import olefile
import zlib
import struct

from pathlib import Path
from typing import Any, Dict, List, Optional

from llama_index.readers.base import BaseReader
from llama_index.readers.schema.base import Document

class HWPReader(BaseReader):
    """Hangeul Reader. Reads contents from Hangeul file.
    Args: None
    """
    def __init__(
            self,
            *args: Any,
            **kwargs: Any
    ) -> None:
        super().__init__(*args, **kwargs)
        self.FILE_HEADER_SECTION = "FileHeader"
        self.HWP_SUMMARY_SECTION = "\x05HwpSummaryInformation"
        self.SECTION_NAME_LENGTH = len("Section")
        self.BODYTEXT_SECTION = "BodyText"
        self.HWP_TEXT_TAGS = [67]

    def load_data(
            self,
            file: Path,
    ) -> Document:
        """Load data and extract table from PDF file.

        Args:
            file (Path): Path for the PDF file.

        Returns:
            List[Document]: List of documents.
        """
        load_file = olefile.OleFileIO(file)
        file_dir = load_file.listdir()

        if self.is_valid(file_dir) == False:
            raise Exception("Not Valid HwpFile")

        result_text = self._get_text(load_file, file_dir)
        result = self._text_to_document(text=result_text)
        return result

    def is_valid(self, dirs):
        if [self.FILE_HEADER_SECTION] not in dirs:
            return False

        return [self.HWP_SUMMARY_SECTION] in dirs

    def get_body_sections(self, dirs):
        m = []
        for d in dirs:
            if d[0] == self.BODYTEXT_SECTION:
                m.append(int(d[1][self.SECTION_NAME_LENGTH:]))

        return ["BodyText/Section"+str(x) for x in sorted(m)]

    def _text_to_document(self, text: str, extra_info: Optional[Dict] = None) -> Document:

        return Document(
            text=text,
            extra_info=extra_info or {}
        )

    def get_text(self):
        return self.text

        # 전체 text 추출
    def _get_text(self, load_file, file_dir):
        sections = self.get_body_sections(file_dir)
        text = ""
        for section in sections:
            text += self.get_text_from_section(load_file, section)
            text += "\n"

        self.text = text
        return self.text

    def is_compressed(self, load_file):
        header = load_file.openstream("FileHeader")
        header_data = header.read()
        return (header_data[36] & 1) == 1

    def get_text_from_section(self, load_file, section):
        bodytext = load_file.openstream(section)
        data = bodytext.read()

        unpacked_data = zlib.decompress(data, -15) if self.is_compressed(load_file) else data
        size = len(unpacked_data)

        i = 0

        text = ""
        while i < size:
            header = struct.unpack_from("<I", unpacked_data, i)[0]
            rec_type = header & 0x3ff
            level = (header >> 10) & 0x3ff
            rec_len = (header >> 20) & 0xfff

            if rec_type in self.HWP_TEXT_TAGS:
                rec_data = unpacked_data[i+4:i+4+rec_len]
                text += rec_data.decode('utf-16')
                text += "\n"

            i += 4 + rec_len

        return text