AIRegulation-DocAnalysis/backend/app/services/parser/pdf_parser.py

"""PDF文档解析 - 使用PyMuPDF基础解析"""

import fitz  # PyMuPDF
from typing import List, Dict, Optional, Tuple
from dataclasses import dataclass, field
from loguru import logger
import re


@dataclass
class PDFPageContent:
    """PDF页面内容"""
    page_number: int
    text: str
    tables: List[str] = field(default_factory=list)
    images: List[str] = field(default_factory=list)  # 图片路径列表
    blocks: List[Dict] = field(default_factory=list)


@dataclass
class PDFDocumentContent:
    """PDF文档完整内容"""
    file_path: str
    total_pages: int
    pages: List[PDFPageContent]
    metadata: Dict[str, str] = field(default_factory=dict)
    markdown_text: str = ""


class PDFParser:
    """PDF文档解析器 - 基于PyMuPDF"""

    def __init__(self):
        self.pdf = None

    def parse(self, file_path: str, extract_tables: bool = True, extract_images: bool = False) -> PDFDocumentContent:
        """
        解析PDF文档

        Args:
            file_path: PDF文件路径
            extract_tables: 是否提取表格
            extract_images: 是否提取图片

        Returns:
            PDFDocumentContent: 解析后的文档内容
        """
        logger.info(f"开始解析PDF文档: {file_path}")

        try:
            self.pdf = fitz.open(file_path)
            doc_content = PDFDocumentContent(
                file_path=file_path,
                total_pages=self.pdf.page_count,
                pages=[]
            )

            # 提取文档元数据
            doc_content.metadata = self._extract_metadata()

            # 逐页解析
            for page_num in range(self.pdf.page_count):
                page = self.pdf[page_num]
                page_content = self._parse_page(page, page_num + 1, extract_tables, extract_images)
                doc_content.pages.append(page_content)

            # 生成Markdown格式文本
            doc_content.markdown_text = self._generate_markdown(doc_content)

            self.pdf.close()
            logger.success(f"PDF解析完成，共{doc_content.total_pages}页")

            return doc_content

        except Exception as e:
            logger.error(f"PDF解析失败: {e}")
            raise

    def _extract_metadata(self) -> Dict[str, str]:
        """提取PDF元数据"""
        metadata = {}
        try:
            meta = self.pdf.metadata
            metadata = {
                "title": meta.get("title", ""),
                "author": meta.get("author", ""),
                "subject": meta.get("subject", ""),
                "keywords": meta.get("keywords", ""),
                "creator": meta.get("creator", ""),
                "producer": meta.get("producer", ""),
                "creation_date": meta.get("creationDate", ""),
                "mod_date": meta.get("modDate", ""),
            }
        except Exception as e:
            logger.warning(f"提取元数据失败: {e}")
        return metadata

    def _parse_page(self, page: fitz.Page, page_num: int,
                   extract_tables: bool, extract_images: bool) -> PDFPageContent:
        """解析单页内容"""
        page_content = PDFPageContent(page_number=page_num, text="")

        # 提取文本块（保留结构）
        blocks = page.get_text("dict", flags=fitz.TEXT_PRESERVE_WHITESPACE)["blocks"]
        page_content.blocks = blocks

        # 提取纯文本
        text = page.get_text("text", flags=fitz.TEXT_PRESERVE_WHITESPACE)
        page_content.text = text.strip()

        # 提取表格（使用PyMuPDF的表格提取功能）
        if extract_tables:
            tables = self._extract_tables_from_page(page)
            page_content.tables = tables

        # 提取图片
        if extract_images:
            images = self._extract_images_from_page(page, page_num)
            page_content.images = images

        return page_content

    def _extract_tables_from_page(self, page: fitz.Page) -> List[str]:
        """
        从页面提取表格（基于文本块分析）
        注意：PyMuPDF基础版表格提取能力有限，复杂表格建议使用MinerU
        """
        tables = []

        try:
            # 使用PyMuPDF的表格提取方法（2.4+版本）
            # 对于更复杂的表格，需要在mineru_parser中使用更高级的方法
            tabs = page.find_tables()
            if tabs:
                for tab in tabs:
                    table_text = tab.extract()
                    # 将表格转换为Markdown格式
                    markdown_table = self._table_to_markdown(table_text)
                    tables.append(markdown_table)

        except AttributeError:
            # 旧版本PyMuPDF没有表格提取功能
            logger.warning("PyMuPDF版本不支持表格提取，请升级到2.4+版本")
        except Exception as e:
            logger.warning(f"表格提取失败: {e}")

        return tables

    def _table_to_markdown(self, table_data: List[List[str]]) -> str:
        """将表格数据转换为Markdown格式"""
        if not table_data or len(table_data) < 1:
            return ""

        lines = []
        # 表头
        if len(table_data) >= 1:
            header = table_data[0]
            lines.append("| " + " | ".join(str(cell).strip() for cell in header) + " |")
            lines.append("| " + " | ".join("---" for _ in header) + " |")

        # 数据行
        for row in table_data[1:]:
            lines.append("| " + " | ".join(str(cell).strip() for cell in row) + " |")

        return "\n".join(lines)

    def _extract_images_from_page(self, page: fitz.Page, page_num: int) -> List[str]:
        """提取页面图片"""
        images = []
        # 图片提取功能（可选实现）
        # 这里仅记录图片信息，实际图片需要额外保存
        try:
            image_list = page.get_images()
            for img_index, img in enumerate(image_list):
                xref = img[0]
                images.append(f"image_p{page_num}_i{img_index}_xref{xref}")
        except Exception as e:
            logger.warning(f"图片提取失败: {e}")
        return images

    def _generate_markdown(self, doc_content: PDFDocumentContent) -> str:
        """生成Markdown格式文本"""
        lines = []

        # 文档标题
        title = doc_content.metadata.get("title", "")
        if title:
            lines.append(f"# {title}\n")
        else:
            lines.append(f"# {doc_content.file_path}\n")

        # 元数据信息
        lines.append("\n## 文档信息\n")
        for key, value in doc_content.metadata.items():
            if value and key in ["author", "subject", "keywords", "creation_date"]:
                lines.append(f"- **{key}**: {value}")

        # 正文内容
        lines.append("\n## 正文\n")

        for page in doc_content.pages:
            # 页码标记
            lines.append(f"\n---\n**第 {page.page_number} 页**\n")

            # 处理文本内容，识别标题结构
            text = self._process_page_text(page.text, page.blocks)
            lines.append(text)

            # 添加表格
            for table in page.tables:
                lines.append("\n" + table + "\n")

        return "\n".join(lines)

    def _process_page_text(self, text: str, blocks: List[Dict]) -> str:
        """处理页面文本，识别标题结构"""
        # 基于字体大小识别标题
        processed_text = text

        # 尝试识别标题（基于字号）
        # 法规文档通常有明确的层级结构：章、节、条
        processed_text = self._detect_headers(text, blocks)

        return processed_text

    def _detect_headers(self, text: str, blocks: List[Dict]) -> str:
        """检测并标记标题（基于字号或内容模式）"""
        lines = text.split("\n")
        processed_lines = []

        for line in lines:
            line = line.strip()
            if not line:
                continue

            # 法规标题模式检测
            # 第一章、第X章、第X节、第X条等
            if re.match(r'^第[一二三四五六七八九十百]+章\s', line):
                processed_lines.append(f"\n## {line}\n")
            elif re.match(r'^第[一二三四五六七八九十百]+节\s', line):
                processed_lines.append(f"\n### {line}\n")
            elif re.match(r'^第[一二三四五六七八九十百]+条\s', line):
                processed_lines.append(f"\n#### {line}\n")
            elif re.match(r'^[一二三四五六七八九十]+\s*[、.]', line):
                # 条款子项
                processed_lines.append(f"- {line}")
            else:
                processed_lines.append(line)

        return "\n".join(processed_lines)

    def parse_to_markdown(self, file_path: str) -> str:
        """直接解析并返回Markdown文本"""
        doc_content = self.parse(file_path)
        return doc_content.markdown_text


def parse_pdf(file_path: str, **kwargs) -> PDFDocumentContent:
    """便捷函数：解析PDF文档"""
    parser = PDFParser()
    return parser.parse(file_path, **kwargs)


def parse_pdf_to_markdown(file_path: str) -> str:
    """便捷函数：解析PDF并返回Markdown"""
    parser = PDFParser()
    return parser.parse_to_markdown(file_path)