feat: rewriter layer

internal/rule/engine.go

@@ -0,0 +1,45 @@
+package rule
+
+import (
+	"github.com/expr-lang/expr"
+	"github.com/expr-lang/expr/vm"
+	"github.com/pkg/errors"
+)
+
+type Engine[E any] struct {
+	rules []*vm.Program
+}
+
+func (e *Engine[E]) Apply(env E) ([]any, error) {
+	results := make([]any, 0, len(e.rules))
+	for i, r := range e.rules {
+		result, err := expr.Run(r, env)
+		if err != nil {
+			return nil, errors.Wrapf(err, "could not run rule #%d", i)
+		}
+
+		results = append(results, result)
+	}
+
+	return results, nil
+}
+
+func NewEngine[E any](funcs ...OptionFunc) (*Engine[E], error) {
+	opts := NewOptions(funcs...)
+
+	engine := &Engine[E]{
+		rules: make([]*vm.Program, 0, len(opts.Rules)),
+	}
+
+	for i, r := range opts.Rules {
+
+		program, err := expr.Compile(r, opts.Expr...)
+		if err != nil {
+			return nil, errors.Wrapf(err, "could not compile rule #%d", i)
+		}
+
+		engine.rules = append(engine.rules, program)
+	}
+
+	return engine, nil
+}