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

from fastapi import HTTPException, status
from sqlalchemy import Date as SQLDate
from sqlalchemy import DateTime as SQLDateTime
from sqlalchemy import Numeric as SQLNumeric
from sqlalchemy import Select, func, select
from sqlalchemy.sql.schema import Column
from sqlalchemy.orm import Session

from app.core.constants import ActorValue
from app.modules.audit.constants import AuditRiskLevel, AuditSource
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


def _coerce_column_value(column: Column, value: Any) -> Any:
    """Coerce API JSON values into the Python type expected by a SQLAlchemy column."""

    if value is None:
        return None
    if isinstance(column.type, SQLDateTime) and isinstance(value, str):
        return datetime.fromisoformat(value.replace("Z", "+00:00"))
    if isinstance(column.type, SQLDate) and isinstance(value, str):
        return date.fromisoformat(value)
    if isinstance(column.type, SQLNumeric) and not isinstance(value, Decimal):
        return Decimal(str(value))
    return value


def _model_payload(model: Any, data: dict[str, Any]) -> dict[str, Any]:
    """Filter unknown keys and coerce values according to model column types."""

    columns = {column.name: column for column in model.__table__.columns if column.name != "id"}
    payload: dict[str, Any] = {}
    for key, value in data.items():
        column = columns.get(key)
        if column is None:
            continue
        try:
            payload[key] = _coerce_column_value(column, value)
        except (ValueError, TypeError, InvalidOperation) as exc:
            raise HTTPException(
                status_code=status.HTTP_422_UNPROCESSABLE_ENTITY,
                detail=f"Invalid value for field '{key}'",
            ) from exc
    return payload


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 = ActorValue.API,
    ) -> dict[str, Any]:
        model = get_domain_model(domain)
        payload = _model_payload(model, data)
        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=AuditSource.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 = ActorValue.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",
            )
        for key, value in _model_payload(model, data).items():
            setattr(record, key, value)
        self.db.commit()
        self.db.refresh(record)
        result = serialize_model(record)
        self.audit.log(
            AuditLogCreate(
                actor=actor,
                source=AuditSource.API,
                action=f"update:{domain}",
                target_type=domain,
                target_id=str(record.id),
                risk_level=(
                    AuditRiskLevel.HIGH if domain in HIGH_RISK_DOMAINS else AuditRiskLevel.LOW
                ),
                request_payload={"data": data, "approval_ticket_id": approval_ticket_id},
                response_payload=result,
            )
        )
        return result