52 lines
1.8 KiB
Go
52 lines
1.8 KiB
Go
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// bexpr is an implementation of a generic boolean expression evaluator.
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// The general goal is to be able to evaluate some expression against some
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// arbitrary data and get back a boolean of whether or not the data
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// was matched by the expression
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package bexpr
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//go:generate pigeon -o grammar/grammar.go -optimize-parser grammar/grammar.peg
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//go:generate goimports -w grammar/grammar.go
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import (
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"github.com/hashicorp/go-bexpr/grammar"
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"github.com/mitchellh/pointerstructure"
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)
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// HookFn provides a way to translate one reflect.Value to another during
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// evaluation by bexpr. This facilitates making Go structures appear in a way
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// that matches the expected JSON Pointers used for evaluation. This is
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// helpful, for example, when working with protocol buffers' well-known types.
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type ValueTransformationHookFn = pointerstructure.ValueTransformationHookFn
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type Evaluator struct {
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// The syntax tree
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ast grammar.Expression
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tagName string
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valueTransformationHook ValueTransformationHookFn
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}
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func CreateEvaluator(expression string, opts ...Option) (*Evaluator, error) {
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parsedOpts := getOpts(opts...)
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var parserOpts []grammar.Option
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if parsedOpts.withMaxExpressions != 0 {
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parserOpts = append(parserOpts, grammar.MaxExpressions(parsedOpts.withMaxExpressions))
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}
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ast, err := grammar.Parse("", []byte(expression), parserOpts...)
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if err != nil {
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return nil, err
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}
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eval := &Evaluator{
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ast: ast.(grammar.Expression),
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tagName: parsedOpts.withTagName,
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valueTransformationHook: parsedOpts.withHookFn,
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}
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return eval, nil
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}
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func (eval *Evaluator) Evaluate(datum interface{}) (bool, error) {
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return evaluate(eval.ast, datum, WithTagName(eval.tagName), WithHookFn(eval.valueTransformationHook))
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}
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