from typing import Any, Dict, List, Optional

from fastapi import APIRouter, Request

from core.sap import forward_to_sapb1


def _build_sap_params(
    skip: int,
    top: int,
    fields: Optional[str],
    filter: Optional[str],
    orderby: Optional[str] = None,
) -> Dict[str, Any]:
    sap_params: Dict[str, Any] = {
        "$skip": skip,
        "$top": top,
        "$inlinecount": "allpages",
    }
    if fields:
        sap_params["$select"] = fields.replace(" ", "")
    if filter:
        sap_params["$filter"] = filter
    if orderby:
        sap_params["$orderby"] = orderby
    return sap_params


def _build_list_headers(top: int, filter: Optional[str]) -> Dict[str, str]:
    headers = {"B1S-PageSize": str(top)}
    if filter:
        headers["B1S-CaseInsensitive"] = "true"
    return headers


def make_crud_router(
    resource: str,
    *,
    tags: List[str],
    key_field: Optional[str] = None,
    key_quoted: bool = False,
    supports_orderby: bool = False,
    supports_get_by_key: bool = True,
    supports_create: bool = True,
    supports_patch: bool = True,
    patch_headers: Optional[Dict[str, str]] = None,
) -> APIRouter:
    """
    Genera el router list/get/create/update repetido antes en cada módulo de
    routers/ (mismo bloque de $skip/$top/$filter y de forward_to_sapb1, solo
    cambiaba el nombre del recurso OData). Centralizarlo evita que un
    copy-paste entre recursos deje, por ejemplo, un PATCH apuntando al
    endpoint_path de otro recurso.
    """
    router = APIRouter(tags=tags)

    def key_expr(key: str) -> str:
        return f"{resource}('{key}')" if key_quoted else f"{resource}({key})"

    if supports_orderby:
        @router.get(f"/api/{resource}", name=f"list_{resource}")
        async def list_resource(
            skip: int = 0,
            top: int = 50,
            fields: Optional[str] = None,
            filter: Optional[str] = None,
            orderby: Optional[str] = None,
        ):
            sap_params = _build_sap_params(skip, top, fields, filter, orderby)
            return forward_to_sapb1(
                method="GET",
                endpoint_path=resource,
                params=sap_params,
                extra_headers=_build_list_headers(top, filter),
            ).json()
    else:
        @router.get(f"/api/{resource}", name=f"list_{resource}")
        async def list_resource(
            skip: int = 0,
            top: int = 50,
            fields: Optional[str] = None,
            filter: Optional[str] = None,
        ):
            sap_params = _build_sap_params(skip, top, fields, filter)
            return forward_to_sapb1(
                method="GET",
                endpoint_path=resource,
                params=sap_params,
                extra_headers=_build_list_headers(top, filter),
            ).json()

    if supports_get_by_key:
        @router.get(f"/api/{resource}/{{key}}", name=f"get_{resource}_by_key")
        async def get_by_key(key: str):
            return forward_to_sapb1(
                method="GET",
                endpoint_path=key_expr(key),
            ).json()

    if supports_create:
        @router.post(f"/api/{resource}", status_code=201, name=f"create_{resource}")
        async def create_resource(request: Request):
            data = await request.json()
            resp = forward_to_sapb1(
                method="POST",
                endpoint_path=resource,
                json_data=data,
            )
            created = resp.json()
            return {key_field: created[key_field]}

    if supports_patch:
        @router.patch(f"/api/{resource}/{{key}}", status_code=204, name=f"update_{resource}")
        async def update_resource(key: str, request: Request):
            data = await request.json()
            # Las cabeceras de Service Layer (B1S-*) las decide quien llama
            # (el frontend), no el backend: cualquier header "B1S-*" que
            # venga en el request se reenvía tal cual a SAP. Ej.:
            # B1S-ReplaceCollectionsOnPatch para reemplazar una colección
            # hija (StockTransferLines) en vez de mergearla por LineNum,
            # necesario solo cuando ese PATCH agrega o quita líneas.
            headers = dict(patch_headers or {})
            headers.update(
                {k: v for k, v in request.headers.items() if k.lower().startswith("b1s-")}
            )
            forward_to_sapb1(
                method="PATCH",
                endpoint_path=key_expr(key),
                json_data=data,
                extra_headers=headers or None,
            )

    return router