from typing import Any
import httpx
from mcp.server.fastmcp import FastMCP

# 初始化 FastMCP server
mcp = FastMCP("weather")

# Constants
NWS_API_BASE = "https://api.weather.gov"
USER_AGENT = "weather-app/1.0"

async def make_nws_request(url: str) -> dict[str, Any] | None:
    """向 NWS API 发送请求，并进行适当的错误处理。"""
    headers = {
        "User-Agent": USER_AGENT,
        "Accept": "application/geo+json"
    }
    async with httpx.AsyncClient() as client:
        try:
            response = await client.get(url, headers=headers, timeout=30.0)
            response.raise_for_status()
            return response.json()
        except Exception:
            return None

def format_alert(feature: dict) -> str:
    """将警报 feature 格式化为可读的字符串。"""
    props = feature["properties"]
    return f"""
事件: {props.get('event', 'Unknown')}
区域: {props.get('areaDesc', 'Unknown')}
严重性: {props.get('severity', 'Unknown')}
描述: {props.get('description', 'No description available')}
指示: {props.get('instruction', 'No specific instructions provided')}
"""

@mcp.tool()
async def get_alerts(state: str) -> str:
    """获取美国州的天气警报。

    Args:
        state: 两个字母的美国州代码（例如 CA、NY）
    """
    url = f"{NWS_API_BASE}/alerts/active/area/{state}"
    data = await make_nws_request(url)

    if not data or "features" not in data:
        return "无法获取警报或未找到警报。"

    if not data["features"]:
        return "该州没有活跃的警报。"

    alerts = [format_alert(feature) for feature in data["features"]]
    return "\n---\n".join(alerts)

@mcp.tool()
async def get_forecast(latitude: float, longitude: float) -> str:
    """获取某个位置的天气预报。

    Args:
        latitude: 位置的纬度
        longitude: 位置的经度
    """
    # 首先获取预报网格 endpoint
    points_url = f"{NWS_API_BASE}/points/{latitude},{longitude}"
    points_data = await make_nws_request(points_url)

    if not points_data:
        return "无法获取此位置的预报数据。"

    # 从 points response 中获取预报 URL
    forecast_url = points_data["properties"]["forecast"]
    forecast_data = await make_nws_request(forecast_url)

    if not forecast_data:
        return "无法获取详细预报。"

    # 将 periods 格式化为可读的预报
    periods = forecast_data["properties"]["periods"]
    forecasts = []
    for period in periods[:5]:  # 仅显示接下来的 5 个 periods
        forecast = f"""
{period['name']}:
温度: {period['temperature']}°{period['temperatureUnit']}
风: {period['windSpeed']} {period['windDirection']}
预报: {period['detailedForecast']}
"""
        forecasts.append(forecast)

    return "\n---\n".join(forecasts)

def main() -> None:
    """模块入口，供 `python -m weather` 或 `weather:main` 脚本调用。

    该函数会启动 MCP server 并阻塞，使用 stdio 作为传输层（用于 VS Code MCP 集成）。
    """
    mcp.run(transport="stdio")


if __name__ == "__main__":
    # 直接运行时打印错误再抛出，便于调试依赖或运行时问题
    try:
        main()
    except Exception as e:
        import sys
        print(f"启动 MCP 服务失败: {e}", file=sys.stderr)
        raise

uv run weather.py

uv venv     //在当前工作目录创建uv虚拟环境
.venv\Scripts\activate      //启动虚拟环境
uv add mcp[cli] httpx       //安装依赖包