rafa/src/core/Message.js

Rafa.js is a Javascript framework for building concurrent applications.

// # constructor(value: Any): Message
// A message is the container that contains the values and errors sent through
// a stream.
function Message(value) {
  this.value = value;
}

inherit(Message, Rafa, {
  isMessage: true,
  isValue: true, 
  isError: false, 
  isDone: false,

  // # collect(collector: A => B): Message
  // Return a new message whose value is the result of applying the `collector`
  // function to this Message's value. Return `undefined` if the `collector`
  // returns `null` or `undefined`.
  collect(collector) {
    var value = collector(this.value);
    /*eslint-disable*/
    if (value != null) return this.copy(value);
    /*eslint-enable*/
  },

  // # copy(value: A): Message
  // Copy this message and set the new Message"s value to value.
  copy(value) {
    return new this.constructor(value);
  },

  // # filter(predicate: A => Bool): Message
  // Return this message if the predicate function `a => b` returns true when
  // this message's `value` is applied as `a`, otherwise return undefined.
  filter(predicate) {
    if (predicate(this.value)) return this;
  },

  // # fold(initial: A, folder: (A, A) => A): Message
  // Return a new message whose value is the result of applying a folder 
  // function to the value of this message and an initial value.
  fold(initial, folder) {
    return this.copy(folder(initial, this.value));
  },

  // # map(mapper: A => B): Message
  // Return a new message whose value is the result of applying the funciton 
  // `mapper` to this stream's value.
  map(mapper) {
    return this.copy(mapper(this.value));
  },

  // # push(Stream, done: A => _)
  // Push this message through a stream
  push(stream, done) {
    stream.push(this.context(done), this);
  },

  // # toError(): ErrorMessage
  // Convert this object to an ErrorMessage if it is a Message or DoneMessage.
  toError() {
    if (!this.isError) return this.errorMessage(this.value);
    return this;
  },

  // # toDone(): DoneMessage
  // Convert this object to an DoneMessage if it is an ErrorMessage or Message.
  toDone() {
    if (!this.isDone) {
      if (this.isError) return this.errordoneMessage(this.error);
      return this.doneMessage(this.value);
    }
    return this;
  },

  // # toKind(): String
  // Return a string representing the kind of message (Message, ErrorMessage, 
  // or DoneMessage).
  toKind() {
    let kind;
    if (this.isError) kind = "Error";
    else if (this.isDone) kind = "Done";
    return `${kind}Message`;
  },

  // # toString(): String
  // Return a Javascript normalized String with this message's kind.
  toString() {
    return `[object ${this.toKind()}]`;
  },

  // # toRepr(): String
  // Return a string that displays the kind and value of this message.
  toRepr() {
    return `${this.toKind()}(${this.value})`;
  },
  
  // # toValue(): Message
  // Convert this object to a Message if it is an ErrorMessage or DoneMessage.
  toValue() {
    if (!this.isValue || this.isDone) return this.message(this.value);
    return this;
  }
});