@wmfs/tymly/lib/plugin/components/services/functions/index.js

A framework for building and sharing workflows in Node.js

'use strict'

// Getting args from a function:
//   http://stackoverflow.com/questions/1007981/how-to-get-function-parameter-names-values-dynamically-from-javascript

const _ = require('lodash')
const dottie = require('dottie')

const STRIP_COMMENTS = /((\/\/.*$)|(\/\*[\s\S]*?\*\/))/mg
const ARGUMENT_NAMES = /(?:^|,)\s*([^\s,=]+)/g

class FunctionsService {
  boot (options) {
    this.functions = {}

    // Sandbox where blueprint-functions can play
    const ctx = {
      services: options.bootedServices,
      blueprintComponents: options.blueprintComponents,
      utils: {
        _,
        dottie
      }
    }

    const functions = dottie.get(options, 'blueprintComponents.functions')

    if (functions) {
      options.messages.info('Adding functions')

      for (const [functionId, functionGenerator] of Object.entries(functions)) {
        if (!isFunction(functionGenerator)) {
          continue
        }
        const func = functionGenerator(ctx) // Closures in play!
        const args = FunctionsService.getFunctionParameters(func)
        const functionInfo = {
          functionId,
          func,
          args,
          functionIsAsync: (args.length > 0 && args[args.length - 1] === 'callback')
        }

        this.functions[functionId] = functionInfo

        options.messages.detail(functionId + ' (' + args.join(',') + ')')
      }
    }
  }

  /**
   * Returns a function that's been supplied via a blueprint
   * @param {string} namespace The namespace of the blueprint contributing the function that's required
   * @param {string} functionName And the name of the function, in the specified namespace, that's required
   * @returns {Function} A Javascript function as supplied via blueprint
   * @example
   * var func = functions.getFunction('myCompany', 'magicFormula')
   */
  getFunction (namespace, functionName) {
    const functionId = namespace + '_' + functionName
    return this.functions[functionId].func
  }

  /**
   * Returns an array of argument names from any specified function
   * @param {Function} func Any Javascript function
   * @returns {Array<string>} A list of argument names
   * @example
   * var argList = functions.getFunctionParameters(function (a,b,c){})
   * console.log(argList) // ['a','b','c']
   */
  static getFunctionParameters (func) {
    const fnStr = func.toString().replace(STRIP_COMMENTS, '')
    const argsList = fnStr.slice(fnStr.indexOf('(') + 1, fnStr.indexOf(')'))
    const result = argsList.match(ARGUMENT_NAMES)

    if (result === null) {
      return []
    } else {
      const stripped = []
      for (let i = 0; i < result.length; i++) {
        stripped.push(result[i].replace(/[\s,]/g, ''))
      }
      return stripped
    }
  }
}

function isFunction (candidate) {
  return typeof candidate === 'function'
}

module.exports = {
  serviceClass: FunctionsService,
  bootBefore: ['statebox']
}