add some string processors

internal/processing/string-filter.go

@@ -0,0 +1,59 @@
+package processing
+
+import (
+	"context"
+	"fmt"
+	"regexp"
+)
+
+type StringFilter struct {
+	config  ProcessorConfig
+	Pattern *regexp.Regexp
+}
+
+func (se *StringFilter) Process(ctx context.Context, payload any) (any, error) {
+	payloadString, ok := payload.(string)
+
+	if !ok {
+		return nil, fmt.Errorf("string.filter processor only accepts a string")
+	}
+
+	if !se.Pattern.MatchString(payloadString) {
+		return nil, nil
+	}
+
+	return payloadString, nil
+}
+
+func (se *StringFilter) Type() string {
+	return se.config.Type
+}
+
+func init() {
+	RegisterProcessor(ProcessorRegistration{
+		Type: "string.filter",
+		New: func(config ProcessorConfig) (Processor, error) {
+			params := config.Params
+
+			pattern, ok := params["pattern"]
+
+			if !ok {
+				return nil, fmt.Errorf("http.request.filter requires an pattern parameter")
+			}
+
+			patternString, ok := pattern.(string)
+
+			if !ok {
+				return nil, fmt.Errorf("http.request.filter pattern must be a string")
+			}
+
+			patternRegexp, err := regexp.Compile(fmt.Sprintf("^%s$", patternString))
+
+			if err != nil {
+				return nil, err
+			}
+
+			return &StringFilter{config: config, Pattern: patternRegexp}, nil
+		},
+	})
+}