from collections.abc import AsyncIterator

from contextlib import asynccontextmanager

from dataclasses import dataclass

from mcp.server import MCPServer

from mcp.server.mcpserver import Context

class Database:

@classmethod

async def connect(cls) -> "Database":

return cls()

async def disconnect(self) -> None: ...

def query(self) -> int:

return 3

@dataclass

class AppContext:

db: Database

@asynccontextmanager

async def app_lifespan(server: MCPServer) -> AsyncIterator[AppContext]:

db = await Database.connect()

try:

yield AppContext(db=db)

finally:

await db.disconnect()

mcp = MCPServer("Bookshop", lifespan=app_lifespan)

@mcp.tool()

def count_books(genre: str, ctx: Context[AppContext]) -> str:

"""Count the books in a genre."""

db = ctx.request_context.lifespan_context.db

return f"{db.query()} books in {genre!r}."