add expr lang processor

internal/processing/debug-expr.go

@@ -0,0 +1,57 @@
+package processing
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/expr-lang/expr"
+	"github.com/expr-lang/expr/vm"
+)
+
+// NOTE(jwetzell): see language definition https://expr-lang.org/docs/language-definition
+type DebugExpr struct {
+	config  ProcessorConfig
+	Program *vm.Program
+}
+
+func (dl *DebugExpr) Process(ctx context.Context, payload any) (any, error) {
+
+	output, err := expr.Run(dl.Program, payload)
+	if err != nil {
+		return nil, err
+	}
+
+	return output, nil
+}
+
+func (dl *DebugExpr) Type() string {
+	return dl.config.Type
+}
+
+func init() {
+	RegisterProcessor(ProcessorRegistration{
+		Type: "debug.expr",
+		New: func(config ProcessorConfig) (Processor, error) {
+			params := config.Params
+
+			expression, ok := params["expression"]
+
+			if !ok {
+				return nil, fmt.Errorf("debug.expr requires an expression parameter")
+			}
+
+			expressionString, ok := expression.(string)
+
+			if !ok {
+				return nil, fmt.Errorf("debug.expr url must be a string")
+			}
+
+			program, err := expr.Compile(expressionString)
+			if err != nil {
+				return nil, err
+			}
+
+			return &DebugExpr{config: config, Program: program}, nil
+		},
+	})
+}