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import asyncio
from contextlib import asynccontextmanager
from fastapi import FastAPI, HTTPException, Query
from fastapi.middleware.cors import CORSMiddleware
from starlette.requests import Request
from app.schemas import (
TranscriptFailedResponse,
TranscriptQueuedResponse,
TranscriptResponse,
TranscriptResultResponse,
TranscriptSegment,
)
from app.storage import TranscriptStore
from app.transcriber import InvalidURLError, create_api, extract_video_id
from app.worker import run_worker
from datetime import datetime
# How long to wait before retrying a failed video, per error_type (seconds).
# All failures are retryable; cooldowns avoid hammering YouTube or a blocked IP.
RETRY_COOLDOWN_SECONDS: dict[str, float] = {
"not_available": 120.0, # subtitles may not be generated yet
"transcript_disabled": 120.0, # rarely changes, but allow eventual recheck
"ip_blocked": 120.0, # back off when our IP is blocked
"internal_error": 120.0, # transient bugs / network blips
}
DEFAULT_RETRY_COOLDOWN_SECONDS = 120.0
def _failed_entry_is_retryable(entry: dict) -> bool:
"""Return True if a failed queue entry has cooled down enough to retry."""
cooldown = RETRY_COOLDOWN_SECONDS.get(
entry["error_type"] or "", DEFAULT_RETRY_COOLDOWN_SECONDS
)
updated_at = entry.get("updated_at")
if not updated_at:
return True
age = (datetime.utcnow() - datetime.fromisoformat(updated_at)).total_seconds()
return age >= cooldown
@asynccontextmanager
async def lifespan(app: FastAPI):
store = TranscriptStore("data/transcripts.db")
await store.initialize()
api = create_api()
shutdown_event = asyncio.Event()
worker_task = asyncio.create_task(run_worker(store, api, shutdown_event))
app.state.store = store
try:
yield
finally:
shutdown_event.set()
worker_task.cancel()
try:
await worker_task
except asyncio.CancelledError:
pass
await store.close()
app = FastAPI(
title="YouTube Transcriber",
description="API for fetching YouTube video transcripts",
version="0.2.0",
lifespan=lifespan,
)
app.add_middleware(
CORSMiddleware,
allow_origins=["*"],
allow_methods=["*"],
allow_headers=["*"],
)
@app.get("/health")
async def health() -> dict[str, str]:
return {"status": "ok"}
@app.get("/api/transcript", response_model=TranscriptResponse)
async def get_transcript(
request: Request,
url: str = Query(..., description="YouTube video URL", min_length=1),
) -> TranscriptResponse:
try:
video_id = extract_video_id(url)
except InvalidURLError:
raise HTTPException(status_code=400, detail=f"Invalid YouTube URL: {url}")
store: TranscriptStore = request.app.state.store
cached = await store.get_transcript(video_id)
if cached is not None:
return TranscriptResultResponse(
video_id=cached["video_id"],
full_text=cached["full_text"],
segments=[TranscriptSegment(**s) for s in cached["segments"]],
)
entry = await store.get_queue_entry(video_id)
if entry is not None:
if entry["status"] == "failed":
# All failures are retryable once their cooldown has elapsed.
if _failed_entry_is_retryable(entry):
await store.requeue_failed(video_id)
estimate = await store.get_position_and_estimate(video_id)
return TranscriptQueuedResponse(
status="queued",
video_id=video_id,
position=estimate["position"],
estimated_seconds=estimate["estimated_seconds"],
)
return TranscriptFailedResponse(
video_id=video_id,
error=entry["error"] or "",
error_type=entry["error_type"] or "",
)
# pending or processing
estimate = await store.get_position_and_estimate(video_id)
api_status = "processing" if entry["status"] == "processing" else "queued"
return TranscriptQueuedResponse(
status=api_status,
video_id=video_id,
position=estimate["position"],
estimated_seconds=estimate["estimated_seconds"],
)
# Not cached and not queued — enqueue it.
await store.enqueue(video_id)
estimate = await store.get_position_and_estimate(video_id)
return TranscriptQueuedResponse(
status="queued",
video_id=video_id,
position=estimate["position"],
estimated_seconds=estimate["estimated_seconds"],
)
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