Chain of Responsibility

Using the Chain of Responsibility pattern is another way to organize your Bottender actions in your Bottender app. This pattern lets you explicitly prioritize your actions by specifying the order of the actions.

Considering a customer service bot app with three very different layers:

• RuleBased: Use JavaScript rules to handle incoming events.
• MachineLearning: Use machine learning models to handle incoming events.
• HumanAgent: Use human agents to handle incoming events.

In general, you may want to put the cheapest layer at the top of the chain. For example, you may put the RuleBased action at the top:

const { chain } = require('bottender');

function RuleBased(context, props) {
  if (context.event.text === 'hi') {
    // discontinue and return the `SayHi` action
    return SayHi;
  }
  // continue to the `next` action
  return props.next;
}

function MachineLearningBased(context, props) {
  /* ...skip */
}

function HumanAgent(context, props) {
  /* ...skip */
}

function App() {
  return chain([
    // execute in the following order
    RuleBased,
    MachineLearningBased,
    HumanAgent,
  ]);
}

If your bot receives a "hi" text message, the RuleBased action returns the SayHi action and exits the chain. Otherwise, the RuleBased action returns props.next and goes down to the MachineLearningBased action.

The chain function takes an array of actions and returns an action as the return value, so it can work with all patterns that compatible with the Bottender actions.

Using with Router

You can use the Chain of Responsibility pattern with the routing mechanism that Bottender provides. For example, you may use the router function to create a router within the RuleBased layer:

function RuleBased(context, { next }) {
  return router([
    // return the `SayHi` action when receiving a "hi" text message
    text('hi', SayHi),
    // return the `next` action
    route('*', next),
  ]);
}

function App() {
  return chain([
    // execute in the following order
    RuleBased,
    MachineLearningBased,
    HumanAgent,
  ]);
}