"""
Console Engine Approval Manager

Handles approval requests, pending state, and decision recording.
State is derived from scroll on init, kept in memory during runtime.
"""

from __future__ import annotations

from dataclasses import dataclass, field, asdict
from datetime import datetime, timezone, timedelta
from pathlib import Path
from typing import Any, Dict, List, Optional, Literal

import json

from .receipts import emit_console_receipt, get_emitter


ApprovalStatus = Literal["pending", "approved", "rejected", "expired"]


@dataclass
class ApprovalRequest:
    """An approval request waiting for decision."""
    approval_id: str
    session_id: str
    action_type: str
    action_details: Dict[str, Any]
    requested_by: str
    approvers: List[str]
    expires_at: str
    status: ApprovalStatus = "pending"
    created_at: str = field(
        default_factory=lambda: datetime.now(timezone.utc).isoformat()
    )


class ApprovalManager:
    """
    Manages pending approval requests.

    State is derived from scroll on init, kept in memory during runtime.
    """

    def __init__(self, vaultmesh_root: Optional[str] = None):
        self.vaultmesh_root = vaultmesh_root
        self._pending: Dict[str, ApprovalRequest] = {}
        self._load_pending_from_scroll()

    # --------------------------------------------------------------------- #
    # Internal helpers
    # --------------------------------------------------------------------- #

    def _load_pending_from_scroll(self) -> None:
        """
        Reconstruct pending approvals from Console scroll.

        Algorithm:
        - Scan all receipts.
        - Collect all console_approval_request receipts as candidates.
        - Remove any whose approval_id appears in a console_approval receipt.
        - Drop any that are expired.
        """
        emitter = get_emitter(self.vaultmesh_root)
        events_path = Path(emitter.events_path)

        if not events_path.exists():
            return

        requests: Dict[str, ApprovalRequest] = {}
        decided_ids: set = set()

        for line in events_path.read_text(encoding="utf-8").splitlines():
            if not line.strip():
                continue
            try:
                r = json.loads(line)
            except Exception:
                continue

            r_type = r.get("type")
            payload = r.get("payload") or {}

            if r_type == "console_approval_request":
                approval_id = payload.get("approval_id")
                if not approval_id:
                    continue
                req = ApprovalRequest(
                    approval_id=approval_id,
                    session_id=payload.get("session_id") or r.get("session_id"),
                    action_type=payload.get("action_type", ""),
                    action_details=payload.get("action_details", {}),
                    requested_by=payload.get("requested_by", ""),
                    approvers=payload.get("approvers", []),
                    expires_at=payload.get("expires_at", ""),
                    status=payload.get("status", "pending"),
                    created_at=payload.get("created_at", r.get("ts")),
                )
                requests[approval_id] = req

            elif r_type == "console_approval":
                approval_id = payload.get("approval_id")
                if approval_id:
                    decided_ids.add(approval_id)

        # Filter to pending and not expired
        now = datetime.now(timezone.utc)
        for approval_id, req in requests.items():
            if approval_id in decided_ids:
                continue
            try:
                exp = datetime.fromisoformat(req.expires_at.replace("Z", "+00:00"))
            except Exception:
                exp = now
            if exp < now:
                continue  # expired; skip
            req.status = "pending"
            self._pending[approval_id] = req

    # --------------------------------------------------------------------- #
    # Public API
    # --------------------------------------------------------------------- #

    def request_approval(
        self,
        session_id: str,
        action_type: str,
        action_details: Dict[str, Any],
        requested_by: str,
        approvers: List[str],
        timeout_minutes: int = 60,
    ) -> ApprovalRequest:
        """Create a new approval request and emit receipt."""
        now = datetime.now(timezone.utc)
        approval_id = f"approval-{now.strftime('%Y-%m-%d-%H%M%S')}"
        expires_at = (now + timedelta(minutes=timeout_minutes)).isoformat()

        request = ApprovalRequest(
            approval_id=approval_id,
            session_id=session_id,
            action_type=action_type,
            action_details=action_details,
            requested_by=requested_by,
            approvers=approvers,
            expires_at=expires_at,
        )

        emit_console_receipt(
            "console_approval_request",
            asdict(request),
            session_id=session_id,
        )

        self._pending[approval_id] = request
        return request

    def decide(
        self,
        approval_id: str,
        approved: bool,
        approver: str,
        reason: str = "",
    ) -> bool:
        """Record approval decision and emit receipt."""
        if approval_id not in self._pending:
            # Let caller decide whether to treat this as error
            raise KeyError(f"Approval not found: {approval_id}")

        request = self._pending[approval_id]
        if approver not in request.approvers:
            raise PermissionError(f"{approver} not in approver pool")

        request.status = "approved" if approved else "rejected"

        emit_console_receipt(
            "console_approval",
            {
                "approval_id": approval_id,
                "action_type": request.action_type,
                "approved": approved,
                "approver": approver,
                "reason": reason,
                "decided_at": datetime.now(timezone.utc).isoformat(),
            },
            session_id=request.session_id,
        )

        del self._pending[approval_id]
        return True

    def list_pending(self, session_id: Optional[str] = None) -> List[ApprovalRequest]:
        """List pending approval requests."""
        requests = list(self._pending.values())
        if session_id:
            requests = [r for r in requests if r.session_id == session_id]
        return requests


# Singleton
_manager: Optional[ApprovalManager] = None


def get_approval_manager(vaultmesh_root: Optional[str] = None) -> ApprovalManager:
    """Get or create the ApprovalManager singleton."""
    global _manager
    if _manager is None:
        _manager = ApprovalManager(vaultmesh_root)
    return _manager