"""Policy decision primitives for permission-aware operations."""

from __future__ import annotations

from dataclasses import dataclass, field
from enum import Enum
from typing import Any

from .primitives import compact_dict, new_id, utc_now


class PolicyEffect(str, Enum):
    ALLOW = "allow"
    DENY = "deny"
    REDACT = "redact"
    REQUIRE_REVIEW = "require_review"
    DRY_RUN_ONLY = "dry_run_only"
    FAIL_CLOSED = "fail_closed"


@dataclass(frozen=True)
class PolicyDecision:
    effect: PolicyEffect
    subject_id: str
    action: str
    resource: str
    reason: str = ""
    decision_id: str = field(default_factory=lambda: new_id("policy"))
    obligations: dict[str, Any] = field(default_factory=dict)
    context: dict[str, Any] = field(default_factory=dict)
    decided_at: str = field(default_factory=lambda: utc_now().isoformat())

    @classmethod
    def allow(cls, subject_id: str, action: str, resource: str, **kwargs: Any) -> "PolicyDecision":
        return cls(PolicyEffect.ALLOW, subject_id, action, resource, **kwargs)

    @classmethod
    def deny(
        cls,
        subject_id: str,
        action: str,
        resource: str,
        *,
        reason: str,
        **kwargs: Any,
    ) -> "PolicyDecision":
        return cls(PolicyEffect.DENY, subject_id, action, resource, reason=reason, **kwargs)

    @classmethod
    def fail_closed(
        cls,
        subject_id: str,
        action: str,
        resource: str,
        *,
        reason: str = "Permission context is missing or ambiguous",
        **kwargs: Any,
    ) -> "PolicyDecision":
        return cls(PolicyEffect.FAIL_CLOSED, subject_id, action, resource, reason=reason, **kwargs)

    @property
    def allowed(self) -> bool:
        return self.effect == PolicyEffect.ALLOW

    def to_dict(self) -> dict[str, Any]:
        return compact_dict(
            {
                "decision_id": self.decision_id,
                "effect": self.effect.value,
                "subject_id": self.subject_id,
                "action": self.action,
                "resource": self.resource,
                "reason": self.reason,
                "obligations": dict(self.obligations),
                "context": dict(self.context),
                "decided_at": self.decided_at,
            }
        )

    @classmethod
    def from_dict(cls, data: dict[str, Any]) -> "PolicyDecision":
        return cls(
            decision_id=data["decision_id"],
            effect=PolicyEffect(data["effect"]),
            subject_id=data["subject_id"],
            action=data["action"],
            resource=data["resource"],
            reason=data.get("reason", ""),
            obligations=dict(data.get("obligations", {})),
            context=dict(data.get("context", {})),
            decided_at=data["decided_at"],
        )