import trio
import contextvars

LAST_TASK_ID = 0
TASK_ID: contextvars.ContextVar[str] = contextvars.ContextVar("task_id")


async def producer(num_items: int, send_channel: trio.MemorySendChannel) -> None:
    task_id = TASK_ID.get()
    iden = f"Producer {task_id}"
    print(f"{iden} - Started")
    async with send_channel:
        for k in range(num_items):
            await send_channel.send({"task_id": task_id, "message": f"Message {k}"})
            await trio.sleep(0.3)
    print(f"{iden} - Done")


async def consumer(receive_channel: trio.MemoryReceiveChannel) -> None:
    task_id = TASK_ID.get()
    iden = f"Consumer #{task_id}"
    print(f"Starting {iden}")
    async for event in receive_channel:
        assert event["task_id"] == task_id
        message = event["message"]
        print(f"{iden} - Received: {message!r}")
        result = await process(message)
        print(f"{iden} - Result: {result!r}")
    print(f"{iden} - Done")


async def process(message: str) -> str:
    task_id = TASK_ID.get()
    print(f"Processor {task_id} - Processing message")
    return message[::-1]


async def job(nursery):
    # Set up the task_id for the current job.
    global LAST_TASK_ID
    task_id = LAST_TASK_ID + 1
    LAST_TASK_ID = task_id
    TASK_ID.set(task_id)

    # Start other concurrent tasks.
    send_channel, receive_channel = trio.open_memory_channel(0)
    nursery.start_soon(producer, 10, send_channel)
    nursery.start_soon(consumer, receive_channel)


async def main():
    async with trio.open_nursery() as nursery:
        for _ in range(3):
            nursery.start_soon(job, nursery)
            await trio.sleep(1)


trio.run(main)