07-rule-chaining.mts

/*
 * This is an advanced example demonstrating rules that passed based off the
 * results of other rules by adding runtime facts.  It also demonstrates
 * accessing the runtime facts after engine execution.
 *
 * Usage:
 *   node ./examples/07-rule-chaining.js
 *
 * For detailed output:
 *   DEBUG=json-rules-engine node ./examples/07-rule-chaining.js
 */

import "colors";
import { Almanac, Engine } from "json-rules-engine";
import apiClient from "./support/account-api-client.mjs";

async function start() {
  /**
   * Setup a new engine
   */
  const engine = new Engine();

  /**
   * Rule for identifying people who may like screwdrivers
   */
  const drinkRule = {
    conditions: {
      all: [
        {
          fact: "drinksOrangeJuice",
          operator: "equal",
          value: true,
        },
        {
          fact: "enjoysVodka",
          operator: "equal",
          value: true,
        },
      ],
    },
    event: { type: "drinks-screwdrivers" },
    priority: 10, // IMPORTANT!  Set a higher priority for the drinkRule, so it runs first
    onSuccess: async function (_event: unknown, almanac: Almanac) {
      almanac.addFact("screwdriverAficionado", true);

      // asychronous operations can be performed within callbacks
      // engine execution will not proceed until the returned promises is resolved
      const accountId = await almanac.factValue<string>("accountId");
      const accountInfo = await apiClient.getAccountInformation(accountId);
      almanac.addFact("accountInfo", accountInfo);
    },
    onFailure: function (_event: unknown, almanac: Almanac) {
      almanac.addFact("screwdriverAficionado", false);
    },
  };
  engine.addRule(drinkRule);

  /**
   * Rule for identifying people who should be invited to a screwdriver social
   * - Only invite people who enjoy screw drivers
   * - Only invite people who are sociable
   */
  const inviteRule = {
    conditions: {
      all: [
        {
          fact: "screwdriverAficionado", // this fact value is set when the drinkRule is evaluated
          operator: "equal",
          value: true,
        },
        {
          fact: "isSociable",
          operator: "equal",
          value: true,
        },
        {
          fact: "accountInfo",
          path: "$.company",
          operator: "equal",
          value: "microsoft",
        },
      ],
    },
    event: { type: "invite-to-screwdriver-social" },
    priority: 5, // Set a lower priority for the drinkRule, so it runs later (default: 1)
  };
  engine.addRule(inviteRule);

  /**
   * Register listeners with the engine for rule success and failure
   */
  engine
    .on("success", async (event, almanac) => {
      const accountInfo = await almanac.factValue<{ company: string }>(
        "accountInfo",
      );
      const accountId = await almanac.factValue("accountId");
      console.log(
        `${accountId}(${accountInfo.company}) ` +
          "DID".green +
          ` meet conditions for the ${event.type.underline} rule.`,
      );
    })
    .on("failure", async (event, almanac) => {
      const accountId = await almanac.factValue("accountId");
      console.log(
        `${accountId} did ` +
          "NOT".red +
          ` meet conditions for the ${event.type.underline} rule.`,
      );
    });

  // define fact(s) known at runtime
  let facts = {
    accountId: "washington",
    drinksOrangeJuice: true,
    enjoysVodka: true,
    isSociable: true,
    accountInfo: {},
  };

  // first run, using washington's facts
  let results = await engine.run(facts);

  // isScrewdriverAficionado was a fact set by engine.run()
  let isScrewdriverAficionado = await results.almanac.factValue<boolean>(
    "screwdriverAficionado",
  );
  console.log(
    `${facts.accountId} ${isScrewdriverAficionado ? "IS".green : "IS NOT".red} a screwdriver aficionado`,
  );

  facts = {
    accountId: "jefferson",
    drinksOrangeJuice: true,
    enjoysVodka: false,
    isSociable: true,
    accountInfo: {},
  };
  results = await engine.run(facts); // second run, using jefferson's facts; facts & evaluation are independent of the first run

  isScrewdriverAficionado = await results.almanac.factValue(
    "screwdriverAficionado",
  );
  console.log(
    `${facts.accountId} ${isScrewdriverAficionado ? "IS".green : "IS NOT".red} a screwdriver aficionado`,
  );
}

export default start();

/*
 * OUTPUT:
 *
 * loading account information for "washington"
 * washington(microsoft) DID meet conditions for the drinks-screwdrivers rule.
 * washington(microsoft) DID meet conditions for the invite-to-screwdriver-social rule.
 * washington IS a screwdriver aficionado
 * jefferson did NOT meet conditions for the drinks-screwdrivers rule.
 * jefferson did NOT meet conditions for the invite-to-screwdriver-social rule.
 * jefferson IS NOT a screwdriver aficionado
 */