/rules-ticks

Generic Rules engine in golang

Primary LanguageGoMIT LicenseMIT

Golang Rules Engine Build Status codecov

Rules engine written in golang with the help of antlr.

This package will be very helpful in situations where you have a generic rule and want to verify if your values (specified using map[string]interface{}) satisfy the rule.

Here are some examples:

  parser.Evaluate("x eq 1", map[string]interface{}{"x": 1})
  parser.Evaluate("x == 1", map[string]interface{}{"x": 1})
  parser.Evaluate("x lt 1", map[string]interface{}{"x": 1})
  parser.Evaluate("x < 1", map[string]interface{}{"x": 1})
  parser.Evaluate("x gt 1", map[string]interface{}{"x": 1})
  
  parser.Evaluate("x.a == 1 and x.b.c <= 2", map[string]interface{}{
    "x": map[string]interface{}{
       "a": 1,
       "b": map[string]interface{}{
          "c": 2,
       },
    },
  })
  

  parser.Evaluate("y == 4 and (x > 1)", map[string]interface{}{"x": 1})

  parser.Evaluate("y == 4 and (x IN [1,2,3])", map[string]interface{}{"x": 1})

  parser.Evaluate("y == 4 and (x eq 1.2.3)", map[string]interface{}{"x": "1.2.3"})

Operations

All the operations can be written capitalized or lowercase (ex: eq or EQ can be used)

Logical Operations supported are AND OR

Compare Expression and their definitions (a|b means you can use either one of the two a or b):

eq|==: equals to 
ne|!=: not equals to
lt|<: less than 
gt|>: greater than
le|<=: less than equal to
ge|>=: greater than equal to 
co: contains 
sw: starts with 
ew: ends with
in: in a list
pr: present
not: not of a logical expression

How to use it

Use your dependency manager to import github.com/nikunjy/rules/parser. This will let you parse a rule and keep the parsed representation around. Alternatively, you can also use github.com/nikunjy/rules directly to call the root Evaluate(string, map[string]interface{}) method.

I would recommend importing github.com/nikunjy/rules/parser

How to extend the grammar

  1. Please look at this antlr tutorial, the link will show you how to setup antlr. The article has a whole lot of detail about antlr I encourage you to read it, you might also like my blog post about this repo.
  2. After taking a look at the antlr tutorial, you can extend the JsonQuery.g4 file.
  3. Compile the parser antlr4 -Dlanguage=Go -visitor -no-listener JsonQuery.g4 -o ./ (Note: -o is the output directory, make sure all the stuff it generates is in the parser directory of the root repo folder)