Full application rewrite

internal/metadata/default.go

@@ -0,0 +1,53 @@
+package metadata
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"path/filepath"
+	"strings"
+	"time"
+)
+
+const timeFormat = "20060102_150405"
+
+var (
+	ErrBadPrefix     = errors.New("bad prefix")
+	ErrBadNameFormat = errors.New("bad name format")
+)
+
+type Default struct {
+	TimeFormat string
+	Prefix     string
+}
+
+func (d *Default) Extract(fp string, _ io.Reader) (Metadata, error) {
+	format := d.TimeFormat
+	if format == "" {
+		format = timeFormat
+	}
+
+	if d.Prefix != "" && !strings.HasPrefix(fp, d.Prefix) {
+		return Metadata{}, fmt.Errorf("%w: expect a prefix %s, got %s", ErrBadPrefix, d.Prefix, fp)
+	}
+
+	fp = filepath.Base(fp)
+
+	leftLimit := len(d.Prefix)
+	rightLimit := leftLimit + len(format)
+
+	if len(fp) < rightLimit {
+		return Metadata{}, fmt.Errorf("%w: too short", ErrBadNameFormat)
+	}
+
+	created, err := time.Parse(format, fp[leftLimit:rightLimit])
+	if err != nil {
+		return Metadata{}, fmt.Errorf("parse time: %w", err)
+	}
+
+	meta := Metadata{
+		Created: created,
+	}
+
+	return meta, nil
+}