import pytest
import httpx
import json
from typing import List, AsyncGenerator

from app.services import call_llm_api_real
from app.models import ChatMessage
from app.core.config import Settings

# Sample SSE chunks to simulate a streaming response
SSE_STREAM_CHUNKS = [
    'data: {"choices": [{"delta": {"role": "assistant", "content": "Hello"}}]}',
    'data: {"choices": [{"delta": {"content": " world!"}}]}',
    'data: {"choices": [{"delta": {"tool_calls": [{"index": 0, "id": "call_123", "function": {"name": "get_weather", "arguments": ""}}]}}]}',
    'data: {"choices": [{"delta": {"tool_calls": [{"index": 0, "function": {"arguments": "{\\"location\\":"}}]}}]}',
    'data: {"choices": [{"delta": {"tool_calls": [{"index": 0, "function": {"arguments": " \\"San Francisco\\"}"}}]}}]}',
    'data: [DONE]',
]

# Mock settings for the test
@pytest.fixture
def mock_settings() -> Settings:
    """Provides mock settings for tests."""
    return Settings(
        REAL_LLM_API_URL="http://fake-llm-api.com/chat",
        REAL_LLM_API_KEY="fake-key"
    )

# Async generator to mock the streaming response
async def mock_aiter_lines() -> AsyncGenerator[str, None]:
    for chunk in SSE_STREAM_CHUNKS:
        yield chunk

# Mock for the httpx.Response object
class MockStreamResponse:
    def __init__(self, status_code: int = 200):
        self._status_code = status_code

    def raise_for_status(self):
        if self._status_code != 200:
            raise httpx.HTTPStatusError(
                message="Error", request=httpx.Request("POST", ""), response=httpx.Response(self._status_code)
            )

    def aiter_lines(self) -> AsyncGenerator[str, None]:
        return mock_aiter_lines()
    
    async def __aenter__(self):
        return self
    
    async def __aexit__(self, exc_type, exc_val, exc_tb):
        pass

# Mock for the httpx.AsyncClient
class MockAsyncClient:
    def stream(self, method, url, headers, json, timeout):
        return MockStreamResponse()

    async def __aenter__(self):
        return self
    
    async def __aexit__(self, exc_type, exc_val, exc_tb):
        pass

@pytest.mark.anyio
async def test_call_llm_api_real_streaming(monkeypatch, mock_settings):
    """
    Tests that `call_llm_api_real` correctly handles an SSE stream,
    parses the chunks, and assembles the final response message.
    """
    # Patch httpx.AsyncClient to use our mock
    monkeypatch.setattr(httpx, "AsyncClient", MockAsyncClient)

    messages = [ChatMessage(role="user", content="What is the weather in San Francisco?")]

    # Call the function
    result = await call_llm_api_real(messages, mock_settings)

    # Define the expected assembled result
    expected_result = {
        "role": "assistant",
        "content": "Hello world!",
        "tool_calls": [
            {
                "id": "call_123",
                "type": "function",
                "function": {
                    "name": "get_weather",
                    "arguments": '{"location": "San Francisco"}',
                },
            }
        ],
    }

    # Assert that the result matches the expected output
    assert result == expected_result