backend/utils/file_parser.py

import os
import re
from typing import Tuple, Optional
from pathlib import Path
from pypdf import PdfReader
from docx import Document

_EMOJI_RE = re.compile(
    "[\U0001F600-\U0001F64F"  # emoticons (😀 😂 🥹 etc.)
    "\U0001F300-\U0001F5FF"  # misc symbols & pictographs (🌍 🎉 🔥 etc.)
    "\U0001F680-\U0001F6FF"  # transport & map (🚀 ✈️ 🚗 etc.)
    "\U0001F1E0-\U0001F1FF"  # regional indicator letters (flags 🇺🇸)
    "\U0001F900-\U0001F9FF"  # supplemental symbols (🤔 🤣 🧠 etc.)
    "\U0001FA00-\U0001FA6F"  # chess / extended pictographic
    "\U0001FA70-\U0001FAFF"  # symbols & pictographs extended-A
    "]+",
    flags=re.UNICODE,
)

class FileParser:
    """
    Parse multiple file formats and extract text.
    Supports: PDF, DOCX, TXT, and raw text input.
    """
    
    SUPPORTED_FORMATS = {".pdf", ".docx", ".doc", ".txt"}
    
    @staticmethod
    def parse_file(file_path: str) -> Tuple[str, str, Optional[Exception]]:
        """
        Parse a file and extract text.
        
        Args:
            file_path: Path to the file
            
        Returns:
            Tuple of (text, format, error)
            - text: Extracted text content
            - format: File format (pdf, docx, txt)
            - error: Exception if parsing failed, None if successful
        """
        file_extension = Path(file_path).suffix.lower()
        
        if file_extension not in FileParser.SUPPORTED_FORMATS:
            error = ValueError(f"Unsupported file format: {file_extension}")
            return "", "", error
        
        if file_extension == ".pdf":
            return FileParser.parse_pdf(file_path)
        elif file_extension in {".docx", ".doc"}:
            return FileParser.parse_docx(file_path)
        elif file_extension == ".txt":
            return FileParser.parse_txt(file_path)
        
        return "", "", ValueError("Unknown error")
    
    @staticmethod
    def parse_pdf(file_path: str) -> Tuple[str, str, Optional[Exception]]:
        """Extract text from PDF file"""
        try:
            text = ""
            with open(file_path, 'rb') as pdf_file:
                pdf_reader = PdfReader(pdf_file)
                
                # Extract text from all pages
                for page_num in range(len(pdf_reader.pages)):
                    page = pdf_reader.pages[page_num]
                    text += page.extract_text() + "\n"
            
            return text.strip(), "pdf", None
        
        except Exception as e:
            return "", "pdf", e
    
    @staticmethod
    def parse_docx(file_path: str) -> Tuple[str, str, Optional[Exception]]:
        """Extract text from DOCX file"""
        try:
            doc = Document(file_path)
            text = ""
            
            # Extract text from all paragraphs
            for paragraph in doc.paragraphs:
                text += paragraph.text + "\n"
            
            # Also extract text from tables if present
            for table in doc.tables:
                for row in table.rows:
                    for cell in row.cells:
                        text += cell.text + "\n"
            
            return text.strip(), "docx", None
        
        except Exception as e:
            return "", "docx", e
    
    @staticmethod
    def parse_txt(file_path: str) -> Tuple[str, str, Optional[Exception]]:
        """Extract text from plain text file"""
        try:
            with open(file_path, 'r', encoding='utf-8') as txt_file:
                text = txt_file.read()
            
            return text.strip(), "txt", None
        
        except UnicodeDecodeError:
            # Try with different encoding
            try:
                with open(file_path, 'r', encoding='latin-1') as txt_file:
                    text = txt_file.read()
                return text.strip(), "txt", None
            except Exception as e:
                return "", "txt", e
        
        except Exception as e:
            return "", "txt", e
    
    @staticmethod
    def parse_raw_text(text: str) -> Tuple[str, str, Optional[Exception]]:
        """Process raw text input"""
        try:
            cleaned_text = text.strip()
            if not cleaned_text:
                return "", "raw", ValueError("Empty text provided")
            return cleaned_text, "raw", None
        except Exception as e:
            return "", "raw", e

class TextCleaner:
    """Clean and normalize extracted text"""
    
    @staticmethod
    def clean(text: str) -> str:
        """
        Clean and normalize text.
        Removes extra whitespace, normalizes line breaks, etc.
        """
        # Remove extra whitespace
        text = ' '.join(text.split())
        
        # Normalize line breaks
        text = text.replace('\r\n', '\n').replace('\r', '\n')
        
        return text
    
    @staticmethod
    def get_text_stats(text: str) -> dict:
        """Get statistics about text"""
        words = text.split()
        sentences = text.split('.')

        return {
            "character_count": len(text),
            "word_count": len(words),
            "sentence_count": len([s for s in sentences if s.strip()]),
            "average_word_length": len(text) / len(words) if words else 0,
            "average_sentence_length": len(words) / len(sentences) if sentences else 0,
            "emoji_count": sum(len(m) for m in _EMOJI_RE.findall(text)),
            "em_dash_count": text.count('\u2014'),
            "arrow_count": text.count('\u2192'),
        }