import json

import pytest

from src.api.endpoints import chat
from src.backends.chat import ChatInput, ChatResult, FormUpdate, TextDelta
from src.schemas.models import ProcessRequest_chat


def make_request(**overrides):
    payload = {
        "sessionId": "session-001",
        "timeStamp": "20260726120000",
        "text": "发生了交通事故",
        "needFormUpdate": True,
    }
    payload.update(overrides)
    return ProcessRequest_chat(**payload)


async def response_text(response):
    chunks = []
    async for chunk in response.body_iterator:
        chunks.append(chunk.decode() if isinstance(chunk, bytes) else chunk)
    return "".join(chunks)


def parse_sse(body):
    events = []
    for block in body.strip().split("\n\n"):
        lines = block.splitlines()
        event = lines[0].removeprefix("event: ")
        data = json.loads(lines[1].removeprefix("data: "))
        events.append((event, data))
    return events


class OrderedBackend:
    async def stream(self, chat_input: ChatInput):
        yield TextDelta("<sta")
        yield TextDelta("te>1002</state>")
        yield FormUpdate({"jdcsl": 2})
        yield TextDelta("第一句。")
        yield TextDelta("第二句。")

    async def complete(self, chat_input: ChatInput):
        return ChatResult("<state>1002</state>第一句。第二句。", "1002", {"jdcsl": 2})


class MissingPrefixBackend:
    async def stream(self, chat_input: ChatInput):
        yield TextDelta("没有状态前缀")

    async def complete(self, chat_input: ChatInput):
        return ChatResult("没有状态前缀")


@pytest.mark.asyncio
async def test_sse_success_event_order_and_cardinality():
    response = await chat(make_request(), stream=True, backend=OrderedBackend())
    events = parse_sse(await response_text(response))
    names = [name for name, _ in events]

    assert names == [
        "stage_code",
        "formUpdate",
        "text_delta",
        "text_delta",
        "done",
    ]
    assert names.count("stage_code") == 1
    assert names.count("formUpdate") == 1
    assert names.count("done") == 1
    assert "error" not in names
    assert "".join(data["text"] for name, data in events if name == "text_delta") == (
        "第一句。第二句。"
    )


@pytest.mark.asyncio
async def test_use_text_chunk_only_changes_delta_boundaries():
    request = make_request(useTextChunk=True)
    response = await chat(request, stream=True, backend=OrderedBackend())
    events = parse_sse(await response_text(response))

    assert "".join(data["text"] for name, data in events if name == "text_delta") == (
        "第一句。第二句。"
    )
    assert [name for name, _ in events].count("done") == 1


@pytest.mark.asyncio
async def test_missing_stream_prefix_characterizes_current_legacy_behavior():
    response = await chat(
        make_request(needFormUpdate=False),
        stream=True,
        backend=MissingPrefixBackend(),
    )
    events = parse_sse(await response_text(response))

    assert [name for name, _ in events] == ["text_delta", "done"]
    assert events[0][1]["text"] == "没有状态前缀"


@pytest.mark.asyncio
async def test_missing_non_stream_prefix_returns_compatible_business_error():
    response = await chat(
        make_request(needFormUpdate=False),
        stream=False,
        backend=MissingPrefixBackend(),
    )

    assert response.code == "500"
    assert response.outputText == ""
    assert response.nextStageCode == ""
    assert response.msg == "大模型服务返回消息不完整"