backend/api/server.py

"""
Speech-to-Video Server  (api/ — warm-load version)
====================================================
Models are loaded ONCE at server startup (lifespan), not at /connect.
This means /connect is instant for subsequent sessions.

Model loading split:
  lifespan  → MuseTalk bundle + Kokoro TTS + UNet warmup (stay in VRAM)
  /connect  → Room, Publisher, MuseTalkWorker, Pipeline (per-session)
  /disconnect → session objects torn down; models stay loaded

Run:
  cd backend && python api/server.py
  # or: uvicorn api.server:app --host 0.0.0.0 --port 8767
"""
from __future__ import annotations

import asyncio
import logging
import sys
import time
from contextlib import asynccontextmanager
from pathlib import Path
from typing import Optional

# ── path setup ────────────────────────────────────────────────────────────────
_current_file = Path(__file__).resolve()
_api_dir      = _current_file.parent        # backend/api/
_backend_dir  = _api_dir.parent             # backend/
_project_dir  = _backend_dir.parent         # speech_to_video/

for p in [_backend_dir, _project_dir]:
    if str(p) not in sys.path:
        sys.path.insert(0, str(p))

# ── imports ───────────────────────────────────────────────────────────────────
import numpy as np
import uvicorn
from fastapi import FastAPI, HTTPException
from fastapi.middleware.cors import CORSMiddleware
from pydantic import BaseModel
from livekit import rtc
from livekit import api as lk_api

from config import (
    HOST,
    PORT,
    LIVEKIT_URL,
    LIVEKIT_API_KEY,
    LIVEKIT_API_SECRET,
    LIVEKIT_ROOM_NAME,
    VIDEO_FPS,
    DEFAULT_AVATAR,
    DEVICE,
)
from tts.kokoro_tts import KokoroTTS
from musetalk.worker import load_musetalk_models, MuseTalkWorker, MuseTalkBundle
from publisher.livekit_publisher import AVPublisher
from api.pipeline import StreamingPipeline

import torch
torch.set_float32_matmul_precision("high")
torch._dynamo.config.suppress_errors = True

log = logging.getLogger(__name__)
logging.basicConfig(
    level=logging.INFO,
    format="%(asctime)s  %(levelname)-7s  %(name)s  %(message)s",
)

# ── global model state (loaded once, lives for server lifetime) ───────────────
_musetalk_bundle: Optional[MuseTalkBundle] = None
_tts: Optional[KokoroTTS] = None

# ── session state (created/destroyed on connect/disconnect) ──────────────────
_pipeline:  Optional[StreamingPipeline] = None
_room:      Optional[rtc.Room]          = None
_publisher: Optional[AVPublisher]       = None


# ── lifespan: load models once at startup ────────────────────────────────────

@asynccontextmanager
async def lifespan(app: FastAPI):
    global _musetalk_bundle, _tts

    t_start = time.monotonic()
    log.info("=== Speech-to-Video Server Starting ===")
    log.info("Device: %s  Avatar: %s", DEVICE, DEFAULT_AVATAR)

    # 1. Load MuseTalk (VAE + UNet + Whisper + avatar latents)
    log.info("Loading MuseTalk models...")
    _musetalk_bundle = await asyncio.to_thread(
        load_musetalk_models, DEFAULT_AVATAR, DEVICE
    )
    log.info("MuseTalk loaded  (%.1fs)", time.monotonic() - t_start)

    # 2. Load Kokoro TTS
    log.info("Loading Kokoro TTS...")
    _tts = await asyncio.to_thread(KokoroTTS)
    log.info("Kokoro TTS loaded")

    # 3. UNet warmup — prime GPU caches
    worker_tmp = MuseTalkWorker(_musetalk_bundle)
    dummy_audio = np.zeros(int(0.32 * 24_000), dtype=np.float32)
    feats, _ = await worker_tmp.extract_features(dummy_audio)
    t0 = time.monotonic()
    n = min(8, len(_musetalk_bundle.avatar_assets.frame_list))
    await worker_tmp.generate_batch(feats, 0, n)
    log.info("UNet warm-up done  (%.1fs)", time.monotonic() - t0)
    worker_tmp.shutdown()

    _tts.synthesize_full("Hello.")
    log.info("TTS warm-up done")

    log.info("=== Server ready in %.1fs — waiting for /connect (port %d) ===",
             time.monotonic() - t_start, PORT)

    yield  # ── server running ────────────────────────────────────────────────

    # ── shutdown ──────────────────────────────────────────────────────────────
    global _pipeline, _room, _publisher
    if _pipeline:
        await _pipeline.stop()
    if _publisher:
        await _publisher.stop()
    if _room:
        await _room.disconnect()
    log.info("=== Server Shutdown ===")


# ── FastAPI app ───────────────────────────────────────────────────────────────

app = FastAPI(
    title="Speech-to-Video (api — 3-queue)",
    description="Text → Kokoro TTS → Whisper → MuseTalk → LiveKit",
    version="2.0.0",
    lifespan=lifespan,
)

app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_methods=["*"],
    allow_headers=["*"],
)


# ── request models ────────────────────────────────────────────────────────────

class SpeakRequest(BaseModel):
    text: str
    voice: Optional[str] = None
    speed: Optional[float] = None

class TokenRequest(BaseModel):
    room_name: str = LIVEKIT_ROOM_NAME
    identity: str = "user"


# ── /health and /status ───────────────────────────────────────────────────────

@app.get("/health")
async def health():
    return {
        "status": "ok",
        "models_loaded": _musetalk_bundle is not None and _tts is not None,
        "pipeline_active": _pipeline is not None and getattr(_pipeline, "_running", False),
    }

@app.get("/status")
async def status():
    vram = {}
    if torch.cuda.is_available():
        vram = {
            "allocated_gb": round(torch.cuda.memory_allocated() / 1024**3, 2),
            "reserved_gb":  round(torch.cuda.memory_reserved()  / 1024**3, 2),
        }
    return {
        "pipeline": "api-3-queue",
        "models_loaded": _musetalk_bundle is not None,
        "pipeline_active": _pipeline is not None and getattr(_pipeline, "_running", False),
        "avatar": DEFAULT_AVATAR,
        "device": DEVICE,
        "vram": vram,
    }


# ── /connect ──────────────────────────────────────────────────────────────────

@app.post("/connect")
async def connect():
    global _room, _publisher, _pipeline

    if _musetalk_bundle is None or _tts is None:
        raise HTTPException(status_code=503, detail="Server still loading models")

    if _pipeline is not None and getattr(_pipeline, "_running", False):
        raise HTTPException(status_code=400, detail="Already connected")

    log.info("Connecting to LiveKit room...")
    t0 = time.monotonic()

    try:
        first_frame = _musetalk_bundle.avatar_assets.frame_list[0]
        actual_h, actual_w = first_frame.shape[:2]

        room = rtc.Room()
        token = (
            lk_api.AccessToken(LIVEKIT_API_KEY, LIVEKIT_API_SECRET)
            .with_identity("backend-agent")
            .with_name("Speech-to-Video Agent")
        )
        token.with_grants(lk_api.VideoGrants(
            room_join=True,
            room=LIVEKIT_ROOM_NAME,
            can_publish=True,
            can_subscribe=True,
        ))

        publisher = AVPublisher(
            room,
            video_width=actual_w,
            video_height=actual_h,
            video_fps=VIDEO_FPS,
        )

        # MuseTalkWorker wraps the already-loaded bundle — no model reload
        musetalk_worker = MuseTalkWorker(_musetalk_bundle)

        pipeline = StreamingPipeline(
            tts=_tts,
            musetalk=musetalk_worker,
            publisher=publisher,
            avatar_assets=_musetalk_bundle.avatar_assets,
        )

        await room.connect(url=LIVEKIT_URL, token=token.to_jwt())
        log.info("Connected to LiveKit: %s", LIVEKIT_ROOM_NAME)

        await publisher.start()
        await pipeline.start()

        # Fast warmup (models already hot in VRAM)
        dummy_audio = np.zeros(int(0.32 * 24_000), dtype=np.float32)
        feats, _ = await musetalk_worker.extract_features(dummy_audio)
        n = min(8, len(_musetalk_bundle.avatar_assets.frame_list))
        await musetalk_worker.generate_batch(feats, 0, n)
        log.info("Session warm-up done")

        _room      = room
        _publisher = publisher
        _pipeline  = pipeline

        log.info("/connect done in %.1fs", time.monotonic() - t0)
        return {"status": "connected", "room": LIVEKIT_ROOM_NAME, "url": LIVEKIT_URL}

    except Exception as exc:
        log.error("Connection failed: %s", exc, exc_info=True)
        raise HTTPException(status_code=500, detail=str(exc))


# ── /disconnect ───────────────────────────────────────────────────────────────

@app.post("/disconnect")
async def disconnect():
    global _room, _publisher, _pipeline

    if _pipeline is None:
        raise HTTPException(status_code=400, detail="Not connected")

    log.info("Disconnecting...")

    if _pipeline:
        await _pipeline.stop()
    if _publisher:
        await _publisher.stop()
    if _room:
        await _room.disconnect()

    _room = _publisher = _pipeline = None
    # NOTE: _musetalk_bundle and _tts are intentionally NOT cleared —
    # models stay in VRAM so the next /connect is instant.
    log.info("Disconnected — models remain loaded for next session")
    return {"status": "disconnected"}


# ── /speak ────────────────────────────────────────────────────────────────────

@app.post("/speak")
async def speak(request: SpeakRequest):
    if _pipeline is None or not getattr(_pipeline, "_running", False):
        raise HTTPException(status_code=400, detail="Not connected")

    t0 = time.monotonic()
    await _pipeline.push_text(request.text)
    return {"status": "processing", "latency_ms": round((time.monotonic() - t0) * 1000, 1)}


# ── /get-token ────────────────────────────────────────────────────────────────

@app.post("/get-token")
@app.get("/livekit-token")
async def get_token(request: TokenRequest = TokenRequest()):
    room     = request.room_name or LIVEKIT_ROOM_NAME
    identity = request.identity  or "frontend-user"

    token = (
        lk_api.AccessToken(LIVEKIT_API_KEY, LIVEKIT_API_SECRET)
        .with_identity(identity)
        .with_name(identity)
    )
    token.with_grants(lk_api.VideoGrants(
        room_join=True,
        room=room,
        can_publish=True,
        can_subscribe=True,
    ))
    return {"token": token.to_jwt(), "url": LIVEKIT_URL, "room": room}


# ── entry point ───────────────────────────────────────────────────────────────

if __name__ == "__main__":
    uvicorn.run(app, host=HOST, port=PORT, reload=False, log_level="info")