app.py

import os
import re
import time
import logging
import zipfile
import requests
import bibtexparser
from tqdm import tqdm
from urllib.parse import quote, urlencode
import gradio as gr
from bs4 import BeautifulSoup
import io
from docx import Document
from docx.shared import Inches
from docx.enum.text import WD_ALIGN_PARAGRAPH


# Configure logging
logging.basicConfig(level=logging.INFO, 
                    format='%(asctime)s - %(levelname)s: %(message)s')
logger = logging.getLogger(__name__)

class PaperDownloader:
    def __init__(self, output_dir='papers'):
        self.output_dir = output_dir
        os.makedirs(output_dir, exist_ok=True)
        
         # Updated download sources
        self.download_sources = [
            'https://sci-hub.ee/',
            'https://sci-hub.st/',
            'https://sci-hub.ru/',
            'https://sci-hub.ren/',
            'https://sci-hub.mksa.top/',
            'https://sci-hub.se/',
            'https://libgen.rs/scimag/'
        ]

        # Request headers
        self.headers = {
            'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/114.0.0.0 Safari/537.36',
            'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,*/*;q=0.8'
        }

    def clean_doi(self, doi):
        """Clean and encode DOI for URL"""
        if not isinstance(doi, str):
           return None
        return quote(doi.strip()) if doi else None

    def download_paper_scihub(self, doi):
        """Improved method to download paper from Sci-Hub"""
        if not doi:
            logger.warning("DOI not provided")
            return None

        for base_url in self.download_sources:
            try:
                scihub_url = f"{base_url}{self.clean_doi(doi)}"
                
                # Request with more tolerance
                response = requests.get(scihub_url, 
                                        headers=self.headers, 
                                        allow_redirects=True, 
                                        timeout=15)
                
                # Search for multiple PDF URL patterns
                pdf_patterns = [
                    r'(https?://[^\s<>"]+?\.pdf)',
                    r'(https?://[^\s<>"]+?download/[^\s<>"]+)',
                    r'(https?://[^\s<>"]+?\/pdf\/[^\s<>"]+)',
                ]
                
                pdf_urls = []
                for pattern in pdf_patterns:
                    pdf_urls.extend(re.findall(pattern, response.text))
                
                # Try downloading from found URLs
                for pdf_url in pdf_urls:
                    try:
                        pdf_response = requests.get(pdf_url, 
                                                    headers=self.headers, 
                                                    timeout=10)
                        
                        # Verify if it's a PDF
                        if 'application/pdf' in pdf_response.headers.get('Content-Type', ''):
                            logger.debug(f"Found PDF from: {pdf_url}")
                            return pdf_response.content
                    except Exception as e:
                        logger.debug(f"Error downloading PDF from {pdf_url}: {e}")
                
            except Exception as e:
                logger.debug(f"Error trying to download {doi} from {base_url}: {e}")
        
        return None
    
    def download_paper_libgen(self, doi):
      """Download from Libgen, handles the query and the redirection"""
      if not doi:
        return None

      base_url = 'https://libgen.rs/scimag/'
      try:
        search_url = f"{base_url}?q={self.clean_doi(doi)}"
        response = requests.get(search_url, headers=self.headers, allow_redirects=True, timeout=10)
        response.raise_for_status()

        if "No results" in response.text:
          logger.debug(f"No results for DOI: {doi} on libgen")
          return None

        soup = BeautifulSoup(response.text, 'html.parser')
        
        # Find the link using a specific selector
        links = soup.select('table.c > tbody > tr:nth-child(2) > td:nth-child(1) > a')

        if links:
          link = links[0]
          pdf_url = link['href']
          pdf_response = requests.get(pdf_url, headers=self.headers, allow_redirects=True, timeout=10)
          if 'application/pdf' in pdf_response.headers.get('Content-Type', ''):
              logger.debug(f"Found PDF from: {pdf_url}")
              return pdf_response.content

      except Exception as e:
            logger.debug(f"Error trying to download {doi} from libgen: {e}")
      return None
    
    def download_paper_google_scholar(self, doi):
        """Search google scholar to find an article with the given doi, try to get the pdf"""
        if not doi:
            return None
        
        try:
           
           query = f'doi:"{doi}"'
           params = {'q': query}
           url = f'https://scholar.google.com/scholar?{urlencode(params)}'
           
           response = requests.get(url, headers = self.headers, timeout = 10)
           response.raise_for_status()
           
           soup = BeautifulSoup(response.text, 'html.parser')
           
           # Find any links with [PDF]
           links = soup.find_all('a', string=re.compile(r'\[PDF\]', re.IGNORECASE))
           
           if links:
               pdf_url = links[0]['href']
               pdf_response = requests.get(pdf_url, headers = self.headers, timeout=10)
               if 'application/pdf' in pdf_response.headers.get('Content-Type', ''):
                   logger.debug(f"Found PDF from: {pdf_url}")
                   return pdf_response.content
        except Exception as e:
             logger.debug(f"Google Scholar error for {doi}: {e}")

        return None

    def download_paper_crossref(self, doi):
        """Alternative search method using Crossref"""
        if not doi:
            return None
        
        try:
            # Search for open access link
            url = f"https://api.crossref.org/works/{doi}"
            response = requests.get(url, headers=self.headers, timeout=10)
            
            if response.status_code == 200:
                data = response.json()
                work = data.get('message', {})
                
                # Search for open access links
                links = work.get('link', [])
                for link in links:
                    if link.get('content-type') == 'application/pdf':
                        pdf_url = link.get('URL')
                        if pdf_url:
                            pdf_response = requests.get(pdf_url, headers=self.headers)
                            if 'application/pdf' in pdf_response.headers.get('Content-Type', ''):
                                logger.debug(f"Found PDF from: {pdf_url}")
                                return pdf_response.content
        
        except Exception as e:
            logger.debug(f"Crossref error for {doi}: {e}")
        
        return None
    

    def download_with_retry(self, doi, max_retries=3, initial_delay=2):
      """Downloads a paper using multiple strategies with exponential backoff"""
      pdf_content = None
      retries = 0
      delay = initial_delay

      while retries < max_retries and not pdf_content:
          try:
              pdf_content = (
                 self.download_paper_scihub(doi) or
                 self.download_paper_libgen(doi) or
                 self.download_paper_google_scholar(doi) or
                 self.download_paper_crossref(doi)
                 
              )

              if pdf_content:
                  return pdf_content
          except Exception as e:
              logger.error(f"Error in download attempt {retries + 1} for DOI {doi}: {e}")
          
          if not pdf_content:
            retries += 1
            logger.warning(f"Retry attempt {retries} for DOI: {doi} after {delay} seconds")
            time.sleep(delay)
            delay *= 2 # Exponential backoff
          
      return None
    
    def download_single_doi(self, doi):
        """Downloads a single paper using a DOI"""
        if not doi:
            return None, "Error: DOI not provided", "Error: DOI not provided", None, None

        try:
            pdf_content = self.download_with_retry(doi)
            
            if pdf_content:
                if doi is None:
                     return None, "Error: DOI not provided", "", None, None
                filename = f"{str(doi).replace('/', '_').replace('.', '_')}.pdf"
                filepath = os.path.join(self.output_dir, filename)
                with open(filepath, 'wb') as f:
                    f.write(pdf_content)
                logger.info(f"Successfully downloaded: {filename}")
                return filepath, f'<a href="https://doi.org/{doi}">{doi}</a>', "", None
            else:
                logger.warning(f"Could not download: {doi}")
                return None, f"Could not download {doi}", f'<a href="https://doi.org/{doi}">{doi}</a>', None, None

        except Exception as e:
            logger.error(f"Error processing {doi}: {e}")
            return None, f"Error processing {doi}: {e}", f"Error processing {doi}: {e}", None, None
    


# Create PaperDownloader instance
downloader = PaperDownloader()

def download_doi_callback(doi):
    filepath, success_message, fail_message, _, _ = downloader.download_single_doi(doi)
    if filepath:
        return filepath, success_message, fail_message
    else:
        return None, fail_message, success_message


# Test or connect to a Gradio interface
iface = gr.Interface(
    fn=download_doi_callback,
    inputs=gr.Textbox(label="Enter DOI", placeholder="Enter DOI to download"),
    outputs=[
        gr.File(label="Download Paper"),
        gr.HTML(label="Success Message"),
        gr.HTML(label="Failure Message")
    ],
    live=True,
)

iface.launch()