#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
驗證函數模組
提供安全驗證、路徑防護、檔案上傳驗證等功能
"""

import re
import os
import unicodedata
from pathlib import Path
import pandas as pd
from services.logger_manager import SystemLogger

sys_log = SystemLogger("Validators").get_logger()

# ==========================================
# SQL Injection 防護
# ==========================================

# 允許的資料表白名單
ALLOWED_TABLES = {
    'products', 'price_records', 'promo_products',
    'monthly_summary_analysis', 'realtime_sales_monthly',
    'realtime_sales_daily', 'daily_sales_snapshot',
    'festival_products'
}


def validate_table_name(table_name):
    """
    驗證資料表名稱，防止 SQL Injection

    Args:
        table_name: 要驗證的資料表名稱

    Returns:
        str: 驗證通過的表名

    Raises:
        ValueError: 表名不在白名單中
    """
    table_name = str(table_name).strip()

    if not table_name:
        raise ValueError("表名不能為空")

    if not re.match(r'^[a-zA-Z0-9_]+$', table_name):
        raise ValueError(f"表名包含非法字符: {table_name}")

    if table_name not in ALLOWED_TABLES:
        sys_log.warning(f"[Security] 表名不在白名單中: {table_name}")
        sql_keywords = ['SELECT', 'INSERT', 'UPDATE', 'DELETE', 'DROP', 'CREATE', 'ALTER', 'UNION', 'WHERE', 'FROM']
        if any(keyword in table_name.upper() for keyword in sql_keywords):
            raise ValueError(f"表名包含 SQL 關鍵字: {table_name}")

    return table_name


def validate_column_names(column_names):
    """
    驗證欄位名稱列表，防止 SQL Injection

    Args:
        column_names: 欄位名稱列表

    Returns:
        list: 驗證通過的欄位名稱列表

    Raises:
        ValueError: 欄位名稱包含非法字符
    """
    if isinstance(column_names, str):
        column_names = [column_names]

    validated = []
    for col in column_names:
        col = str(col).strip()
        if not re.match(r'^[\w\u4e00-\u9fff]+$', col):
            raise ValueError(f"欄位名稱包含非法字符: {col}")
        validated.append(col)

    return validated


def safe_read_sql(table_name, columns=None, engine=None, where_clause=None, limit=None, params=None):
    """
    安全的 SQL 查詢函數，防止 SQL Injection

    Args:
        table_name: 資料表名稱
        columns: 欄位列表，None 表示 *
        engine: SQLAlchemy engine
        where_clause: WHERE 子句
        limit: 限制筆數
        params: 參數化查詢的參數字典

    Returns:
        DataFrame: 查詢結果
    """
    from sqlalchemy import text

    table_name = validate_table_name(table_name)

    if columns:
        columns = validate_column_names(columns)
        col_str = ', '.join([f'"{col}"' for col in columns])
    else:
        col_str = '*'

    try:
        query = f'SELECT {col_str} FROM "{table_name}"'
        if where_clause:
            query += f' WHERE {where_clause}'

        if limit:
            query += f' LIMIT {int(limit)}'

        return pd.read_sql(text(query), engine, params=params)
    except Exception as e:
        sys_log.error(f"[Security] SQL 查詢失敗: {e}")
        raise


# ==========================================
# 路徑遍歷防護
# ==========================================

def safe_join(base, *paths):
    """
    安全的路徑拼接，防止路徑遍歷攻擊

    Args:
        base: 基礎目錄（絕對路徑）
        *paths: 子路徑組件

    Returns:
        Path: 安全的完整路徑

    Raises:
        ValueError: 偵測到路徑遍歷嘗試
    """
    base = Path(base).resolve()

    for path_component in paths:
        path_str = str(path_component)

        if '\\' in path_str:
            sys_log.warning(f"[Security] 偵測到路徑遍歷嘗試 (Windows 反斜線) | Base: {base} | Requested: {paths}")
            raise ValueError(f"路徑遍歷偵測: 不允許使用反斜線")

        if '..' in path_str.replace('\\', '/'):
            sys_log.warning(f"[Security] 偵測到路徑遍歷嘗試 (雙點) | Base: {base} | Requested: {paths}")
            raise ValueError(f"路徑遍歷偵測: 不允許使用 '..'")

    full_path = (base / Path(*paths)).resolve()

    try:
        full_path.relative_to(base)
    except ValueError:
        sys_log.warning(f"[Security] 偵測到路徑遍歷嘗試 | Base: {base} | Requested: {paths}")
        raise ValueError(f"路徑遍歷偵測: 不允許存取基礎目錄外的檔案")

    return full_path


# ==========================================
# 檔案上傳安全驗證
# ==========================================

ALLOWED_UPLOAD_EXTENSIONS = {'xlsx', 'xls', 'csv'}
ALLOWED_MIME_TYPES = {
    'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
    'application/vnd.ms-excel',
    'text/csv',
    'application/octet-stream'
}


def secure_filename_unicode(filename):
    """
    支援中文的安全檔案名稱清理

    Args:
        filename: 原始檔案名稱

    Returns:
        str: 清理後的安全檔案名稱
    """
    filename = unicodedata.normalize('NFKC', filename)
    safe_chars = re.sub(r'[^\u4e00-\u9fa5a-zA-Z0-9\s\(\)_\-\.]', '', filename)
    safe_chars = re.sub(r'\s+', ' ', safe_chars)
    safe_chars = safe_chars.strip()
    return safe_chars


def allowed_file(filename):
    """
    檢查檔案副檔名是否在白名單中

    Args:
        filename: 檔案名稱

    Returns:
        bool: 是否允許上傳
    """
    if not filename or '.' not in filename:
        return False

    parts = filename.rsplit('.', 1)
    if len(parts) != 2:
        return False

    basename, ext = parts

    if not basename or basename.strip() == '':
        return False

    return ext.lower() in ALLOWED_UPLOAD_EXTENSIONS


def validate_upload_file(file):
    """
    完整的檔案上傳驗證（副檔名、檔案名稱清理）

    Args:
        file: Flask request.files 物件

    Returns:
        tuple: (is_valid, error_message, safe_filename)
    """
    if not file or file.filename == '':
        return False, '未選擇檔案', None

    original_filename = file.filename

    if '..' in original_filename:
        sys_log.warning(f"[Security] 檔案上傳 - 偵測到路徑遍歷嘗試（雙點）: {original_filename}")
        return False, '檔案名稱包含非法字元', None

    if os.path.sep in original_filename or (os.path.altsep and os.path.altsep in original_filename):
        if original_filename.startswith(('/', '\\')) or './' in original_filename or '.\\' in original_filename:
            sys_log.warning(f"[Security] 檔案上傳 - 偵測到路徑遍歷嘗試（路徑分隔符）: {original_filename}")
            return False, '檔案名稱包含非法字元', None

    safe_name = secure_filename_unicode(original_filename)
    if not safe_name:
        return False, '檔案名稱不合法', None

    if not allowed_file(safe_name):
        return False, f'不支援的檔案格式，僅允許: {", ".join(ALLOWED_UPLOAD_EXTENSIONS)}', None

    return True, None, safe_name