"""Port defining the common interface for data import services.

All import services (Atomic Red Team, Sigma, CALDERA, etc.) follow the
same contract: they receive a database session and return a summary dict
with import statistics.

New import sources can be added by:
1. Implementing the ``ImportService`` protocol in a new module
2. Registering the handler in the ``IMPORT_REGISTRY``

This satisfies the Open/Closed Principle — the system is open for new
import sources without modifying existing code.
"""

from __future__ import annotations

from typing import Any, Protocol, runtime_checkable

from sqlalchemy.orm import Session


@runtime_checkable
class ImportService(Protocol):
    """Contract for any data-import operation.

    Each implementation is a callable ``(Session) -> dict`` that
    downloads, parses, and upserts records from an external source.
    """

    def __call__(self, db: Session) -> dict[str, Any]: ...


class ImportServiceEntry:
    """Lazy-loading wrapper that resolves a module-level function on first call."""

    __slots__ = ("_module_path", "_func_name", "_resolved")

    def __init__(self, module_path: str, func_name: str) -> None:
        self._module_path = module_path
        self._func_name = func_name
        self._resolved: ImportService | None = None

    def __call__(self, db: Session) -> dict[str, Any]:
        if self._resolved is None:
            import importlib
            mod = importlib.import_module(self._module_path)
            self._resolved = getattr(mod, self._func_name)
        return self._resolved(db)

    @property
    def source_info(self) -> str:
        return f"{self._module_path}.{self._func_name}"


IMPORT_REGISTRY: dict[str, ImportServiceEntry] = {
    "atomic_red_team": ImportServiceEntry(
        "app.services.atomic_import_service", "import_atomic_red_team",
    ),
    "sigma": ImportServiceEntry(
        "app.services.sigma_import_service", "sync",
    ),
    "lolbas": ImportServiceEntry(
        "app.services.lolbas_import_service", "sync",
    ),
    "gtfobins": ImportServiceEntry(
        "app.services.lolbas_import_service", "sync_gtfobins",
    ),
    "caldera": ImportServiceEntry(
        "app.services.caldera_import_service", "sync",
    ),
    "elastic_rules": ImportServiceEntry(
        "app.services.elastic_import_service", "sync",
    ),
    "mitre_cti": ImportServiceEntry(
        "app.services.threat_actor_import_service", "sync",
    ),
    "d3fend": ImportServiceEntry(
        "app.services.d3fend_import_service", "sync",
    ),
}


def get_import_handler(source_name: str) -> ImportServiceEntry | None:
    """Look up the import handler for *source_name*.

    Returns ``None`` when no handler is registered.
    """
    return IMPORT_REGISTRY.get(source_name)