[chore] tidy up media manager, add calling func to errors, build-script improvements (#1835)

* media manager tidy-up: de-interface and remove unused PostDataFunc

Signed-off-by: kim <grufwub@gmail.com>

* remove last traces of media.Manager being an interface

Signed-off-by: kim <grufwub@gmail.com>

* update error to provide caller, allow tuneable via build tags

Signed-off-by: kim <grufwub@gmail.com>

* remove kim-specific build script changes

Signed-off-by: kim <grufwub@gmail.com>

* fix merge conflicts

Signed-off-by: kim <grufwub@gmail.com>

* update build-script to support externally setting build variables

Signed-off-by: kim <grufwub@gmail.com>

---------

Signed-off-by: kim <grufwub@gmail.com>

9 files changed, 140 insertions, 220 deletions

diff --git a/internal/media/manager.go b/internal/media/manager.go
index b12b6ace2..ec95b67e9 100644
--- a/internal/media/manager.go
+++ b/internal/media/manager.go
@@ -21,8 +21,10 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"io"
 	"time"
 
+	"codeberg.org/gruf/go-iotools"
 	"codeberg.org/gruf/go-runners"
 	"codeberg.org/gruf/go-sched"
 	"codeberg.org/gruf/go-store/v2/storage"
@@ -47,112 +49,7 @@ var SupportedEmojiMIMETypes = []string{
 	mimeImagePng,
 }
 
-// Manager provides an interface for managing media: parsing, storing, and retrieving media objects like photos, videos, and gifs.
-type Manager interface {
-	/*
-		PROCESSING FUNCTIONS
-	*/
-
-	// PreProcessMedia begins the process of decoding and storing the given data as an attachment.
-	// It will return a pointer to a ProcessingMedia struct upon which further actions can be performed, such as getting
-	// the finished media, thumbnail, attachment, etc.
-	//
-	// data should be a function that the media manager can call to return a reader containing the media data.
-	//
-	// postData will be called after data has been called; it can be used to clean up any remaining resources.
-	// The provided function can be nil, in which case it will not be executed.
-	//
-	// accountID should be the account that the media belongs to.
-	//
-	// ai is optional and can be nil. Any additional information about the attachment provided will be put in the database.
-	//
-	// Note: unlike ProcessMedia, this will NOT queue the media to be asynchronously processed.
-	PreProcessMedia(ctx context.Context, data DataFunc, postData PostDataCallbackFunc, accountID string, ai *AdditionalMediaInfo) (*ProcessingMedia, error)
-
-	// PreProcessMediaRecache refetches, reprocesses, and recaches an existing attachment that has been uncached via pruneRemote.
-	//
-	// Note: unlike ProcessMedia, this will NOT queue the media to be asychronously processed.
-	PreProcessMediaRecache(ctx context.Context, data DataFunc, postData PostDataCallbackFunc, attachmentID string) (*ProcessingMedia, error)
-
-	// ProcessMedia will call PreProcessMedia, followed by queuing the media to be processing in the media worker queue.
-	ProcessMedia(ctx context.Context, data DataFunc, postData PostDataCallbackFunc, accountID string, ai *AdditionalMediaInfo) (*ProcessingMedia, error)
-
-	// PreProcessEmoji begins the process of decoding and storing the given data as an emoji.
-	// It will return a pointer to a ProcessingEmoji struct upon which further actions can be performed, such as getting
-	// the finished media, thumbnail, attachment, etc.
-	//
-	// data should be a function that the media manager can call to return a reader containing the emoji data.
-	//
-	// postData will be called after data has been called; it can be used to clean up any remaining resources.
-	// The provided function can be nil, in which case it will not be executed.
-	//
-	// shortcode should be the emoji shortcode without the ':'s around it.
-	//
-	// id is the database ID that should be used to store the emoji.
-	//
-	// uri is the ActivityPub URI/ID of the emoji.
-	//
-	// ai is optional and can be nil. Any additional information about the emoji provided will be put in the database.
-	//
-	// Note: unlike ProcessEmoji, this will NOT queue the emoji to be asynchronously processed.
-	PreProcessEmoji(ctx context.Context, data DataFunc, postData PostDataCallbackFunc, shortcode string, id string, uri string, ai *AdditionalEmojiInfo, refresh bool) (*ProcessingEmoji, error)
-
-	// ProcessEmoji will call PreProcessEmoji, followed by queuing the emoji to be processing in the emoji worker queue.
-	ProcessEmoji(ctx context.Context, data DataFunc, postData PostDataCallbackFunc, shortcode string, id string, uri string, ai *AdditionalEmojiInfo, refresh bool) (*ProcessingEmoji, error)
-
-	/*
-		PRUNING/UNCACHING FUNCTIONS
-	*/
-
-	// PruneAll runs all of the below pruning/uncacheing functions, and then cleans up any resulting
-	// empty directories from the storage driver. It can be called as a shortcut for calling the below
-	// pruning functions one by one.
-	//
-	// If blocking is true, then any errors encountered during the prune will be combined + returned to
-	// the caller. If blocking is false, the prune is run in the background and errors are just logged
-	// instead.
-	PruneAll(ctx context.Context, mediaCacheRemoteDays int, blocking bool) error
-	// UncacheRemote uncaches all remote media attachments older than the given amount of days.
-	//
-	// In this context, uncacheing means deleting media files from storage and marking the attachment
-	// as cached=false in the database.
-	//
-	// If 'dry' is true, then only a dry run will be performed: nothing will actually be changed.
-	//
-	// The returned int is the amount of media that was/would be uncached by this function.
-	UncacheRemote(ctx context.Context, olderThanDays int, dry bool) (int, error)
-	// PruneUnusedRemote prunes unused/out of date headers and avatars cached on this instance.
-	//
-	// The returned int is the amount of media that was pruned by this function.
-	PruneUnusedRemote(ctx context.Context, dry bool) (int, error)
-	// PruneUnusedLocal prunes unused media attachments that were uploaded by
-	// a user on this instance, but never actually attached to a status, or attached but
-	// later detached.
-	//
-	// The returned int is the amount of media that was pruned by this function.
-	PruneUnusedLocal(ctx context.Context, dry bool) (int, error)
-	// PruneOrphaned prunes files that exist in storage but which do not have a corresponding
-	// entry in the database.
-	//
-	// If dry is true, then nothing will be changed, only the amount that *would* be removed
-	// is returned to the caller.
-	PruneOrphaned(ctx context.Context, dry bool) (int, error)
-
-	/*
-		REFETCHING FUNCTIONS
-		Useful when data loss has occurred.
-	*/
-
-	// RefetchEmojis iterates through remote emojis (for the given domain, or all if domain is empty string).
-	//
-	// For each emoji, the manager will check whether both the full size and static images are present in storage.
-	// If not, the manager will refetch and reprocess full size and static images for the emoji.
-	//
-	// The provided DereferenceMedia function will be used when it's necessary to refetch something this way.
-	RefetchEmojis(ctx context.Context, domain string, dereferenceMedia DereferenceMedia) (int, error)
-}
-
-type manager struct {
+type Manager struct {
 	state *state.State
 }
 
@@ -162,13 +59,24 @@ type manager struct {
 // a limited number of media will be processed in parallel. The numbers of workers
 // is determined from the $GOMAXPROCS environment variable (usually no. CPU cores).
 // See internal/concurrency.NewWorkerPool() documentation for further information.
-func NewManager(state *state.State) Manager {
-	m := &manager{state: state}
+func NewManager(state *state.State) *Manager {
+	m := &Manager{state: state}
 	scheduleCleanupJobs(m)
 	return m
 }
 
-func (m *manager) PreProcessMedia(ctx context.Context, data DataFunc, postData PostDataCallbackFunc, accountID string, ai *AdditionalMediaInfo) (*ProcessingMedia, error) {
+// PreProcessMedia begins the process of decoding and storing the given data as an attachment.
+// It will return a pointer to a ProcessingMedia struct upon which further actions can be performed, such as getting
+// the finished media, thumbnail, attachment, etc.
+//
+// data should be a function that the media manager can call to return a reader containing the media data.
+//
+// accountID should be the account that the media belongs to.
+//
+// ai is optional and can be nil. Any additional information about the attachment provided will be put in the database.
+//
+// Note: unlike ProcessMedia, this will NOT queue the media to be asynchronously processed.
+func (m *Manager) PreProcessMedia(ctx context.Context, data DataFunc, accountID string, ai *AdditionalMediaInfo) (*ProcessingMedia, error) {
 	id, err := id.NewRandomULID()
 	if err != nil {
 		return nil, err
@@ -248,14 +156,16 @@ func (m *manager) PreProcessMedia(ctx context.Context, data DataFunc, postData P
 	processingMedia := &ProcessingMedia{
 		media:  attachment,
 		dataFn: data,
-		postFn: postData,
 		mgr:    m,
 	}
 
 	return processingMedia, nil
 }
 
-func (m *manager) PreProcessMediaRecache(ctx context.Context, data DataFunc, postData PostDataCallbackFunc, attachmentID string) (*ProcessingMedia, error) {
+// PreProcessMediaRecache refetches, reprocesses, and recaches an existing attachment that has been uncached via pruneRemote.
+//
+// Note: unlike ProcessMedia, this will NOT queue the media to be asychronously processed.
+func (m *Manager) PreProcessMediaRecache(ctx context.Context, data DataFunc, attachmentID string) (*ProcessingMedia, error) {
 	// get the existing attachment from database.
 	attachment, err := m.state.DB.GetAttachmentByID(ctx, attachmentID)
 	if err != nil {
@@ -265,7 +175,6 @@ func (m *manager) PreProcessMediaRecache(ctx context.Context, data DataFunc, pos
 	processingMedia := &ProcessingMedia{
 		media:   attachment,
 		dataFn:  data,
-		postFn:  postData,
 		recache: true, // indicate it's a recache
 		mgr:     m,
 	}
@@ -273,9 +182,10 @@ func (m *manager) PreProcessMediaRecache(ctx context.Context, data DataFunc, pos
 	return processingMedia, nil
 }
 
-func (m *manager) ProcessMedia(ctx context.Context, data DataFunc, postData PostDataCallbackFunc, accountID string, ai *AdditionalMediaInfo) (*ProcessingMedia, error) {
+// ProcessMedia will call PreProcessMedia, followed by queuing the media to be processing in the media worker queue.
+func (m *Manager) ProcessMedia(ctx context.Context, data DataFunc, accountID string, ai *AdditionalMediaInfo) (*ProcessingMedia, error) {
 	// Create a new processing media object for this media request.
-	media, err := m.PreProcessMedia(ctx, data, postData, accountID, ai)
+	media, err := m.PreProcessMedia(ctx, data, accountID, ai)
 	if err != nil {
 		return nil, err
 	}
@@ -286,7 +196,22 @@ func (m *manager) ProcessMedia(ctx context.Context, data DataFunc, postData Post
 	return media, nil
 }
 
-func (m *manager) PreProcessEmoji(ctx context.Context, data DataFunc, postData PostDataCallbackFunc, shortcode string, emojiID string, uri string, ai *AdditionalEmojiInfo, refresh bool) (*ProcessingEmoji, error) {
+// PreProcessEmoji begins the process of decoding and storing the given data as an emoji.
+// It will return a pointer to a ProcessingEmoji struct upon which further actions can be performed, such as getting
+// the finished media, thumbnail, attachment, etc.
+//
+// data should be a function that the media manager can call to return a reader containing the emoji data.
+//
+// shortcode should be the emoji shortcode without the ':'s around it.
+//
+// id is the database ID that should be used to store the emoji.
+//
+// uri is the ActivityPub URI/ID of the emoji.
+//
+// ai is optional and can be nil. Any additional information about the emoji provided will be put in the database.
+//
+// Note: unlike ProcessEmoji, this will NOT queue the emoji to be asynchronously processed.
+func (m *Manager) PreProcessEmoji(ctx context.Context, data DataFunc, shortcode string, emojiID string, uri string, ai *AdditionalEmojiInfo, refresh bool) (*ProcessingEmoji, error) {
 	instanceAccount, err := m.state.DB.GetInstanceAccount(ctx, "")
 	if err != nil {
 		return nil, fmt.Errorf("preProcessEmoji: error fetching this instance account from the db: %s", err)
@@ -299,36 +224,38 @@ func (m *manager) PreProcessEmoji(ctx context.Context, data DataFunc, postData P
 	)
 
 	if refresh {
+		// Look for existing emoji by given ID.
 		emoji, err = m.state.DB.GetEmojiByID(ctx, emojiID)
 		if err != nil {
 			return nil, fmt.Errorf("preProcessEmoji: error fetching emoji to refresh from the db: %s", err)
 		}
 
 		// if this is a refresh, we will end up with new images
-		// stored for this emoji, so we can use the postData function
+		// stored for this emoji, so we can use an io.Closer callback
 		// to perform clean up of the old images from storage
-		originalPostData := postData
+		originalData := data
 		originalImagePath := emoji.ImagePath
 		originalImageStaticPath := emoji.ImageStaticPath
-		postData = func(innerCtx context.Context) error {
-			// trigger the original postData function if it was provided
-			if originalPostData != nil {
-				if err := originalPostData(innerCtx); err != nil {
-					return err
-				}
+		data = func(ctx context.Context) (io.ReadCloser, int64, error) {
+			// Call original data func.
+			rc, sz, err := originalData(ctx)
+			if err != nil {
+				return nil, 0, err
 			}
 
-			l := log.WithContext(ctx).
-				WithField("shortcode@domain", emoji.Shortcode+"@"+emoji.Domain)
-			l.Debug("postData: cleaning up old emoji files for refreshed emoji")
-			if err := m.state.Storage.Delete(innerCtx, originalImagePath); err != nil && !errors.Is(err, storage.ErrNotFound) {
-				l.Errorf("postData: error cleaning up old emoji image at %s for refreshed emoji: %s", originalImagePath, err)
-			}
-			if err := m.state.Storage.Delete(innerCtx, originalImageStaticPath); err != nil && !errors.Is(err, storage.ErrNotFound) {
-				l.Errorf("postData: error cleaning up old emoji static image at %s for refreshed emoji: %s", originalImageStaticPath, err)
-			}
+			// Wrap closer to cleanup old data.
+			c := iotools.CloserCallback(rc, func() {
+				if err := m.state.Storage.Delete(ctx, originalImagePath); err != nil && !errors.Is(err, storage.ErrNotFound) {
+					log.Errorf(ctx, "error removing old emoji %s@%s from storage: %v", emoji.Shortcode, emoji.Domain, err)
+				}
+
+				if err := m.state.Storage.Delete(ctx, originalImageStaticPath); err != nil && !errors.Is(err, storage.ErrNotFound) {
+					log.Errorf(ctx, "error removing old static emoji %s@%s from storage: %v", emoji.Shortcode, emoji.Domain, err)
+				}
+			})
 
-			return nil
+			// Return newly wrapped readcloser and size.
+			return iotools.ReadCloser(rc, c), sz, nil
 		}
 
 		newPathID, err = id.NewRandomULID()
@@ -410,16 +337,16 @@ func (m *manager) PreProcessEmoji(ctx context.Context, data DataFunc, postData P
 		refresh:   refresh,
 		newPathID: newPathID,
 		dataFn:    data,
-		postFn:    postData,
 		mgr:       m,
 	}
 
 	return processingEmoji, nil
 }
 
-func (m *manager) ProcessEmoji(ctx context.Context, data DataFunc, postData PostDataCallbackFunc, shortcode string, id string, uri string, ai *AdditionalEmojiInfo, refresh bool) (*ProcessingEmoji, error) {
+// ProcessEmoji will call PreProcessEmoji, followed by queuing the emoji to be processing in the emoji worker queue.
+func (m *Manager) ProcessEmoji(ctx context.Context, data DataFunc, shortcode string, id string, uri string, ai *AdditionalEmojiInfo, refresh bool) (*ProcessingEmoji, error) {
 	// Create a new processing emoji object for this emoji request.
-	emoji, err := m.PreProcessEmoji(ctx, data, postData, shortcode, id, uri, ai, refresh)
+	emoji, err := m.PreProcessEmoji(ctx, data, shortcode, id, uri, ai, refresh)
 	if err != nil {
 		return nil, err
 	}
@@ -430,7 +357,7 @@ func (m *manager) ProcessEmoji(ctx context.Context, data DataFunc, postData Post
 	return emoji, nil
 }
 
-func scheduleCleanupJobs(m *manager) {
+func scheduleCleanupJobs(m *Manager) {
 	const day = time.Hour * 24
 
 	// Calculate closest midnight.
diff --git a/internal/media/manager_test.go b/internal/media/manager_test.go
index fb0784034..2bee1091d 100644
--- a/internal/media/manager_test.go
+++ b/internal/media/manager_test.go
@@ -55,7 +55,7 @@ func (suite *ManagerTestSuite) TestEmojiProcessBlocking() {
 	emojiID := "01GDQ9G782X42BAMFASKP64343"
 	emojiURI := "http://localhost:8080/emoji/01GDQ9G782X42BAMFASKP64343"
 
-	processingEmoji, err := suite.manager.ProcessEmoji(ctx, data, nil, "rainbow_test", emojiID, emojiURI, nil, false)
+	processingEmoji, err := suite.manager.ProcessEmoji(ctx, data, "rainbow_test", emojiID, emojiURI, nil, false)
 	suite.NoError(err)
 
 	// do a blocking call to fetch the emoji
@@ -125,7 +125,7 @@ func (suite *ManagerTestSuite) TestEmojiProcessBlockingRefresh() {
 	emojiID := emojiToUpdate.ID
 	emojiURI := emojiToUpdate.URI
 
-	processingEmoji, err := suite.manager.ProcessEmoji(ctx, data, nil, "yell", emojiID, emojiURI, &media.AdditionalEmojiInfo{
+	processingEmoji, err := suite.manager.ProcessEmoji(ctx, data, "yell", emojiID, emojiURI, &media.AdditionalEmojiInfo{
 		CreatedAt:      &emojiToUpdate.CreatedAt,
 		Domain:         &emojiToUpdate.Domain,
 		ImageRemoteURL: &newImageRemoteURL,
@@ -209,7 +209,7 @@ func (suite *ManagerTestSuite) TestEmojiProcessBlockingTooLarge() {
 	emojiID := "01GDQ9G782X42BAMFASKP64343"
 	emojiURI := "http://localhost:8080/emoji/01GDQ9G782X42BAMFASKP64343"
 
-	processingEmoji, err := suite.manager.ProcessEmoji(ctx, data, nil, "big_panda", emojiID, emojiURI, nil, false)
+	processingEmoji, err := suite.manager.ProcessEmoji(ctx, data, "big_panda", emojiID, emojiURI, nil, false)
 	suite.NoError(err)
 
 	// do a blocking call to fetch the emoji
@@ -233,7 +233,7 @@ func (suite *ManagerTestSuite) TestEmojiProcessBlockingTooLargeNoSizeGiven() {
 	emojiID := "01GDQ9G782X42BAMFASKP64343"
 	emojiURI := "http://localhost:8080/emoji/01GDQ9G782X42BAMFASKP64343"
 
-	processingEmoji, err := suite.manager.ProcessEmoji(ctx, data, nil, "big_panda", emojiID, emojiURI, nil, false)
+	processingEmoji, err := suite.manager.ProcessEmoji(ctx, data, "big_panda", emojiID, emojiURI, nil, false)
 	suite.NoError(err)
 
 	// do a blocking call to fetch the emoji
@@ -258,7 +258,7 @@ func (suite *ManagerTestSuite) TestEmojiProcessBlockingNoFileSizeGiven() {
 	emojiURI := "http://localhost:8080/emoji/01GDQ9G782X42BAMFASKP64343"
 
 	// process the media with no additional info provided
-	processingEmoji, err := suite.manager.ProcessEmoji(ctx, data, nil, "rainbow_test", emojiID, emojiURI, nil, false)
+	processingEmoji, err := suite.manager.ProcessEmoji(ctx, data, "rainbow_test", emojiID, emojiURI, nil, false)
 	suite.NoError(err)
 
 	// do a blocking call to fetch the emoji
@@ -319,7 +319,7 @@ func (suite *ManagerTestSuite) TestSimpleJpegProcessBlocking() {
 	accountID := "01FS1X72SK9ZPW0J1QQ68BD264"
 
 	// process the media with no additional info provided
-	processingMedia, err := suite.manager.ProcessMedia(ctx, data, nil, accountID, nil)
+	processingMedia, err := suite.manager.ProcessMedia(ctx, data, accountID, nil)
 	suite.NoError(err)
 	// fetch the attachment id from the processing media
 	attachmentID := processingMedia.AttachmentID()
@@ -391,7 +391,7 @@ func (suite *ManagerTestSuite) TestSlothVineProcessBlocking() {
 	accountID := "01FS1X72SK9ZPW0J1QQ68BD264"
 
 	// process the media with no additional info provided
-	processingMedia, err := suite.manager.ProcessMedia(ctx, data, nil, accountID, nil)
+	processingMedia, err := suite.manager.ProcessMedia(ctx, data, accountID, nil)
 	suite.NoError(err)
 	// fetch the attachment id from the processing media
 	attachmentID := processingMedia.AttachmentID()
@@ -467,7 +467,7 @@ func (suite *ManagerTestSuite) TestLongerMp4ProcessBlocking() {
 	accountID := "01FS1X72SK9ZPW0J1QQ68BD264"
 
 	// process the media with no additional info provided
-	processingMedia, err := suite.manager.ProcessMedia(ctx, data, nil, accountID, nil)
+	processingMedia, err := suite.manager.ProcessMedia(ctx, data, accountID, nil)
 	suite.NoError(err)
 	// fetch the attachment id from the processing media
 	attachmentID := processingMedia.AttachmentID()
@@ -543,7 +543,7 @@ func (suite *ManagerTestSuite) TestBirdnestMp4ProcessBlocking() {
 	accountID := "01FS1X72SK9ZPW0J1QQ68BD264"
 
 	// process the media with no additional info provided
-	processingMedia, err := suite.manager.ProcessMedia(ctx, data, nil, accountID, nil)
+	processingMedia, err := suite.manager.ProcessMedia(ctx, data, accountID, nil)
 	suite.NoError(err)
 	// fetch the attachment id from the processing media
 	attachmentID := processingMedia.AttachmentID()
@@ -621,7 +621,7 @@ func (suite *ManagerTestSuite) TestNotAnMp4ProcessBlocking() {
 	accountID := "01FS1X72SK9ZPW0J1QQ68BD264"
 
 	// pre processing should go fine but...
-	processingMedia, err := suite.manager.ProcessMedia(ctx, data, nil, accountID, nil)
+	processingMedia, err := suite.manager.ProcessMedia(ctx, data, accountID, nil)
 	suite.NoError(err)
 
 	// we should get an error while loading
@@ -646,7 +646,7 @@ func (suite *ManagerTestSuite) TestSimpleJpegProcessBlockingNoContentLengthGiven
 	accountID := "01FS1X72SK9ZPW0J1QQ68BD264"
 
 	// process the media with no additional info provided
-	processingMedia, err := suite.manager.ProcessMedia(ctx, data, nil, accountID, nil)
+	processingMedia, err := suite.manager.ProcessMedia(ctx, data, accountID, nil)
 	suite.NoError(err)
 	// fetch the attachment id from the processing media
 	attachmentID := processingMedia.AttachmentID()
@@ -719,7 +719,7 @@ func (suite *ManagerTestSuite) TestSimpleJpegProcessBlockingReadCloser() {
 	accountID := "01FS1X72SK9ZPW0J1QQ68BD264"
 
 	// process the media with no additional info provided
-	processingMedia, err := suite.manager.ProcessMedia(ctx, data, nil, accountID, nil)
+	processingMedia, err := suite.manager.ProcessMedia(ctx, data, accountID, nil)
 	suite.NoError(err)
 	// fetch the attachment id from the processing media
 	attachmentID := processingMedia.AttachmentID()
@@ -791,7 +791,7 @@ func (suite *ManagerTestSuite) TestPngNoAlphaChannelProcessBlocking() {
 	accountID := "01FS1X72SK9ZPW0J1QQ68BD264"
 
 	// process the media with no additional info provided
-	processingMedia, err := suite.manager.ProcessMedia(ctx, data, nil, accountID, nil)
+	processingMedia, err := suite.manager.ProcessMedia(ctx, data, accountID, nil)
 	suite.NoError(err)
 	// fetch the attachment id from the processing media
 	attachmentID := processingMedia.AttachmentID()
@@ -863,7 +863,7 @@ func (suite *ManagerTestSuite) TestPngAlphaChannelProcessBlocking() {
 	accountID := "01FS1X72SK9ZPW0J1QQ68BD264"
 
 	// process the media with no additional info provided
-	processingMedia, err := suite.manager.ProcessMedia(ctx, data, nil, accountID, nil)
+	processingMedia, err := suite.manager.ProcessMedia(ctx, data, accountID, nil)
 	suite.NoError(err)
 	// fetch the attachment id from the processing media
 	attachmentID := processingMedia.AttachmentID()
@@ -932,18 +932,10 @@ func (suite *ManagerTestSuite) TestSimpleJpegProcessBlockingWithCallback() {
 		return io.NopCloser(bytes.NewBuffer(b)), int64(len(b)), nil
 	}
 
-	// test the callback function by setting a simple boolean
-	var calledPostData bool
-	postData := func(_ context.Context) error {
-		calledPostData = true
-		return nil
-	}
-	suite.False(calledPostData) // not called yet (obvs)
-
 	accountID := "01FS1X72SK9ZPW0J1QQ68BD264"
 
 	// process the media with no additional info provided
-	processingMedia, err := suite.manager.ProcessMedia(ctx, data, postData, accountID, nil)
+	processingMedia, err := suite.manager.ProcessMedia(ctx, data, accountID, nil)
 	suite.NoError(err)
 	// fetch the attachment id from the processing media
 	attachmentID := processingMedia.AttachmentID()
@@ -953,9 +945,6 @@ func (suite *ManagerTestSuite) TestSimpleJpegProcessBlockingWithCallback() {
 	suite.NoError(err)
 	suite.NotNil(attachment)
 
-	// the post data callback should have been called
-	suite.True(calledPostData)
-
 	// make sure it's got the stuff set on it that we expect
 	// the attachment ID and accountID we expect
 	suite.Equal(attachmentID, attachment.ID)
@@ -1019,7 +1008,7 @@ func (suite *ManagerTestSuite) TestSimpleJpegProcessAsync() {
 	accountID := "01FS1X72SK9ZPW0J1QQ68BD264"
 
 	// process the media with no additional info provided
-	processingMedia, err := suite.manager.ProcessMedia(ctx, data, nil, accountID, nil)
+	processingMedia, err := suite.manager.ProcessMedia(ctx, data, accountID, nil)
 	suite.NoError(err)
 
 	// fetch the attachment id from the processing media
@@ -1101,7 +1090,7 @@ func (suite *ManagerTestSuite) TestSimpleJpegQueueSpamming() {
 	inProcess := []*media.ProcessingMedia{}
 	for i := 0; i < spam; i++ {
 		// process the media with no additional info provided
-		processingMedia, err := suite.manager.ProcessMedia(ctx, data, nil, accountID, nil)
+		processingMedia, err := suite.manager.ProcessMedia(ctx, data, accountID, nil)
 		suite.NoError(err)
 		inProcess = append(inProcess, processingMedia)
 	}
@@ -1202,7 +1191,7 @@ func (suite *ManagerTestSuite) TestSimpleJpegProcessBlockingWithDiskStorage() {
 	suite.manager = diskManager
 
 	// process the media with no additional info provided
-	processingMedia, err := diskManager.ProcessMedia(ctx, data, nil, accountID, nil)
+	processingMedia, err := diskManager.ProcessMedia(ctx, data, accountID, nil)
 	suite.NoError(err)
 	// fetch the attachment id from the processing media
 	attachmentID := processingMedia.AttachmentID()
diff --git a/internal/media/media_test.go b/internal/media/media_test.go
index 323f87bf4..c7c73bae6 100644
--- a/internal/media/media_test.go
+++ b/internal/media/media_test.go
@@ -35,7 +35,7 @@ type MediaStandardTestSuite struct {
 	db                  db.DB
 	storage             *storage.Driver
 	state               state.State
-	manager             media.Manager
+	manager             *media.Manager
 	transportController transport.Controller
 	testAttachments     map[string]*gtsmodel.MediaAttachment
 	testAccounts        map[string]*gtsmodel.Account
diff --git a/internal/media/processingemoji.go b/internal/media/processingemoji.go
index b2da54289..7c3db8196 100644
--- a/internal/media/processingemoji.go
+++ b/internal/media/processingemoji.go
@@ -36,16 +36,15 @@ import (
 // ProcessingEmoji represents an emoji currently processing. It exposes
 // various functions for retrieving data from the process.
 type ProcessingEmoji struct {
-	instAccID string               // instance account ID
-	emoji     *gtsmodel.Emoji      // processing emoji details
-	refresh   bool                 // whether this is an existing emoji being refreshed
-	newPathID string               // new emoji path ID to use if refreshed
-	dataFn    DataFunc             // load-data function, returns media stream
-	postFn    PostDataCallbackFunc // post data callback function
-	done      bool                 // done is set when process finishes with non ctx canceled type error
-	proc      runners.Processor    // proc helps synchronize only a singular running processing instance
-	err       error                // error stores permanent error value when done
-	mgr       *manager             // mgr instance (access to db / storage)
+	instAccID string            // instance account ID
+	emoji     *gtsmodel.Emoji   // processing emoji details
+	refresh   bool              // whether this is an existing emoji being refreshed
+	newPathID string            // new emoji path ID to use if refreshed
+	dataFn    DataFunc          // load-data function, returns media stream
+	done      bool              // done is set when process finishes with non ctx canceled type error
+	proc      runners.Processor // proc helps synchronize only a singular running processing instance
+	err       error             // error stores permanent error value when done
+	mgr       *Manager          // mgr instance (access to db / storage)
 }
 
 // EmojiID returns the ID of the underlying emoji without blocking processing.
@@ -158,17 +157,6 @@ func (p *ProcessingEmoji) load(ctx context.Context) (*gtsmodel.Emoji, bool, erro
 // and updates the underlying attachment fields as necessary. It will then stream
 // bytes from p's reader directly into storage so that it can be retrieved later.
 func (p *ProcessingEmoji) store(ctx context.Context) error {
-	defer func() {
-		if p.postFn == nil {
-			return
-		}
-
-		// Ensure post callback gets called.
-		if err := p.postFn(ctx); err != nil {
-			log.Errorf(ctx, "error executing postdata function: %v", err)
-		}
-	}()
-
 	// Load media from provided data fn.
 	rc, sz, err := p.dataFn(ctx)
 	if err != nil {
diff --git a/internal/media/processingmedia.go b/internal/media/processingmedia.go
index fc75c3136..5c66f561d 100644
--- a/internal/media/processingmedia.go
+++ b/internal/media/processingmedia.go
@@ -40,12 +40,11 @@ import (
 type ProcessingMedia struct {
 	media   *gtsmodel.MediaAttachment // processing media attachment details
 	dataFn  DataFunc                  // load-data function, returns media stream
-	postFn  PostDataCallbackFunc      // post data callback function
 	recache bool                      // recaching existing (uncached) media
 	done    bool                      // done is set when process finishes with non ctx canceled type error
 	proc    runners.Processor         // proc helps synchronize only a singular running processing instance
 	err     error                     // error stores permanent error value when done
-	mgr     *manager                  // mgr instance (access to db / storage)
+	mgr     *Manager                  // mgr instance (access to db / storage)
 }
 
 // AttachmentID returns the ID of the underlying media attachment without blocking processing.
@@ -143,17 +142,6 @@ func (p *ProcessingMedia) load(ctx context.Context) (*gtsmodel.MediaAttachment,
 // and updates the underlying attachment fields as necessary. It will then stream
 // bytes from p's reader directly into storage so that it can be retrieved later.
 func (p *ProcessingMedia) store(ctx context.Context) error {
-	defer func() {
-		if p.postFn == nil {
-			return
-		}
-
-		// ensure post callback gets called.
-		if err := p.postFn(ctx); err != nil {
-			log.Errorf(ctx, "error executing postdata function: %v", err)
-		}
-	}()
-
 	// Load media from provided data fun
 	rc, sz, err := p.dataFn(ctx)
 	if err != nil {
diff --git a/internal/media/prune.go b/internal/media/prune.go
index f0d0516e1..71c8e00ce 100644
--- a/internal/media/prune.go
+++ b/internal/media/prune.go
@@ -37,7 +37,14 @@ const (
 	unusedLocalAttachmentDays = 3  // Number of days to keep local media in storage if not attached to a status.
 )
 
-func (m *manager) PruneAll(ctx context.Context, mediaCacheRemoteDays int, blocking bool) error {
+// PruneAll runs all of the below pruning/uncacheing functions, and then cleans up any resulting
+// empty directories from the storage driver. It can be called as a shortcut for calling the below
+// pruning functions one by one.
+//
+// If blocking is true, then any errors encountered during the prune will be combined + returned to
+// the caller. If blocking is false, the prune is run in the background and errors are just logged
+// instead.
+func (m *Manager) PruneAll(ctx context.Context, mediaCacheRemoteDays int, blocking bool) error {
 	const dry = false
 
 	f := func(innerCtx context.Context) error {
@@ -93,7 +100,10 @@ func (m *manager) PruneAll(ctx context.Context, mediaCacheRemoteDays int, blocki
 	return nil
 }
 
-func (m *manager) PruneUnusedRemote(ctx context.Context, dry bool) (int, error) {
+// PruneUnusedRemote prunes unused/out of date headers and avatars cached on this instance.
+//
+// The returned int is the amount of media that was pruned by this function.
+func (m *Manager) PruneUnusedRemote(ctx context.Context, dry bool) (int, error) {
 	var (
 		totalPruned int
 		maxID       string
@@ -152,7 +162,12 @@ func (m *manager) PruneUnusedRemote(ctx context.Context, dry bool) (int, error)
 	return totalPruned, nil
 }
 
-func (m *manager) PruneOrphaned(ctx context.Context, dry bool) (int, error) {
+// PruneOrphaned prunes files that exist in storage but which do not have a corresponding
+// entry in the database.
+//
+// If dry is true, then nothing will be changed, only the amount that *would* be removed
+// is returned to the caller.
+func (m *Manager) PruneOrphaned(ctx context.Context, dry bool) (int, error) {
 	// Emojis are stored under the instance account, so we
 	// need the ID of the instance account for the next part.
 	instanceAccount, err := m.state.DB.GetInstanceAccount(ctx, "")
@@ -200,7 +215,7 @@ func (m *manager) PruneOrphaned(ctx context.Context, dry bool) (int, error) {
 	return m.removeFiles(ctx, orphanedKeys...)
 }
 
-func (m *manager) orphaned(ctx context.Context, key string, instanceAccountID string) (bool, error) {
+func (m *Manager) orphaned(ctx context.Context, key string, instanceAccountID string) (bool, error) {
 	pathParts := regexes.FilePath.FindStringSubmatch(key)
 	if len(pathParts) != 6 {
 		// This doesn't match our expectations so
@@ -239,7 +254,15 @@ func (m *manager) orphaned(ctx context.Context, key string, instanceAccountID st
 	return orphaned, nil
 }
 
-func (m *manager) UncacheRemote(ctx context.Context, olderThanDays int, dry bool) (int, error) {
+// UncacheRemote uncaches all remote media attachments older than the given amount of days.
+//
+// In this context, uncacheing means deleting media files from storage and marking the attachment
+// as cached=false in the database.
+//
+// If 'dry' is true, then only a dry run will be performed: nothing will actually be changed.
+//
+// The returned int is the amount of media that was/would be uncached by this function.
+func (m *Manager) UncacheRemote(ctx context.Context, olderThanDays int, dry bool) (int, error) {
 	if olderThanDays < 0 {
 		return 0, nil
 	}
@@ -276,7 +299,12 @@ func (m *manager) UncacheRemote(ctx context.Context, olderThanDays int, dry bool
 	return totalPruned, nil
 }
 
-func (m *manager) PruneUnusedLocal(ctx context.Context, dry bool) (int, error) {
+// PruneUnusedLocal prunes unused media attachments that were uploaded by
+// a user on this instance, but never actually attached to a status, or attached but
+// later detached.
+//
+// The returned int is the amount of media that was pruned by this function.
+func (m *Manager) PruneUnusedLocal(ctx context.Context, dry bool) (int, error) {
 	olderThan := time.Now().Add(-time.Hour * 24 * time.Duration(unusedLocalAttachmentDays))
 
 	if dry {
@@ -313,7 +341,7 @@ func (m *manager) PruneUnusedLocal(ctx context.Context, dry bool) (int, error) {
 	Handy little helpers
 */
 
-func (m *manager) deleteAttachment(ctx context.Context, attachment *gtsmodel.MediaAttachment) error {
+func (m *Manager) deleteAttachment(ctx context.Context, attachment *gtsmodel.MediaAttachment) error {
 	if _, err := m.removeFiles(ctx, attachment.File.Path, attachment.Thumbnail.Path); err != nil {
 		return err
 	}
@@ -322,7 +350,7 @@ func (m *manager) deleteAttachment(ctx context.Context, attachment *gtsmodel.Med
 	return m.state.DB.DeleteAttachment(ctx, attachment.ID)
 }
 
-func (m *manager) uncacheAttachment(ctx context.Context, attachment *gtsmodel.MediaAttachment) error {
+func (m *Manager) uncacheAttachment(ctx context.Context, attachment *gtsmodel.MediaAttachment) error {
 	if _, err := m.removeFiles(ctx, attachment.File.Path, attachment.Thumbnail.Path); err != nil {
 		return err
 	}
@@ -332,7 +360,7 @@ func (m *manager) uncacheAttachment(ctx context.Context, attachment *gtsmodel.Me
 	return m.state.DB.UpdateAttachment(ctx, attachment, "cached")
 }
 
-func (m *manager) removeFiles(ctx context.Context, keys ...string) (int, error) {
+func (m *Manager) removeFiles(ctx context.Context, keys ...string) (int, error) {
 	errs := make(gtserror.MultiError, 0, len(keys))
 
 	for _, key := range keys {
diff --git a/internal/media/prune_test.go b/internal/media/prune_test.go
index 64823e640..375ce0c06 100644
--- a/internal/media/prune_test.go
+++ b/internal/media/prune_test.go
@@ -312,7 +312,7 @@ func (suite *PruneTestSuite) TestUncacheAndRecache() {
 		testStatusAttachment,
 		testHeader,
 	} {
-		processingRecache, err := suite.manager.PreProcessMediaRecache(ctx, data, nil, original.ID)
+		processingRecache, err := suite.manager.PreProcessMediaRecache(ctx, data, original.ID)
 		suite.NoError(err)
 
 		// synchronously load the recached attachment
diff --git a/internal/media/refetch.go b/internal/media/refetch.go
index 8fb08f88b..80dfe4f60 100644
--- a/internal/media/refetch.go
+++ b/internal/media/refetch.go
@@ -32,7 +32,13 @@ import (
 
 type DereferenceMedia func(ctx context.Context, iri *url.URL) (io.ReadCloser, int64, error)
 
-func (m *manager) RefetchEmojis(ctx context.Context, domain string, dereferenceMedia DereferenceMedia) (int, error) {
+// RefetchEmojis iterates through remote emojis (for the given domain, or all if domain is empty string).
+//
+// For each emoji, the manager will check whether both the full size and static images are present in storage.
+// If not, the manager will refetch and reprocess full size and static images for the emoji.
+//
+// The provided DereferenceMedia function will be used when it's necessary to refetch something this way.
+func (m *Manager) RefetchEmojis(ctx context.Context, domain string, dereferenceMedia DereferenceMedia) (int, error) {
 	// normalize domain
 	if domain == "" {
 		domain = db.EmojiAllDomains
@@ -107,7 +113,7 @@ func (m *manager) RefetchEmojis(ctx context.Context, domain string, dereferenceM
 			return dereferenceMedia(ctx, emojiImageIRI)
 		}
 
-		processingEmoji, err := m.PreProcessEmoji(ctx, dataFunc, nil, emoji.Shortcode, emoji.ID, emoji.URI, &AdditionalEmojiInfo{
+		processingEmoji, err := m.PreProcessEmoji(ctx, dataFunc, emoji.Shortcode, emoji.ID, emoji.URI, &AdditionalEmojiInfo{
 			Domain:               &emoji.Domain,
 			ImageRemoteURL:       &emoji.ImageRemoteURL,
 			ImageStaticRemoteURL: &emoji.ImageStaticRemoteURL,
@@ -131,7 +137,7 @@ func (m *manager) RefetchEmojis(ctx context.Context, domain string, dereferenceM
 	return totalRefetched, nil
 }
 
-func (m *manager) emojiRequiresRefetch(ctx context.Context, emoji *gtsmodel.Emoji) (bool, error) {
+func (m *Manager) emojiRequiresRefetch(ctx context.Context, emoji *gtsmodel.Emoji) (bool, error) {
 	if has, err := m.state.Storage.Has(ctx, emoji.ImagePath); err != nil {
 		return false, err
 	} else if !has {
diff --git a/internal/media/types.go b/internal/media/types.go
index 1619029c6..35c62a947 100644
--- a/internal/media/types.go
+++ b/internal/media/types.go
@@ -110,9 +110,3 @@ type AdditionalEmojiInfo struct {
 
 // DataFunc represents a function used to retrieve the raw bytes of a piece of media.
 type DataFunc func(ctx context.Context) (reader io.ReadCloser, fileSize int64, err error)
-
-// PostDataCallbackFunc represents a function executed after the DataFunc has been executed,
-// and the returned reader has been read. It can be used to clean up any remaining resources.
-//
-// This can be set to nil, and will then not be executed.
-type PostDataCallbackFunc func(ctx context.Context) error