Rule Engine with AST

This is a Rule Engine with AST. It is an implementation of Rule Engine with AST in Javascript. It is a rule engine that uses AST to evaluate JSON data against a given rule string or multiple rule strings that are combined into a single AST and then evaluates the JSON data against the AST. It can be used to perform the following tasks:

Create a new AST from a given rule string
Combine multiple rule strings into a single AST
Evaluate a JSON data against the AST

Data Structure and Database schema

Data Structure

I used a node with left and right pointer to create a tree like structure for easy evaluation.

It is basically of two types:

Operator:

{
  "type": "operator",
  "left": Node,
  "right": Node,
  "value": string ("AND" or "OR")
}

Operand(leaf node):

{
  "type": "operand",
  "left": null,
  "right": null,
  "value": string (e.g. "Salary>50000")
}

Database schema

Rule:

{
  "name": string,
  "description": string,
  "ruleString": string(e.g. "(age > 30 AND department = 'Marketing')"),
  "ast": Node,
  "createdAt": date,
  "updatedAt": date,
}

Features

Some features of the RuleEngine:

Parsed the rule string in Linear Time
Easy to add more operators or add priority to operators in future
Implemented error handling in Rule string parsing like invalid syntax and invalid type comparison.
Used promise in rule evaluation for parallel processing to fasten the process

Usage

Run git clone in terminal

 git clone https://github.com/jatinxkirito/RuleEngine_ATS.git

In zeotap_backend folder
- Create config.env file with following content
```
 DATABASE_LINK="Your MongoDB database link"
```
- Run following in terminal
```
  npm install
  npm start
```
In zeotap__frontend folder
- Run following in terminal
```
  npm install
  npm run dev
```
Open http://localhost:5173 in you browser
To run tests, go to zeotap_backend folder and run following command in terminal
```
 npx mocha --file test/testSetup.js test/**/*.test.js
```