import os
import uuid
import logging
from datetime import datetime
from fastapi import FastAPI, HTTPException, Depends, Request
from fastapi.security import HTTPBearer, HTTPAuthorizationCredentials
from fastapi.responses import HTMLResponse
from pydantic import BaseModel
from transformers import AutoTokenizer, AutoModelForSequenceClassification
import torch
from typing import List, Optional

# ------------------- 1. 日志配置 -------------------
logging.basicConfig(
    level=logging.INFO,
    format="%(asctime)s - %(name)s - %(levelname)s - %(message)s",
    datefmt="%Y-%m-%d %H:%M:%S"
)
logger = logging.getLogger("cross-encoder-api")

# ------------------- 2. 基础配置（缓存 + 环境变量） -------------------
os.environ["TRANSFORMERS_CACHE"] = "/tmp/huggingface_cache"
os.environ["HUGGINGFACE_HUB_CACHE"] = "/tmp/huggingface_cache"

# 从环境变量获取 API Key（OpenAI 风格）
API_KEY = os.getenv("OPENAI_API_KEY")
if not API_KEY:
    logger.error("环境变量 OPENAI_API_KEY 未设置")
    raise ValueError("请设置环境变量 OPENAI_API_KEY")
logger.info("API Key 加载成功")

# ------------------- 3. 初始化 FastAPI 应用 -------------------
app = FastAPI(
    title="OpenAI 兼容的 Cross-Encoder 重排序 API",
    description="基于 cross-encoder/ms-marco-MiniLM-L-6-v2 的文本相关性排序接口",
    version="1.0.0"
)

# ------------------- 4. OpenAI 风格认证（Bearer Token） -------------------
oauth2_scheme = HTTPBearer(auto_error=False)

def verify_api_key(credentials: HTTPAuthorizationCredentials = Depends(oauth2_scheme)):
    """验证 API Key：必须通过 Authorization: Bearer YOUR_API_KEY 传递"""
    request_id = str(uuid.uuid4())[:8]  # 生成短请求ID用于日志追踪
    if not credentials:
        logger.warning(f"请求 {request_id}：缺少认证信息")
        raise HTTPException(
            status_code=401,
            detail="缺少认证信息（请使用 'Authorization: Bearer YOUR_API_KEY'）",
            headers={"WWW-Authenticate": "Bearer"}
        )
    if credentials.scheme != "Bearer":
        logger.warning(f"请求 {request_id}：认证方案错误，应为 Bearer，实际为 {credentials.scheme}")
        raise HTTPException(
            status_code=401,
            detail="认证方案错误（请使用 'Bearer' 方案）",
            headers={"WWW-Authenticate": "Bearer"}
        )
    if credentials.credentials != API_KEY:
        logger.warning(f"请求 {request_id}：无效的 API Key")
        raise HTTPException(
            status_code=401,
            detail="无效的 API Key",
            headers={"WWW-Authenticate": "Bearer"}
        )
    logger.info(f"请求 {request_id}：API Key 验证通过")
    return (credentials.credentials, request_id)  # 返回API Key和请求ID

# ------------------- 5. 数据模型定义 -------------------
class RerankRequest(BaseModel):
    query: str
    documents: List[str]
    top_k: Optional[int] = 3
    truncation: Optional[bool] = True

class DocumentScore(BaseModel):
    document: str
    relevance_score: float
    index: int

class RerankResponse(BaseModel):
    request_id: str
    query: str
    top_k: int
    results: List[DocumentScore]
    model: str = "cross-encoder/ms-marco-MiniLM-L-6-v2"
    timestamp: str = datetime.now().strftime("%Y-%m-%d %H:%M:%S.%f")[:-3]

# GPT 兼容的请求/响应模型
class GPTMessage(BaseModel):
    role: str
    content: str

class GPTRequest(BaseModel):
    model: str
    messages: List[GPTMessage]
    top_k: Optional[int] = 3

class Choice(BaseModel):
    index: int
    message: GPTMessage
    finish_reason: str = "stop"

class GPTResponse(BaseModel):
    id: str = f"chatcmpl-{uuid.uuid4().hex}"
    object: str = "chat.completion"
    created: int = int(datetime.now().timestamp())
    model: str
    choices: List[Choice]
    usage: dict = {"prompt_tokens": 0, "completion_tokens": 0, "total_tokens": 0}

# ------------------- 6. 加载 Cross-Encoder 模型 -------------------
class CrossEncoderModel:
    def __init__(self, model_name: str = "cross-encoder/ms-marco-MiniLM-L-6-v2"):
        self.model_name = model_name
        logger.info(f"开始加载模型：{model_name}")
        
        # 验证缓存目录可写
        cache_dir = os.environ.get("TRANSFORMERS_CACHE", "/tmp/huggingface_cache")
        try:
            test_file = os.path.join(cache_dir, "test.txt")
            with open(test_file, "w") as f:
                f.write("test")
            os.remove(test_file)
            logger.info(f"缓存目录可写：{cache_dir}")
        except Exception as e:
            logger.error(f"缓存目录不可写：{str(e)}")
            raise RuntimeError(f"缓存目录不可写：{str(e)}")
        
        # 加载模型
        try:
            logger.info("开始加载分词器...")
            self.tokenizer = AutoTokenizer.from_pretrained(model_name, cache_dir=cache_dir)
            logger.info("分词器加载完成")
            
            logger.info("开始加载模型权重...")
            self.model = AutoModelForSequenceClassification.from_pretrained(model_name, cache_dir=cache_dir)
            logger.info("模型权重加载完成")
            
            self.device = "cuda" if torch.cuda.is_available() else "cpu"
            self.model.to(self.device)
            self.model.eval()
            logger.info(f"模型加载完成，使用设备：{self.device}")
        except Exception as e:
            logger.error(f"模型加载失败：{str(e)}")
            raise

    def rerank(self, query: str, documents: List[str], top_k: int, truncation: bool, request_id: str) -> List[DocumentScore]:
        """核心重排序逻辑，增加详细日志"""
        logger.info(f"请求 {request_id}：开始重排序处理，查询长度: {len(query)}, 文档数量: {len(documents)}, top_k: {top_k}")
        
        # 参数校验
        if not documents:
            logger.warning(f"请求 {request_id}：候选文档列表为空")
            raise ValueError("候选文档不能为空")
        if top_k <= 0:
            logger.warning(f"请求 {request_id}：无效的 top_k 值: {top_k}")
            raise ValueError("top_k 必须为正整数")
        
        # 自动将 top_k 限制为文档数量（避免超出）
        adjusted_top_k = min(top_k, len(documents))
        if adjusted_top_k != top_k:
            logger.info(f"请求 {request_id}：top_k 从 {top_k} 调整为 {adjusted_top_k}（文档数量限制）")
        
        # 计算每篇文档的相关性分数
        doc_scores = []
        try:
            for i, doc in enumerate(documents):
                if i % 5 == 0:  # 每处理5个文档输出一次日志
                    logger.info(f"请求 {request_id}：正在处理第 {i+1}/{len(documents)} 个文档")
                
                inputs = self.tokenizer(
                    f"{query} {self.tokenizer.sep_token} {doc}",
                    return_tensors="pt",
                    padding="max_length",
                    truncation=truncation,
                    max_length=512
                ).to(self.device)
                
                with torch.no_grad():
                    outputs = self.model(**inputs)
                
                score = outputs.logits.item()
                doc_scores.append((doc, score))
                logger.debug(f"请求 {request_id}：文档 {i+1} 分数: {score:.4f}")
            
            # 排序并返回结果
            sorted_docs = sorted(doc_scores, key=lambda x: x[1], reverse=True)[:adjusted_top_k]
            logger.info(f"请求 {request_id}：重排序完成，返回 {len(sorted_docs)} 个结果")
            
            return [
                DocumentScore(document=doc, relevance_score=round(score, 4), index=i)
                for i, (doc, score) in enumerate(sorted_docs)
            ]
        except Exception as e:
            logger.error(f"请求 {request_id}：重排序过程出错: {str(e)}")
            raise

# 初始化模型（全局唯一）
try:
    reranker = CrossEncoderModel()
except Exception as e:
    logger.critical(f"模型初始化失败，服务无法启动: {str(e)}")
    raise

# ------------------- 7. API 端点（OpenAI 风格路径） -------------------
# 7.1 根路径首页
@app.get("/", response_class=HTMLResponse)
async def home_page(request: Request):
    client_ip = request.client.host
    current_time = datetime.now().strftime("%Y-%m-%d %H:%M:%S")
    logger.info(f"首页访问来自 {client_ip}")
    return f"""
<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <meta charset="UTF-8">
    <title>OpenAI 兼容重排序 API</title>
    <style>
        body {{ font-family: Arial, sans-serif; max-width: 1200px; margin: 0 auto; padding: 20px; }}
        h1 {{ color: #2c3e50; border-bottom: 2px solid #3498db; padding-bottom: 10px; }}
        h2 {{ color: #34495e; margin-top: 30px; }}
        pre {{ background: #f8f9fa; padding: 15px; border-radius: 5px; border: 1px solid #e9ecef; overflow-x: auto; }}
        table {{ border-collapse: collapse; width: 100%; margin: 20px 0; }}
        th, td {{ border: 1px solid #e9ecef; padding: 12px; text-align: left; }}
        th {{ background-color: #f1f5f9; }}
    </style>
</head>
<body>
    <h1>OpenAI 兼容的 Cross-Encoder 重排序 API</h1>
    <p>基于 <code>cross-encoder/ms-marco-MiniLM-L-6-v2</code> 模型，支持 OpenAI 风格 API 调用。</p>

    <h2>接口列表</h2>
    <table>
        <tr>
            <th>接口</th>
            <th>URL</th>
            <th>方法</th>
            <th>认证</th>
        </tr>
        <tr>
            <td>基础重排序</td>
            <td class="api-url">/v1/rerank</td>
            <td>POST</td>
            <td>Authorization: Bearer API_KEY</td>
        </tr>
        <tr>
            <td>GPT 兼容重排序</td>
            <td class="api-url">/v1/chat/completions</td>
            <td>POST</td>
            <td>Authorization: Bearer API_KEY</td>
        </tr>
        <tr>
            <td>健康检查</td>
            <td class="api-url">/v1/health</td>
            <td>GET</td>
            <td>无需认证</td>
        </tr>
    </table>

    <h2>调用示例（Python）</h2>
    <pre><code>import openai

client = openai.OpenAI(
    api_key="YOUR_API_KEY",
    base_url="https://your-space.hf.space/v1"  # 替换为你的 Space URL
)

response = client.chat.completions.create(
    model="cross-encoder/ms-marco-MiniLM-L-6-v2",
    messages=[
        {{
            "role": "user",
            "content": "query: 什么是机器学习?; documents: 机器学习是AI的分支; Python是编程语言;"
        }}
    ],
    top_k=2
)

print(response.choices[0].message.content)</code></pre>
</body>
</html>
"""

# 7.2 基础重排序接口（/v1/rerank）
@app.post("/v1/rerank", response_model=RerankResponse)
async def base_rerank(
    request: RerankRequest,
    auth_result: tuple = Depends(verify_api_key)
):
    api_key, request_id = auth_result
    try:
        logger.info(f"请求 {request_id}：收到 /v1/rerank 请求，query: {request.query[:50]}...（截断显示）")
        
        # 执行重排序
        results = reranker.rerank(
            query=request.query,
            documents=request.documents,
            top_k=request.top_k,
            truncation=request.truncation,
            request_id=request_id
        )
        
        # 构建响应
        response = RerankResponse(
            request_id=request_id,
            query=request.query,
            top_k=min(request.top_k, len(request.documents)),
            results=results
        )
        
        logger.info(f"请求 {request_id}：处理完成，返回 {len(results)} 个结果")
        return response
        
    except ValueError as e:
        logger.warning(f"请求 {request_id}：参数错误 - {str(e)}")
        raise HTTPException(status_code=400, detail=str(e))
    except Exception as e:
        logger.error(f"请求 {request_id}：服务器错误 - {str(e)}", exc_info=True)
        raise HTTPException(status_code=500, detail=f"服务器错误：{str(e)}")

# 7.3 GPT 兼容接口（/v1/chat/completions）
@app.post("/v1/chat/completions", response_model=GPTResponse)
async def gpt_compatible_rerank(
    request: GPTRequest,
    auth_result: tuple = Depends(verify_api_key)
):
    api_key, request_id = auth_result
    try:
        logger.info(f"请求 {request_id}：收到 /v1/chat/completions 请求，模型: {request.model}")
        
        # 验证模型名
        if request.model != reranker.model_name:
            error_msg = f"仅支持模型：{reranker.model_name}，实际请求：{request.model}"
            logger.warning(f"请求 {request_id}：{error_msg}")
            raise ValueError(error_msg)
        
        # 验证消息格式
        if not request.messages:
            logger.warning(f"请求 {request_id}：消息列表为空")
            raise ValueError("消息列表不能为空")
        if request.messages[-1].role != "user":
            error_msg = f"最后一条消息必须是 'user' 角色，实际为：{request.messages[-1].role}"
            logger.warning(f"请求 {request_id}：{error_msg}")
            raise ValueError(error_msg)
        
        # 解析输入内容
        content = request.messages[-1].content
        logger.info(f"请求 {request_id}：用户输入: {content[:100]}...（截断显示）")
        
        if "; documents: " not in content:
            error_msg = "输入格式需为 'query: [查询]; documents: [文档1]; [文档2]; ...'"
            logger.warning(f"请求 {request_id}：{error_msg}")
            raise ValueError(error_msg)
        
        query_part, docs_part = content.split("; documents: ")
        query = query_part.replace("query: ", "").strip()
        documents = [doc.strip() for doc in docs_part.split(";") if doc.strip()]
        
        logger.info(f"请求 {request_id}：解析完成，query: {query[:50]}..., 文档数量: {len(documents)}")
        
        # 执行重排序
        results = reranker.rerank(
            query=query,
            documents=documents,
            top_k=request.top_k,
            truncation=True,
            request_id=request_id
        )
        
        # 构建 GPT 风格响应
        response = GPTResponse(
            model=request.model,
            choices=[
                Choice(
                    index=0,
                    message=GPTMessage(
                        role="assistant",
                        content=f"重排序结果：{results}"
                    )
                )
            ]
        )
        
        logger.info(f"请求 {request_id}：处理完成，返回 {len(results)} 个结果")
        return response
        
    except ValueError as e:
        logger.warning(f"请求 {request_id}：参数错误 - {str(e)}")
        raise HTTPException(status_code=400, detail=str(e))
    except Exception as e:
        logger.error(f"请求 {request_id}：服务器错误 - {str(e)}", exc_info=True)
        raise HTTPException(status_code=500, detail=f"服务器错误：{str(e)}")

# 7.4 健康检查接口（/v1/health）
@app.get("/v1/health")
async def health_check(request: Request):
    client_ip = request.client.host
    status = {
        "status": "healthy",
        "model": reranker.model_name,
        "device": reranker.device,
        "timestamp": datetime.now().strftime("%Y-%m-%d %H:%M:%S"),
        "uptime": datetime.now().strftime("%Y-%m-%d %H:%M:%S")  # 简化版uptime
    }
    logger.info(f"健康检查来自 {client_ip}：{status['status']}")
    return status

# ------------------- 8. 本地运行入口 -------------------
if __name__ == "__main__":
    import uvicorn
    logger.info("启动本地开发服务器...")
    uvicorn.run(
        app,
        host="0.0.0.0",
        port=7860,
        log_config=None  # 使用自定义日志配置
    )