azure_function_rule_engine.ts

import { AzureFunction, Context, HttpRequest } from '@azure/functions'
import { Engine } from 'json-rules-engine'

/**
 * Setup a new engine
 */
const engine = new Engine()

// define a rule for detecting the player has exceeded foul limits.  Foul out any player who:
// (has committed 5 fouls AND game is less 40 minutes) OR (has committed 6 fouls AND game is less 48 minutes)
engine.addRule({
  conditions: {
    any: [
      {
        all: [
          {
            fact: 'gameDuration',
            operator: 'lessThanInclusive',
            value: 40
          },
          {
            fact: 'personalFoulCount',
            operator: 'greaterThanInclusive',
            value: 5
          }
        ]
      },
      {
        all: [
          {
            fact: 'gameDuration',
            operator: 'lessThanInclusive',
            value: 48
          },
          {
            fact: 'personalFoulCount',
            operator: 'greaterThanInclusive',
            value: 6
          }
        ]
      }
    ]
  },
  event: {
    // define the event to fire when the conditions evaluate truthy
    type: 'fouledOut',
    params: {
      message: 'Player has fouled out!'
    }
  }
});

engine.addRule({
    conditions: {
        any: [{
            all: [{
                fact: 'gameDuration',
                operator: 'lessThanInclusive',
                value: 35
            }, {
                fact: 'personalFoulCount',
                operator: 'greaterThanInclusive',
                value: 4
            }]
        }]
    },
    event: {  // define the event to fire when the conditions evaluate truthy
        type: 'warned',
        params: {
            message: 'Player got a warning!'
        }
    }
});

engine.addRule({
    conditions: {
        any: [{
            all: [{
                fact: 'gameDuration',
                operator: 'greaterThan',
                value: 48
            }]
        }]
    },
    event: {  // define the event to fire when the conditions evaluate truthy
        type: 'userError',
        params: {
            message: 'A basketball game only has 48 minutes'
        }
    }
});

/**
 * Some example facts, the first one is used by default when the rule is not defined in the request
 */
const factCollection = [
  {
    personalFoulCount: 6,
    gameDuration: 40
  },
  {
    personalFoulCount: 4,
    gameDuration: 30
  }
]

const httpTrigger: AzureFunction = async function (
  context: Context,
  req: HttpRequest
): Promise<void> {
  context.log('Rule experiment processed a request.');
  const body = req.body || factCollection[0];

  // Run the engine to evaluate

  const results = await engine.run(body);

  context.res = {
    // status: 200, /* Defaults to 200 */
    body: results,
    headers: {
      'Content-Type': 'application/json'
    }
  }
}

export default httpTrigger