# utils/file_handler.py - 文件读取工具（支持 txt / md / pdf / docx）
import os
from typing import List


def read_file_auto(file_path: str) -> str:
    """
    自动识别文件类型并读取文本内容。

    支持格式：.txt / .md / .pdf / .docx / 其他（按 UTF-8 读取）

    Args:
        file_path: 文件路径

    Returns:
        文件文本内容

    Raises:
        FileNotFoundError: 文件不存在
        RuntimeError:      读取失败
    """
    if not os.path.exists(file_path):
        raise FileNotFoundError(f"文件不存在: {file_path}")

    ext = os.path.splitext(file_path)[1].lower()

    try:
        if ext == ".pdf":
            return _read_pdf(file_path)
        elif ext in (".docx", ".doc"):
            return _read_docx(file_path)
        else:
            # txt / md / 其他文本格式
            with open(file_path, "r", encoding="utf-8", errors="replace") as f:
                return f.read()
    except Exception as e:
        raise RuntimeError(f"读取文件失败 [{file_path}]: {e}")


def _read_pdf(file_path: str) -> str:
    """读取 PDF 文件文本"""
    try:
        from pypdf import PdfReader
    except ImportError:
        raise RuntimeError("读取 PDF 需要安装 pypdf：pip install pypdf")

    reader = PdfReader(file_path)
    pages  = [page.extract_text() or "" for page in reader.pages]
    return "\n".join(pages)


def _read_docx(file_path: str) -> str:
    """读取 Word 文档文本"""
    try:
        from docx import Document
    except ImportError:
        raise RuntimeError("读取 docx 需要安装 python-docx：pip install python-docx")

    doc        = Document(file_path)
    paragraphs = [p.text for p in doc.paragraphs if p.text.strip()]
    return "\n".join(paragraphs)


def merge_knowledge_files(file_paths: List[str]) -> str:
    """
    合并多个知识库文件为单一文本。

    Args:
        file_paths: 文件路径列表

    Returns:
        合并后的文本（各文件以分隔线隔开）
    """
    parts = []
    for path in file_paths:
        try:
            content = read_file_auto(path)
            parts.append(f"--- {os.path.basename(path)} ---\n{content}")
        except Exception as e:
            parts.append(f"--- {os.path.basename(path)} [读取失败: {e}] ---")
    return "\n\n".join(parts)