Added support for Badger as an alternative storage backend

internal/datastore/badger_datastore/document_iterator.go

@@ -0,0 +1,60 @@
+package badgerdatastore
+
+import (
+	"bytes"
+	"encoding/gob"
+
+	"github.com/dgraph-io/badger/v4"
+	"github.com/pikami/cosmium/internal/datastore"
+	"github.com/pikami/cosmium/internal/logger"
+)
+
+type BadgerDocumentIterator struct {
+	txn    *badger.Txn
+	it     *badger.Iterator
+	prefix string
+}
+
+func NewBadgerDocumentIterator(txn *badger.Txn, prefix string) *BadgerDocumentIterator {
+	opts := badger.DefaultIteratorOptions
+	opts.Prefix = []byte(prefix)
+
+	it := txn.NewIterator(opts)
+	it.Rewind()
+
+	return &BadgerDocumentIterator{
+		txn:    txn,
+		it:     it,
+		prefix: prefix,
+	}
+}
+
+func (i *BadgerDocumentIterator) Next() (datastore.Document, datastore.DataStoreStatus) {
+	if !i.it.Valid() {
+		i.it.Close()
+		return datastore.Document{}, datastore.IterEOF
+	}
+
+	item := i.it.Item()
+	val, err := item.ValueCopy(nil)
+	if err != nil {
+		logger.ErrorLn("Error while copying value:", err)
+		return datastore.Document{}, datastore.Unknown
+	}
+
+	current := &datastore.Document{}
+	err = gob.NewDecoder(bytes.NewReader(val)).Decode(current)
+	if err != nil {
+		logger.ErrorLn("Error while decoding value:", err)
+		return datastore.Document{}, datastore.Unknown
+	}
+
+	i.it.Next()
+
+	return *current, datastore.StatusOk
+}
+
+func (i *BadgerDocumentIterator) Close() {
+	i.it.Close()
+	i.txn.Discard()
+}