rpc-stream/index.js

very simple rpc. use with any thing that has .pipe()

var through = require('through')
var serialize = require('stream-serializer')()

function get(obj, path) {
  if(Array.isArray(path)) {
    for(var i in path)
      obj = obj[path[i]]
    return obj
  }
  return obj[path]
}

module.exports = function (obj, opts) {
  if('boolean' == typeof opts) opts = { raw: opts }
  opts = opts || {}
  var cbs = {}, count = 1, local = obj || {}
  var flattenError = opts.flattenError || function (err) {
    if(!(err instanceof Error)) return err
    var err2 = { message: err.message }
    for(var k in err)
      err2[k] = err[k] 
    return err2
  }
  function expandError(err) {
    if (!err || !err.message) return err
    var err2 = new Error(err.message)
    for(var k in err)
      err2[k] = err[k]
    return err2
  }

  if(obj) {
    local = {}
    function callable (k) {
      return function (args, cb) {
        return obj[k].apply(obj, cb ? args.concat(cb) : args)
      }
    }
    for(var k in obj)
      local[k] = callable(k)

  }
  var s = through(function (data) {
    //write - on incoming call 
    data = data.slice()
    var i = data.pop(), args = data.pop(), name = data.pop()
    //if(~i) then there was no callback.    

    if (args[0]) args[0] = expandError(args[0])

    if(name != null) {
      var called = 0
      var cb = function () {
        if (called++) return
        var args = [].slice.call(arguments)
        args[0] = flattenError(args[0])
        if(~i) s.emit('data', [args, i]) //responses don't have a name.
      }
      try {
        local[name].call(obj, args, cb)
      } catch (err) {
        if(~i) s.emit('data', [[flattenError(err)], i])
      }
    } else if(!cbs[i]) {
      //there is no callback with that id.
      //either one end mixed up the id or
      //it was called twice.
      //log this error, but don't throw.
      //this process shouldn't crash because another did wrong

      s.emit('invalid callback id')
      return console.error('ERROR: unknown callback id: '+i, data)
    } else {
      //call the callback.
      var cb = cbs[i]
      delete cbs[i] //delete cb before calling it, incase cb throws.
      cb.apply(null, args)
    }
  })

  var rpc = s.rpc = function (name, args, cb) {
    if(cb) cbs[++count] = cb
    if('string' !== typeof name)
      throw new Error('name *must* be string')
    s.emit('data', [name, args, cb ? count : -1])
    if(cb && count == 9007199254740992) count = 0 //reset if max
    //that is 900 million million.
    //if you reach that, dm me,
    //i'll buy you a beer. @dominictarr
  }

  function keys (obj) {
    var keys = []
    for(var k in obj) keys.push(k)
    return keys
  }

  s.createRemoteCall = function (name) {
    return function () {
      var args = [].slice.call(arguments)
      var cb = ('function' == typeof args[args.length - 1])
               ? args.pop()
               : null
      rpc(name, args, cb)
    }
  }

  s.createLocalCall = function (name, fn) {
     local[name] = fn
  }

  s.wrap = function (remote, _path) {
    _path = _path || []
    var w = {}
    ;(Array.isArray(remote)     ? remote
    : 'string' == typeof remote ? [remote]
    : remote = keys(remote)
    ).forEach(function (k) {
      w[k] = s.createRemoteCall(k)
    })
    return w
  }
  if(opts.raw)
    return s

  return serialize(s)
}