from __future__ import annotations

from typing import Any, cast

from fastapi import FastAPI, Request
from fastapi.responses import JSONResponse
from fastapi.testclient import TestClient

from services.dataplane_router import build_router


class SessionBoundaryProbe:
    def __init__(self) -> None:
        self.seen_headers: dict[str, str] = {}

    async def handle(
        self, request: Request, project_slug: str, environment: str
    ) -> JSONResponse:
        self.seen_headers = dict(request.headers)
        return JSONResponse(
            {
                "jsonrpc": "2.0",
                "id": 1,
                "result": {"project": project_slug, "environment": environment},
            },
            headers={
                "Mcp-Session-Id": "contextforge-session",
                "Mcp-Protocol-Version": request.headers.get(
                    "mcp-protocol-version", "missing"
                ),
            },
        )


def _client(probe: SessionBoundaryProbe) -> TestClient:
    app = FastAPI()
    app.include_router(build_router(cast(Any, probe)))
    return TestClient(app)


def _assert_stateless_boundary(protocol_version: str) -> None:
    probe = SessionBoundaryProbe()

    with _client(probe) as client:
        response = client.post(
            "/mcp/gitea-all/prod",
            headers={
                "Mcp-Session-Id": "stale-client-session",
                "Mcp-Protocol-Version": protocol_version,
            },
            json={"jsonrpc": "2.0", "id": 1, "method": "tools/list"},
        )

    assert response.status_code == 200
    assert "mcp-session-id" not in probe.seen_headers
    assert probe.seen_headers["mcp-protocol-version"] == protocol_version
    assert "mcp-session-id" not in response.headers
    assert response.headers["mcp-protocol-version"] == protocol_version


def test_modern_public_route_does_not_bridge_mcp_session_state() -> None:
    _assert_stateless_boundary("2026-07-28")


def test_legacy_public_route_is_also_deliberately_stateless() -> None:
    # 2025-11-25 permits a server to omit Mcp-Session-Id. The Hub must do so
    # because no public feature depends on transport-scoped server state.
    _assert_stateless_boundary("2025-11-25")


def test_initialize_without_protocol_header_never_mints_public_session() -> None:
    probe = SessionBoundaryProbe()

    with _client(probe) as client:
        response = client.post(
            "/mcp/gitea-all/prod",
            json={
                "jsonrpc": "2.0",
                "id": 1,
                "method": "initialize",
                "params": {
                    "protocolVersion": "2025-11-25",
                    "capabilities": {},
                    "clientInfo": {"name": "test", "version": "1"},
                },
            },
        )

    assert "mcp-session-id" not in probe.seen_headers
    assert "mcp-session-id" not in response.headers