from django.db.models import Q
from ninja import Query, Router, Schema

from apps.users.models import Major, University
from core.api.schemas import ErrorSchema, MessageSchema
from core.authentication import jwt_auth

meta_router = Router(tags=['meta'])


class MetaOptionSchema(Schema):
    id: int
    code: str
    label: str
    is_active: bool = True
    user_count: int = 0


class PagedMetaOptionSchema(Schema):
    count: int
    results: list[MetaOptionSchema]


class MetaOptionWriteSchema(Schema):
    code: str
    name: str
    is_active: bool = True


def _is_staff(user):
    return bool(user and (user.is_staff or user.is_superuser))


def _option_payload(obj, user_count=0):
    return {
        "id": obj.id,
        "code": obj.code,
        "label": obj.name,
        "is_active": obj.is_active,
        "user_count": user_count,
    }


def _list_options(model, search, limit, offset, active_only=True):
    queryset = model.objects.filter(is_deleted=False).order_by("name")
    if active_only:
        queryset = queryset.filter(is_active=True)
    if search:
        queryset = queryset.filter(Q(code__icontains=search) | Q(name__icontains=search))
    count = queryset.count()
    return count, list(queryset[offset : offset + limit])


@meta_router.get("/majors", response=PagedMetaOptionSchema)
def list_majors(
    request,
    search: str | None = Query(None),
    limit: int = Query(20, ge=1, le=100),
    offset: int = Query(0, ge=0),
):
    count, majors = _list_options(Major, search, limit, offset)
    return {"count": count, "results": [_option_payload(m) for m in majors]}


@meta_router.get("/universities", response=PagedMetaOptionSchema)
def list_universities(
    request,
    search: str | None = Query(None),
    limit: int = Query(20, ge=1, le=100),
    offset: int = Query(0, ge=0),
):
    count, universities = _list_options(University, search, limit, offset)
    return {"count": count, "results": [_option_payload(u) for u in universities]}


@meta_router.get("/admin/majors", response={200: PagedMetaOptionSchema, 403: ErrorSchema}, auth=jwt_auth)
def admin_list_majors(
    request,
    search: str | None = Query(None),
    limit: int = Query(20, ge=1, le=100),
    offset: int = Query(0, ge=0),
):
    if not _is_staff(request.auth):
        return 403, {"error": "Permission denied"}
    count, majors = _list_options(Major, search, limit, offset, active_only=False)
    return 200, {
        "count": count,
        "results": [_option_payload(m, m.users.filter(is_deleted=False).count()) for m in majors],
    }


@meta_router.post("/admin/majors", response={201: MetaOptionSchema, 403: ErrorSchema, 400: ErrorSchema}, auth=jwt_auth)
def admin_create_major(request, payload: MetaOptionWriteSchema):
    if not _is_staff(request.auth):
        return 403, {"error": "Permission denied"}
    if Major.all_objects.filter(code=payload.code).exists():
        return 400, {"error": "Major code already exists"}
    major = Major.objects.create(code=payload.code.strip(), name=payload.name.strip(), is_active=payload.is_active)
    return 201, _option_payload(major)


@meta_router.put("/admin/majors/{int:item_id}", response={200: MetaOptionSchema, 403: ErrorSchema, 400: ErrorSchema}, auth=jwt_auth)
def admin_update_major(request, item_id: int, payload: MetaOptionWriteSchema):
    if not _is_staff(request.auth):
        return 403, {"error": "Permission denied"}
    try:
        major = Major.objects.get(id=item_id)
    except Major.DoesNotExist:
        return 400, {"error": "Major not found"}
    conflict = Major.all_objects.filter(code=payload.code).exclude(id=item_id).exists()
    if conflict:
        return 400, {"error": "Major code already exists"}
    major.code = payload.code.strip()
    major.name = payload.name.strip()
    major.is_active = payload.is_active
    major.save(update_fields=["code", "name", "is_active", "updated_at"])
    return 200, _option_payload(major, major.users.filter(is_deleted=False).count())


@meta_router.delete("/admin/majors/{int:item_id}", response={200: MessageSchema, 403: ErrorSchema, 400: ErrorSchema}, auth=jwt_auth)
def admin_delete_major(request, item_id: int):
    if not request.auth.is_superuser:
        return 403, {"error": "Only superusers can delete majors"}
    try:
        major = Major.objects.get(id=item_id)
    except Major.DoesNotExist:
        return 400, {"error": "Major not found"}
    major.delete()
    return 200, {"message": "Major deleted"}


@meta_router.post("/admin/majors/{int:item_id}/restore", response={200: MessageSchema, 403: ErrorSchema, 400: ErrorSchema}, auth=jwt_auth)
def admin_restore_major(request, item_id: int):
    if not request.auth.is_superuser:
        return 403, {"error": "Only superusers can restore majors"}
    try:
        major = Major.deleted_objects.get(id=item_id)
    except Major.DoesNotExist:
        return 400, {"error": "Major not found"}
    major.restore()
    return 200, {"message": "Major restored"}


@meta_router.get("/admin/universities", response={200: PagedMetaOptionSchema, 403: ErrorSchema}, auth=jwt_auth)
def admin_list_universities(
    request,
    search: str | None = Query(None),
    limit: int = Query(20, ge=1, le=100),
    offset: int = Query(0, ge=0),
):
    if not _is_staff(request.auth):
        return 403, {"error": "Permission denied"}
    count, universities = _list_options(University, search, limit, offset, active_only=False)
    return 200, {
        "count": count,
        "results": [_option_payload(u, u.users.filter(is_deleted=False).count()) for u in universities],
    }


@meta_router.post("/admin/universities", response={201: MetaOptionSchema, 403: ErrorSchema, 400: ErrorSchema}, auth=jwt_auth)
def admin_create_university(request, payload: MetaOptionWriteSchema):
    if not _is_staff(request.auth):
        return 403, {"error": "Permission denied"}
    if University.all_objects.filter(code=payload.code).exists():
        return 400, {"error": "University code already exists"}
    university = University.objects.create(code=payload.code.strip(), name=payload.name.strip(), is_active=payload.is_active)
    return 201, _option_payload(university)


@meta_router.put("/admin/universities/{int:item_id}", response={200: MetaOptionSchema, 403: ErrorSchema, 400: ErrorSchema}, auth=jwt_auth)
def admin_update_university(request, item_id: int, payload: MetaOptionWriteSchema):
    if not _is_staff(request.auth):
        return 403, {"error": "Permission denied"}
    try:
        university = University.objects.get(id=item_id)
    except University.DoesNotExist:
        return 400, {"error": "University not found"}
    conflict = University.all_objects.filter(code=payload.code).exclude(id=item_id).exists()
    if conflict:
        return 400, {"error": "University code already exists"}
    university.code = payload.code.strip()
    university.name = payload.name.strip()
    university.is_active = payload.is_active
    university.save(update_fields=["code", "name", "is_active", "updated_at"])
    return 200, _option_payload(university, university.users.filter(is_deleted=False).count())


@meta_router.delete("/admin/universities/{int:item_id}", response={200: MessageSchema, 403: ErrorSchema, 400: ErrorSchema}, auth=jwt_auth)
def admin_delete_university(request, item_id: int):
    if not request.auth.is_superuser:
        return 403, {"error": "Only superusers can delete universities"}
    try:
        university = University.objects.get(id=item_id)
    except University.DoesNotExist:
        return 400, {"error": "University not found"}
    university.delete()
    return 200, {"message": "University deleted"}


@meta_router.post("/admin/universities/{int:item_id}/restore", response={200: MessageSchema, 403: ErrorSchema, 400: ErrorSchema}, auth=jwt_auth)
def admin_restore_university(request, item_id: int):
    if not request.auth.is_superuser:
        return 403, {"error": "Only superusers can restore universities"}
    try:
        university = University.deleted_objects.get(id=item_id)
    except University.DoesNotExist:
        return 400, {"error": "University not found"}
    university.restore()
    return 200, {"message": "University restored"}