: 'callUpdateStyle',
  addEvent: 'callAddEvent',
  removeEvent: 'callRemoveEvent'
}

/**
 * Create a task handler.
 * @param {string} id
 * @param {function} handler
 * @return {function} taskHandler
 */
export function createHandler (id, handler) {
  const defaultHandler = handler || global.callNative

  /* istanbul ignore if */
  if (typeof defaultHandler !== 'function') {
    console.error('[JS Runtime] no default handler')
  }

  return function taskHandler (tasks) {
    /* istanbul ignore if */
    if (!Array.isArray(tasks)) {
      tasks = [tasks]
    }
    for (let i = 0; i < tasks.length; i++) {
      const returnValue = dispatchTask(id, tasks[i], defaultHandler)
      if (returnValue === -1) {
        return returnValue
      }
    }
  }
}

/**
 * Check if there is a corresponding available handler in the environment.
 * @param {string} module
 * @param {string} method
 * @return {boolean}
 */
function hasAvailableHandler (module, method) {
  return module === 'dom'
    && handlerMap[method]
    && typeof global[handlerMap[method]] === 'function'
}

/**
 * Dispatch the task to the specified handler.
 * @param {string} id
 * @param {object} task
 * @param {function} defaultHandler
 * @return {number} signal returned from native
 */
function dispatchTask (id, task, defaultHandler) {
  const { module, method, args } = task

  if (hasAvailableHandler(module, method)) {
    return global[handlerMap[method]](id, ...args, '-1')
  }

  return defaultHandler(id, [task], '-1')
}