"""Idempotency-Registry für wiederholbare Commands (§6.2, §23.2)."""

from __future__ import annotations

from collections import OrderedDict
from typing import Any


class IdempotencyRegistry:
    """Merkt sich command_id → Ergebnis; Wiederholungen liefern dasselbe Ack."""

    def __init__(self, capacity: int = 4096) -> None:
        if capacity <= 0:
            raise ValueError("capacity must be positive")
        self._capacity = capacity
        self._entries: OrderedDict[str, Any] = OrderedDict()

    def register(self, command_id: str) -> bool:
        """False, wenn die command_id bereits bekannt ist (Duplikat)."""
        if command_id in self._entries:
            self._entries.move_to_end(command_id)
            return False
        self._entries[command_id] = None  # Ergebnis folgt mit complete()
        if len(self._entries) > self._capacity:
            self._entries.popitem(last=False)
        return True

    def complete(self, command_id: str, result: Any) -> None:
        if command_id in self._entries:
            self._entries[command_id] = result
            self._entries.move_to_end(command_id)

    def result(self, command_id: str) -> Any | None:
        return self._entries.get(command_id)

    def __len__(self) -> int:
        return len(self._entries)