nikunjy / Rules
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Golang Rules Engine
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
- 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.
- After taking a look at the antlr tutorial, you can extend the JsonQuery.g4 file.
- 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 theparser
directory of the root repo folder)