Reworked the way metadata/tags for files work. Simplified it at lot.

File Metadata.go

@@ -0,0 +1,62 @@
+/*
+File Name:  File Metadata.go
+Copyright:  2021 Peernet s.r.o.
+Author:     Peter Kleissner
+
+Metadata tags provide meta information about files.
+*/
+
+package core
+
+import (
+	"encoding/binary"
+	"errors"
+	"time"
+)
+
+// List of defined file tags.
+const (
+	TagName        = 0 // Name of file.
+	TagFolder      = 1 // Folder name.
+	TagDescription = 2 // Arbitrary description of the file. May contain hashtags.
+	TagDateShared  = 3 // When the file was published on the blockchain. Cannot be set manually (virtual read-only tag).
+	TagDateCreated = 4 // Date when the file was originally created. This may differ from the date in the block record, which indicates when the file was shared.
+)
+
+// Future tags to be defined for audio/video: Artist, Album, Title, Length, Bitrate, Codec
+// Windows list: https://docs.microsoft.com/en-us/windows/win32/wmdm/metadata-constants
+
+// ---- encoding ----
+
+// Date returns the tags data as date encoded
+func (tag *BlockRecordFileTag) Date() (time.Time, error) {
+	if len(tag.Data) != 8 {
+		return time.Time{}, errors.New("file tag date invalid size")
+	}
+
+	timeB := int64(binary.LittleEndian.Uint64(tag.Data[0:8]))
+	return time.Unix(timeB, 0).UTC(), nil
+}
+
+// Text returns the tags data as text encoded
+func (tag *BlockRecordFileTag) Text() string {
+	return string(tag.Data)
+}
+
+// IsVirtual checks if the tag is virtual.
+func (tag *BlockRecordFileTag) IsVirtual() bool {
+	return tag.Type == TagDateShared
+}
+
+// TagFromDate returns a tag from date
+func TagFromDate(Type uint16, Date time.Time) BlockRecordFileTag {
+	var tempDate [8]byte
+	binary.LittleEndian.PutUint64(tempDate[0:8], uint64(Date.UTC().Unix()))
+
+	return BlockRecordFileTag{Type: Type, Data: tempDate[:]}
+}
+
+// TagFromText returns a tag from text
+func TagFromText(Type uint16, Text string) BlockRecordFileTag {
+	return BlockRecordFileTag{Type: Type, Data: []byte(Text)}
+}