"""TTL and idle-reap expiry candidate selection."""

from __future__ import annotations

from dataclasses import dataclass
from datetime import UTC, datetime
from typing import Literal

from sandboxer.lifecycle.store import SandboxStore
from sandboxer.lifecycle.ttl import is_idle_expired, is_past_expiry
from sandboxer.models import SandboxState, SandboxStatus
from sandboxer.profiles.loader import load_profile

ExpireReason = Literal["ttl", "idle"]


@dataclass
class ExpireCandidate:
    sandbox_id: str
    profile_id: str
    reason: ExpireReason
    expires_at: datetime | None = None
    updated_at: datetime | None = None


_LIVE_STATES = frozenset({SandboxState.READY, SandboxState.ACTIVE})


def find_expire_candidates(
    store: SandboxStore,
    *,
    now: datetime | None = None,
) -> list[ExpireCandidate]:
    ref = now or datetime.now(UTC)
    candidates: list[ExpireCandidate] = []
    seen: set[str] = set()

    for status in store.list_all():
        if status.state not in _LIVE_STATES:
            continue

        if is_past_expiry(status.expires_at, now=ref):
            candidates.append(
                ExpireCandidate(
                    sandbox_id=status.sandbox_id,
                    profile_id=status.profile_id,
                    reason="ttl",
                    expires_at=status.expires_at,
                )
            )
            seen.add(status.sandbox_id)
            continue

        try:
            profile = load_profile(status.profile_id)
        except FileNotFoundError:
            continue

        if is_idle_expired(status.updated_at, profile.ttl.idle_reap, now=ref):
            candidates.append(
                ExpireCandidate(
                    sandbox_id=status.sandbox_id,
                    profile_id=status.profile_id,
                    reason="idle",
                    updated_at=status.updated_at,
                )
            )
            seen.add(status.sandbox_id)

    return sorted(candidates, key=lambda c: c.sandbox_id)


def apply_expired_state(status: SandboxStatus, *, now: datetime | None = None) -> SandboxStatus:
    ref = now or datetime.now(UTC)
    status.state = SandboxState.EXPIRED
    status.updated_at = ref
    return status