"""
文件处理模块 - 处理文件上传和读取
"""
import os
from config import MAX_FILE_CHARS, SUPPORTED_FILE_TYPES
from cache_manager import file_cache


def load_gdl_text(uploaded_files, max_chars=MAX_FILE_CHARS):
    """
    读取上传的 GDL 文本文件
    
    Args:
        uploaded_files: 上传的文件列表
        max_chars: 最大字符数限制
        
    Returns:
        str: 合并后的文本内容
    """
    if not uploaded_files:
        return ""
    
    files = uploaded_files if isinstance(uploaded_files, (list, tuple)) else [uploaded_files]
    parts = []
    total_size = 0
    
    for f in files:
        try:
            path = getattr(f, "name", None) or str(f)
            
            # 检查文件是否存在
            if not os.path.exists(path):
                parts.append(f"\n# FILE_NOT_FOUND: {os.path.basename(path)}\n")
                continue
                
            # 检查文件扩展名
            file_ext = os.path.splitext(path)[1].lower()
            if file_ext not in SUPPORTED_FILE_TYPES:
                parts.append(f"\n# UNSUPPORTED_FILE_TYPE: {os.path.basename(path)} (expected: {', '.join(SUPPORTED_FILE_TYPES)})\n")
                continue
                
            # 检查文件大小
            file_size = os.path.getsize(path)
            if file_size > max_chars:
                parts.append(f"\n# FILE_TOO_LARGE: {os.path.basename(path)} ({file_size} bytes, skipped)\n")
                continue
                
            # 尝试从缓存获取
            txt = file_cache.get(path)
            if txt is None:
                # 缓存未命中，读取文件
                with open(path, "r", encoding="utf-8", errors="ignore") as fh:
                    txt = fh.read()
                # 存入缓存
                file_cache.set(path, txt)
                
            # 检查内容长度
            if len(txt) + total_size > max_chars:
                remaining = max_chars - total_size
                if remaining > 100:  # 至少保留100字符
                    txt = txt[:remaining] + "\n[...TRUNCATED...]"
                else:
                    parts.append(f"\n# FILE_SKIPPED: {os.path.basename(path)} (would exceed limit)\n")
                    continue
                    
            parts.append(f"\n# FILE: {os.path.basename(path)}\n{txt}\n")
            total_size += len(txt)
            
        except PermissionError:
            parts.append(f"\n# FILE_PERMISSION_ERROR: {os.path.basename(path)} (access denied)\n")
        except UnicodeDecodeError as e:
            parts.append(f"\n# FILE_ENCODING_ERROR: {os.path.basename(path)} ({str(e)})\n")
        except Exception as e:
            parts.append(f"\n# FILE_READ_ERROR: {os.path.basename(path)} ({type(e).__name__}: {str(e)})\n")
    
    text = "\n".join(parts).strip()
    return text


def validate_file_upload(files):
    """
    验证文件上传的有效性
    
    Args:
        files: 上传的文件列表
        
    Returns:
        tuple: (is_valid, error_message)
    """
    if not files:
        return True, ""
    
    file_list = files if isinstance(files, (list, tuple)) else [files]
    
    for f in file_list:
        path = getattr(f, "name", None) or str(f)
        
        if not os.path.exists(path):
            return False, f"文件不存在: {os.path.basename(path)}"
            
        file_ext = os.path.splitext(path)[1].lower()
        if file_ext not in SUPPORTED_FILE_TYPES:
            return False, f"不支持的文件类型: {os.path.basename(path)} (支持: {', '.join(SUPPORTED_FILE_TYPES)})"
            
        file_size = os.path.getsize(path)
        if file_size > MAX_FILE_CHARS:
            return False, f"文件过大: {os.path.basename(path)} ({file_size} bytes, 最大: {MAX_FILE_CHARS})"
    
    return True, ""