Printer module

Author: aopoltorzhicky

pkg/modules/printer/module.go

@@ -0,0 +1,95 @@
+package printer
+
+import (
+	"context"
+	"fmt"
+	"sync"
+
+	"github.com/dipdup-net/indexer-sdk/pkg/modules"
+	"github.com/pkg/errors"
+	"github.com/rs/zerolog/log"
+)
+
+// input name
+const (
+	InputName = "input"
+)
+
+// Printer - the structure which is responsible for print received messages
+type Printer struct {
+	input *modules.Input
+
+	wg *sync.WaitGroup
+}
+
+// NewPrinter - constructor of printer structure
+func NewPrinter() *Printer {
+	return &Printer{
+		input: modules.NewInput(InputName),
+
+		wg: new(sync.WaitGroup),
+	}
+}
+
+// Name -
+func (printer *Printer) Name() string {
+	return "printer"
+}
+
+// Input - returns input by name
+func (printer *Printer) Input(name string) (*modules.Input, error) {
+	switch name {
+	case InputName:
+		return printer.input, nil
+	default:
+		return nil, errors.Wrap(modules.ErrUnknownInput, name)
+	}
+}
+
+// Output - returns output by name
+func (printer *Printer) Output(name string) (*modules.Output, error) {
+	return nil, errors.Wrap(modules.ErrUnknownOutput, name)
+}
+
+// AttachTo - attach input to output with name
+func (printer *Printer) AttachTo(name string, input *modules.Input) error {
+	output, err := printer.Output(name)
+	if err != nil {
+		return err
+	}
+	output.Attach(input)
+	return nil
+}
+
+// Close - gracefully stops module
+func (printer *Printer) Close() error {
+	printer.wg.Wait()
+
+	if err := printer.input.Close(); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// Start - starts module
+func (printer *Printer) Start(ctx context.Context) {
+	printer.wg.Add(1)
+	go printer.listen(ctx)
+}
+
+func (printer *Printer) listen(ctx context.Context) {
+	defer printer.wg.Done()
+
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case msg, ok := <-printer.input.Listen():
+			if !ok {
+				return
+			}
+			log.Info().Str("obj_type", fmt.Sprintf("%T", msg)).Msgf("%##v", msg)
+		}
+	}
+}