import asyncio
from dataclasses import dataclass
from datetime import datetime, timezone
from uuid import UUID, uuid4

from app.models import CheckStatus, Monitor, MonitorCreate, MonitorUpdate


@dataclass(frozen=True)
class Snapshot:
    monitor: Monitor
    revision: int


class MonitorStore:
    def __init__(self) -> None:
        self._lock = asyncio.Lock()
        self._items: dict[UUID, tuple[Monitor, int]] = {}

    async def create(self, data: MonitorCreate) -> Monitor:
        now = datetime.now(timezone.utc)
        item = Monitor(id=uuid4(), name=data.name, url=data.url, created_at=now,
                       updated_at=now, status=CheckStatus())
        async with self._lock:
            self._items[item.id] = (item, 1)
        return item.model_copy(deep=True)

    async def list(self) -> list[Monitor]:
        async with self._lock:
            values = [item.model_copy(deep=True) for item, _ in self._items.values()]
        return sorted(values, key=lambda item: (item.created_at, str(item.id)))

    async def snapshot(self, monitor_id: UUID) -> Snapshot | None:
        async with self._lock:
            stored = self._items.get(monitor_id)
            if stored is None:
                return None
            item, revision = stored
            return Snapshot(item.model_copy(deep=True), revision)

    async def update(self, monitor_id: UUID, data: MonitorUpdate) -> Monitor | None:
        async with self._lock:
            stored = self._items.get(monitor_id)
            if stored is None:
                return None
            item, revision = stored
            changes = data.model_dump(exclude_none=True)
            if "url" in changes:
                changes["status"] = CheckStatus()
            changes["updated_at"] = datetime.now(timezone.utc)
            updated = item.model_copy(update=changes)
            self._items[monitor_id] = (updated, revision + 1)
            return updated.model_copy(deep=True)

    async def delete(self, monitor_id: UUID) -> bool:
        async with self._lock:
            return self._items.pop(monitor_id, None) is not None

    async def apply_status(self, monitor_id: UUID, revision: int,
                           status: CheckStatus) -> bool:
        async with self._lock:
            stored = self._items.get(monitor_id)
            if stored is None or stored[1] != revision:
                return False
            item, current_revision = stored
            updated = item.model_copy(update={"status": status})
            self._items[monitor_id] = (updated, current_revision)
            return True