add processor to pull method out of struct

internal/processor/struct-method-get.go

@@ -0,0 +1,65 @@
+package processor
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"reflect"
+
+	"github.com/jwetzell/showbridge-go/internal/config"
+)
+
+type StructMethodGet struct {
+	config config.ProcessorConfig
+	Name   string
+}
+
+func (sm *StructMethodGet) Process(ctx context.Context, payload any) (any, error) {
+	s := reflect.ValueOf(payload)
+
+	if s.Kind() != reflect.Struct {
+		return nil, errors.New("struct.method.get processor only accepts a struct payload")
+	}
+
+	method := s.MethodByName(sm.Name)
+	if !method.IsValid() {
+		return nil, fmt.Errorf("struct.method.get method '%s' does not exist", sm.Name)
+	}
+
+	value := method.Call(nil)
+
+	if len(value) == 0 {
+		return nil, nil
+	}
+
+	if len(value) == 1 {
+		return value[0].Interface(), nil
+	}
+
+	results := make([]any, len(value))
+
+	for i, v := range value {
+		results[i] = v.Interface()
+	}
+
+	return results, nil
+}
+
+func (sm *StructMethodGet) Type() string {
+	return sm.config.Type
+}
+
+func init() {
+	RegisterProcessor(ProcessorRegistration{
+		Type: "struct.method.get",
+		New: func(config config.ProcessorConfig) (Processor, error) {
+			params := config.Params
+			nameString, err := params.GetString("name")
+			if err != nil {
+				return nil, fmt.Errorf("struct.method.get name error: %w", err)
+			}
+
+			return &StructMethodGet{config: config, Name: nameString}, nil
+		},
+	})
+}