# -*- coding: utf-8 -*-
import os
import pandas as pd
import io
import hashlib
from pathlib import Path
from typing import Optional, Iterator
from config.app_config import app_config
from utils.cache_manager import CacheManager

# 初始化缓存管理器
data_cache = CacheManager(
    cache_dir=app_config.cache_dir,
    enabled=app_config.data_cache_enabled
)

def load_and_profile_data(file_paths: list) -> str:
    """
    加载数据并生成数据画像
    
    Args:
        file_paths: 文件路径列表
        
    Returns:
        包含数据画像的Markdown字符串
    """
    profile_summary = "# 数据画像报告 (Data Profile)\n\n"
    
    if not file_paths:
        return profile_summary + "未提供数据文件。"
        
    for file_path in file_paths:
        file_name = os.path.basename(file_path)
        profile_summary += f"## 文件: {file_name}\n\n"
        
        if not os.path.exists(file_path):
            profile_summary += f"[WARN] 文件不存在: {file_path}\n\n"
            continue
            
        try:
            # 根据扩展名选择加载方式
            ext = os.path.splitext(file_path)[1].lower()
            if ext == '.csv':
                # 尝试多种编码
                try:
                    df = pd.read_csv(file_path, encoding='utf-8')
                except UnicodeDecodeError:
                    try:
                        df = pd.read_csv(file_path, encoding='gbk')
                    except Exception:
                        df = pd.read_csv(file_path, encoding='latin1')
            elif ext in ['.xlsx', '.xls']:
                df = pd.read_excel(file_path)
            else:
                profile_summary += f"[WARN] 不支持的文件格式: {ext}\n\n"
                continue
                
            # 基础信息
            rows, cols = df.shape
            profile_summary += f"- **维度**: {rows} 行 x {cols} 列\n"
            profile_summary += f"- **列名**: `{', '.join(df.columns)}`\n\n"
            
            profile_summary += "### 列详细分布:\n"
            
            # 遍历分析每列
            for col in df.columns:
                dtype = df[col].dtype
                null_count = df[col].isnull().sum()
                null_ratio = (null_count / rows) * 100
                
                profile_summary += f"#### {col} ({dtype})\n"
                if null_count > 0:
                    profile_summary += f"- [WARN] 空值: {null_count} ({null_ratio:.1f}%)\n"
                
                # 数值列分析
                if pd.api.types.is_numeric_dtype(dtype):
                    desc = df[col].describe()
                    profile_summary += f"- 统计: Min={desc['min']:.2f}, Max={desc['max']:.2f}, Mean={desc['mean']:.2f}\n"
                
                # 文本/分类列分析
                elif pd.api.types.is_object_dtype(dtype) or pd.api.types.is_categorical_dtype(dtype):
                    unique_count = df[col].nunique()
                    profile_summary += f"- 唯一值数量: {unique_count}\n"
                    
                    # 如果唯一值较少（<50）或者看起来是分类数据，显示Top分布
                    # 这对识别“高频问题”至关重要
                    if unique_count > 0:
                        top_n = df[col].value_counts().head(5)
                        top_items_str = ", ".join([f"{k}({v})" for k, v in top_n.items()])
                        profile_summary += f"- **TOP 5 高频值**: {top_items_str}\n"
                        
                # 时间列分析
                elif pd.api.types.is_datetime64_any_dtype(dtype):
                    profile_summary += f"- 范围: {df[col].min()} 至 {df[col].max()}\n"
                
                profile_summary += "\n"
                
        except Exception as e:
            profile_summary += f"[ERROR] 读取或分析文件失败: {str(e)}\n\n"
            
    return profile_summary


def get_file_hash(file_path: str) -> str:
    """计算文件哈希值，用于缓存键"""
    hasher = hashlib.md5()
    hasher.update(file_path.encode())
    
    # 添加文件修改时间
    if os.path.exists(file_path):
        mtime = os.path.getmtime(file_path)
        hasher.update(str(mtime).encode())
    
    return hasher.hexdigest()


def load_data_chunked(file_path: str, chunksize: Optional[int] = None) -> Iterator[pd.DataFrame]:
    """
    流式读取大文件，分块返回DataFrame
    
    Args:
        file_path: 文件路径
        chunksize: 每块行数，默认使用配置值
        
    Yields:
        DataFrame块
    """
    if chunksize is None:
        chunksize = app_config.chunk_size
    
    ext = os.path.splitext(file_path)[1].lower()
    
    if ext == '.csv':
        # 尝试多种编码
        for encoding in ['utf-8', 'gbk', 'latin1']:
            try:
                chunks = pd.read_csv(file_path, encoding=encoding, chunksize=chunksize)
                for chunk in chunks:
                    yield chunk
                break
            except UnicodeDecodeError:
                continue
            except Exception as e:
                print(f"[ERROR] 读取CSV文件失败: {e}")
                break
    elif ext in ['.xlsx', '.xls']:
        # Excel文件不支持chunksize，直接读取
        try:
            df = pd.read_excel(file_path)
            # 手动分块
            for i in range(0, len(df), chunksize):
                yield df.iloc[i:i+chunksize]
        except Exception as e:
            print(f"[ERROR] 读取Excel文件失败: {e}")


def load_data_with_cache(file_path: str, force_reload: bool = False) -> Optional[pd.DataFrame]:
    """
    带缓存的数据加载
    
    Args:
        file_path: 文件路径
        force_reload: 是否强制重新加载
        
    Returns:
        DataFrame或None
    """
    if not os.path.exists(file_path):
        print(f"[WARN] 文件不存在: {file_path}")
        return None
    
    # 检查文件大小
    file_size_mb = os.path.getsize(file_path) / (1024 * 1024)
    
    # 对于大文件，建议使用流式处理
    if file_size_mb > app_config.max_file_size_mb:
        print(f"[WARN] 文件过大 ({file_size_mb:.1f}MB)，建议使用 load_data_chunked() 流式处理")
    
    # 生成缓存键
    cache_key = get_file_hash(file_path)
    
    # 尝试从缓存加载
    if not force_reload and app_config.data_cache_enabled:
        cached_data = data_cache.get(cache_key)
        if cached_data is not None:
            print(f"[CACHE] 从缓存加载数据: {os.path.basename(file_path)}")
            return cached_data
    
    # 加载数据
    ext = os.path.splitext(file_path)[1].lower()
    df = None
    
    try:
        if ext == '.csv':
            # 尝试多种编码
            for encoding in ['utf-8', 'gbk', 'latin1']:
                try:
                    df = pd.read_csv(file_path, encoding=encoding)
                    break
                except UnicodeDecodeError:
                    continue
        elif ext in ['.xlsx', '.xls']:
            df = pd.read_excel(file_path)
        else:
            print(f"[WARN] 不支持的文件格式: {ext}")
            return None
        
        # 缓存数据
        if df is not None and app_config.data_cache_enabled:
            data_cache.set(cache_key, df)
            print(f"[OK] 数据已缓存: {os.path.basename(file_path)}")
        
        return df
        
    except Exception as e:
        print(f"[ERROR] 加载数据失败: {e}")
        return None