"""
Policy Registry — versioned promotion pipeline for trained policies.

Lifecycle:
    CANDIDATE → BACKTESTED → SELF_PLAY_CONFIRMED → SHADOW → TINY_LIVE → ACTIVE
                                         ↓
                                       REJECTED

Promotion gates:
    1. Unit tests pass
    2. Replay verification pass
    3. Self-play robust score pass (bootstrap CI)
    4. Shadow live discrepancy pass
    5. Tiny live risk pass
    6. Manual or rule-based promotion

Active policy is loaded by the engine via params_provider.
Hot-reload via CONTROL_PLANE HOT_RELOAD_POLICY command.
"""
from __future__ import annotations

import json
import time
from dataclasses import dataclass, field
from enum import Enum
from typing import Any, Mapping, Optional

from malkhut.state import FulfilmentPolicyParams
from malkhut.storage.ch_store import MalkhutCHStore


class PolicyStage(str, Enum):
    CANDIDATE = "CANDIDATE"
    BACKTESTED = "BACKTESTED"
    SELF_PLAY_CONFIRMED = "SELF_PLAY_CONFIRMED"
    SHADOW = "SHADOW"
    TINY_LIVE = "TINY_LIVE"
    ACTIVE = "ACTIVE"
    RETIRED = "RETIRED"
    REJECTED = "REJECTED"


@dataclass(frozen=True, slots=True)
class PolicyRecord:
    version: str
    stage: PolicyStage
    params: FulfilmentPolicyParams
    score: float
    created_ts_ns: int
    promoted_ts_ns: int = 0
    evaluation_summary: Mapping[str, Any] = field(default_factory=dict)
    promotion_reason: str = ""


class PolicyRegistry:
    """
    Versioned promotion pipeline with CH persistence.

    One ACTIVE policy at a time.
    Multiple CANDIDATE/SHADOW policies in flight.
    RETIRED policies kept for audit.
    """

    def __init__(self, store: Optional[MalkhutCHStore] = None) -> None:
        self._store = store
        self._records: dict[str, PolicyRecord] = {}
        self._active_version: Optional[str] = None

        # Ensure CH table exists
        if self._store:
            self._store.ensure_tables()

    def register_candidate(
        self,
        params: FulfilmentPolicyParams,
        score: float,
        evaluation_summary: Optional[Mapping[str, Any]] = None,
    ) -> PolicyRecord:
        """Register a new candidate policy."""
        record = PolicyRecord(
            version=params.version,
            stage=PolicyStage.CANDIDATE,
            params=params,
            score=score,
            created_ts_ns=time.time_ns(),
            evaluation_summary=evaluation_summary or {},
        )
        self._records[params.version] = record
        self._persist(record)
        return record

    def promote(self, version: str, stage: PolicyStage, reason: str = "") -> PolicyRecord:
        """Promote a policy to a new stage."""
        if version not in self._records:
            raise KeyError(f"Policy {version} not found")

        old = self._records[version]
        new = PolicyRecord(
            version=old.version,
            stage=stage,
            params=old.params,
            score=old.score,
            created_ts_ns=old.created_ts_ns,
            promoted_ts_ns=time.time_ns(),
            evaluation_summary=old.evaluation_summary,
            promotion_reason=reason,
        )
        self._records[version] = new
        self._persist(new)

        if stage == PolicyStage.ACTIVE:
            self._active_version = version

        return new

    def reject(self, version: str, reason: str = "") -> PolicyRecord:
        """Reject a candidate policy."""
        return self.promote(version, PolicyStage.REJECTED, reason)

    def retire(self, version: str, reason: str = "") -> PolicyRecord:
        """Retire the current active policy."""
        return self.promote(version, PolicyStage.RETIRED, reason)

    def load_active(self) -> Optional[FulfilmentPolicyParams]:
        """Load the currently active policy parameters."""
        if self._active_version and self._active_version in self._records:
            record = self._records[self._active_version]
            if record.stage == PolicyStage.ACTIVE:
                return record.params

        # Fallback: scan records for ACTIVE
        for record in self._records.values():
            if record.stage == PolicyStage.ACTIVE:
                self._active_version = record.version
                return record.params

        return None

    def get_record(self, version: str) -> Optional[PolicyRecord]:
        return self._records.get(version)

    def get_by_stage(self, stage: PolicyStage) -> list[PolicyRecord]:
        return [r for r in self._records.values() if r.stage == stage]

    @property
    def active_version(self) -> Optional[str]:
        return self._active_version

    @property
    def record_count(self) -> int:
        return len(self._records)

    def _persist(self, record: PolicyRecord) -> None:
        if self._store:
            self._store.store_policy_snapshot(
                version=record.version,
                score=record.score,
                params_str=json.dumps({
                    "stage": record.stage.value,
                    "promotion_reason": record.promotion_reason,
                    "created_ts_ns": record.created_ts_ns,
                    "promoted_ts_ns": record.promoted_ts_ns,
                }),
                evaluation_summary=json.dumps(dict(record.evaluation_summary)),
            )