"""DRF permission classes built on :class:`AuthorizationService`.

Enforcement model
-----------------
* A superuser is always allowed.
* A **tenant owner** (``TenantMembership.is_owner`` for the resolved tenant) is
  allowed — ownership is a capability, not a permission row.
* Otherwise the request user must hold **any** of the view's
  ``required_permissions`` (set ``require_all = True`` to demand all of them).
* A view with no ``required_permissions`` falls back to the model-derived
  codename (see :class:`AutoPermission`).
* Declared gates (``infrasynth_gates``) run first for everyone, including owners
  and superusers; use :class:`infrasynth.gates.PermissionGate` when even the
  owner must hold a codename.

The underlying :class:`AuthorizationService` is deliberately strict (owners are
not implicitly granted every codename) so it stays a pure permission resolver;
ownership is handled at the HTTP boundary here.
"""

from __future__ import annotations

from typing import Any

from rest_framework.permissions import BasePermission

from infrasynth.gates import evaluate_gates
from infrasynth.shared.settings_utils import get_setting

from .services import AuthorizationService


def is_tenant_owner(user: Any) -> bool:
    """True when ``user`` owns the currently bound tenant."""
    if not user or not getattr(user, "is_authenticated", False):
        return False
    # System users (API keys) are not database-backed memberships.
    if not hasattr(user, "_meta") or getattr(user, "pk", None) is None:
        return False
    from infrasynth.tenancy.context import get_current_tenant
    from infrasynth.tenancy.models import TenantMembership

    tenant = get_current_tenant()
    if tenant is None:
        return False
    return TenantMembership.objects.filter(
        tenant=tenant,
        user=user,
        is_active=True,
        is_owner=True,
    ).exists()


class HybridPermission(BasePermission):
    """Authenticated, then permission-checked, with an owner/superuser bypass.

    A view declares ``required_permissions`` (any-of by default; set
    ``require_all = True`` for all-of). With none declared, the model-derived
    codename is enforced via :func:`evaluate_auto_permission`.
    """

    def has_permission(self, request, view):
        user = getattr(request, "user", None)
        if not user or not getattr(user, "is_authenticated", False):
            return False
        # Declared gates apply to everyone, including owners and superusers.
        evaluate_gates(request, view)
        if getattr(user, "is_superuser", False):
            return True
        if is_tenant_owner(user):
            return True
        required = getattr(view, "required_permissions", []) or []
        if not required:
            # No explicit permission: fall back to the model-derived codename.
            return evaluate_auto_permission(request, view)
        authz = AuthorizationService()
        if getattr(view, "require_all", False):
            return authz.has_all_permissions(user, list(required))
        return authz.has_any_permission(user, list(required))


class AutoPermission(BasePermission):
    """Derives and enforces ``{app}.{action}_{model}`` permissions automatically.

    Only applies to model-backed DRF viewsets (and only when ``AUTO_PERMISSIONS``
    is enabled); it abstains on plain APIViews so it is safe in
    ``DEFAULT_PERMISSION_CLASSES``. Tenant owners and superusers bypass, matching
    ``HybridPermission``.
    """

    message = "You do not have permission to perform this action."

    def has_permission(self, request, view):
        user = getattr(request, "user", None)
        if not user or not getattr(user, "is_authenticated", False):
            return False
        if getattr(user, "is_superuser", False):
            return True
        return evaluate_auto_permission(request, view)


# Backwards-compatible alias: ``IsAuthenticatedAndPermitted`` is the documented
# idiom name for kit views but is exactly ``HybridPermission``.
IsAuthenticatedAndPermitted = HybridPermission


def resolve_view_model(view) -> Any:
    """Best-effort concrete model behind a DRF view, or ``None``."""
    model = getattr(getattr(view, "queryset", None), "model", None)
    if model is not None:
        return model
    get_queryset = getattr(view, "get_queryset", None)
    if callable(get_queryset):
        try:
            return getattr(get_queryset(), "model", None)
        except Exception:  # noqa: BLE001 - not every queryset is safe to build
            return None
    return None


def automatic_permissions(view) -> list[str]:
    """The codenames a view requires, explicitly declared or auto-derived.

    Priority: ``required_permissions`` (explicit) → ``action_permissions`` for
    the current action → derived ``{app}.{verb}_{model}`` → ``[]``.
    """
    explicit = getattr(view, "required_permissions", None)
    if explicit:
        return list(explicit)
    action = getattr(view, "action", None)
    if not action:
        return []
    action_map = getattr(view, "action_permissions", None) or {}
    if action in action_map:
        return [action_map[action]]
    model = resolve_view_model(view)
    if model is None:
        return []
    from .catalog import permission_for

    return [permission_for(model, action)]


def auto_permissions_enabled(view) -> bool:
    """Whether model-derived enforcement applies to ``view``."""
    mode = get_setting("INFRASYNTH_SECURITY", "AUTO_PERMISSIONS", "global")
    if mode in (False, None, "off", "disabled"):
        return False
    if getattr(view, "auto_permissions", None) is False:
        return False
    if mode == "opt_in":
        return bool(getattr(view, "auto_permissions", False))
    return True


def evaluate_auto_permission(request, view) -> bool:
    """Runs the auto-permission check, abstaining when nothing is derivable."""
    if not auto_permissions_enabled(view):
        return True
    codenames = automatic_permissions(view)
    if not codenames:
        return True
    user = getattr(request, "user", None)
    if not user or not getattr(user, "is_authenticated", False):
        return False
    if getattr(user, "is_superuser", False):
        return True
    if is_tenant_owner(user):
        return True
    return AuthorizationService().has_any_permission(user, codenames)