"""Policy engine: hard constraints independent of LLM for AGI."""

from typing import Any

from fusionagi.schemas.policy import PolicyEffect, PolicyRule
from fusionagi._logger import logger


class PolicyEngine:
    """Evaluates policy rules; higher priority first; first match wins (allow/deny)."""

    def __init__(self) -> None:
        self._rules: list[PolicyRule] = []

    def add_rule(self, rule: PolicyRule) -> None:
        self._rules.append(rule)
        self._rules.sort(key=lambda r: -r.priority)
        logger.debug("PolicyEngine: rule added", extra={"rule_id": rule.rule_id})

    def get_rules(self) -> list[PolicyRule]:
        """Return all rules (copy)."""
        return list(self._rules)

    def get_rule(self, rule_id: str) -> PolicyRule | None:
        """Return rule by id or None."""
        for r in self._rules:
            if r.rule_id == rule_id:
                return r
        return None

    def update_rule(self, rule_id: str, updates: dict[str, Any]) -> bool:
        """
        Update an existing rule by id. Updates can include condition, effect, reason, priority.
        Returns True if updated, False if rule_id not found.
        """
        for i, r in enumerate(self._rules):
            if r.rule_id == rule_id:
                allowed = {"condition", "effect", "reason", "priority"}
                data = r.model_dump()
                for k, v in updates.items():
                    if k in allowed:
                        data[k] = v
                self._rules[i] = PolicyRule.model_validate(data)
                self._rules.sort(key=lambda x: -x.priority)
                logger.debug("PolicyEngine: rule updated", extra={"rule_id": rule_id})
                return True
        return False

    def remove_rule(self, rule_id: str) -> bool:
        """Remove a rule by id. Returns True if removed."""
        for i, r in enumerate(self._rules):
            if r.rule_id == rule_id:
                self._rules.pop(i)
                logger.debug("PolicyEngine: rule removed", extra={"rule_id": rule_id})
                return True
        return False

    def check(self, action: str, context: dict[str, Any]) -> tuple[bool, str]:
        """
        Returns (allowed, reason). Context has e.g. tool_name, domain, data_class, agent_id.
        """
        for rule in self._rules:
            if self._match(rule.condition, context):
                if rule.effect == PolicyEffect.DENY:
                    return False, rule.reason or "Policy denied"
                return True, rule.reason or "Policy allowed"
        return True, ""

    def _match(self, condition: dict[str, Any], context: dict[str, Any]) -> bool:
        for k, v in condition.items():
            if context.get(k) != v:
                return False
        return True