"""Widget descriptors for cross-domain UI composition.

Each widget type describes a UI fragment that one domain contributes to
another domain's page.  Host apps iterate widgets generically — they never
name the contributing domain.
"""
from __future__ import annotations

from dataclasses import dataclass
from typing import Callable


@dataclass(frozen=True, slots=True)
class NavWidget:
    """Renders nav items on a container page (entries, calendars, markets)."""
    domain: str
    order: int
    context_fn: Callable   # async (session, *, container_type, container_id, **kw) -> dict
    template: str


@dataclass(frozen=True, slots=True)
class CardWidget:
    """Decorates content cards in listings with domain data."""
    domain: str
    order: int
    batch_fn: Callable     # async (session, post_ids) -> dict[int, list]
    context_key: str       # key injected into each post dict
    template: str


@dataclass(frozen=True, slots=True)
class AccountPageWidget:
    """Sub-page under /auth/<slug>/."""
    domain: str
    slug: str
    label: str
    order: int
    context_fn: Callable   # async (session, *, user_id, **kw) -> dict
    template: str


@dataclass(frozen=True, slots=True)
class AccountNavLink:
    """Nav link on account page (internal or external)."""
    label: str
    order: int
    href_fn: Callable      # () -> str
    external: bool = False