"""Per-request MCP context: who is calling, and which app they are calling.

The /mcp transport bypasses Quart's request pipeline, so neither `session`
nor `current_app` exists inside a tool. The ASGI auth wrapper in server.py
sets these from the resolved bearer token before dispatching; tools read them
through `current_caller()` and `mcp_app()`.

Neither falls back to a default: a tool reached without an authenticated
caller is a bug in the transport, and it raises rather than acting for nobody.
"""
from __future__ import annotations
from contextvars import ContextVar
from typing import TYPE_CHECKING

if TYPE_CHECKING:
    from quart import Quart
    from steward.core.api_tokens import Caller

_caller_ctx: ContextVar["Caller | None"] = ContextVar("steward_mcp_caller", default=None)
_app_ctx: ContextVar["Quart | None"] = ContextVar("steward_mcp_app", default=None)
# The scheme and host the caller reached /mcp on, e.g. "https://steward.example".
_base_url_ctx: ContextVar[str] = ContextVar("steward_mcp_base_url", default="")


def current_caller() -> "Caller":
    caller = _caller_ctx.get()
    if caller is None:
        raise RuntimeError("no MCP caller in context: the request was not bearer-authenticated")
    return caller


def current_caller_or_none() -> "Caller | None":
    return _caller_ctx.get()


def mcp_app() -> "Quart":
    app = _app_ctx.get()
    if app is None:
        raise RuntimeError("no Steward app in MCP context")
    return app


def public_url() -> str:
    """Steward's externally reachable base URL, as the web side's
    public_base_url() gives it: Settings → General → Public base URL when set,
    else the scheme and host this MCP request arrived on; "" when neither is
    known."""
    app = _app_ctx.get()
    configured = (app.config.get("PUBLIC_BASE_URL") or "").strip() if app is not None else ""
    return (configured or _base_url_ctx.get()).rstrip("/")