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

from fastapi import HTTPException, status
from sqlalchemy import Select, func, select
from sqlalchemy.orm import Session

from app.modules.audit.schemas import AuditLogCreate
from app.modules.audit.service import AuditService
from app.modules.approvals.service import ApprovalService
from app.modules.business.registry import HIGH_RISK_DOMAINS, get_domain_model


def serialize_model(record: Any) -> dict[str, Any]:
    """Convert a SQLAlchemy model instance into a JSON-friendly dictionary."""

    data: dict[str, Any] = {}
    for column in record.__table__.columns:
        value = getattr(record, column.name)
        if isinstance(value, (datetime, date)):
            data[column.name] = value.isoformat()
        elif isinstance(value, Decimal):
            data[column.name] = float(value)
        else:
            data[column.name] = value
    return data


class BusinessService:
    """Manage generic CRUD operations across registered business domains."""

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

    def list_records(
        self,
        domain: str,
        limit: int = 50,
        offset: int = 0,
        status_filter: str | None = None,
    ) -> tuple[int, list[dict[str, Any]]]:
        model = get_domain_model(domain)
        stmt: Select = select(model)
        count_stmt = select(func.count()).select_from(model)
        if status_filter and hasattr(model, "status"):
            stmt = stmt.where(model.status == status_filter)
            count_stmt = count_stmt.where(model.status == status_filter)
        stmt = stmt.order_by(model.id.desc()).limit(min(limit, 500)).offset(max(offset, 0))
        total = int(self.db.execute(count_stmt).scalar() or 0)
        return total, [serialize_model(item) for item in self.db.execute(stmt).scalars()]

    def get_record(self, domain: str, record_id: int) -> dict[str, Any]:
        model = get_domain_model(domain)
        record = self.db.get(model, record_id)
        if record is None:
            raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="Record not found")
        return serialize_model(record)

    def create_record(
        self,
        domain: str,
        data: dict[str, Any],
        actor: str = "api",
    ) -> dict[str, Any]:
        model = get_domain_model(domain)
        allowed = {column.name for column in model.__table__.columns if column.name != "id"}
        payload = {key: value for key, value in data.items() if key in allowed}
        record = model(**payload)
        self.db.add(record)
        self.db.commit()
        self.db.refresh(record)
        result = serialize_model(record)
        self.audit.log(
            AuditLogCreate(
                actor=actor,
                source="api",
                action=f"create:{domain}",
                target_type=domain,
                target_id=str(record.id),
                request_payload=data,
                response_payload=result,
            )
        )
        return result

    def update_record(
        self,
        domain: str,
        record_id: int,
        data: dict[str, Any],
        actor: str = "api",
        approval_ticket_id: str | None = None,
    ) -> dict[str, Any]:
        if domain in HIGH_RISK_DOMAINS:
            if not approval_ticket_id:
                raise HTTPException(
                    status_code=status.HTTP_409_CONFLICT,
                    detail="High-risk domain update requires approval_ticket_id",
                )
            if not ApprovalService(self.db).is_approved_for(
                approval_ticket_id,
                domain,
                record_id,
                f"update:{domain}",
            ):
                raise HTTPException(
                    status_code=status.HTTP_403_FORBIDDEN,
                    detail="Approval ticket is not approved for this update",
                )
        model = get_domain_model(domain)
        record = self.db.get(model, record_id)
        if record is None:
            raise HTTPException(
                status_code=status.HTTP_404_NOT_FOUND,
                detail="Record not found",
            )
        allowed = {column.name for column in model.__table__.columns if column.name != "id"}
        for key, value in data.items():
            if key in allowed:
                setattr(record, key, value)
        self.db.commit()
        self.db.refresh(record)
        result = serialize_model(record)
        self.audit.log(
            AuditLogCreate(
                actor=actor,
                source="api",
                action=f"update:{domain}",
                target_type=domain,
                target_id=str(record.id),
                risk_level="high" if domain in HIGH_RISK_DOMAINS else "low",
                request_payload={"data": data, "approval_ticket_id": approval_ticket_id},
                response_payload=result,
            )
        )
        return result