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

# --- 工具函数：URL 标准化 ---
def normalize_url(url: str) -> str:
    """
    标准化 URL，确保末尾斜杠、大小写等不影响唯一性判定
    """
    if not url:
        return url
    
    # 1. 解析 URL
    parsed = urlparse(url.strip())
    
    # 2. 转换协议和域名为小写 (Domain 是不区分大小写的)
    scheme = parsed.scheme.lower()
    netloc = parsed.netloc.lower()
    
    # 3. 处理路径：去除末尾的斜杠
    path = parsed.path
    if path.endswith('/'):
        path = path.rstrip('/')
    
    # 4. 去除 Fragment (#部分)，保留 Query 参数
    # 如果需要忽略 Query 参数，可以将 query 设置为 ""
    query = parsed.query
    
    # 5. 重新拼接
    normalized = urlunparse((scheme, netloc, path, parsed.params, query, ""))
    return normalized

# --- 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 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:
        # engine_args 确保连接池在 Dify 高并发下更稳定
        return SQLDatabase.from_uri(db_url, engine_args={
            "pool_pre_ping": True,
            "pool_recycle": 3600
        })
    except Exception as e:
        raise RuntimeError(f"DB_CONNECT_ERROR: {str(e)}")

# --- Dify 节点主入口 ---
def main(inputs: dict):
    """
    Dify 节点主入口函数
    """
    ret = {"code": 0, "msg": "unknown", "data": None}
    
    # 预设数据库连接字符串 (建议在 Dify 环境变量中配置)
    db_url = inputs.get("db_url") 

    try:
        # 1. 初始化数据库
        db = get_db_connection(db_url)
        
        # 2. 执行具体的业务逻辑
        result_data = _logic_handler(db, inputs)

        ret["code"] = 1
        ret["msg"] = "success"
        ret["data"] = result_data

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

    return ret

# -------------------------------------------------
# 业务逻辑处理器：每个节点只需修改这里
# -------------------------------------------------
def _logic_handler(db: SQLDatabase, inputs: dict):
    """
    在这里编写具体的业务操作
    """
    engine = db._engine
    metadata = MetaData()
    
    # 示例：获取并标准化 URL
    raw_url = inputs.get("url", "")
    clean_url = normalize_url(raw_url)
    
    # 反射获取表对象
    # tasks = Table('crawl_tasks', metadata, autoload_with=engine)
    
    # 使用 SQLAlchemy Core 进行操作（无需写原生SQL）
    # with engine.begin() as conn:
    #     stmt = select(tasks).where(tasks.c.root_url == clean_url)
    #     result = conn.execute(stmt).fetchone()
    
    return {
        "processed_url": clean_url,
        "info": "逻辑已执行"
    }