Source code for flex_menu.utils

"""Helper functions for URL resolution and parameter extraction."""

import contextlib

from django.urls import get_resolver
from django.urls.exceptions import NoReverseMatch




def get_required_url_params(view_name: str) -> frozenset:
    """Return the required URL parameter names for a Django view name.

    Supports both simple view names ("home") and namespaced view names
    ("app:home"). Parameters captured by parent resolver prefixes (e.g.
    "<str:uuid>/" in an include() prefix) are included.

    Relies on Django's own pre-built resolver structures (namespace_dict,
    reverse_dict), so each call is O(1) dict lookups with no caching needed.

    Args:
        view_name: A Django view name as used in reverse(), optionally
            namespaced (e.g. "app:home").

    Returns:
        The names of the required URL parameters, e.g. {"pk"} or {"slug"}.

    Raises:
        NoReverseMatch: If the namespace or view name cannot be found.
    """
    resolver = get_resolver()
    parts = view_name.split(":")
    name = parts[-1]
    namespaces = parts[:-1]

    accumulated_params: set[str] = set()
    current = resolver

    for ns in namespaces:
        entry = current.namespace_dict.get(ns)
        if entry is None:
            raise NoReverseMatch(f"Namespace ''{ns}'' not found in ''{view_name}''.")
        _app_name, sub_resolver = entry
        pat = sub_resolver.pattern
        if hasattr(pat, "converters") and pat.converters:
            accumulated_params.update(pat.converters.keys())
        elif hasattr(pat, "regex"):
            # A pattern without a compiled regex contributes no named params.
            with contextlib.suppress(Exception):
                accumulated_params.update(pat.regex.groupindex.keys())
        current = sub_resolver

    # reverse_dict.get() returns a 4-tuple (bits, p_pattern, defaults, converters)
    # where bits = [(format_str, [param_names]), ...].
    matches = current.reverse_dict.get(name)
    if matches is None:
        raise NoReverseMatch(f"No URL pattern found for view name ''{view_name}''.")

    bits, _p_pattern, _defaults, _converters = matches
    local_params: set[str] = set()
    for _fmt, param_names in bits:
        local_params.update(param_names)

    return frozenset(accumulated_params | local_params)