import hashlib
import logging
import os
import re
import time
from abc import ABC, abstractmethod
from typing import List, Any

from fastapi import UploadFile
from langchain_core.documents import Document
from langchain_mineru import MinerULoader
from pypdf import PdfReader

from config.settings import MINERU_TOKEN, TXT_CACHE_DIR

MINERU_MAX_PAGES = 200
_HASH_CHUNK_SIZE = 4096


def get_upload_file_hash(upload_file: UploadFile) -> str:
    """Compute MD5 from in-memory UploadFile bytes without writing to disk."""
    upload_file.file.seek(0)
    hasher = hashlib.md5()
    for chunk in iter(lambda: upload_file.file.read(_HASH_CHUNK_SIZE), b""):
        hasher.update(chunk)
    upload_file.file.seek(0)
    return hasher.hexdigest()


def get_file_hash(file_path: str) -> str:
    """Compute MD5 of a file on disk. Identical content → identical hash."""
    hasher = hashlib.md5()
    with open(file_path, "rb") as file_handle:
        for chunk in iter(lambda: file_handle.read(_HASH_CHUNK_SIZE), b""):
            hasher.update(chunk)
    return hasher.hexdigest()


class BaseParser(ABC):
    """Abstract base for PDF parsers with MinerU loading and file-system caching."""

    def __init__(self) -> None:
        os.makedirs(TXT_CACHE_DIR, exist_ok=True)

    # ---- cache helpers ----

    def _cache_path_for(self, file_hash: str) -> str:
        return os.path.join(TXT_CACHE_DIR, f"{file_hash}.txt")

    def _read_cache(self, cache_path: str) -> str | None:
        if os.path.exists(cache_path):
            print(f"✅ 找到缓存，直接读取：{cache_path}")
            with open(cache_path, "r", encoding="utf-8") as file_handle:
                return file_handle.read()
        return None

    def _write_cache(self, cache_path: str, content: str) -> None:
        with open(cache_path, "w", encoding="utf-8") as file_handle:
            file_handle.write(content)
        print(f"✅ 已保存解析结果到缓存：{cache_path}")

    def _count_pdf_pages(self, file_path: str) -> int:
        try:
            return len(PdfReader(file_path).pages)
        except Exception as exc:
            print(f"获取PDF页数失败：{exc}")
            return 1

    # ---- core loading ----

    def load_pdf(self, file_path: str) -> List[Document]:
        start_time = time.time()

        file_hash = get_file_hash(file_path)
        cache_path = self._cache_path_for(file_hash)

        cached_content = self._read_cache(cache_path)
        if cached_content is not None:
            return [Document(
                page_content=cached_content,
                metadata={
                    "parser": "MinerULoader-Cache",
                    "source": file_path,
                    "from_cache": True,
                },
            )]

        total_pages = self._count_pdf_pages(file_path)
        print(f"PDF总页数：{total_pages}")

        all_documents: List[Document] = []
        for start in range(1, total_pages + 1, MINERU_MAX_PAGES):
            end = min(start + MINERU_MAX_PAGES - 1, total_pages)
            print(f"正在加载分片：{start} ~ {end} 页")

            loader = MinerULoader(
                source=file_path,
                mode="precision",
                token=MINERU_TOKEN,
                pages=f"{start}-{end}",
            )
            all_documents.extend(loader.load())

        full_text_pages: List[str] = []
        for idx, doc in enumerate(all_documents):
            cleaned = self.clean_mineru_text(doc.page_content)
            doc.page_content = cleaned
            doc.metadata["parser"] = "MinerULoader"
            doc.metadata["page_number"] = idx + 1
            doc.metadata["total_pages"] = total_pages
            full_text_pages.append(cleaned)

        all_content = "\n".join(full_text_pages)
        self._write_cache(cache_path, all_content)

        elapsed = round(time.time() - start_time, 2)
        print(f"PDF 完整加载完成 | 总页数：{total_pages} | 总耗时：{elapsed} 秒")
        return all_documents

    @staticmethod
    def clean_mineru_text(text: str) -> str:
        """Strip MinerU-specific markup tokens from extracted text."""
        if not text:
            return ""
        text = re.sub(r"</?table[^>]*>", "", text, flags=re.IGNORECASE)
        text = re.sub(r"</?tr[^>]*>", " - ", text, flags=re.IGNORECASE)
        text = re.sub(r"<img\s+[^>]*>", "", text, flags=re.IGNORECASE)
        text = re.sub(r"<td\s*[^>]*>", "|", text, flags=re.IGNORECASE)
        text = re.sub(r"</td>", "|", text, flags=re.IGNORECASE)
        text = re.sub(r"!\[.*?\]\(.*?\)", "", text)
        return text.strip()

    @abstractmethod
    def parse(self, file_path: str) -> Any:
        ...