Rework TTS algorithm

tts.go

@@ -13,11 +13,11 @@ import (
 	"net/url"
 	"path"
 	"strings"
-	"sync"
 
 	"github.com/carlmjohnson/requests"
 	"go.goblog.app/app/pkgs/bufferpool"
 	"go.goblog.app/app/pkgs/mp3merge"
+	"golang.org/x/sync/errgroup"
 )
 
 const ttsParameter = "tts"
@@ -72,52 +72,41 @@ func (a *goBlog) createPostTTSAudio(p *post) error {
 	parts = append(parts, strings.Split(htmlText(a.postHtml(&postHtmlOptions{p: p})), "\n\n")...)
 
 	// Create TTS audio for each part
-	partWriters := make([]io.Writer, len(parts))
-	partReaders := make([]io.Reader, len(parts))
-	for i := range parts {
-		buf := bufferpool.Get()
-		defer bufferpool.Put(buf)
-		partWriters[i] = buf
-		partReaders[i] = buf
-	}
-	errs := make([]error, len(parts))
-	var wg sync.WaitGroup
-	for i, part := range parts {
-		// Increase wait group
-		wg.Add(1)
-		go func(i int, part string) {
-			defer wg.Done()
+	partReaders := []io.Reader{}
+	var g errgroup.Group
+	for _, part := range parts {
+		part := part
+		pr, pw := io.Pipe()
+		defer func() {
+			pw.Close()
+		}()
+		partReaders = append(partReaders, pr)
+		g.Go(func() error {
 			// Build SSML
 			ssml := "<speak>" + html.EscapeString(part) + "<break time=\"500ms\"/></speak>"
 			// Create TTS audio
-			err := a.createTTSAudio(lang, ssml, partWriters[i])
-			if err != nil {
-				errs[i] = err
-				return
-			}
-		}(i, part)
-	}
-
-	// Wait for all parts to be created
-	wg.Wait()
-
-	// Check if any errors occurred
-	for _, err := range errs {
-		if err != nil {
+			err := a.createTTSAudio(lang, ssml, pw)
+			_ = pw.CloseWithError(err)
 			return err
-		}
+		})
 	}
 
-	// Merge partsBuffers into final buffer
-	final := bufferpool.Get()
-	defer bufferpool.Put(final)
+	// Merge parts together (needs buffer because the hash is needed before the file can be uploaded)
+	buf := bufferpool.Get()
+	defer bufferpool.Put(buf)
 	hash := sha256.New()
-	if err := mp3merge.MergeMP3(io.MultiWriter(final, hash), partReaders...); err != nil {
+	err := mp3merge.MergeMP3(io.MultiWriter(buf, hash), partReaders...)
+	if err != nil {
+		return err
+	}
+
+	// Check if other errors appeared
+	if err = g.Wait(); err != nil {
 		return err
 	}
 
 	// Save audio
-	loc, err := a.saveMediaFile(fmt.Sprintf("%x.mp3", hash.Sum(nil)), final)
+	loc, err := a.saveMediaFile(fmt.Sprintf("%x.mp3", hash.Sum(nil)), buf)
 	if err != nil {
 		return err
 	}
@@ -125,6 +114,7 @@ func (a *goBlog) createPostTTSAudio(p *post) error {
 		return errors.New("no media location for tts audio")
 	}
 
+	// Check existing tts parameter
 	if old := p.firstParameter(ttsParameter); old != "" && old != loc {
 		// Already has tts audio, but with different location
 		// Try to delete the old audio file