judge_json

An Elixir rule engine where rules are json objects. The judge gives verdicts on data and returns any matched rules.

Installation

If available in Hex, the package can be installed by adding judge_json to your list of dependencies in mix.exs:

def deps do
  [
    {:judge_json, "~> 0.1.0"}
  ]
end

Documentation can be generated with ExDoc and published on HexDocs. Once published, the docs can be found at https://hexdocs.pm/judge_json.

About

This project is inspired by:

• https://github.com/santalvarez/python-rule-engine
• https://github.com/CacheControl/json-rules-engine

Quick Start Example

{
    "data": {
        "person": {
            "name": "Lionel",
            "last_name": "Messi",
            "likes": [
                "soccer",
                "hot dogs",
                "sports"
            ]
        }
    },
    "rules": [
        {
            "id": "123456",
            "conditions": {
                "all": [
                    {
                        "path": "/person/name",
                        "operator": "equal",
                        "value": "Lionel"
                    },
                    {
                        "path": "/person/last_name",
                        "operator": "equal",
                        "value": "Messi"
                    },
                    {
                        "path": "/person/likes",
                        "operator": "contains",
                        "value": "soccer"
                    }
                ]
            },
            "action": "collect_signature.exs"
        }
    ]
}

iex> JudgeJson.evaluate(payload)

Return is an array of matched rules

Rule Schema

The rule schema is very flexible and the only strict requirements are on the conditions. You can add your own rule id and action schema. If a rule is matched, the entire object is returned.

Judge Json is storage and action agnostic. Ideally you can store/load rules from a DB and evaluate on incoming json payloads. Handler code can then evaluate rules and action however you like.

Example:

{
    "id": "",
    "conditions": {},
    "action": {}
}

Conditions

Conditions consist of a path, operator, and value. Example:

{
    "path": "/person/name",
    "operator": "contains",
    "value": "ABC"
}

Path

A rfc json-pointer for the supplied json payload.

Operators

• equal
• not_equal
• greater_than
• less_than
• contains
• not_contains
• like
• regex_match

Value

The value to match or operate on

Condition sets

Features:

• all (and) condition sets
• any (or) condition sets
• sets can be nested

Example:

{
    "any": [
        {
            "path": "/source",
            "operator": "contains",
            "value": "X"
        },
        {
            "path": "/product",
            "operator": "contains",
            "value": "Y"
        }
    ]
}

Example:

{
    "all": [
        {
            "path": "/name",
            "operator": "equal",
            "value": "A"
        },
        {
            "any": [
                {
                    "path": "/source",
                    "operator": "contains",
                    "value": "X"
                },
                {
                    "path": "/product",
                    "operator": "contains",
                    "value": "Y"
                }
            ]
        }
    ]
}