Inbox pattern consumer dedupe mock in Python

import json
from collections import deque
from dataclasses import dataclass, field
from hashlib import sha256
from typing import Any


@dataclass
class InboxConsumer:
    max_seen: int = 1000
    seen_ids: set = field(default_factory=set)
    seen_history: deque = field(default_factory=deque)

    def _mark_seen(self, message_id: str) -> None:
        if message_id not in self.seen_ids:
            self.seen_history.append(message_id)
            if len(self.seen_history) > self.max_seen:
                evicted = self.seen_history.popleft()
                self.seen_ids.discard(evicted)

    def consume(self, message: dict[str, Any]) -> None:
        message_id = message.get("id", "")
        message_id = sha256(json.dumps(message).encode()).hexdigest() if not message_id else message_id

        if message_id in self.seen_ids:
            print(f"DEDUPE   id={message_id} payload={message['payload']}")
            return

        self._mark_seen(message_id)
        print(f"CONSUMED id={message_id} payload={message['payload']}")


if __name__ == "__main__":
    inbox = InboxConsumer(max_seen=3)
    messages = [
        {"id": "a1", "payload": "first"},
        {"id": "a2", "payload": "second"},
        {"id": "a1", "payload": "first (duplicate)"},
        {"payload": "no-id-message"},
        {"payload": "no-id-message (duplicate)"},
        {"id": "a3", "payload": "third"},
        {"id": "a4", "payload": "fourth"},
        {"id": "a1", "payload": "first (old, should pass now)"},
    ]
    for msg in messages:
        inbox.consume(msg)