add rule chaining example

Author: Cache Hamm

examples/07-rule-chaining.js

@@ -0,0 +1,94 @@
+'use strict'
+
+/*
+ * This is an advanced example demonstrating rules that passed based off the
+ * results of other rules
+ *
+ * Usage:
+ *   node ./examples/07-rule-chaining.js
+ *
+ * For detailed output:
+ *   DEBUG=json-rules-engine node ./examples/07-rule-chaining.js
+ */
+
+require('colors')
+let Engine = require('../dist').Engine
+
+/**
+ * Setup a new engine
+ */
+let engine = new Engine()
+
+/**
+ * Rule for identifying people who may like screwdrivers
+ */
+let 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
+}
+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
+ */
+let 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
+    }]
+  },
+  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
+ */
+let facts
+engine
+  .on('success', (event, almanac) => {
+    console.log(facts.accountId + ' DID '.green + 'meet conditions for the ' + event.type.underline + ' rule.')
+    almanac.addRuntimeFact('screwdriverAficionado', true)
+  })
+  .on('failure', rule => {
+    console.log(facts.accountId + ' did ' + 'NOT'.red + ' meet conditions for the ' + rule.event.type.underline + ' rule.')
+  })
+
+// define fact(s) known at runtime
+facts = { accountId: 'washington', drinksOrangeJuice: true, enjoysVodka: true, isSociable: true, screwdriverAficionado: false }
+engine
+  .run(facts)  // first run, using washington's facts
+  .then(() => {
+    facts = { accountId: 'jefferson', drinksOrangeJuice: true, enjoysVodka: false, isSociable: true, screwdriverAficionado: false }
+    return engine.run(facts) // second run, using jefferson's facts; facts & evaluation are independent of the first run
+  })
+  .catch(console.log)
+
+/*
+ * OUTPUT:
+ *
+ * washington DID meet conditions for the drinks-screwdrivers rule.
+ * washington DID meet conditions for the invite-to-screwdriver-social rule.
+ * jefferson did NOT meet conditions for the drinks-screwdrivers rule.
+ * jefferson did NOT meet conditions for the invite-to-screwdriver-social rule.
+ */