[feature] Media attachment placeholders (#2331)

* [feature] Use placeholders for unknown media types

* fix read of underreported small files

* switch to reduce nesting

* simplify cleanup

internal/media/processingmedia.go

@@ -20,12 +20,12 @@ package media
 import (
 	"bytes"
 	"context"
-	"fmt"
+	"errors"
 	"image/jpeg"
 	"io"
 	"time"
 
-	"codeberg.org/gruf/go-errors/v2"
+	errorsv2 "codeberg.org/gruf/go-errors/v2"
 	"codeberg.org/gruf/go-runners"
 	"github.com/disintegration/imaging"
 	"github.com/h2non/filetype"
@@ -33,11 +33,14 @@ import (
 	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
 	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
 	"github.com/superseriousbusiness/gotosocial/internal/log"
+	"github.com/superseriousbusiness/gotosocial/internal/storage"
 	"github.com/superseriousbusiness/gotosocial/internal/uris"
+	"github.com/superseriousbusiness/gotosocial/internal/util"
 )
 
-// ProcessingMedia represents a piece of media that is currently being processed. It exposes
-// various functions for retrieving data from the process.
+// ProcessingMedia represents a piece of media
+// currently being processed. It exposes functions
+// for retrieving data from the process.
 type ProcessingMedia struct {
 	media   *gtsmodel.MediaAttachment // processing media attachment details
 	dataFn  DataFunc                  // load-data function, returns media stream
@@ -48,39 +51,56 @@ type ProcessingMedia struct {
 	mgr     *Manager                  // mgr instance (access to db / storage)
 }
 
-// AttachmentID returns the ID of the underlying media attachment without blocking processing.
+// AttachmentID returns the ID of the underlying
+// media attachment without blocking processing.
 func (p *ProcessingMedia) AttachmentID() string {
 	return p.media.ID // immutable, safe outside mutex.
 }
 
-// LoadAttachment blocks until the thumbnail and fullsize content has been processed, and then returns the completed attachment.
+// LoadAttachment blocks until the thumbnail and
+// fullsize content has been processed, and then
+// returns the attachment.
+//
+// If processing could not be completed fully
+// then an error will be returned. The attachment
+// will still be returned in that case, but it will
+// only be partially complete and should be treated
+// as a placeholder.
 func (p *ProcessingMedia) LoadAttachment(ctx context.Context) (*gtsmodel.MediaAttachment, error) {
 	// Attempt to load synchronously.
 	media, done, err := p.load(ctx)
-
 	if err == nil {
 		// No issue, return media.
 		return media, nil
 	}
 
 	if !done {
-		// Provided context was cancelled, e.g. request cancelled
-		// early. Queue this item for asynchronous processing.
+		// Provided context was cancelled,
+		// e.g. request aborted early before
+		// its context could be used to finish
+		// loading the attachment. Enqueue for
+		// asynchronous processing, which will
+		// use a background context.
 		log.Warnf(ctx, "reprocessing media %s after canceled ctx", p.media.ID)
 		go p.mgr.state.Workers.Media.Enqueue(p.Process)
 	}
 
-	return nil, err
+	// Media could not be retrieved FULLY,
+	// but partial attachment should be present.
+	return media, err
 }
 
-// Process allows the receiving object to fit the runners.WorkerFunc signature. It performs a (blocking) load and logs on error.
+// Process allows the receiving object to fit the
+// runners.WorkerFunc signature. It performs a
+// (blocking) load and logs on error.
 func (p *ProcessingMedia) Process(ctx context.Context) {
 	if _, _, err := p.load(ctx); err != nil {
-		log.Errorf(ctx, "error processing media: %v", err)
+		log.Errorf(ctx, "error(s) processing media: %v", err)
 	}
 }
 
-// load performs a concurrency-safe load of ProcessingMedia, only marking itself as complete when returned error is NOT a context cancel.
+// load performs a concurrency-safe load of ProcessingMedia, only
+// marking itself as complete when returned error is NOT a context cancel.
 func (p *ProcessingMedia) load(ctx context.Context) (*gtsmodel.MediaAttachment, bool, error) {
 	var (
 		done bool
@@ -95,7 +115,7 @@ func (p *ProcessingMedia) load(ctx context.Context) (*gtsmodel.MediaAttachment,
 
 		defer func() {
 			// This is only done when ctx NOT cancelled.
-			done = err == nil || !errors.Comparable(err,
+			done = err == nil || !errorsv2.Comparable(err,
 				context.Canceled,
 				context.DeadlineExceeded,
 			)
@@ -109,34 +129,61 @@ func (p *ProcessingMedia) load(ctx context.Context) (*gtsmodel.MediaAttachment,
 			p.err = err
 		}()
 
+		// Gather errors as we proceed.
+		var errs = gtserror.NewMultiError(4)
+
 		// Attempt to store media and calculate
 		// full-size media attachment details.
-		if err = p.store(ctx); err != nil {
-			return err
+		//
+		// This will update p.media as it goes.
+		storeErr := p.store(ctx)
+		if storeErr != nil {
+			errs.Append(storeErr)
 		}
 
 		// Finish processing by reloading media into
 		// memory to get dimension and generate a thumb.
-		if err = p.finish(ctx); err != nil {
-			return err
+		//
+		// This will update p.media as it goes.
+		if finishErr := p.finish(ctx); finishErr != nil {
+			errs.Append(finishErr)
 		}
 
-		if p.recache {
-			// Existing attachment we're recaching, so only update.
-			err = p.mgr.state.DB.UpdateAttachment(ctx, p.media)
-			return err
+		// If this isn't a file we were able to process,
+		// we may have partially stored it (eg., it's a
+		// jpeg, which is fine, but streaming it to storage
+		// was interrupted halfway through and so it was
+		// never decoded). Try to clean up in this case.
+		if p.media.Type == gtsmodel.FileTypeUnknown {
+			deleteErr := p.mgr.state.Storage.Delete(ctx, p.media.File.Path)
+			if deleteErr != nil && !errors.Is(deleteErr, storage.ErrNotFound) {
+				errs.Append(deleteErr)
+			}
 		}
 
-		// First time caching this attachment, insert it.
-		err = p.mgr.state.DB.PutAttachment(ctx, p.media)
+		var dbErr error
+		switch {
+		case !p.recache:
+			// First time caching this attachment, insert it.
+			dbErr = p.mgr.state.DB.PutAttachment(ctx, p.media)
+
+		case p.recache && len(errs) == 0:
+			// Existing attachment we're recaching, update it.
+			//
+			// (We only want to update if everything went OK so far,
+			// otherwise we'd better leave previous version alone.)
+			dbErr = p.mgr.state.DB.UpdateAttachment(ctx, p.media)
+		}
+
+		if dbErr != nil {
+			errs.Append(dbErr)
+		}
+
+		err = errs.Combine()
 		return err
 	})
 
-	if err != nil {
-		return nil, done, err
-	}
-
-	return p.media, done, nil
+	return p.media, done, err
 }
 
 // store calls the data function attached to p if it hasn't been called yet,
@@ -156,17 +203,47 @@ func (p *ProcessingMedia) store(ctx context.Context) error {
 		}
 	}()
 
-	// Byte buffer to read file header into.
-	// See: https://en.wikipedia.org/wiki/File_format#File_header
-	// and https://github.com/h2non/filetype
-	hdrBuf := make([]byte, 261)
+	// Assume we're given correct file
+	// size, we can overwrite this later
+	// once we know THE TRUTH.
+	fileSize := int(sz)
+	p.media.File.FileSize = fileSize
 
-	// Read the first 261 header bytes into buffer as much as possible.
-	if _, err := rc.Read(hdrBuf); err != nil {
-		return gtserror.Newf("error reading incoming media: %w", err)
+	// Prepare to read bytes from
+	// file header or magic number.
+	hdrBuf := newHdrBuf(fileSize)
+
+	// Read into buffer as much as possible.
+	//
+	// UnexpectedEOF means we couldn't read up to the
+	// given size, but we may still have read something.
+	//
+	// EOF means we couldn't read anything at all.
+	//
+	// Any other error likely means the connection messed up.
+	//
+	// In other words, rather counterintuitively, we
+	// can only proceed on no error or unexpected error!
+	n, err := io.ReadFull(rc, hdrBuf)
+	if err != nil {
+		if err != io.ErrUnexpectedEOF {
+			return gtserror.Newf("error reading first bytes of incoming media: %w", err)
+		}
+
+		// Initial file size was misreported, so we didn't read
+		// fully into hdrBuf. Reslice it to the size we did read.
+		log.Warnf(ctx,
+			"recovered from misreported file size; reported %d; read %d",
+			fileSize, n,
+		)
+		hdrBuf = hdrBuf[:n]
+		fileSize = n
+		p.media.File.FileSize = fileSize
 	}
 
 	// Parse file type info from header buffer.
+	// This should only ever error if the buffer
+	// is empty (ie., the attachment is 0 bytes).
 	info, err := filetype.Match(hdrBuf)
 	if err != nil {
 		return gtserror.Newf("error parsing file type: %w", err)
@@ -175,38 +252,77 @@ func (p *ProcessingMedia) store(ctx context.Context) error {
 	// Recombine header bytes with remaining stream
 	r := io.MultiReader(bytes.NewReader(hdrBuf), rc)
 
+	// Assume we'll put
+	// this file in storage.
+	store := true
+
 	switch info.Extension {
 	case "mp4":
-		p.media.Type = gtsmodel.FileTypeVideo
+		// No problem.
 
 	case "gif":
-		p.media.Type = gtsmodel.FileTypeImage
+		// No problem
 
 	case "jpg", "jpeg", "png", "webp":
-		p.media.Type = gtsmodel.FileTypeImage
-		if sz > 0 {
-			// A file size was provided so we can clean exif data from image.
-			r, err = terminator.Terminate(r, int(sz), info.Extension)
+		if fileSize > 0 {
+			// A file size was provided so we can clean
+			// exif data from image as we're streaming it.
+			r, err = terminator.Terminate(r, fileSize, info.Extension)
 			if err != nil {
 				return gtserror.Newf("error cleaning exif data: %w", err)
 			}
 		}
 
 	default:
-		return gtserror.Newf("unsupported file type: %s", info.Extension)
+		// The file is not a supported format that
+		// we can process, so we can't do much with it.
+		log.Warnf(ctx,
+			"media extension '%s' not officially supported, will be processed as "+
+				"type '%s' with minimal metadata, and will not be cached locally",
+			info.Extension, gtsmodel.FileTypeUnknown,
+		)
+
+		// Don't bother storing this.
+		store = false
 	}
 
-	// Calculate attachment file path.
-	p.media.File.Path = fmt.Sprintf(
-		"%s/%s/%s/%s.%s",
+	// Fill in correct attachment
+	// data now we're parsed it.
+	p.media.URL = uris.URIForAttachment(
 		p.media.AccountID,
-		TypeAttachment,
-		SizeOriginal,
+		string(TypeAttachment),
+		string(SizeOriginal),
 		p.media.ID,
 		info.Extension,
 	)
 
-	// This shouldn't already exist, but we do a check as it's worth logging.
+	// Prefer discovered mime type, fall back to
+	// generic "this contains some bytes" type.
+	mime := info.MIME.Value
+	if mime == "" {
+		mime = "application/octet-stream"
+	}
+	p.media.File.ContentType = mime
+
+	// Calculate attachment file path.
+	p.media.File.Path = uris.StoragePathForAttachment(
+		p.media.AccountID,
+		string(TypeAttachment),
+		string(SizeOriginal),
+		p.media.ID,
+		info.Extension,
+	)
+
+	// We should only try to store the file if it's
+	// a format we can keep processing, otherwise be
+	// a bit cheeky: don't store it and let users
+	// click through to the remote server instead.
+	if !store {
+		return nil
+	}
+
+	// File shouldn't already exist in storage at this point,
+	// but we do a check as it's worth logging / cleaning up.
 	if have, _ := p.mgr.state.Storage.Has(ctx, p.media.File.Path); have {
 		log.Warnf(ctx, "media already exists at storage path: %s", p.media.File.Path)
 
@@ -216,59 +332,99 @@ func (p *ProcessingMedia) store(ctx context.Context) error {
 		}
 	}
 
-	// Write the final image reader stream to our storage.
-	sz, err = p.mgr.state.Storage.PutStream(ctx, p.media.File.Path, r)
+	// Write the final reader stream to our storage.
+	wroteSize, err := p.mgr.state.Storage.PutStream(ctx, p.media.File.Path, r)
 	if err != nil {
 		return gtserror.Newf("error writing media to storage: %w", err)
 	}
 
-	// Set written image size.
-	p.media.File.FileSize = int(sz)
+	// Set actual written size
+	// as authoritative file size.
+	p.media.File.FileSize = int(wroteSize)
 
-	// Fill in remaining attachment data now it's stored.
-	p.media.URL = uris.GenerateURIForAttachment(
-		p.media.AccountID,
-		string(TypeAttachment),
-		string(SizeOriginal),
-		p.media.ID,
-		info.Extension,
-	)
-	p.media.File.ContentType = info.MIME.Value
-	p.media.Cached = func() *bool {
-		ok := true
-		return &ok
-	}()
+	// We can now consider this cached.
+	p.media.Cached = util.Ptr(true)
 
 	return nil
 }
 
 func (p *ProcessingMedia) finish(ctx context.Context) error {
-	// Fetch a stream to the original file in storage.
+	// Make a jolly assumption about thumbnail type.
+	p.media.Thumbnail.ContentType = mimeImageJpeg
+
+	// Calculate attachment thumbnail file path
+	p.media.Thumbnail.Path = uris.StoragePathForAttachment(
+		p.media.AccountID,
+		string(TypeAttachment),
+		string(SizeSmall),
+		p.media.ID,
+		// Always encode attachment
+		// thumbnails as jpg.
+		"jpg",
+	)
+
+	// Calculate attachment thumbnail serve path.
+	p.media.Thumbnail.URL = uris.URIForAttachment(
+		p.media.AccountID,
+		string(TypeAttachment),
+		string(SizeSmall),
+		p.media.ID,
+		// Always encode attachment
+		// thumbnails as jpg.
+		"jpg",
+	)
+
+	// If original file hasn't been stored, there's
+	// likely something wrong with the data, or we
+	// don't want to store it. Skip everything else.
+	if !*p.media.Cached {
+		p.media.Processing = gtsmodel.ProcessingStatusProcessed
+		return nil
+	}
+
+	// Get a stream to the original file for further processing.
 	rc, err := p.mgr.state.Storage.GetStream(ctx, p.media.File.Path)
 	if err != nil {
 		return gtserror.Newf("error loading file from storage: %w", err)
 	}
 	defer rc.Close()
 
+	// fullImg is the processed version of
+	// the original (stripped + reoriented).
 	var fullImg *gtsImage
 
+	// Depending on the content type, we
+	// can do various types of decoding.
 	switch p.media.File.ContentType {
+
 	// .jpeg, .gif, .webp image type
 	case mimeImageJpeg, mimeImageGif, mimeImageWebp:
-		fullImg, err = decodeImage(rc, imaging.AutoOrientation(true))
+		fullImg, err = decodeImage(
+			rc,
+			imaging.AutoOrientation(true),
+		)
 		if err != nil {
 			return gtserror.Newf("error decoding image: %w", err)
 		}
 
+		// Mark as no longer unknown type now
+		// we know for sure we can decode it.
+		p.media.Type = gtsmodel.FileTypeImage
+
 	// .png image (requires ancillary chunk stripping)
 	case mimeImagePng:
-		fullImg, err = decodeImage(&pngAncillaryChunkStripper{
-			Reader: rc,
-		}, imaging.AutoOrientation(true))
+		fullImg, err = decodeImage(
+			&pngAncillaryChunkStripper{Reader: rc},
+			imaging.AutoOrientation(true),
+		)
 		if err != nil {
 			return gtserror.Newf("error decoding image: %w", err)
 		}
 
+		// Mark as no longer unknown type now
+		// we know for sure we can decode it.
+		p.media.Type = gtsmodel.FileTypeImage
+
 	// .mp4 video type
 	case mimeVideoMp4:
 		video, err := decodeVideoFrame(rc)
@@ -283,9 +439,14 @@ func (p *ProcessingMedia) finish(ctx context.Context) error {
 		p.media.FileMeta.Original.Duration = &video.duration
 		p.media.FileMeta.Original.Framerate = &video.framerate
 		p.media.FileMeta.Original.Bitrate = &video.bitrate
+
+		// Mark as no longer unknown type now
+		// we know for sure we can decode it.
+		p.media.Type = gtsmodel.FileTypeVideo
 	}
 
-	// The image should be in-memory by now.
+	// fullImg should be in-memory by
+	// now so we're done with storage.
 	if err := rc.Close(); err != nil {
 		return gtserror.Newf("error closing file: %w", err)
 	}
@@ -296,15 +457,6 @@ func (p *ProcessingMedia) finish(ctx context.Context) error {
 	p.media.FileMeta.Original.Size = int(fullImg.Size())
 	p.media.FileMeta.Original.Aspect = fullImg.AspectRatio()
 
-	// Calculate attachment thumbnail file path
-	p.media.Thumbnail.Path = fmt.Sprintf(
-		"%s/%s/%s/%s.jpg",
-		p.media.AccountID,
-		TypeAttachment,
-		SizeSmall,
-		p.media.ID,
-	)
-
 	// Get smaller thumbnail image
 	thumbImg := fullImg.Thumbnail()
 
@@ -312,16 +464,20 @@ func (p *ProcessingMedia) finish(ctx context.Context) error {
 	// now take our large son.
 	fullImg = nil
 
-	// Blurhash needs generating from thumb.
-	hash, err := thumbImg.Blurhash()
-	if err != nil {
-		return gtserror.Newf("error generating blurhash: %w", err)
+	// Only generate blurhash
+	// from thumb if necessary.
+	if p.media.Blurhash == "" {
+		hash, err := thumbImg.Blurhash()
+		if err != nil {
+			return gtserror.Newf("error generating blurhash: %w", err)
+		}
+
+		// Set the attachment blurhash.
+		p.media.Blurhash = hash
 	}
 
-	// Set the attachment blurhash.
-	p.media.Blurhash = hash
-
-	// This shouldn't already exist, but we do a check as it's worth logging.
+	// Thumbnail shouldn't already exist in storage at this point,
+	// but we do a check as it's worth logging / cleaning up.
 	if have, _ := p.mgr.state.Storage.Has(ctx, p.media.Thumbnail.Path); have {
 		log.Warnf(ctx, "thumbnail already exists at storage path: %s", p.media.Thumbnail.Path)
 
@@ -333,7 +489,9 @@ func (p *ProcessingMedia) finish(ctx context.Context) error {
 
 	// Create a thumbnail JPEG encoder stream.
 	enc := thumbImg.ToJPEG(&jpeg.Options{
-		Quality: 70, // enough for a thumbnail.
+		// Good enough for
+		// a thumbnail.
+		Quality: 70,
 	})
 
 	// Stream-encode the JPEG thumbnail image into storage.
@@ -342,16 +500,6 @@ func (p *ProcessingMedia) finish(ctx context.Context) error {
 		return gtserror.Newf("error stream-encoding thumbnail to storage: %w", err)
 	}
 
-	// Fill in remaining thumbnail now it's stored
-	p.media.Thumbnail.ContentType = mimeImageJpeg
-	p.media.Thumbnail.URL = uris.GenerateURIForAttachment(
-		p.media.AccountID,
-		string(TypeAttachment),
-		string(SizeSmall),
-		p.media.ID,
-		"jpg", // always jpeg
-	)
-
 	// Set thumbnail dimensions in attachment info.
 	p.media.FileMeta.Small = gtsmodel.Small{
 		Width:  int(thumbImg.Width()),