Introduction

This package was created with inspiration from Thomas' go-ruler to run a simple set of rules against an entity.

This version includes a couple more features including, AND and OR composites and the ability to add custom comparators.

Note: This package only compares two types: string and float64, this plays nicely with encoding/json.

Example

// Create a new instance of an engine with some default comparators
e := NewEngine()

// Add a new, custom comparator
e = e.AddComparator("always-false", func(a, b interface{}) bool {
    return false
})

// Create composites, with rules for the engine to evaluate
e.Composites = []Composite{
    Composite{
        Operator: OperatorOr,
        Rules: []Rule{
            Rule{
                Comparator: "always-false",
                Path: "user.name",
                Value: "Trevor",
            },
            Rule{
                Comparator: "eq",
                Path: "user.name",
                Value: "Trevor",
            },
        },
    },
}

// Give some properties, this map can be deeper and supports interfaces
props := map[string]interface{}{
    "user": map[string]interface{}{
        "name": "Trevor",
    }
}

// Run the engine on the props
res := e.Evaluate(props)
// res == true

Comparators

• eq will return true if a == b
• neq will return true if a != b
• lt will return true if a < b
• lte will return true if a <= b
• gt will return true if a > b
• gte will return true if a >= b
• contains will return true if a contains b
• oneof will return true if a is one of b

contains is different than oneof in that contains expects the first argument to be a slice, and oneof expects the second argument to be a slice.

Benchmarks

Benchmark	N	Speed	Used	Allocs
BenchmarkEqual-8	1000000000	7.26 ns/op	0 B/op	0 allocs/op
BenchmarkNotEqual-8	1000000000	4.95 ns/op	0 B/op	0 allocs/op
BenchmarkLessThan-8	500000000	10.9 ns/op	0 B/op	0 allocs/op
BenchmarkLessThanEqual-8	1000000000	7.79 ns/op	0 B/op	0 allocs/op
BenchmarkGreaterThan-8	200000000	18.1 ns/op	0 B/op	0 allocs/op
BenchmarkGreaterThanEqual-8	300000000	13.9 ns/op	0 B/op	0 allocs/op
BenchmarkContains-8	50000000	73.0 ns/op	64 B/op	2 allocs/op
BenchmarkContainsLong50000-8	100000000	55.6 ns/op	32 B/op	1 allocs/op
BenchmarkNotContains-8	50000000	75.1 ns/op	64 B/op	2 allocs/op
BenchmarkNotContainsLong50000-8	100000000	56.2 ns/op	32 B/op	1 allocs/op
BenchmarkPluckShallow-8	100000000	60.2 ns/op	16 B/op	1 allocs/op
BenchmarkPluckDeep-8	20000000	242 ns/op	112 B/op	1 allocs/op

To run benchmarks:

go test -run none -bench . -benchtime 3s -benchmem

License

Copyright © 2018 Trevor Hutto

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this work except in compliance with the License. You may obtain a copy of the License in the LICENSE file, or at:

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.