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
| expression | meaning |
|---|---|
| eq | equals to |
| == | equals to |
| ne | not equal to |
| != | not equal to |
| lt | less than |
| < | less than |
| gt | greater than |
| > | greater than |
| le | less than or equal to |
| <= | less than or equal to |
| ge | greater than or equal to |
| >= | greater than or equal to |
| co | contains |
| sw | starts with |
| ew | ends with |
| in | in a list |
| pr | present, will be true if you have a key as true |
| 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:-ois the output directory, make sure all the stuff it generates is in theparserdirectory of the root repo folder)