feat: local TTS via piper subprocess with Google fallback

- New src/tts.rs: centralize TTS in synthesize(config, http_client, text)
  Piper subprocess primary, Google Translate fallback on error/missing
- TTS_MODEL_PATH/TTS_VOICE env config (defaults to pl_PL-bass-high)
- Fix Unknown interaction errors: spawn play_tts_in_channel in background
  so voice-state TTS no longer blocks the shard event loop (3s Discord limit)
- Best-effort confirmation replies in /tts to prevent error cascade
- Custom on_error handler: graceful interaction-expired error handling
- Comprehensive tracing logging (engine, model, duration, stderr)

1 files changed, 48 insertions, 31 deletions

diff --git a/src/events/mod.rs b/src/events/mod.rs
index 82b6f19..22fe976 100644
--- a/src/events/mod.rs
+++ b/src/events/mod.rs
@@ -28,32 +28,22 @@ fn format_duration(seconds: f64) -> String {
 }
 
 async fn play_tts_in_channel(
-    _ctx: &serenity::Context,
-    data: &Data,
+    config: crate::config::Config,
+    http_client: reqwest::Client,
+    voice_manager: crate::voice::VoiceManager,
     guild_id: serenity::GuildId,
     channel_id: serenity::ChannelId,
-    text: &str,
+    text: String,
 ) {
-    let tts_url = format!(
-        "https://translate.google.com/translate_tts?ie=UTF-8&q={}&tl=pl&client=tw-ob",
-        crate::commands::tts::urlencoding(text),
-    );
-
-    let audio_data = match data.http_client.get(&tts_url).send().await {
-        Ok(resp) => match resp.bytes().await {
-            Ok(b) => b,
-            Err(e) => {
-                warn!("Failed to read TTS audio bytes: {e}");
-                return;
-            }
-        },
+    let audio_data = match crate::tts::synthesize(&config, &http_client, &text).await {
+        Ok((bytes, _)) => bytes,
         Err(e) => {
-            warn!("Failed to fetch TTS audio: {e}");
+            warn!("Failed to synthesize TTS: {e}");
             return;
         }
     };
 
-    let call = match data.voice_manager.connect(guild_id, channel_id).await {
+    let call = match voice_manager.connect(guild_id, channel_id).await {
         Ok(c) => c,
         Err(e) => {
             warn!("Failed to connect to voice for TTS: {e}");
@@ -93,9 +83,10 @@ pub async fn handle_voice_state_update(
         .and_then(|gid| ctx.cache.guild(gid))
         .and_then(|g| g.members.get(&user_id).cloned());
     if let Some(ref m) = member
-        && m.user.bot {
-            return Ok(());
-        }
+        && m.user.bot
+    {
+        return Ok(());
+    }
 
     let member_name = member
         .as_ref()
@@ -130,7 +121,9 @@ pub async fn handle_voice_state_update(
     let mut tts_channel: Option<serenity::ChannelId> = None;
 
     // ── JOIN ──
-    if old_channel.is_none() && let Some(cid) = new_channel {
+    if old_channel.is_none()
+        && let Some(cid) = new_channel
+    {
         let is_afk = new.self_mute || new.self_deaf;
 
         va.join_time = now;
@@ -274,9 +267,17 @@ pub async fn handle_voice_state_update(
             lang::fmt_ev_undeafened(&display_name)
         };
         if let Some(gid) = guild_id
-            && let Some(cid) = tts_channel.or(new_channel) {
-                play_tts_in_channel(ctx, data, gid, cid, &phrase).await;
-            }
+            && let Some(cid) = tts_channel.or(new_channel)
+        {
+            tokio::spawn(play_tts_in_channel(
+                data.config.clone(),
+                data.http_client.clone(),
+                data.voice_manager.clone(),
+                gid,
+                cid,
+                phrase,
+            ));
+        }
         return Ok(());
     }
 
@@ -287,17 +288,33 @@ pub async fn handle_voice_state_update(
             lang::fmt_ev_unmuted(&display_name)
         };
         if let Some(gid) = guild_id
-            && let Some(cid) = tts_channel.or(new_channel) {
-                play_tts_in_channel(ctx, data, gid, cid, &phrase).await;
-            }
+            && let Some(cid) = tts_channel.or(new_channel)
+        {
+            tokio::spawn(play_tts_in_channel(
+                data.config.clone(),
+                data.http_client.clone(),
+                data.voice_manager.clone(),
+                gid,
+                cid,
+                phrase,
+            ));
+        }
         return Ok(());
     }
 
     // ── Play join/leave TTS if no mute/deafen change ──
     if let (Some(text), Some(cid)) = (tts_text, tts_channel)
-        && let Some(gid) = guild_id {
-            play_tts_in_channel(ctx, data, gid, cid, &text).await;
-        }
+        && let Some(gid) = guild_id
+    {
+        tokio::spawn(play_tts_in_channel(
+            data.config.clone(),
+            data.http_client.clone(),
+            data.voice_manager.clone(),
+            gid,
+            cid,
+            text,
+        ));
+    }
 
     Ok(())
 }