feat(binana): add tokens database

go/app/util/dbutil/writer.go

@@ -0,0 +1,80 @@
+package dbutil
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"os"
+
+	"github.com/parquet-go/parquet-go"
+)
+
+type Writer[T any] struct {
+	write func([]T) (err error)
+	close func() (err error)
+}
+
+func (writer *Writer[T]) WriteEntries(entries []T) (err error) {
+	err = writer.write(entries)
+	return
+}
+
+func (writer *Writer[T]) Close() (err error) {
+	err = writer.close()
+	return
+}
+
+func Open[T any](name string, format DatabaseFormat) (writer *Writer[T], err error) {
+	writer = new(Writer[T])
+	var (
+		file   *os.File
+		output io.Writer
+	)
+	if name == "" {
+		output = os.Stdout
+	} else {
+		file, err = os.Create(name)
+		if err != nil {
+			return
+		}
+		output = file
+	}
+	switch format {
+
+	case DatabaseJSON:
+		encoder := json.NewEncoder(output)
+		writer.write = func(entries []T) (err error) {
+			for _, entry := range entries {
+				if err = encoder.Encode(&entry); err != nil {
+					return
+				}
+			}
+			return
+		}
+		writer.close = func() (err error) {
+			if file != nil {
+				err = file.Close()
+			}
+			return
+		}
+	case DatabaseParquet:
+		generic_writer := parquet.NewGenericWriter[T](output)
+		writer.write = func(entries []T) (err error) {
+			_, err = generic_writer.Write(entries)
+			return
+		}
+		writer.close = func() (err error) {
+			if err = generic_writer.Close(); err != nil {
+				return
+			}
+			if file != nil {
+				err = file.Close()
+			}
+
+			return
+		}
+	default:
+		err = fmt.Errorf("%w: %d", ErrUnknownDatabaseFormat, format)
+	}
+	return
+}