add midi message type filter

internal/processor/midi-message-filter.go

@@ -0,0 +1,55 @@
+//go:build cgo
+
+package processor
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/jwetzell/showbridge-go/internal/config"
+	"gitlab.com/gomidi/midi/v2"
+)
+
+type MIDIMessageFilter struct {
+	config   config.ProcessorConfig
+	MIDIType string
+}
+
+func (mmf *MIDIMessageFilter) Process(ctx context.Context, payload any) (any, error) {
+	payloadMessage, ok := payload.(midi.Message)
+
+	if !ok {
+		return nil, fmt.Errorf("midi.message.filter processor only accepts an midi.Message")
+	}
+
+	if payloadMessage.Type().String() != mmf.MIDIType {
+		return nil, nil
+	}
+
+	return payloadMessage, nil
+}
+
+func (mmf *MIDIMessageFilter) Type() string {
+	return mmf.config.Type
+}
+
+func init() {
+	RegisterProcessor(ProcessorRegistration{
+		Type: "midi.message.filter",
+		New: func(config config.ProcessorConfig) (Processor, error) {
+			params := config.Params
+			midiType, ok := params["type"]
+
+			if !ok {
+				return nil, fmt.Errorf("midi.message.filter requires a type parameter")
+			}
+			midiTypeString, ok := midiType.(string)
+
+			if !ok {
+				return nil, fmt.Errorf("midi.message.filter type must be a string")
+			}
+
+			return &MIDIMessageFilter{config: config, MIDIType: midiTypeString}, nil
+		},
+	})
+}