import json
import uuid
from datetime import date, datetime
from decimal import Decimal
from typing import Any

from fastapi import HTTPException, status
from sqlalchemy import select, update
from sqlalchemy.orm import Session

from app.core.pagination import bounded_limit
from app.core.time import utc_now
from app.modules.approvals.constants import (
    ApprovalActionValue,
    ApprovalErrorDetail,
    ApprovalPayloadKey,
    ApprovalStatus,
    approval_action,
)
from app.modules.approvals.models import ApprovalRequest
from app.modules.approvals.schemas import ApprovalCreate
from app.modules.audit.constants import AuditAction, AuditRiskLevel, AuditSource
from app.modules.audit.schemas import AuditLogCreate
from app.modules.audit.service import AuditService


class ApprovalService:
    """Create, decide, and validate approval tickets for guarded actions."""

    def __init__(self, db: Session):
        self.db = db
        self.audit = AuditService(db)

    def create(self, payload: ApprovalCreate, applicant: str) -> ApprovalRequest:
        ticket = ApprovalRequest(
            ticket_id=f"APR-{uuid.uuid4().hex[:12].upper()}",
            domain=payload.domain,
            record_id=payload.record_id,
            action=payload.action,
            applicant=applicant,
            reason=payload.reason,
            payload=json.dumps(payload.payload, ensure_ascii=False, default=str),
        )
        self.db.add(ticket)
        self.db.commit()
        self.db.refresh(ticket)
        self.audit.log(
            AuditLogCreate(
                actor=applicant,
                source=AuditSource.APPROVAL,
                action=AuditAction.APPROVAL_CREATE,
                target_type=payload.domain,
                target_id=payload.record_id,
                risk_level=AuditRiskLevel.MEDIUM,
                request_payload=payload.model_dump(),
                response_payload={
                    ApprovalPayloadKey.TICKET_ID: ticket.ticket_id,
                    ApprovalPayloadKey.STATUS: ticket.status,
                },
            )
        )
        return ticket

    def list(self, status_filter: str | None = None, limit: int = 100) -> list[ApprovalRequest]:
        stmt = (
            select(ApprovalRequest)
            .order_by(ApprovalRequest.id.desc())
            .limit(bounded_limit(limit))
        )
        if status_filter:
            stmt = stmt.where(ApprovalRequest.status == status_filter)
        return list(self.db.execute(stmt).scalars())

    def get_by_ticket(self, ticket_id: str) -> ApprovalRequest:
        ticket = self.db.execute(
            select(ApprovalRequest).where(ApprovalRequest.ticket_id == ticket_id)
        ).scalar_one_or_none()
        if ticket is None:
            raise HTTPException(
                status_code=status.HTTP_404_NOT_FOUND,
                detail=ApprovalErrorDetail.NOT_FOUND,
            )
        return ticket

    def decide(
        self,
        ticket_id: str,
        approver: str,
        approved: bool,
        comment: str | None,
    ) -> ApprovalRequest:
        ticket = self.get_by_ticket(ticket_id)
        if ticket.status != ApprovalStatus.PENDING:
            raise HTTPException(
                status_code=status.HTTP_409_CONFLICT,
                detail=ApprovalErrorDetail.ALREADY_DECIDED,
            )
        if approved and approver == ticket.applicant:
            raise HTTPException(
                status_code=status.HTTP_403_FORBIDDEN,
                detail=ApprovalErrorDetail.SELF_APPROVAL,
            )
        ticket.status = ApprovalStatus.APPROVED if approved else ApprovalStatus.REJECTED
        ticket.approver = approver
        ticket.decision_comment = comment
        ticket.decided_at = utc_now()
        self.db.commit()
        self.db.refresh(ticket)
        self.audit.log(
            AuditLogCreate(
                actor=approver,
                source=AuditSource.APPROVAL,
                action=AuditAction.APPROVAL_APPROVE if approved else AuditAction.APPROVAL_REJECT,
                target_type=ticket.domain,
                target_id=ticket.record_id,
                risk_level=AuditRiskLevel.HIGH,
                request_payload={
                    ApprovalPayloadKey.TICKET_ID: ticket_id,
                    ApprovalPayloadKey.COMMENT: comment,
                },
                response_payload={ApprovalPayloadKey.STATUS: ticket.status},
            )
        )
        return ticket

    def consume_for(
        self,
        ticket_id: str,
        domain: str,
        record_id: str | int | None,
        action: str,
        payload: dict[str, Any],
        actor: str,
    ) -> ApprovalRequest:
        ticket = self.get_by_ticket(ticket_id)
        if not self._is_ticket_scope_valid(ticket, domain, record_id, action):
            raise HTTPException(
                status_code=status.HTTP_403_FORBIDDEN,
                detail=ApprovalErrorDetail.NOT_APPROVED,
            )
        if not _payload_matches(ticket.payload, payload):
            raise HTTPException(
                status_code=status.HTTP_403_FORBIDDEN,
                detail=ApprovalErrorDetail.PAYLOAD_MISMATCH,
            )
        used_at = utc_now()
        values: dict[str, Any] = {
            ApprovalPayloadKey.STATUS: ApprovalStatus.USED,
            ApprovalPayloadKey.USED_BY: actor,
            ApprovalPayloadKey.USED_AT: used_at,
        }
        if record_id is not None and not ticket.record_id:
            values[ApprovalPayloadKey.RECORD_ID] = str(record_id)
        result = self.db.execute(
            update(ApprovalRequest)
            .where(
                ApprovalRequest.ticket_id == ticket_id,
                ApprovalRequest.status == ApprovalStatus.APPROVED,
            )
            .values(**values)
        )
        if result.rowcount != 1:
            raise HTTPException(
                status_code=status.HTTP_403_FORBIDDEN,
                detail=ApprovalErrorDetail.NOT_APPROVED,
            )
        for key, value in values.items():
            setattr(ticket, key, value)
        return ticket

    def is_approved_for(
        self,
        ticket_id: str,
        domain: str,
        record_id: str | int | None,
        action: str,
    ) -> bool:
        ticket = self.get_by_ticket(ticket_id)
        return self._is_ticket_scope_valid(ticket, domain, record_id, action)

    @staticmethod
    def _is_ticket_scope_valid(
        ticket: ApprovalRequest,
        domain: str,
        record_id: str | int | None,
        action: str,
    ) -> bool:
        if ticket.status != ApprovalStatus.APPROVED:
            return False
        if ticket.domain != domain:
            return False
        if ticket.record_id and (
            record_id is None or str(ticket.record_id) != str(record_id)
        ):
            return False
        return ticket.action in {
            action,
            ApprovalActionValue.UPDATE,
            approval_action(ApprovalActionValue.UPDATE, domain),
        }


def _payload_matches(approved_payload: str | None, requested_payload: dict[str, Any]) -> bool:
    try:
        parsed_payload = json.loads(approved_payload or "{}")
    except json.JSONDecodeError:
        parsed_payload = {}
    return _canonical_payload(parsed_payload) == _canonical_payload(requested_payload)


def _canonical_payload(value: Any) -> str:
    return json.dumps(_json_safe(value), ensure_ascii=False, sort_keys=True, default=str)


def _json_safe(value: Any) -> Any:
    if isinstance(value, Decimal):
        return float(value)
    if isinstance(value, (datetime, date)):
        return value.isoformat()
    if isinstance(value, dict):
        return {str(key): _json_safe(item) for key, item in value.items()}
    if isinstance(value, list):
        return [_json_safe(item) for item in value]
    return value