feat: add FastAPI lifespan hooks for browser pre-warm and clean shutdown (#90)

Closes #90

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/main.py

@@ -1,5 +1,6 @@
 import logging
 import os
+from contextlib import asynccontextmanager
 from datetime import datetime
 
 from fastapi import FastAPI, Request
@@ -16,8 +17,9 @@ logging.basicConfig(
 # from fastapi.staticfiles import StaticFiles
 # from fastapi.templating import Jinja2Templates
 
-from .db_engine import db
-from .routers_v2 import (
+from .db_engine import db  # noqa: E402
+from .routers_v2.players import get_browser, shutdown_browser  # noqa: E402
+from .routers_v2 import (  # noqa: E402
     current,
     awards,
     teams,
@@ -51,8 +53,17 @@ from .routers_v2 import (
     scout_claims,
 )
 
+
+@asynccontextmanager
+async def lifespan(app: FastAPI):
+    await get_browser()
+    yield
+    await shutdown_browser()
+
+
 app = FastAPI(
     # root_path='/api',
+    lifespan=lifespan,
     responses={404: {"description": "Not found"}},
     docs_url="/api/docs",
     redoc_url="/api/redoc",
@@ -114,4 +125,6 @@ async def get_docs(req: Request):
 
 @app.get("/api/openapi.json", include_in_schema=False)
 async def openapi():
-    return get_openapi(title="Paper Dynasty API", version=f"0.1.1", routes=app.routes)
+    return get_openapi(
+        title="Paper Dynasty API", version=f"0.1.1", routes=app.routes  # noqa: F541
+    )

app/routers_v2/players.py

@@ -9,7 +9,7 @@ from typing import Optional, List, Literal
 import logging
 import pydantic
 from pandas import DataFrame
-from playwright.async_api import async_playwright
+from playwright.async_api import async_playwright, Browser
 
 from ..card_creation import get_batter_card_data, get_pitcher_card_data
 from ..db_engine import (
@@ -31,6 +31,28 @@ from ..db_engine import (
 from ..db_helpers import upsert_players
 from ..dependencies import oauth2_scheme, valid_token
 
+_playwright = None
+_browser = None
+
+
+async def get_browser() -> Browser:
+    global _playwright, _browser
+    if _browser is None or not _browser.is_connected():
+        _playwright = await async_playwright().start()
+        _browser = await _playwright.chromium.launch()
+    return _browser
+
+
+async def shutdown_browser():
+    global _playwright, _browser
+    if _browser is not None:
+        await _browser.close()
+        _browser = None
+    if _playwright is not None:
+        await _playwright.stop()
+        _playwright = None
+
+
 # Franchise normalization: Convert city+team names to city-agnostic team names
 # This enables cross-era player matching (e.g., 'Oakland Athletics' -> 'Athletics')
 FRANCHISE_NORMALIZE = {
@@ -144,7 +166,9 @@ async def get_players(
 ):
     all_players = Player.select()
     if all_players.count() == 0:
-        raise HTTPException(status_code=404, detail=f"There are no players to filter")
+        raise HTTPException(
+            status_code=404, detail=f"There are no players to filter"  # noqa: F541
+        )
 
     if name is not None:
         all_players = all_players.where(fn.Lower(Player.p_name) == name.lower())
@@ -674,7 +698,7 @@ async def get_batter_card(
         )
 
     headers = {"Cache-Control": "public, max-age=86400"}
-    filename = (
+    filename = (  # noqa: F841
         f"{this_player.description} {this_player.p_name} {card_type} {d}-v{variant}"
     )
     if (
@@ -799,16 +823,17 @@ async def get_batter_card(
     logging.debug(f"body:\n{html_response.body.decode('UTF-8')}")
 
     file_path = f"storage/cards/cardset-{this_player.cardset.id}/{card_type}/{player_id}-{d}-v{variant}.png"
-    async with async_playwright() as p:
-        browser = await p.chromium.launch()
-        page = await browser.new_page()
+    browser = await get_browser()
+    page = await browser.new_page()
+    try:
         await page.set_content(html_response.body.decode("UTF-8"))
         await page.screenshot(
             path=file_path,
             type="png",
             clip={"x": 0.0, "y": 0, "width": 1200, "height": 600},
         )
-        await browser.close()
+    finally:
+        await page.close()
 
     # hti = Html2Image(
     #     browser='chrome',