codebeat: Code quality improvement (#103)

* codebeat: improve & bugfix

* codebeat: refactor to improve readability

* bugfix

* bugfix

* internal/data/codec: improve code coverage

bitcask.go

@@ -284,61 +284,17 @@ func (b *Bitcask) reopen() error {
 	b.mu.Lock()
 	defer b.mu.Unlock()
 
-	fns, err := internal.GetDatafiles(b.path)
+	datafiles, lastID, err := loadDatafiles(b.path, b.config.MaxKeySize, b.config.MaxValueSize)
 	if err != nil {
 		return err
 	}
 
-	ids, err := internal.ParseIds(fns)
+	t, err := loadIndex(b.path, b.indexer, b.config.MaxKeySize, datafiles)
 	if err != nil {
 		return err
 	}
 
-	datafiles := make(map[int]data.Datafile, len(ids))
-
-	for _, id := range ids {
-		df, err := data.NewDatafile(b.path, id, true, b.config.MaxKeySize, b.config.MaxValueSize)
-		if err != nil {
-			return err
-		}
-		datafiles[id] = df
-	}
-
-	t, found, err := b.indexer.Load(filepath.Join(b.path, "index"), b.config.MaxKeySize)
-	if err != nil {
-		return err
-	}
-	if !found {
-		for i, df := range datafiles {
-			var offset int64
-			for {
-				e, n, err := df.Read()
-				if err != nil {
-					if err == io.EOF {
-						break
-					}
-					return err
-				}
-
-				// Tombstone value  (deleted key)
-				if len(e.Value) == 0 {
-					t.Delete(e.Key)
-					offset += n
-					continue
-				}
-				item := internal.Item{FileID: ids[i], Offset: offset, Size: n}
-				t.Insert(e.Key, item)
-				offset += n
-			}
-		}
-	}
-
-	var id int
-	if len(ids) > 0 {
-		id = ids[(len(ids) - 1)]
-	}
-
-	curr, err := data.NewDatafile(b.path, id, false, b.config.MaxKeySize, b.config.MaxValueSize)
+	curr, err := data.NewDatafile(b.path, lastID, false, b.config.MaxKeySize, b.config.MaxValueSize)
 	if err != nil {
 		return err
 	}
@@ -486,3 +442,60 @@ func Open(path string, options ...Option) (*Bitcask, error) {
 
 	return bitcask, nil
 }
+
+func loadDatafiles(path string, maxKeySize uint32, maxValueSize uint64) (datafiles map[int]data.Datafile, lastID int, err error) {
+	fns, err := internal.GetDatafiles(path)
+	if err != nil {
+		return nil, 0, err
+	}
+
+	ids, err := internal.ParseIds(fns)
+	if err != nil {
+		return nil, 0, err
+	}
+
+	datafiles = make(map[int]data.Datafile, len(ids))
+	for _, id := range ids {
+		datafiles[id], err = data.NewDatafile(path, id, true, maxKeySize, maxValueSize)
+		if err != nil {
+			return
+		}
+
+	}
+	if len(ids) > 0 {
+		lastID = ids[len(ids)-1]
+	}
+	return
+}
+
+func loadIndex(path string, indexer index.Indexer, maxKeySize uint32, datafiles map[int]data.Datafile) (art.Tree, error) {
+	t, found, err := indexer.Load(filepath.Join(path, "index"), maxKeySize)
+	if err != nil {
+		return nil, err
+	}
+	if !found {
+		for _, df := range datafiles {
+			var offset int64
+			for {
+				e, n, err := df.Read()
+				if err != nil {
+					if err == io.EOF {
+						break
+					}
+					return nil, err
+				}
+
+				// Tombstone value  (deleted key)
+				if len(e.Value) == 0 {
+					t.Delete(e.Key)
+					offset += n
+					continue
+				}
+				item := internal.Item{FileID: df.FileID(), Offset: offset, Size: n}
+				t.Insert(e.Key, item)
+				offset += n
+			}
+		}
+	}
+	return t, nil
+}