"""Tests for the per-chat SSE channel and pub/sub registry (T16).

Covers:
- 404 from the SSE endpoint when the chat doesn't exist.
- The first event yielded on connect is the ``snapshot`` event with correct
  framing (``event: snapshot\\ndata: {...}\\n\\n``) and includes the chat id.
- ``publish`` fans out to every subscriber of a chat.
- Events published to one chat don't leak to subscribers of another chat.

Notes:
- Starlette's TestClient buffers the entire ASGI response before returning,
  so it cannot read from an indefinitely-open SSE stream. The framing test
  drives the route handler directly and pulls frames from the
  ``StreamingResponse``'s body iterator. The 404 path is still validated via
  TestClient since it returns synchronously without entering the stream.
"""

from __future__ import annotations

import asyncio
import json
from pathlib import Path

import pytest
from fastapi import Request
from fastapi.testclient import TestClient

from chat.app import app
from chat.db.connection import open_db
from chat.eventlog.log import append_event
from chat.eventlog.projector import project


@pytest.fixture
def client(tmp_path, monkeypatch):
    cfg = tmp_path / "config.toml"
    cfg.write_text('featherless_api_key = "test"\n')
    monkeypatch.setenv("CHAT_CONFIG_PATH", str(cfg))
    db = tmp_path / "test.db"
    monkeypatch.setenv("CHAT_DB_PATH", str(db))
    with TestClient(app) as c:
        yield c


def _seed_chat(
    db_path: Path, bot_id: str = "bot_a", chat_id: str = "chat_bot_a"
) -> None:
    with open_db(db_path) as conn:
        append_event(
            conn,
            kind="bot_authored",
            payload={
                "id": bot_id,
                "name": "BotA",
                "persona": "...",
                "voice_samples": [],
                "traits": [],
                "backstory": "",
                "initial_relationship_to_you": "",
                "kickoff_prose": "...",
            },
        )
        append_event(
            conn,
            kind="chat_created",
            payload={
                "id": chat_id,
                "host_bot_id": bot_id,
                "initial_time": "2026-04-26T20:00:00+00:00",
                "narrative_anchor": "Day 1",
                "weather": "",
            },
        )
        project(conn)


def test_sse_endpoint_404_for_missing_chat(client):
    response = client.get("/chats/nonexistent/events")
    assert response.status_code == 404


async def test_sse_streams_initial_snapshot(client, tmp_path):
    """The first SSE frame is a correctly framed ``snapshot`` event."""
    _seed_chat(tmp_path / "test.db")

    # Drive the route directly. The TestClient can't iterate an open stream
    # because Starlette's transport waits for the response to complete.
    from chat.web.bots import get_conn
    from chat.web.sse import chat_events

    disconnect = asyncio.Event()

    async def receive():
        await disconnect.wait()
        return {"type": "http.disconnect"}

    scope = {
        "type": "http",
        "method": "GET",
        "path": "/chats/chat_bot_a/events",
        "headers": [],
        "query_string": b"",
        "app": client.app,
    }
    request = Request(scope, receive=receive)

    conn_gen = get_conn(request)
    conn = next(conn_gen)
    try:
        response = await chat_events("chat_bot_a", request, conn=conn)
        assert response.media_type == "text/event-stream"

        body_iter = response.body_iterator
        first = await asyncio.wait_for(body_iter.__anext__(), timeout=2.0)
        text = first.decode()

        # Framing: starts with the event line, ends with the blank-line
        # terminator that delimits SSE frames.
        assert text.startswith("event: snapshot\n")
        assert "\ndata: " in text
        assert text.endswith("\n\n")

        # Payload is JSON containing the chat id.
        data_line = next(
            line for line in text.splitlines() if line.startswith("data: ")
        )
        payload = json.loads(data_line[len("data: "):])
        assert payload["chat_id"] == "chat_bot_a"

        # Cleanly tear down the generator's ``finally`` (unsubscribe).
        disconnect.set()
        try:
            await asyncio.wait_for(body_iter.aclose(), timeout=2.0)
        except (StopAsyncIteration, RuntimeError):
            pass
    finally:
        try:
            next(conn_gen)
        except StopIteration:
            pass


async def test_pubsub_publish_fanout():
    """Every active subscriber of a chat receives published events."""
    from chat.web.pubsub import publish, subscribe, unsubscribe

    q1 = await subscribe("chat_x")
    q2 = await subscribe("chat_x")
    try:
        await publish("chat_x", {"event": "test", "value": 1})
        e1 = await asyncio.wait_for(q1.get(), timeout=1.0)
        e2 = await asyncio.wait_for(q2.get(), timeout=1.0)
        assert e1 == {"event": "test", "value": 1}
        assert e2 == {"event": "test", "value": 1}
    finally:
        await unsubscribe("chat_x", q1)
        await unsubscribe("chat_x", q2)


async def test_pubsub_isolated_per_chat():
    """Events published to one chat don't leak to a different chat."""
    from chat.web.pubsub import publish, subscribe, unsubscribe

    q_a = await subscribe("chat_a")
    q_b = await subscribe("chat_b")
    try:
        await publish("chat_a", {"event": "for_a"})
        e = await asyncio.wait_for(q_a.get(), timeout=1.0)
        assert e["event"] == "for_a"
        with pytest.raises(asyncio.TimeoutError):
            await asyncio.wait_for(q_b.get(), timeout=0.1)
    finally:
        await unsubscribe("chat_a", q_a)
        await unsubscribe("chat_b", q_b)