"""
Document Conversion API for Hugging Face Spaces
Handles ALL PDF operations: Word↔PDF, Image↔Text, PDF Merge/Split
Self-hosted, FREE forever with unlimited usage!
"""
from flask import Flask, request, send_file, jsonify
from flask_cors import CORS
import subprocess
import os
import tempfile
import uuid
from pathlib import Path
import logging
from PyPDF2 import PdfReader, PdfWriter, PdfMerger
import pytesseract
from PIL import Image
from pdf2docx import Converter
from io import BytesIO
import zipfile

app = Flask(__name__)
CORS(app, origins=["*"])  # In production, replace * with your Vercel domain

# Configure logging
logging.basicConfig(level=logging.INFO)
logger = logging.getLogger(__name__)

# Ensure LibreOffice is available
def check_libreoffice():
    """Check if LibreOffice is installed"""
    try:
        result = subprocess.run(
            ['libreoffice', '--version'],
            capture_output=True,
            text=True,
            timeout=5
        )
        logger.info(f"LibreOffice version: {result.stdout.strip()}")
        return True
    except Exception as e:
        logger.error(f"LibreOffice not found: {e}")
        return False

# Ensure Tesseract is available
def check_tesseract():
    """Check if Tesseract OCR is installed"""
    try:
        result = subprocess.run(
            ['tesseract', '--version'],
            capture_output=True,
            text=True,
            timeout=5
        )
        logger.info(f"Tesseract version: {result.stdout.strip()}")
        return True
    except Exception as e:
        logger.error(f"Tesseract not found: {e}")
        return False

@app.route('/')
def root():
    """Root endpoint with API info"""
    lo_status = "Available ✅" if check_libreoffice() else "Not Found ❌"
    tesseract_status = "Available ✅" if check_tesseract() else "Not Found ❌"
    
    return {
        'name': 'Document Conversion API',
        'version': '2.0.0',
        'backend': {
            'LibreOffice': lo_status,
            'Tesseract OCR': tesseract_status,
            'PyPDF2': 'Available ✅'
        },
        'platform': 'Hugging Face Spaces',
        'features': '100% FREE forever, Unlimited usage, No API keys needed',
        'operations': {
            'word-to-pdf': 'Convert Word/DOCX to PDF',
            'pdf-to-word': 'Convert PDF to Word/DOCX (OCR)',
            'image-to-text': 'Extract text from images (OCR)',
            'pdf-split': 'Split PDF into separate pages',
            'pdf-merge': 'Merge multiple PDFs'
        },
        'endpoints': {
            'POST /convert': 'Word to PDF conversion',
            'POST /pdf-to-word': 'PDF to Word conversion',
            'POST /image-to-text': 'Image OCR to text',
            'POST /pdf-split': 'Split PDF pages',
            'POST /pdf-merge': 'Merge multiple PDFs',
            'GET /health': 'Health check'
        }
    }, 200

@app.route('/health')
def health_check():
    """Health check endpoint"""
    lo_available = check_libreoffice()
    tesseract_available = check_tesseract()
    
    return {
        'status': 'healthy' if (lo_available and tesseract_available) else 'degraded',
        'services': {
            'libreoffice': lo_available,
            'tesseract': tesseract_available,
            'pypdf2': True
        },
        'message': 'All services running' if (lo_available and tesseract_available) else 'Some services unavailable'
    }, 200 if (lo_available and tesseract_available) else 503

@app.route('/convert', methods=['POST'])
def word_to_pdf():
    """Convert Word/Document to PDF using LibreOffice"""
    
    if 'file' not in request.files:
        return jsonify({'error': 'No file provided'}), 400
    
    file = request.files['file']
    
    if file.filename == '':
        return jsonify({'error': 'Empty filename'}), 400
    
    # Get file extension
    file_ext = Path(file.filename).suffix.lower()
    supported_exts = ['.docx', '.doc', '.odt', '.rtf', '.txt']
    
    if file_ext not in supported_exts:
        return jsonify({
            'error': f'Unsupported file format: {file_ext}',
            'supported': supported_exts
        }), 400
    
    # Create unique temporary directory
    temp_dir = tempfile.mkdtemp()
    unique_id = str(uuid.uuid4())
    
    try:
        input_filename = f"input_{unique_id}{file_ext}"
        input_path = os.path.join(temp_dir, input_filename)
        file.save(input_path)
        
        logger.info(f"Converting {input_filename} to PDF...")
        
        # Convert using LibreOffice
        cmd = [
            'libreoffice',
            '--headless',
            '--convert-to', 'pdf',
            '--outdir', temp_dir,
            input_path
        ]
        
        result = subprocess.run(
            cmd,
            capture_output=True,
            text=True,
            timeout=30,
            cwd=temp_dir
        )
        
        if result.returncode != 0:
            logger.error(f"LibreOffice error: {result.stderr}")
            return jsonify({
                'error': 'Conversion failed',
                'details': result.stderr
            }), 500
        
        # Find output PDF
        output_filename = input_filename.rsplit('.', 1)[0] + '.pdf'
        output_path = os.path.join(temp_dir, output_filename)
        
        if not os.path.exists(output_path):
            return jsonify({
                'error': 'PDF file not created',
                'details': 'LibreOffice did not produce output file'
            }), 500
        
        file_size = os.path.getsize(output_path)
        logger.info(f"Conversion successful! Output: {output_filename} ({file_size} bytes)")
        
        return send_file(
            output_path,
            mimetype='application/pdf',
            as_attachment=True,
            download_name='converted.pdf'
        )
        
    except subprocess.TimeoutExpired:
        logger.error("Conversion timeout")
        return jsonify({'error': 'Conversion timeout (>30s)'}), 504
        
    except Exception as e:
        logger.error(f"Conversion error: {str(e)}")
        return jsonify({
            'error': 'Conversion failed',
            'details': str(e)
        }), 500
        
    finally:
        try:
            import shutil
            shutil.rmtree(temp_dir)
        except Exception as e:
            logger.warning(f"Cleanup warning: {e}")

@app.route('/pdf-to-word', methods=['POST'])
def pdf_to_word():
    """Convert PDF to Word/DOCX using pdf2docx"""
    
    if 'file' not in request.files:
        return jsonify({'error': 'No file provided'}), 400
    
    file = request.files['file']
    
    if file.filename == '':
        return jsonify({'error': 'Empty filename'}), 400
    
    temp_dir = tempfile.mkdtemp()
    
    try:
        input_path = os.path.join(temp_dir, 'input.pdf')
        output_path = os.path.join(temp_dir, 'output.docx')
        
        file.save(input_path)
        
        logger.info("Converting PDF to DOCX...")
        
        # Convert PDF to DOCX
        cv = Converter(input_path)
        cv.convert(output_path)
        cv.close()
        
        if not os.path.exists(output_path):
            return jsonify({'error': 'DOCX file not created'}), 500
        
        file_size = os.path.getsize(output_path)
        logger.info(f"PDF to Word conversion successful! ({file_size} bytes)")
        
        return send_file(
            output_path,
            mimetype='application/vnd.openxmlformats-officedocument.wordprocessingml.document',
            as_attachment=True,
            download_name='converted.docx'
        )
        
    except Exception as e:
        logger.error(f"PDF to Word error: {str(e)}")
        return jsonify({
            'error': 'Conversion failed',
            'details': str(e)
        }), 500
        
    finally:
        try:
            import shutil
            shutil.rmtree(temp_dir)
        except Exception as e:
            logger.warning(f"Cleanup warning: {e}")

@app.route('/image-to-text', methods=['POST'])
def image_to_text():
    """Extract text from image using Tesseract OCR with smart preprocessing"""
    
    if 'file' not in request.files:
        return jsonify({'error': 'No file provided'}), 400
    
    file = request.files['file']
    
    if file.filename == '':
        return jsonify({'error': 'Empty filename'}), 400
    
    try:
        # Read image
        image = Image.open(file.stream)
        
        logger.info(f"Extracting text from image ({image.size})...")
        
        # Convert to RGB if necessary
        if image.mode != 'RGB':
            image = image.convert('RGB')
        
        import numpy as np
        import cv2
        
        img_array = np.array(image)
        
        # Try multiple OCR strategies and pick the best result
        results = []
        
        # Strategy 1: Original image (best for colored text, graphics)
        try:
            config1 = r'--oem 3 --psm 3'
            text1 = pytesseract.image_to_string(image, config=config1, lang='eng')
            results.append(('original', text1, len(text1.strip())))
        except Exception as e:
            logger.warning(f"Strategy 1 failed: {e}")
        
        # Strategy 2: Grayscale (good for normal documents)
        try:
            gray = cv2.cvtColor(img_array, cv2.COLOR_RGB2GRAY)
            gray_img = Image.fromarray(gray)
            config2 = r'--oem 3 --psm 6'
            text2 = pytesseract.image_to_string(gray_img, config=config2, lang='eng')
            results.append(('grayscale', text2, len(text2.strip())))
        except Exception as e:
            logger.warning(f"Strategy 2 failed: {e}")
        
        # Strategy 3: High contrast (for faded text)
        try:
            gray = cv2.cvtColor(img_array, cv2.COLOR_RGB2GRAY)
            # Increase contrast
            alpha = 1.5  # Contrast control
            beta = 0     # Brightness control
            contrast = cv2.convertScaleAbs(gray, alpha=alpha, beta=beta)
            contrast_img = Image.fromarray(contrast)
            config3 = r'--oem 3 --psm 3'
            text3 = pytesseract.image_to_string(contrast_img, config=config3, lang='eng')
            results.append(('contrast', text3, len(text3.strip())))
        except Exception as e:
            logger.warning(f"Strategy 3 failed: {e}")
        
        # Pick the result with the most content
        if not results:
            raise Exception("All OCR strategies failed")
        
        # Sort by text length (more text usually means better recognition)
        results.sort(key=lambda x: x[2], reverse=True)
        best_strategy, raw_text, _ = results[0]
        
        logger.info(f"Best strategy: {best_strategy} with {len(raw_text)} characters")
        
        # Clean up the text
        lines = []
        for line in raw_text.split('\n'):
            # Strip whitespace
            line = line.strip()
            
            # Skip empty lines
            if not line:
                continue
            
            # Skip lines that are mostly noise (too many special chars)
            alnum = sum(c.isalnum() or c in ' .,!?-$%()' for c in line)
            if len(line) > 0 and (alnum / len(line)) > 0.4:
                lines.append(line)
        
        text = '\n'.join(lines)
        
        # If result is still too short, try without filtering
        if len(text) < 20 and len(raw_text.strip()) > len(text):
            text = raw_text.strip()
        
        logger.info(f"OCR successful! Extracted {len(text)} characters")
        
        # Create text file
        text_content = f"Extracted Text from {file.filename}\n\n{text}"
        
        # Return as downloadable text file
        buffer = BytesIO()
        buffer.write(text_content.encode('utf-8'))
        buffer.seek(0)
        
        return send_file(
            buffer,
            mimetype='text/plain',
            as_attachment=True,
            download_name='extracted-text.txt'
        )
        
    except Exception as e:
        logger.error(f"OCR error: {str(e)}")
        return jsonify({
            'error': 'Text extraction failed',
            'details': str(e)
        }), 500

@app.route('/pdf-split', methods=['POST'])
def pdf_split():
    """Split PDF into separate pages"""
    
    if 'file' not in request.files:
        return jsonify({'error': 'No file provided'}), 400
    
    file = request.files['file']
    
    if file.filename == '':
        return jsonify({'error': 'Empty filename'}), 400
    
    temp_dir = tempfile.mkdtemp()
    
    try:
        # Read PDF
        pdf_reader = PdfReader(file.stream)
        total_pages = len(pdf_reader.pages)
        
        logger.info(f"Splitting PDF ({total_pages} pages)...")
        
        # Create ZIP file for all pages
        zip_path = os.path.join(temp_dir, 'split_pages.zip')
        
        with zipfile.ZipFile(zip_path, 'w') as zipf:
            for page_num in range(total_pages):
                # Create new PDF for each page
                pdf_writer = PdfWriter()
                pdf_writer.add_page(pdf_reader.pages[page_num])
                
                # Write to buffer
                page_buffer = BytesIO()
                pdf_writer.write(page_buffer)
                page_buffer.seek(0)
                
                # Add to ZIP
                zipf.writestr(f'page_{page_num + 1}.pdf', page_buffer.read())
        
        logger.info(f"Split successful! Created {total_pages} page files")
        
        return send_file(
            zip_path,
            mimetype='application/zip',
            as_attachment=True,
            download_name='split_pages.zip'
        )
        
    except Exception as e:
        logger.error(f"PDF split error: {str(e)}")
        return jsonify({
            'error': 'PDF split failed',
            'details': str(e)
        }), 500
        
    finally:
        try:
            import shutil
            shutil.rmtree(temp_dir)
        except Exception as e:
            logger.warning(f"Cleanup warning: {e}")

@app.route('/pdf-merge', methods=['POST'])
def pdf_merge():
    """Merge multiple PDFs into one"""
    
    if 'files' not in request.files:
        return jsonify({'error': 'No files provided'}), 400
    
    files = request.files.getlist('files')
    
    if len(files) < 2:
        return jsonify({'error': 'At least 2 PDF files required'}), 400
    
    temp_dir = tempfile.mkdtemp()
    
    try:
        logger.info(f"Merging {len(files)} PDF files...")
        
        # Merge PDFs
        merger = PdfMerger()
        
        for file in files:
            if file.filename.lower().endswith('.pdf'):
                merger.append(file.stream)
        
        # Write merged PDF
        output_path = os.path.join(temp_dir, 'merged.pdf')
        merger.write(output_path)
        merger.close()
        
        file_size = os.path.getsize(output_path)
        logger.info(f"Merge successful! Output: {file_size} bytes")
        
        return send_file(
            output_path,
            mimetype='application/pdf',
            as_attachment=True,
            download_name='merged.pdf'
        )
        
    except Exception as e:
        logger.error(f"PDF merge error: {str(e)}")
        return jsonify({
            'error': 'PDF merge failed',
            'details': str(e)
        }), 500
        
    finally:
        try:
            import shutil
            shutil.rmtree(temp_dir)
        except Exception as e:
            logger.warning(f"Cleanup warning: {e}")

if __name__ == '__main__':
    logger.info("🚀 Starting Document Conversion API...")
    
    # Check dependencies on startup
    if check_libreoffice():
        logger.info("✅ LibreOffice is ready!")
    else:
        logger.warning("⚠️ LibreOffice not found")
    
    if check_tesseract():
        logger.info("✅ Tesseract OCR is ready!")
    else:
        logger.warning("⚠️ Tesseract not found")
    
    # Run Flask app
    port = int(os.environ.get('PORT', 7860))
    app.run(host='0.0.0.0', port=port, debug=False)