"""
文档加载器，使用 unstructured 库解析文档。
"""

import logging
from pathlib import Path
from typing import Any, Dict, List, Mapping, Optional, Union

from langchain_core.documents import Document
from unstructured.partition.auto import partition

logger = logging.getLogger(__name__)


class DocumentLoader:
    """从各种文件格式加载文档。"""

    SUPPORTED_EXTENSIONS = {".pdf", ".docx", ".doc", ".txt", ".md", ".html", ".pptx", ".xlsx", ".json"}

    def __init__(
        self,
        extract_images: bool = False,
        strategy: str = "auto",
        ocr_languages: Optional[List[str]] = None,
        languages: Optional[List[str]] = None,
        include_page_breaks: bool = False,
        pdf_infer_table_structure: bool = True,
        partition_kwargs: Optional[Dict[str, Any]] = None,
    ):
        """
        Args:
            extract_images: 是否提取 PDF 中的图片
            strategy: 解析策略 (auto, fast, hi_res, ocr_only)
            ocr_languages: OCR 语言列表，如 ['chi_sim', 'eng']
            languages: 文档主语言，如 ['zh']
            include_page_breaks: 是否包含分页符
            pdf_infer_table_structure: 是否识别表格结构 (需 hi_res 策略)
            partition_kwargs: 额外的 partition 参数字典（高级定制）
        """
        import os
        os.environ["UNSTRUCTURED_LANGUAGE_CHECKS"] = "false"
        self.extract_images = extract_images
        self.strategy = strategy
        self.ocr_languages = ocr_languages or ["chi_sim", "eng"]
        self.languages = languages or ["zh"]
        self.include_page_breaks = include_page_breaks
        self.pdf_infer_table_structure = pdf_infer_table_structure
        self.partition_kwargs = partition_kwargs or {}

    def load_file(self, file_path: Union[str, Path]) -> List[Document]:
        """将单个文件加载为 LangChain Document 对象。"""
        file_path = Path(file_path).resolve()
        if not file_path.exists():
            raise FileNotFoundError(f"文件不存在: {file_path}")

        suffix = file_path.suffix.lower()
        if suffix not in self.SUPPORTED_EXTENSIONS:
            raise ValueError(
                f"不支持的文件扩展名: {suffix}。支持的格式: {self.SUPPORTED_EXTENSIONS}"
            )

        # 根据文件类型动态调整参数
        extra_kwargs = {}
        if suffix == ".pdf":
            extra_kwargs["strategy"] = self.strategy
            extra_kwargs["ocr_languages"] = self.ocr_languages
            extra_kwargs["extract_images_in_pdf"] = self.extract_images
            extra_kwargs["pdf_infer_table_structure"] = self.pdf_infer_table_structure
        
        # languages 参数适用于所有文件类型
        if self.languages:
            extra_kwargs["languages"] = self.languages
        
        extra_kwargs["include_page_breaks"] = self.include_page_breaks

        # 合并用户自定义的额外参数（优先级最高）
        extra_kwargs.update(self.partition_kwargs)

        # 使用 unstructured 解析
        elements = partition(
            filename=str(file_path),

            **extra_kwargs
        )

        documents = []
        for elem in elements:
            text = getattr(elem, "text", "")
            if not text or not text.strip():
                continue

            # 基础元数据
            metadata = {
                "source": str(file_path),
                "file_name": file_path.name,
                "file_type": suffix,
            }
            
            documents.append(Document(page_content=text, metadata=metadata))

        if not documents:
            logger.warning("未从 %s 提取到文本内容", file_path)
            return []

        return documents

    def load_directory(
        self, directory_path: Union[str, Path], recursive: bool = True
    ) -> List[Document]:
        """从目录加载所有支持的文件。"""
        directory_path = Path(directory_path).resolve()
        if not directory_path.is_dir():
            raise NotADirectoryError(f"不是目录: {directory_path}")

        all_documents = []
        pattern = "**/*" if recursive else "*"

        for file_path in directory_path.glob(pattern):
            if file_path.is_file() and file_path.suffix.lower() in self.SUPPORTED_EXTENSIONS:
                try:
                    docs = self.load_file(file_path)
                    all_documents.extend(docs)
                except Exception as e:
                    logger.error("加载 %s 失败: %s", file_path, e)

        return all_documents