app.py

from fastapi import FastAPI, HTTPException, Request
from fastapi.responses import JSONResponse
import requests
import json
import os
import time

app = FastAPI()

# 环境变量配置
STATUS_URL = os.environ.get("STATUS_URL", "https://duckduckgo.com/duckchat/v1/status")
CHAT_URL = os.environ.get("CHAT_URL", "https://duckduckgo.com/duckchat/v1/chat")
REFERER = os.environ.get("REFERER", "https://duckduckgo.com/")
ORIGIN = os.environ.get("ORIGIN", "https://duckduckgo.com")
USER_AGENT = os.environ.get("USER_AGENT", "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/127.0.0.0 Safari/537.36")
COOKIE = os.environ.get("COOKIE", "dcm=3; s=l; bf=1")  # 从环境变量获取 Cookie

DEFAULT_HEADERS = {
    "User-Agent": USER_AGENT,
    "Accept": "text/event-stream",
    "Accept-Language": "en-US,en;q=0.5",
    "Accept-Encoding": "gzip, deflate, br",
    "Referer": REFERER,
    "Content-Type": "application/json",
    "Origin": ORIGIN,
    "Connection": "keep-alive",
    "Cookie": COOKIE,
    "Sec-Fetch-Dest": "empty",
    "Sec-Fetch-Mode": "cors",
    "Sec-Fetch-Site": "same-origin",
    "Pragma": "no-cache",
    "TE": "trailers",
}

SUPPORTED_MODELS = ["o3-mini", "gpt-4o-mini", "claude-3-haiku-20240307", "meta-llama/Llama-3.3-70B-Instruct-Turbo"]

async def get_vqd():
    """获取 DuckDuckGo Chat 的 VQD 值。"""
    headers = {**DEFAULT_HEADERS, "x-vqd-accept": "1"}
    try:
        response = requests.get(STATUS_URL, headers=headers)
        response.raise_for_status()  # 抛出 HTTPError，如果状态码不是 200
        vqd = response.headers.get("x-vqd-4")
        if not vqd:
            raise ValueError("x-vqd-4 header 在响应中未找到。")
        return vqd
    except requests.exceptions.RequestException as e:
        raise HTTPException(status_code=500, detail=f"HTTP 请求失败: {e}")
    except ValueError as e:
        raise HTTPException(status_code=500, detail=str(e))

async def duckduckgo_chat(model, messages):
    """与 DuckDuckGo Chat 进行交互。"""
    try:
        x_vqd_4 = await get_vqd()

        chat_headers = {
            **DEFAULT_HEADERS,
            "x-vqd-4": x_vqd_4,
        }

        body = json.dumps({
            "model": model,
            "messages": messages,
        })

        response = requests.post(CHAT_URL, headers=chat_headers, data=body, stream=True)
        response.raise_for_status()

        full_message = ""
        for line in response.iter_lines():
            if line:
                decoded_line = line.decode('utf-8')
                if decoded_line.startswith("data: "):
                    try:
                        json_data = json.loads(decoded_line[5:])
                        full_message += json_data.get("message", "")
                    except json.JSONDecodeError as e:
                        print(f"JSON 解析错误: {e}, 行: {decoded_line}")
                        pass  # 忽略解析错误

        return full_message

    except requests.exceptions.RequestException as e:
        raise HTTPException(status_code=500, detail=f"HTTP 请求失败: {e}")
    except Exception as e:
        raise HTTPException(status_code=500, detail=f"聊天过程中发生错误: {e}")

@app.post("/v1/chat/completions")
async def chat_completions(request: Request):
    try:
        body = await request.json()
        if not body:
            raise HTTPException(status_code=400, detail="无效的请求体")

        model = body.get("model", "o3-mini")
        if model not in SUPPORTED_MODELS:
            raise HTTPException(status_code=400, detail=f"模型 \"{model}\" 不支持。支持的模型有: {', '.join(SUPPORTED_MODELS)}.")

        messages = body.get("messages")
        if not messages:
            raise HTTPException(status_code=400, detail="未提供任何消息内容")

        # 处理 system 消息
        system_message = next((msg for msg in messages if msg.get("role") == "system"), None)
        system_prompt = f"你将扮演一个{system_message['content']}.\n" if system_message else ""

        # 提取历史消息并格式化
        history_messages = "\n".join(
            f"{msg['role']}: {msg['content']}"
            for msg in messages
            if msg.get("role") != "system" and msg != messages[-1]
        )

        # 提取最后一条用户消息
        last_user_message = messages[-1]
        current_question = last_user_message["content"] if last_user_message.get("role") == "user" else ""

        # 构建合并后的消息
        combined_message_content = f"{system_prompt}以下是历史对话记录：\n{history_messages}\n用户当前提问：{current_question}"
        combined_message = {"role": "user", "content": combined_message_content}

        # 发送单条消息
        response_text = await duckduckgo_chat(model, [combined_message])

        # 构建 OpenAI 风格的响应
        openai_response = {
            "id": f"chatcmpl-{int(time.time() * 1000)}",  # 生成唯一 ID
            "object": "chat.completion",
            "created": int(time.time()),
            "model": model,
            "choices": [
                {
                    "message": {
                        "role": "assistant",
                        "content": response_text,
                    },
                    "finish_reason": "stop",
                    "index": 0,
                },
            ],
            "usage": {
                "prompt_tokens": 0,
                "completion_tokens": 0,
                "total_tokens": 0
            },
        }

        return JSONResponse(content=openai_response)

    except HTTPException as e:
        raise e  # 重新抛出 HTTPException，以便 FastAPI 处理
    except Exception as e:
        print(f"API 错误: {e}")
        raise HTTPException(status_code=500, detail=f"服务器内部错误: {e}")

@app.exception_handler(HTTPException)
async def http_exception_handler(request: Request, exc: HTTPException):
    return JSONResponse(
        status_code=exc.status_code,
        content={"detail": exc.detail},
    )

@app.get("/")
async def greet_json():
    return {"Hello": "World!"}