import json
from urllib.parse import urlparse, urlunparse
from langchain_community.utilities import SQLDatabase
from sqlalchemy import Table, MetaData, select, insert

# --- 1. 工具函数：URL 标准化 ---
def normalize_url(url: str) -> str:
    """
    标准化 URL，解决末尾斜杠、大小写、锚点造成的重复问题
    """
    if not url:
        return ""
    # 去除前后空格
    url = url.strip()
    # 解析 URL
    parsed = urlparse(url)
    # 1. 协议和域名转小写
    scheme = parsed.scheme.lower()
    netloc = parsed.netloc.lower()
    # 2. 路径处理：去除末尾斜杠
    path = parsed.path
    if path.endswith('/'):
        path = path.rstrip('/')
    # 3. 忽略 Query 参数排序或 Fragment (#) 
    # 这里保留 Query 参数，但丢弃 Fragment，因为锚点指向同一页面
    query = parsed.query
    
    # 重新拼接
    return urlunparse((scheme, netloc, path, parsed.params, query, ""))

# --- 2. 数据库连接工厂 ---
def get_db_connection(db_url: str):
    """
    获取通用数据库连接，处理协议兼容性
    """
    if not db_url:
        raise ValueError("数据库连接字符串 (db_url) 不能为空")
        
    # 修复常见协议头报错
    if db_url.startswith("postgres://"):
        db_url = db_url.replace("postgres://", "postgresql+psycopg2://", 1)
    elif db_url.startswith("postgresql://") and "+psycopg2" not in db_url:
        db_url = db_url.replace("postgresql://", "postgresql+psycopg2://", 1)
    
    try:
        # pool_pre_ping=True 用于在获取连接前检查有效性，防止超时断开
        return SQLDatabase.from_uri(db_url, engine_args={"pool_pre_ping": True})
    except Exception as e:
        raise RuntimeError(f"数据库连接失败: {str(e)}")

# --- 3. 核心业务逻辑 ---
def _logic_handler(db: SQLDatabase, inputs: dict):
    """
    业务逻辑：注册任务并初始化队列
    """
    engine = db._engine
    metadata = MetaData()
    
    # 标准化输入 URL
    raw_url = inputs.get("url", "")
    if not raw_url:
        raise ValueError("输入参数 'url' 缺失")
    clean_url = normalize_url(raw_url)

    # 反射获取表结构（无需写SQL）
    tasks_table = Table('crawl_tasks', metadata, autoload_with=engine)
    queue_table = Table('crawl_queue', metadata, autoload_with=engine)
    
    with engine.begin() as conn:
        # 1. 查询该 root_url 是否已存在
        find_stmt = select(tasks_table.c.id).where(tasks_table.c.root_url == clean_url)
        existing_task = conn.execute(find_stmt).fetchone()
        
        if existing_task:
            # 任务已存在，直接返回
            return {
                "task_id": existing_task[0],
                "is_new_task": 0,
                "url": clean_url
            }
        
        # 2. 任务不存在，创建新任务记录
        # .returning(tasks_table.c.id) 是 PostgreSQL 获取自增 ID 的标准写法
        insert_task_stmt = insert(tasks_table).values(
            root_url=clean_url,
            status='running'
        ).returning(tasks_table.c.id)
        
        new_task_id = conn.execute(insert_task_stmt).fetchone()[0]
        
        # 3. 初始化任务队列：将根 URL 作为第一条待爬取数据
        # 确保根 URL 也经过标准化处理
        insert_queue_stmt = insert(queue_table).values(
            task_id=new_task_id,
            url=clean_url,
            status='pending'
        )
        conn.execute(insert_queue_stmt)
        
        return {
            "task_id": new_task_id,
            "is_new_task": 1,
            "url": clean_url
        }

# --- 4. Dify 节点主入口 ---
def main(url: str, DB_URL: str):
    """
    Dify 节点入口函数
    """
    ret = {"code": 0, "msg": "unknown", "data": None}
    
    # 从输入或环境变量获取数据库地址
    db_url = DB_URL

    try:
        # 获取连接
        db = get_db_connection(db_url)
        
        # 处理逻辑
        result_data = _logic_handler(db, url)

        ret["code"] = 1
        ret["msg"] = "注册成功"
        ret["data"] = result_data

    except Exception as e:
        ret["code"] = 0
        ret["msg"] = str(e)
        ret["data"] = None

    return {
        "code": ret["code"],
        "msg": ret["msg"],
        "data": ret["data"]
    }