From ed87ae51c0fa42f9523a9df4d87d452452d1fd84 Mon Sep 17 00:00:00 2001
From: Nick Craig-Wood <nick@craig-wood.com>
Date: Wed, 29 Jun 2022 14:29:15 +0100
Subject: [PATCH] union: support metadata

---
 backend/union/entry.go             | 47 +++++++++++++++++++++++++--
 backend/union/union.go             |  8 ++++-
 backend/union/upstream/upstream.go | 52 ++++++++++++++++++++++++++++++
 3 files changed, 103 insertions(+), 4 deletions(-)

diff --git a/backend/union/entry.go b/backend/union/entry.go
index efd2cbaef..023f3bb45 100644
--- a/backend/union/entry.go
+++ b/backend/union/entry.go
@@ -2,6 +2,7 @@ package union
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -34,9 +35,8 @@ type entry interface {
 	candidates() []upstream.Entry
 }
 
-// UnWrap returns the Object that this Object is wrapping or
-// nil if it isn't wrapping anything
-func (o *Object) UnWrap() *upstream.Object {
+// UnWrapUpstream returns the upstream Object that this Object is wrapping
+func (o *Object) UnWrapUpstream() *upstream.Object {
 	return o.Object
 }
 
@@ -140,6 +140,42 @@ func (o *Object) SetModTime(ctx context.Context, t time.Time) error {
 	return errs.Err()
 }
 
+// GetTier returns storage tier or class of the Object
+func (o *Object) GetTier() string {
+	do, ok := o.Object.Object.(fs.GetTierer)
+	if !ok {
+		return ""
+	}
+	return do.GetTier()
+}
+
+// ID returns the ID of the Object if known, or "" if not
+func (o *Object) ID() string {
+	do, ok := o.Object.Object.(fs.IDer)
+	if !ok {
+		return ""
+	}
+	return do.ID()
+}
+
+// MimeType returns the content type of the Object if known
+func (o *Object) MimeType(ctx context.Context) (mimeType string) {
+	if do, ok := o.Object.Object.(fs.MimeTyper); ok {
+		mimeType = do.MimeType(ctx)
+	}
+	return mimeType
+}
+
+// SetTier performs changing storage tier of the Object if
+// multiple storage classes supported
+func (o *Object) SetTier(tier string) error {
+	do, ok := o.Object.Object.(fs.SetTierer)
+	if !ok {
+		return errors.New("underlying remote does not support SetTier")
+	}
+	return do.SetTier(tier)
+}
+
 // ModTime returns the modification date of the directory
 // It returns the latest ModTime of all candidates
 func (d *Directory) ModTime(ctx context.Context) (t time.Time) {
@@ -164,3 +200,8 @@ func (d *Directory) Size() (s int64) {
 	}
 	return s
 }
+
+// Check the interfaces are satisfied
+var (
+	_ fs.FullObject = (*Object)(nil)
+)
diff --git a/backend/union/union.go b/backend/union/union.go
index 9776c55d2..e1ec53e85 100644
--- a/backend/union/union.go
+++ b/backend/union/union.go
@@ -30,6 +30,9 @@ func init() {
 		Name:        "union",
 		Description: "Union merges the contents of several upstream fs",
 		NewFs:       NewFs,
+		MetadataInfo: &fs.MetadataInfo{
+			Help: `Any metadata supported by the underlying remote is read and written.`,
+		},
 		Options: []fs.Option{{
 			Name:     "upstreams",
 			Help:     "List of space separated upstreams.\n\nCan be 'upstreama:test/dir upstreamb:', '\"upstreama:test/space:ro dir\" upstreamb:', etc.",
@@ -219,7 +222,7 @@ func (f *Fs) Copy(ctx context.Context, src fs.Object, remote string) (fs.Object,
 		fs.Debugf(src, "Can't copy - not same remote type")
 		return nil, fs.ErrorCantCopy
 	}
-	o := srcObj.UnWrap()
+	o := srcObj.UnWrapUpstream()
 	su := o.UpstreamFs()
 	if su.Features().Copy == nil {
 		return nil, fs.ErrorCantCopy
@@ -881,6 +884,9 @@ func NewFs(ctx context.Context, name, root string, m configmap.Mapper) (fs.Fs, e
 		BucketBased:             true,
 		SetTier:                 true,
 		GetTier:                 true,
+		ReadMetadata:            true,
+		WriteMetadata:           true,
+		UserMetadata:            true,
 	}).Fill(ctx, f)
 	canMove := true
 	for _, f := range upstreams {
diff --git a/backend/union/upstream/upstream.go b/backend/union/upstream/upstream.go
index 1a85d783f..c6e906107 100644
--- a/backend/union/upstream/upstream.go
+++ b/backend/union/upstream/upstream.go
@@ -245,6 +245,53 @@ func (o *Object) Update(ctx context.Context, in io.Reader, src fs.ObjectInfo, op
 	return nil
 }
 
+// GetTier returns storage tier or class of the Object
+func (o *Object) GetTier() string {
+	do, ok := o.Object.(fs.GetTierer)
+	if !ok {
+		return ""
+	}
+	return do.GetTier()
+}
+
+// ID returns the ID of the Object if known, or "" if not
+func (o *Object) ID() string {
+	do, ok := o.Object.(fs.IDer)
+	if !ok {
+		return ""
+	}
+	return do.ID()
+}
+
+// MimeType returns the content type of the Object if known
+func (o *Object) MimeType(ctx context.Context) (mimeType string) {
+	if do, ok := o.Object.(fs.MimeTyper); ok {
+		mimeType = do.MimeType(ctx)
+	}
+	return mimeType
+}
+
+// SetTier performs changing storage tier of the Object if
+// multiple storage classes supported
+func (o *Object) SetTier(tier string) error {
+	do, ok := o.Object.(fs.SetTierer)
+	if !ok {
+		return errors.New("underlying remote does not support SetTier")
+	}
+	return do.SetTier(tier)
+}
+
+// Metadata returns metadata for an object
+//
+// It should return nil if there is no Metadata
+func (o *Object) Metadata(ctx context.Context) (fs.Metadata, error) {
+	do, ok := o.Object.(fs.Metadataer)
+	if !ok {
+		return nil, nil
+	}
+	return do.Metadata(ctx)
+}
+
 // About gets quota information from the Fs
 func (f *Fs) About(ctx context.Context) (*fs.Usage, error) {
 	if atomic.LoadInt64(&f.cacheExpiry) <= time.Now().Unix() {
@@ -363,3 +410,8 @@ func (f *Fs) updateUsageCore(lock bool) error {
 	f.usage = usage
 	return nil
 }
+
+// Check the interfaces are satisfied
+var (
+	_ fs.FullObject = (*Object)(nil)
+)