gulp-environment/src/index.js

Adds easy environment configuration and conditional piping to Gulp, based on NODE_ENV or parameters with yargs.

var yargs = require('yargs')
var log = require('fancy-log')
var noop = require('gulp-noop')

var config = require('./config')

// set up --env=x parameter, without choices/default as it'll get
// checked later at the same time as as NODE_ENV
yargs.option('env', {
  alias: ["environment", "NODE_ENV"],
  required: false,
  type: 'string'
})

// returns a boolean representing whether or not {env} and
// {toCheck} represent the same environment
function isEnvironment(env, toCheck) {
  if (typeof toCheck === 'object') {
    return toCheck === env
  }

  return toCheck === env.name || env.aliases.indexOf(toCheck) > -1
}

// returns the environment represented by {param}
// this could be either an environment name, an environment alias,
// or from passing an environment object directly
function getEnvironment(param) {
  var defaultEnvironment

  for (i in environments) {
    var environment = environments[i]

    if (environment.is(param)) {
      return environment
    }

    if (environment.is(config.default)) {
      defaultEnvironment = environment
    }
  }

  return defaultEnvironment
}

// returns {ifTrue} if the current environment is {environment}
// otherwise returns either {ifFalse} or a noop if {ifFalse} is undefined
function pipeIf(environment, ifTrue, ifFalse) {
  if (currentEnvironment.is(environment)) {
    return ifTrue
  } else {
    return ifFalse || noop() // noop noop [pingu noises]
  }
}

// returns a noop if the current environment is {environment}
// otherwise returns {ifFalse}
function pipeIfNot(environment, ifFalse) {
  return pipeIf(environment, noop(), ifFalse)
}

var envModule = {
  get current() {
    return currentEnvironment
  },

  set current(newEnv) {
    currentEnvironment = getEnvironment(newEnv)
  }
}

// expose the bare functions if someone would rather use those
// than chaining things together
envModule.is = isEnvironment
envModule.if = pipeIf
envModule.if.not = pipeIfNot

// add if/else/not conditional piping functions to the exported module
// and convenience functions for each environment
var environments = config.environments.map(function(env) {
  var key = env.name

  // enables comparison of environment objects directly through
  // env.current.is(env.environment) or env.current.is('environment')
  env.is = function(toCompare) {
    return envModule.is(env, toCompare)
  }

  envModule[key] = env

  // enables checking of current env quickly through env.is.environment()
  envModule.is[key] = function() {
    return envModule.is(currentEnvironment, env)
  }

  envModule.if[key] = function(trueOp) {
    var result = envModule.if(env, trueOp)

    // augument {ifTrue} with a cute chaining function which allows for better
    // syntax of else statements; env.if.environment(trueFn, falseFn) vs.
    // env.if.environment(trueFn).else(falseFn)
    result.else = function(falseOp) {
      return result === trueOp ? trueOp : falseOp
    }

    return result
  }

  envModule.if.not[key] = function(ifFalse) {
    return envModule.if.not(env, ifFalse)
  }

  return env
})

// get env from parameters or, if it's not there,
// try and read it from the system's environment variables
// if no/an invalid environment has been passed, default to production
var currentEnvironment = getEnvironment(yargs.argv.env || process.env.NODE_ENV)

log('Running in %s mode', currentEnvironment.name)

module.exports = envModule