"""Reader 内部共享工具模块。

此模块包含各 reader 实现共享的内部工具函数，仅供 readers 包内部使用。
"""

import re
import zipfile
from pathlib import Path
from typing import List, Optional, Tuple


# ============================================================================
# 通用解析器包装函数
# ============================================================================

def parse_via_markitdown(
    file_path: str,
) -> Tuple[Optional[str], Optional[str]]:
    """使用 MarkItDown 库解析文件。

    Args:
        file_path: 文件路径

    Returns:
        (markdown_content, error_message): 成功时 (content, None)，失败时 (None, error)
    """
    try:
        from markitdown import MarkItDown

        md = MarkItDown()
        result = md.convert(file_path)
        if not result.text_content.strip():
            return None, "文档为空"
        return result.text_content, None
    except ImportError:
        return None, "MarkItDown 库未安装"
    except Exception as e:
        return None, f"MarkItDown 解析失败: {str(e)}"


def parse_via_docling(file_path: str) -> Tuple[Optional[str], Optional[str]]:
    """使用 docling 库解析文件。

    Args:
        file_path: 文件路径

    Returns:
        (markdown_content, error_message): 成功时 (content, None)，失败时 (None, error)
    """
    try:
        from docling.document_converter import DocumentConverter
    except ImportError:
        return None, "docling 库未安装"

    try:
        converter = DocumentConverter()
        result = converter.convert(file_path)
        markdown_content = result.document.export_to_markdown()
        if not markdown_content.strip():
            return None, "文档为空"
        return markdown_content, None
    except Exception as e:
        return None, f"docling 解析失败: {str(e)}"


# ============================================================================
# 格式化工具
# ============================================================================

def build_markdown_table(rows_data: List[List[str]]) -> str:
    """将二维列表格式化为 Markdown 表格。

    Args:
        rows_data: 二维列表，第一行为表头

    Returns:
        Markdown 格式的表格字符串
    """
    if not rows_data or not rows_data[0]:
        return ""

    md_lines = []
    for i, row_data in enumerate(rows_data):
        row_text = [cell if cell else "" for cell in row_data]
        md_lines.append("| " + " | ".join(row_text) + " |")
        if i == 0:
            md_lines.append("| " + " | ".join(["---"] * len(row_text)) + " |")
    return "\n".join(md_lines) + "\n\n"


# ============================================================================
# 列表处理工具
# ============================================================================

def flush_list_stack(list_stack: List[str], target: List[str]) -> None:
    """将列表堆栈中的非空项添加到目标列表并清空堆栈。

    用于处理嵌套列表的格式化输出。

    Args:
        list_stack: 列表堆栈
        target: 目标列表
    """
    for item in list_stack:
        if item:
            target.append(item + "\n")
    list_stack.clear()


# ============================================================================
# ZIP 文件安全处理
# ============================================================================

def safe_open_zip(zip_file: zipfile.ZipFile, name: str) -> Optional[zipfile.ZipExtFile]:
    """安全地从 ZipFile 中打开文件，防止路径遍历攻击。

    Args:
        zip_file: ZipFile 对象
        name: 文件名

    Returns:
        ZipExtFile 对象，如果路径不安全则返回 None
    """
    if not name:
        return None

    try:
        normalized = Path(name).as_posix()
        # 检查是否包含父目录引用
        if ".." in Path(normalized).parts:
            return None
        # 检查是否为绝对路径
        if Path(normalized).is_absolute():
            return None
        return zip_file.open(name)
    except (ValueError, OSError, KeyError):
        return None


# ============================================================================
# unstructured 库相关
# ============================================================================

# unstructured 噪声匹配模式
_UNSTRUCTURED_RGB_PATTERN = re.compile(r"^R:\d+\s+G:\d+\s+B:\d+$")
_UNSTRUCTURED_PAGE_NUMBER_PATTERN = re.compile(r"^—\s*\d+\s*—$")


def convert_unstructured_to_markdown(
    elements: list, trust_titles: bool = True
) -> str:
    """将 unstructured 解析出的元素列表转换为 Markdown 文本。

    Args:
        elements: unstructured 解析的元素列表
        trust_titles: 是否信任 unstructured 的标题检测

    Returns:
        Markdown 格式的文本
    """
    try:
        import markdownify as md_lib
        from unstructured.documents.elements import (
            Footer,
            Header,
            Image,
            ListItem,
            PageBreak,
            PageNumber,
            Table,
            Title,
        )
    except ImportError:
        return "\n\n".join(
            el.text for el in elements if hasattr(el, "text") and el.text and el.text.strip()
        )

    skip_types = (Header, Footer, PageBreak, PageNumber)
    parts = []

    for el in elements:
        if isinstance(el, skip_types):
            continue
        text = el.text.strip() if hasattr(el, "text") else str(el).strip()
        if not text or _UNSTRUCTURED_RGB_PATTERN.match(text) or _UNSTRUCTURED_PAGE_NUMBER_PATTERN.match(text):
            continue

        if isinstance(el, Table):
            html = getattr(el.metadata, "text_as_html", None)
            if html:
                parts.append(md_lib.markdownify(html, strip=["img"]).strip())
            else:
                parts.append(str(el))
        elif isinstance(el, Title) and trust_titles:
            depth = getattr(el.metadata, "category_depth", None) or 1
            depth = min(max(depth, 1), 4)
            parts.append(f"{'#' * depth} {text}")
        elif isinstance(el, ListItem):
            parts.append(f"- {text}")
        elif isinstance(el, Image):
            path = getattr(el.metadata, "image_path", None) or ""
            if path:
                parts.append(f"![image]({path})")
        else:
            parts.append(text)

    return "\n\n".join(parts)