Ready to implement a loading bar

internal/page/scrollerPage.go

@@ -2,7 +2,11 @@ package page
 
 import (
 	"fmt"
+	"io"
 	"math"
+	"net/http"
+	"os"
+	"path/filepath"
 	"strings"
 
 	"github.com/go-gl/gl/v3.3-core/gl"
@@ -23,6 +27,87 @@ const (
 	defaultProclamationPlayCount int    = 1
 )
 
+// ProgressUpdate is sent over a channel as bytes are read from the network
+// during a download. Read/Total let a consumer compute percentage; Done
+// signals a clean finish; Err signals failure. The channel carrying these
+// is closed after the final update (whether that's a Done or an Err), so
+// ranging over it is sufficient to know when the download has finished.
+type ProgressUpdate struct {
+	Read  int64
+	Total int64
+	Done  bool
+	Err   error
+}
+
+// ProgressReader wraps an io.Reader and emits a ProgressUpdate on every
+// Read() call. It never blocks on the send: if nobody is currently
+// listening on updates (or the consumer is behind), the update is dropped
+// rather than stalling the download itself.
+type ProgressReader struct {
+	Reader  io.Reader
+	Total   int64
+	read    int64
+	updates chan<- ProgressUpdate
+}
+
+func (pr *ProgressReader) Read(p []byte) (int, error) {
+	n, err := pr.Reader.Read(p)
+	if n > 0 {
+		pr.read += int64(n)
+		select {
+		case pr.updates <- ProgressUpdate{Read: pr.read, Total: pr.Total}:
+		default:
+		}
+	}
+	return n, err
+}
+
+// downloadFile starts the download in its own goroutine and returns
+// immediately with a channel of progress updates. The caller ranges over
+// the returned channel to observe progress; the channel is closed when the
+// download finishes, successfully or not, so the loop ends naturally.
+func downloadFile(url, destPath string) <-chan ProgressUpdate {
+	updates := make(chan ProgressUpdate, 16)
+
+	go func() {
+		defer close(updates)
+
+		resp, err := http.Get(url)
+		if err != nil {
+			updates <- ProgressUpdate{Err: err}
+			return
+		}
+		defer resp.Body.Close()
+
+		if resp.StatusCode != http.StatusOK {
+			updates <- ProgressUpdate{Err: fmt.Errorf("bad status: %s", resp.Status)}
+			return
+		}
+
+		out, err := os.Create(destPath)
+		if err != nil {
+			updates <- ProgressUpdate{Err: err}
+			return
+		}
+		defer out.Close()
+
+		pr := &ProgressReader{
+			Reader:  resp.Body,
+			Total:   resp.ContentLength, // -1 if server didn't send it
+			updates: updates,
+		}
+
+		if _, err := io.Copy(out, pr); err != nil {
+			updates <- ProgressUpdate{Err: err}
+			return
+		}
+
+		updates <- ProgressUpdate{Read: pr.read, Total: pr.Total, Done: true}
+	}()
+
+	return updates
+}
+
 type ScrollerProclamation struct {
 	db.Proclamation
 	colorPattern.ColorPattern
@@ -260,31 +345,42 @@ func (p *ScrollerPage) Init(ctx *PageCtx) error {
 		}
 	}
 
-	audioFilePath := p.Context.DbPtr.Find
+	var selectedAudio db.AudioFile
 
-	// Download if it doesn't exist
-	fmt.Printf("%s", audioFilePath)
+	if err := p.Context.DbPtr.Where("Selected = ?", true).First(&selectedAudio).Error; err != nil {
+		logger.Error("error querying database for selected audio: %v", err)
+	} else {
+		_, err = os.Stat(selectedAudio.Path)
+		if err != nil { // If err == nil, then the file was most likely not found
+			url := "https://files.radiantwavetech.com/audio/" + filepath.Base(selectedAudio.Path)
 
-	// // Check if the track has previously been downloaded
-	// // TODO: Download audio via a goroutine
-	// // this is a path
-	// // figure out how to get the filename, not the path, from the path.
-	// _, err = os.Stat(audioFilePath)
-	// if err != nil {
-	// 	filename := filepath.Base(audioFilePath)
-	// 	url := "https://files.radiantwavetech.com/audio/" + filename
-	// 	logger.Info("%s not present. Downloading...", entry.DisplayName)
-	// 	// Download the track if not, display loading bar
-	// 	if err = netreq.Download(filename, filepath.Join(p.Base.Context.CfgPtr.AssetsDir, "audio"), url); err != nil {
-	// 		logger.Error("Failed to download file: %v", err)
-	// 		return
-	// 	}
-	// 	logger.Info("Downloaded %s", entry.DisplayName)
-	// }
+			updates := downloadFile(url, selectedAudio.Path)
+			var downloadErr error
+			for u := range updates {
+				if u.Err != nil {
+					downloadErr = u.Err
+					break
+				}
+				if u.Total > 0 {
+					pct := float64(u.Read) / float64(u.Total) * 100
+					fmt.Printf("\rDownloaded %d / %d bytes (%.1f%%)", u.Read, u.Total, pct)
+				} else {
+					fmt.Printf("\rDownloaded %d bytes", u.Read)
+				}
+				if u.Done {
+					fmt.Println()
+				}
+			}
+			if downloadErr != nil {
+				return fmt.Errorf("failed to downoad audio file: %v", downloadErr)
+			}
+		}
+	}
 
-	// if err := mixer.Play(audioFile, true, p.Context.CfgPtr); err != nil {
-	// 	logger.Error("Mixer returned an error: %v", err)
-	// }
+	logger.Info("Playing %s", selectedAudio.Path)
+	if err := mixer.Play(selectedAudio.Path, true, p.Context.CfgPtr); err != nil {
+		logger.Error("Mixer returned an error: %v", err)
+	}
 
 	currentDevice := mixer.CurrentDevice()
 	if currentDevice == "" {