"""Tests for SSE streaming support in /v1/chat/completions."""

from __future__ import annotations

import asyncio
import json
from unittest.mock import AsyncMock, MagicMock

import pytest
import pytest_asyncio

from nanobot.api.server import (
    _sse_chunk,
    _SSE_DONE,
    create_app,
)

try:
    from aiohttp.test_utils import TestClient, TestServer

    HAS_AIOHTTP = True
except ImportError:
    HAS_AIOHTTP = False

pytest_plugins = ("pytest_asyncio",)


# ---------------------------------------------------------------------------
# Unit tests for SSE helpers
# ---------------------------------------------------------------------------


def test_sse_chunk_with_delta() -> None:
    raw = _sse_chunk("hello", "test-model", "chatcmpl-abc123")
    line = raw.decode()
    assert line.startswith("data: ")
    payload = json.loads(line[len("data: "):])
    assert payload["id"] == "chatcmpl-abc123"
    assert payload["object"] == "chat.completion.chunk"
    assert payload["model"] == "test-model"
    assert payload["choices"][0]["delta"]["content"] == "hello"
    assert payload["choices"][0]["finish_reason"] is None


def test_sse_chunk_finish_reason() -> None:
    raw = _sse_chunk("", "m", "id1", finish_reason="stop")
    payload = json.loads(raw.decode().split("data: ", 1)[1])
    assert payload["choices"][0]["delta"] == {}
    assert payload["choices"][0]["finish_reason"] == "stop"


def test_sse_done_format() -> None:
    assert _SSE_DONE == b"data: [DONE]\n\n"


# ---------------------------------------------------------------------------
# Integration tests with aiohttp TestClient
# ---------------------------------------------------------------------------


def _make_streaming_agent(tokens: list[str]) -> MagicMock:
    """Create a mock agent that streams tokens via on_stream callback."""
    agent = MagicMock()
    agent._connect_mcp = AsyncMock()
    agent.close_mcp = AsyncMock()

    async def fake_process_direct(*, content="", media=None, session_key="",
                                  channel="", chat_id="", on_stream=None,
                                  on_stream_end=None, **kwargs):
        if on_stream:
            for token in tokens:
                await on_stream(token)
        if on_stream_end:
            await on_stream_end()
        return " ".join(tokens)

    agent.process_direct = fake_process_direct
    return agent


@pytest_asyncio.fixture
async def aiohttp_client():
    clients: list[TestClient] = []

    async def _make_client(app):
        client = TestClient(TestServer(app))
        await client.start_server()
        clients.append(client)
        return client

    try:
        yield _make_client
    finally:
        for client in clients:
            await client.close()


@pytest.mark.skipif(not HAS_AIOHTTP, reason="aiohttp not installed")
@pytest.mark.asyncio
async def test_stream_true_returns_sse(aiohttp_client) -> None:
    """stream=true should return text/event-stream with SSE chunks."""
    agent = _make_streaming_agent(["Hello", " world"])
    app = create_app(agent, model_name="test-model")
    client = await aiohttp_client(app)

    resp = await client.post(
        "/v1/chat/completions",
        json={"messages": [{"role": "user", "content": "hi"}], "stream": True},
    )
    assert resp.status == 200
    assert resp.content_type == "text/event-stream"

    body = await resp.text()
    lines = [l for l in body.split("\n") if l.startswith("data: ")]

    # Should have: 2 token chunks + 1 finish chunk + [DONE]
    data_lines = [l[len("data: "):] for l in lines]
    assert data_lines[-1] == "[DONE]"

    chunks = [json.loads(l) for l in data_lines[:-1]]
    assert chunks[0]["choices"][0]["delta"]["content"] == "Hello"
    assert chunks[1]["choices"][0]["delta"]["content"] == " world"
    # Last chunk before [DONE] should have finish_reason=stop
    assert chunks[-1]["choices"][0]["finish_reason"] == "stop"
    assert chunks[-1]["choices"][0]["delta"] == {}


@pytest.mark.skipif(not HAS_AIOHTTP, reason="aiohttp not installed")
@pytest.mark.asyncio
async def test_stream_false_returns_json(aiohttp_client) -> None:
    """stream=false should still return regular JSON response."""
    agent = MagicMock()
    agent.process_direct = AsyncMock(return_value="normal reply")
    agent._connect_mcp = AsyncMock()
    agent.close_mcp = AsyncMock()

    app = create_app(agent, model_name="m")
    client = await aiohttp_client(app)

    resp = await client.post(
        "/v1/chat/completions",
        json={"messages": [{"role": "user", "content": "hi"}], "stream": False},
    )
    assert resp.status == 200
    body = await resp.json()
    assert body["object"] == "chat.completion"
    assert body["choices"][0]["message"]["content"] == "normal reply"


@pytest.mark.skipif(not HAS_AIOHTTP, reason="aiohttp not installed")
@pytest.mark.asyncio
async def test_stream_default_is_false(aiohttp_client) -> None:
    """Omitting stream should behave like stream=false."""
    agent = MagicMock()
    agent.process_direct = AsyncMock(return_value="default reply")
    agent._connect_mcp = AsyncMock()
    agent.close_mcp = AsyncMock()

    app = create_app(agent, model_name="m")
    client = await aiohttp_client(app)

    resp = await client.post(
        "/v1/chat/completions",
        json={"messages": [{"role": "user", "content": "hi"}]},
    )
    assert resp.status == 200
    body = await resp.json()
    assert body["object"] == "chat.completion"


@pytest.mark.skipif(not HAS_AIOHTTP, reason="aiohttp not installed")
@pytest.mark.asyncio
async def test_stream_sse_chunk_ids_are_consistent(aiohttp_client) -> None:
    """All SSE chunks in a single stream should share the same id."""
    agent = _make_streaming_agent(["A", "B", "C"])
    app = create_app(agent, model_name="m")
    client = await aiohttp_client(app)

    resp = await client.post(
        "/v1/chat/completions",
        json={"messages": [{"role": "user", "content": "go"}], "stream": True},
    )
    body = await resp.text()
    data_lines = [l[len("data: "):] for l in body.split("\n") if l.startswith("data: ") and l != "data: [DONE]"]
    chunks = [json.loads(l) for l in data_lines]

    chunk_ids = {c["id"] for c in chunks}
    assert len(chunk_ids) == 1, f"Expected single chunk id, got {chunk_ids}"
    assert chunk_ids.pop().startswith("chatcmpl-")


@pytest.mark.skipif(not HAS_AIOHTTP, reason="aiohttp not installed")
@pytest.mark.asyncio
async def test_stream_passes_on_stream_callbacks(aiohttp_client) -> None:
    """process_direct should be called with on_stream and on_stream_end when streaming."""
    captured_kwargs: dict = {}

    async def fake_process_direct(**kwargs):
        captured_kwargs.update(kwargs)
        if kwargs.get("on_stream_end"):
            await kwargs["on_stream_end"]()
        return "done"

    agent = MagicMock()
    agent.process_direct = fake_process_direct
    agent._connect_mcp = AsyncMock()
    agent.close_mcp = AsyncMock()

    app = create_app(agent, model_name="m")
    client = await aiohttp_client(app)

    resp = await client.post(
        "/v1/chat/completions",
        json={"messages": [{"role": "user", "content": "hi"}], "stream": True},
    )
    assert resp.status == 200
    assert captured_kwargs.get("on_stream") is not None
    assert captured_kwargs.get("on_stream_end") is not None


@pytest.mark.skipif(not HAS_AIOHTTP, reason="aiohttp not installed")
@pytest.mark.asyncio
async def test_stream_with_session_id(aiohttp_client) -> None:
    """Streaming should respect session_id for session key routing."""
    captured_key: str = ""

    async def fake_process_direct(*, session_key="", on_stream=None, on_stream_end=None, **kwargs):
        nonlocal captured_key
        captured_key = session_key
        if on_stream:
            await on_stream("ok")
        if on_stream_end:
            await on_stream_end()
        return "ok"

    agent = MagicMock()
    agent.process_direct = fake_process_direct
    agent._connect_mcp = AsyncMock()
    agent.close_mcp = AsyncMock()

    app = create_app(agent, model_name="m")
    client = await aiohttp_client(app)

    resp = await client.post(
        "/v1/chat/completions",
        json={
            "messages": [{"role": "user", "content": "hi"}],
            "stream": True,
            "session_id": "my-session",
        },
    )
    assert resp.status == 200
    assert captured_key == "api:my-session"


@pytest.mark.skipif(not HAS_AIOHTTP, reason="aiohttp not installed")
@pytest.mark.asyncio
async def test_streaming_backend_failure_does_not_emit_success_terminator(aiohttp_client) -> None:
    """Backend exceptions should not surface as a normal stop+[DONE] stream."""
    agent = MagicMock()

    async def boom(**kwargs):
        raise RuntimeError("backend blew up")

    agent.process_direct = boom
    agent._connect_mcp = AsyncMock()
    agent.close_mcp = AsyncMock()

    app = create_app(agent, model_name="m")
    client = await aiohttp_client(app)

    resp = await client.post(
        "/v1/chat/completions",
        json={"messages": [{"role": "user", "content": "hi"}], "stream": True},
    )

    assert resp.status == 200
    body = await resp.text()
    assert '"finish_reason": "stop"' not in body
    assert "[DONE]" not in body