Fix inline audio duration detection

src/audio/clip_player.rs

@@ -5,7 +5,7 @@
 //! shared status snapshot at its redraw cadence.
 
 use crate::files::AttachmentId;
-use rodio::{Decoder, DeviceSinkBuilder, MixerDeviceSink, Player, Source};
+use rodio::{Decoder, DeviceSinkBuilder, MixerDeviceSink, Player, Source, decoder::DecoderError};
 use std::io::Cursor;
 use std::sync::{Arc, Mutex, mpsc};
 use std::time::Duration;
@@ -103,7 +103,11 @@ fn playback_worker(command_rx: mpsc::Receiver<ClipCommand>, status: SharedClipSt
     loop {
         match command_rx.recv_timeout(Duration::from_millis(100)) {
             Ok(ClipCommand::Play(id, bytes)) => {
-                let source = match Decoder::new(Cursor::new(bytes)) {
+                // In-memory readers do not expose file metadata to rodio. Pass
+                // the known attachment length explicitly so formats without a
+                // duration in their headers (notably MP3 and Vorbis) can derive
+                // a total duration and support reliable seeking.
+                let source = match decode_clip(bytes) {
                     Ok(source) => source,
                     Err(error) => {
                         fail(
@@ -194,6 +198,14 @@ fn playback_worker(command_rx: mpsc::Receiver<ClipCommand>, status: SharedClipSt
     }
 }
 
+fn decode_clip(bytes: Vec<u8>) -> Result<Decoder<Cursor<Vec<u8>>>, DecoderError> {
+    let byte_len = bytes.len() as u64;
+    Decoder::builder()
+        .with_data(Cursor::new(bytes))
+        .with_byte_len(byte_len)
+        .build()
+}
+
 fn fail(status: &SharedClipStatus, id: AttachmentId, error: String, invalid_audio: bool) {
     crate::log_msg(&format!("Inline audio playback failed: {error}"));
     update_status(status, |s| {
@@ -248,6 +260,20 @@ pub fn seek_target(fraction: f32, total: Duration) -> Duration {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use base64::Engine;
+
+    #[test]
+    fn in_memory_mp3_reports_duration() {
+        // One headerless constant-bitrate MP3 frame repeated to model files
+        // that do not carry an Xing/VBR duration header.
+        let frame = base64::engine::general_purpose::STANDARD
+            .decode("//sQxAAABIQVWVRggDCqCKiDNlAAAAGgS4BgAmTT2AQAABCxOD5d7gQOfqBAEHS4Ph/EAIRI7//0A0KBNpABgMRIDCSI04PcIFdF0PJKFgzlUf5eAoF8BRIPfh4FTvUDQl+dUi5pc0w=")
+            .expect("valid test fixture");
+        let bytes = frame.repeat(20);
+
+        let decoder = decode_clip(bytes).expect("CBR MP3 should decode");
+        assert!(decoder.total_duration().is_some());
+    }
 
     #[test]
     fn formats_clip_time() {