import os
import sqlite3
import uuid
import hashlib
import datetime
from flask import Flask, render_template, request, redirect, url_for, flash, session, send_from_directory
from werkzeug.utils import secure_filename
from functools import wraps

app = Flask(__name__)
app.secret_key = os.environ.get('SECRET_KEY', os.urandom(24))

# Configuration
UPLOAD_FOLDER = os.path.join(os.path.dirname(os.path.abspath(__file__)), 'uploads')
ALLOWED_EXTENSIONS = {'pdf', 'docx', 'xlsx', 'jpg', 'png', 'mp4', 'txt'}
DB_PATH = os.path.join(os.path.dirname(os.path.abspath(__file__)), 'dms.db')

# Create upload folder if it doesn't exist
if not os.path.exists(UPLOAD_FOLDER):
    os.makedirs(UPLOAD_FOLDER)

app.config['UPLOAD_FOLDER'] = UPLOAD_FOLDER
app.config['MAX_CONTENT_LENGTH'] = 16 * 1024 * 1024  # 16MB max upload size

# Production configuration
app.config['PREFERRED_URL_SCHEME'] = 'https'
app.config['SESSION_COOKIE_SECURE'] = False
app.config['SESSION_COOKIE_HTTPONLY'] = True
app.config['PERMANENT_SESSION_LIFETIME'] = datetime.timedelta(days=1)

# Database initialization
def init_db():
    conn = sqlite3.connect(DB_PATH)
    cursor = conn.cursor()
    
    # Create users table
    cursor.execute('''
    CREATE TABLE IF NOT EXISTS users (
        id INTEGER PRIMARY KEY AUTOINCREMENT,
        username TEXT UNIQUE NOT NULL,
        password TEXT NOT NULL,
        email TEXT UNIQUE NOT NULL,
        role TEXT NOT NULL,
        created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
    )
    ''')
    
    # Create documents table
    cursor.execute('''
    CREATE TABLE IF NOT EXISTS documents (
        id INTEGER PRIMARY KEY AUTOINCREMENT,
        filename TEXT NOT NULL,
        original_filename TEXT NOT NULL,
        custom_filename TEXT NOT NULL,
        file_type TEXT NOT NULL,
        file_size INTEGER NOT NULL,
        category TEXT NOT NULL,
        user_id INTEGER NOT NULL,
        visibility TEXT NOT NULL,
        created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
        updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
        FOREIGN KEY (user_id) REFERENCES users (id)
    )
    ''')
    
    # Create document_shares table
    cursor.execute('''
    CREATE TABLE IF NOT EXISTS document_shares (
        id INTEGER PRIMARY KEY AUTOINCREMENT,
        document_id INTEGER NOT NULL,
        shared_by INTEGER NOT NULL,
        shared_with INTEGER,
        share_link TEXT,
        qr_code TEXT,
        expires_at TIMESTAMP,
        created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
        FOREIGN KEY (document_id) REFERENCES documents (id),
        FOREIGN KEY (shared_by) REFERENCES users (id),
        FOREIGN KEY (shared_with) REFERENCES users (id)
    )
    ''')
    
    # Create document_versions table
    cursor.execute('''
    CREATE TABLE IF NOT EXISTS document_versions (
        id INTEGER PRIMARY KEY AUTOINCREMENT,
        document_id INTEGER NOT NULL,
        filename TEXT NOT NULL,
        version_number INTEGER NOT NULL,
        created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
        FOREIGN KEY (document_id) REFERENCES documents (id)
    )
    ''')
    
    # Create analytics table
    cursor.execute('''
    CREATE TABLE IF NOT EXISTS analytics (
        id INTEGER PRIMARY KEY AUTOINCREMENT,
        document_id INTEGER NOT NULL,
        action TEXT NOT NULL,
        user_id INTEGER,
        ip_address TEXT,
        created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
        FOREIGN KEY (document_id) REFERENCES documents (id),
        FOREIGN KEY (user_id) REFERENCES users (id)
    )
    ''')
    
    # Insert default admin user if not exists
    cursor.execute("SELECT * FROM users WHERE username = 'admin'")
    if not cursor.fetchone():
        # Password: admin123
        hashed_password = hashlib.sha256("admin123".encode()).hexdigest()
        cursor.execute("INSERT INTO users (username, password, email, role) VALUES (?, ?, ?, ?)",
                      ("admin", hashed_password, "admin@example.com", "admin"))
    
    # Insert default regular user if not exists
    cursor.execute("SELECT * FROM users WHERE username = 'user'")
    if not cursor.fetchone():
        # Password: user123
        hashed_password = hashlib.sha256("user123".encode()).hexdigest()
        cursor.execute("INSERT INTO users (username, password, email, role) VALUES (?, ?, ?, ?)",
                      ("user", hashed_password, "user@example.com", "user"))
    
    conn.commit()
    conn.close()

# Helper functions
def allowed_file(filename):
    return '.' in filename and filename.rsplit('.', 1)[1].lower() in ALLOWED_EXTENSIONS

def get_file_type(filename):
    ext = filename.rsplit('.', 1)[1].lower()
    if ext in ['pdf']:
        return 'pdf'
    elif ext in ['docx', 'doc']:
        return 'document'
    elif ext in ['xlsx', 'xls']:
        return 'spreadsheet'
    elif ext in ['jpg', 'jpeg', 'png', 'gif']:
        return 'image'
    elif ext in ['mp4', 'avi', 'mov']:
        return 'video'
    else:
        return 'other'

def get_db_connection():
    conn = sqlite3.connect(DB_PATH)
    conn.row_factory = sqlite3.Row
    return conn

# Authentication decorator
def login_required(f):
    @wraps(f)
    def decorated_function(*args, **kwargs):
        if 'user_id' not in session:
            flash('Please log in to access this page', 'error')
            return redirect(url_for('login'))
        return f(*args, **kwargs)
    return decorated_function

def admin_required(f):
    @wraps(f)
    def decorated_function(*args, **kwargs):
        if 'user_id' not in session:
            flash('Please log in to access this page', 'error')
            return redirect(url_for('login'))
        
        conn = get_db_connection()
        user = conn.execute('SELECT * FROM users WHERE id = ?', (session['user_id'],)).fetchone()
        conn.close()
        
        if user['role'] != 'admin':
            flash('Admin access required', 'error')
            return redirect(url_for('dashboard'))
        
        return f(*args, **kwargs)
    return decorated_function

# Routes
@app.route('/')
def index():
    if 'user_id' in session:
        return redirect(url_for('dashboard'))
    return render_template('index.html')

@app.route('/login', methods=['GET', 'POST'])
def login():
    if request.method == 'POST':
        username = request.form['username']
        password = request.form['password']
        hashed_password = hashlib.sha256(password.encode()).hexdigest()
        
        conn = get_db_connection()
        user = conn.execute('SELECT * FROM users WHERE username = ? AND password = ?',
                          (username, hashed_password)).fetchone()
        conn.close()
        
        if user:
            session['user_id'] = user['id']
            session['username'] = user['username']
            session['role'] = user['role']
            flash(f'Welcome back, {username}!', 'success')
            return redirect(url_for('dashboard'))
        else:
            flash('Invalid username or password', 'error')
            return render_template('login.html')
    else:
        return render_template('login.html')

@app.route('/logout')
def logout():
    session.clear()
    flash('You have been logged out', 'info')
    return redirect(url_for('index'))

@app.route('/dashboard')
@login_required
def dashboard():
    conn = get_db_connection()
    
    # Get document counts by category
    category_counts = conn.execute('''
        SELECT category, COUNT(*) as count
        FROM documents
        WHERE user_id = ? OR visibility = "public" 
        OR id IN (SELECT document_id FROM document_shares WHERE shared_with = ?)
        GROUP BY category
    ''', (session['user_id'], session['user_id'])).fetchall()
    
    # Get recent documents (limited to 5)
    recent_documents = conn.execute('''
        SELECT * FROM documents 
        WHERE user_id = ? OR visibility = "public" 
        OR id IN (SELECT document_id FROM document_shares WHERE shared_with = ?)
        ORDER BY created_at DESC
        LIMIT 5
    ''', (session['user_id'], session['user_id'])).fetchall()
    
    # Get analytics data for admin
    if session['role'] == 'admin':
        analytics = conn.execute('''
            SELECT documents.custom_filename, COUNT(analytics.id) as view_count
            FROM documents
            LEFT JOIN analytics ON documents.id = analytics.document_id
            WHERE analytics.action = 'view'
            GROUP BY documents.id
            ORDER BY view_count DESC
            LIMIT 5
        ''').fetchall()
        
        # Get user activity
        user_activity = conn.execute('''
            SELECT users.username, COUNT(analytics.id) as action_count
            FROM analytics
            JOIN users ON analytics.user_id = users.id
            GROUP BY analytics.user_id
            ORDER BY action_count DESC
            LIMIT 5
        ''').fetchall()
    else:
        analytics = None
        user_activity = None
    
    conn.close()
    
    return render_template('dashboard.html', 
                          recent_documents=recent_documents, 
                          category_counts=category_counts,
                          analytics=analytics,
                          user_activity=user_activity)

@app.route('/upload', methods=['GET', 'POST'])
@login_required
def upload():
    if request.method == 'POST':
        # Check if the post request has the file part
        if 'file' not in request.files:
            flash('No file part', 'error')
            return redirect(request.url)
        
        file = request.files['file']
        visibility = request.form.get('visibility', 'private')
        custom_filename = request.form.get('custom_filename', '').strip()
        category = request.form.get('category', 'general')
        
        # If user does not select file, browser also
        # submit an empty part without filename
        if file.filename == '':
            flash('No selected file', 'error')
            return redirect(request.url)
        
        if file and allowed_file(file.filename):
            # Generate unique filename
            original_filename = secure_filename(file.filename)
            file_extension = original_filename.rsplit('.', 1)[1].lower()
            unique_filename = f"{uuid.uuid4().hex}.{file_extension}"
            
            # Use custom filename if provided, otherwise use original
            if not custom_filename:
                custom_filename = os.path.splitext(original_filename)[0]
            
            # Save the file
            file_path = os.path.join(app.config['UPLOAD_FOLDER'], unique_filename)
            file.save(file_path)
            
            # Get file size
            file_size = os.path.getsize(file_path)
            
            # Save to database
            conn = get_db_connection()
            cursor = conn.cursor()
            cursor.execute('''
                INSERT INTO documents (filename, original_filename, custom_filename, file_type, file_size, category, user_id, visibility)
                VALUES (?, ?, ?, ?, ?, ?, ?, ?)
            ''', (unique_filename, original_filename, custom_filename, get_file_type(original_filename), file_size, category, session['user_id'], visibility))
            
            document_id = cursor.lastrowid
            
            # Add initial version
            cursor.execute('''
                INSERT INTO document_versions (document_id, filename, version_number)
                VALUES (?, ?, ?)
            ''', (document_id, unique_filename, 1))
            
            conn.commit()
            conn.close()
            
            flash('File successfully uploaded', 'success')
            return redirect(url_for('files'))
        else:
            flash(f'Allowed file types are: {", ".join(ALLOWED_EXTENSIONS)}', 'error')
    
    # Get available categories
    categories = ['admin', 'accounting', 'hr', 'marketing', 'legal', 'general', 'other']
    
    return render_template('upload.html', categories=categories)

@app.route('/files')
@login_required
def files():
    # Get query parameters
    search_query = request.args.get('search', '')
    selected_category = request.args.get('category', 'all')
    page = request.args.get('page', 1, type=int)
    per_page = 10  # Number of documents per page
    
    conn = get_db_connection()
    
    # Base query
    query = '''
        SELECT * FROM documents 
        WHERE (user_id = ? OR visibility = "public" 
        OR id IN (SELECT document_id FROM document_shares WHERE shared_with = ?))
    '''
    params = [session['user_id'], session['user_id']]
    
    # Add search condition if search query provided
    if search_query:
        query += ' AND (custom_filename LIKE ? OR original_filename LIKE ?)'
        params.extend(['%' + search_query + '%', '%' + search_query + '%'])
    
    # Add category filter if specific category selected
    if selected_category != 'all':
        query += ' AND category = ?'
        params.append(selected_category)
    
    # Count total matching documents
    count_query = query.replace('SELECT *', 'SELECT COUNT(*)')
    total_docs = conn.execute(count_query, params).fetchone()[0]
    
    # Add pagination
    query += ' ORDER BY created_at DESC LIMIT ? OFFSET ?'
    offset = (page - 1) * per_page
    params.extend([per_page, offset])
    
    # Execute final query
    documents = conn.execute(query, params).fetchall()
    
    # Get available categories for filter dropdown
    categories = ['admin', 'accounting', 'hr', 'marketing', 'legal', 'general', 'other']
    
    # Calculate pagination info
    total_pages = (total_docs + per_page - 1) // per_page  # Ceiling division
    pagination = {
        'page': page,
        'per_page': per_page,
        'total': total_docs,
        'pages': total_pages
    }
    
    conn.close()
    
    return render_template('files.html', 
                          documents=documents, 
                          categories=categories,
                          selected_category=selected_category,
                          search_query=search_query,
                          pagination=pagination)

@app.route('/document/<int:document_id>/edit', methods=['GET', 'POST'])
@login_required
def edit_document(document_id):
    conn = get_db_connection()
    
    # Get document
    document = conn.execute('SELECT * FROM documents WHERE id = ?', (document_id,)).fetchone()
    
    if not document:
        conn.close()
        flash('Document not found', 'error')
        return redirect(url_for('files'))
    
    # Check ownership
    if document['user_id'] != session['user_id'] and session['role'] != 'admin':
        conn.close()
        flash('You do not have permission to edit this document', 'error')
        return redirect(url_for('files'))
    
    # Get available categories
    categories = ['admin', 'accounting', 'hr', 'marketing', 'legal', 'general', 'other']
    
    if request.method == 'POST':
        custom_filename = request.form.get('custom_filename', '').strip()
        category = request.form.get('category', 'general')
        visibility = request.form.get('visibility', 'private')
        
        # Use custom filename if provided, otherwise keep existing
        if not custom_filename:
            custom_filename = document['custom_filename']
        
        # Update document
        conn.execute('''
            UPDATE documents 
            SET custom_filename = ?, category = ?, visibility = ?, updated_at = CURRENT_TIMESTAMP
            WHERE id = ?
        ''', (custom_filename, category, visibility, document_id))
        
        conn.commit()
        conn.close()
        
        flash('Document updated successfully', 'success')
        return redirect(url_for('view_document', document_id=document_id))
    
    conn.close()
    
    return render_template('edit_document.html', document=document, categories=categories)

@app.route('/document/<int:document_id>')
@login_required
def view_document(document_id):
    conn = get_db_connection()
    
    # Get document
    document = conn.execute('SELECT * FROM documents WHERE id = ?', (document_id,)).fetchone()
    
    if not document:
        conn.close()
        flash('Document not found', 'error')
        return redirect(url_for('dashboard'))
    
    # Check permissions
    if document['visibility'] != 'public' and document['user_id'] != session['user_id']:
        # Check if shared with user
        shared = conn.execute('''
            SELECT * FROM document_shares 
            WHERE document_id = ? AND shared_with = ?
        ''', (document_id, session['user_id'])).fetchone()
        
        if not shared and session['role'] != 'admin':
            conn.close()
            flash('You do not have permission to view this document', 'error')
            return redirect(url_for('dashboard'))
    
    # Record view in analytics
    conn.execute('''
        INSERT INTO analytics (document_id, action, user_id, ip_address)
        VALUES (?, ?, ?, ?)
    ''', (document_id, 'view', session['user_id'], request.remote_addr))
    
    # Get document versions
    versions = conn.execute('''
        SELECT * FROM document_versions
        WHERE document_id = ?
        ORDER BY version_number DESC
    ''', (document_id,)).fetchall()
    
    # Get share information
    shares = conn.execute('''
        SELECT document_shares.*, users.username
        FROM document_shares
        LEFT JOIN users ON document_shares.shared_with = users.id
        WHERE document_id = ?
    ''', (document_id,)).fetchall()
    
    conn.commit()
    conn.close()
    
    return render_template('view_document.html', document=document, versions=versions, shares=shares)


@app.route('/document/<int:document_id>/file')
@login_required
def serve_document_file(document_id):
    conn = get_db_connection()

    # Get document
    document = conn.execute('SELECT * FROM documents WHERE id = ?', (document_id,)).fetchone()

    if not document:
        conn.close()
        flash('Document not found', 'error')
        return redirect(url_for('dashboard'))

    # Check permissions
    if document['visibility'] != 'public' and document['user_id'] != session['user_id']:
        shared = conn.execute(''' 
            SELECT * FROM document_shares 
            WHERE document_id = ? AND shared_with = ? 
        ''', (document_id, session['user_id'])).fetchone()

        if not shared and session['role'] != 'admin':
            conn.close()
            flash('You do not have permission to view this document', 'error')
            return redirect(url_for('dashboard'))

    try:
        # Serve the document without download (viewable in browser)
        return send_from_directory(app.config['UPLOAD_FOLDER'], document['filename'],
                                   as_attachment=False, download_name=document['original_filename'])
    except FileNotFoundError:
        flash('Document file not found', 'error')
        conn.close()
        return redirect(url_for('dashboard'))
    finally:
        conn.close()


@app.route('/document/<int:document_id>/download')
@login_required
def download_document(document_id):
    conn = get_db_connection()
    
    # Get document
    document = conn.execute('SELECT * FROM documents WHERE id = ?', (document_id,)).fetchone()
    
    if not document:
        conn.close()
        flash('Document not found', 'error')
        return redirect(url_for('dashboard'))
    
    # Check permissions
    if document['visibility'] != 'public' and document['user_id'] != session['user_id']:
        # Check if shared with user
        shared = conn.execute('''
            SELECT * FROM document_shares 
            WHERE document_id = ? AND shared_with = ?
        ''', (document_id, session['user_id'])).fetchone()
        
        if not shared and session['role'] != 'admin':
            conn.close()
            flash('You do not have permission to download this document', 'error')
            return redirect(url_for('dashboard'))
    
    # Record download in analytics
    conn.execute('''
        INSERT INTO analytics (document_id, action, user_id, ip_address)
        VALUES (?, ?, ?, ?)
    ''', (document_id, 'download', session['user_id'], request.remote_addr))
    
    conn.commit()
    conn.close()
    
    return send_from_directory(app.config['UPLOAD_FOLDER'], document['filename'], 
                              as_attachment=True, download_name=document['original_filename'])

@app.route('/document/<int:document_id>/share', methods=['GET', 'POST'])
@login_required
def share_document(document_id):
    conn = get_db_connection()
    
    # Get document
    document = conn.execute('SELECT * FROM documents WHERE id = ?', (document_id,)).fetchone()
    
    if not document:
        conn.close()
        flash('Document not found', 'error')
        return redirect(url_for('dashboard'))
    
    # Check ownership
    if document['user_id'] != session['user_id'] and session['role'] != 'admin':
        conn.close()
        flash('You do not have permission to share this document', 'error')
        return redirect(url_for('dashboard'))
    
    if request.method == 'POST':
        share_type = request.form.get('share_type')
        
        if share_type == 'user':
            # Share with specific user
            username = request.form.get('username')
            user = conn.execute('SELECT * FROM users WHERE username = ?', (username,)).fetchone()
            
            if not user:
                flash(f'User {username} not found', 'error')
            else:
                # Check if already shared
                existing = conn.execute('''
                    SELECT * FROM document_shares 
                    WHERE document_id = ? AND shared_with = ?
                ''', (document_id, user['id'])).fetchone()
                
                if existing:
                    flash(f'Document already shared with {username}', 'info')
                else:
                    conn.execute('''
                        INSERT INTO document_shares (document_id, shared_by, shared_with)
                        VALUES (?, ?, ?)
                    ''', (document_id, session['user_id'], user['id']))
                    flash(f'Document shared with {username}', 'success')
        
        elif share_type == 'link':
            # Generate shareable link
            expiry_days = int(request.form.get('expiry', 7))
            expires_at = datetime.datetime.now() + datetime.timedelta(days=expiry_days)
            share_token = uuid.uuid4().hex
            
            conn.execute('''
                INSERT INTO document_shares (document_id, shared_by, share_link, expires_at)
                VALUES (?, ?, ?, ?)
            ''', (document_id, session['user_id'], share_token, expires_at))
            
            flash(f'Shareable link created (expires in {expiry_days} days)', 'success')
        
        conn.commit()
    
    # Get users for sharing
    users = conn.execute('SELECT * FROM users WHERE id != ?', (session['user_id'],)).fetchall()
    
    # Get existing shares
    shares = conn.execute('''
        SELECT document_shares.*, users.username
        FROM document_shares
        LEFT JOIN users ON document_shares.shared_with = users.id
        WHERE document_id = ?
    ''', (document_id,)).fetchall()
    
    conn.close()
    
    return render_template('share_document.html', document=document, users=users, shares=shares)

@app.route('/document/<int:document_id>/delete')
@login_required
def delete_document(document_id):
    conn = get_db_connection()
    
    # Get document
    document = conn.execute('SELECT * FROM documents WHERE id = ?', (document_id,)).fetchone()
    
    if not document:
        conn.close()
        flash('Document not found', 'error')
        return redirect(url_for('dashboard'))
    
    # Check ownership
    if document['user_id'] != session['user_id'] and session['role'] != 'admin':
        conn.close()
        flash('You do not have permission to delete this document', 'error')
        return redirect(url_for('dashboard'))
    
    # Get all versions
    versions = conn.execute('SELECT * FROM document_versions WHERE document_id = ?', (document_id,)).fetchall()
    
    # Delete files
    for version in versions:
        file_path = os.path.join(app.config['UPLOAD_FOLDER'], version['filename'])
        if os.path.exists(file_path):
            os.remove(file_path)
    
    # Delete from database (cascade will handle related records)
    conn.execute('DELETE FROM analytics WHERE document_id = ?', (document_id,))
    conn.execute('DELETE FROM document_shares WHERE document_id = ?', (document_id,))
    conn.execute('DELETE FROM document_versions WHERE document_id = ?', (document_id,))
    conn.execute('DELETE FROM documents WHERE id = ?', (document_id,))
    
    conn.commit()
    conn.close()
    
    flash('Document deleted successfully', 'success')
    return redirect(url_for('dashboard'))

@app.route('/admin')
@admin_required
def admin_panel():
    conn = get_db_connection()
    
    # Get all users
    users = conn.execute('SELECT * FROM users').fetchall()
    
    # Get document statistics
    doc_stats = conn.execute('''
        SELECT 
            COUNT(*) as total_documents,
            SUM(file_size) as total_size,
            COUNT(DISTINCT user_id) as total_contributors
        FROM documents
    ''').fetchone()
    
    # Get activity statistics
    activity_stats = conn.execute('''
        SELECT 
            COUNT(*) as total_actions,
            COUNT(DISTINCT user_id) as active_users,
            COUNT(DISTINCT document_id) as accessed_documents
        FROM analytics
    ''').fetchone()
    
    conn.close()
    
    return render_template('admin.html', users=users, doc_stats=doc_stats, activity_stats=activity_stats)

@app.route('/shared/<share_token>')
def access_shared(share_token):
    conn = get_db_connection()
    
    # Get share information
    share = conn.execute('''
        SELECT document_shares.*, documents.* 
        FROM document_shares
        JOIN documents ON document_shares.document_id = documents.id
        WHERE document_shares.share_link = ?
    ''', (share_token,)).fetchone()
    
    if not share:
        conn.close()
        flash('Invalid or expired share link', 'error')
        return redirect(url_for('index'))
    
    # Check if expired
    if share['expires_at'] and datetime.datetime.strptime(share['expires_at'], '%Y-%m-%d %H:%M:%S.%f') < datetime.datetime.now():
        conn.close()
        flash('This share link has expired', 'error')
        return redirect(url_for('index'))
    
    # Record view in analytics
    user_id = session.get('user_id')
    conn.execute('''
        INSERT INTO analytics (document_id, action, user_id, ip_address)
        VALUES (?, ?, ?, ?)
    ''', (share['document_id'], 'shared_view', user_id, request.remote_addr))
    
    conn.commit()
    
    # Get document versions
    versions = conn.execute('''
        SELECT * FROM document_versions
        WHERE document_id = ?
        ORDER BY version_number DESC
    ''', (share['document_id'],)).fetchall()
    
    conn.close()
    
    return render_template('shared_view.html', document=share, versions=versions, share_token=share_token)

@app.route('/shared/<share_token>/download')
def download_shared(share_token):
    conn = get_db_connection()
    
    # Get share information
    share = conn.execute('''
        SELECT document_shares.*, documents.* 
        FROM document_shares
        JOIN documents ON document_shares.document_id = documents.id
        WHERE document_shares.share_link = ?
    ''', (share_token,)).fetchone()
    
    if not share:
        conn.close()
        flash('Invalid or expired share link', 'error')
        return redirect(url_for('index'))
    
    # Check if expired
    if share['expires_at'] and datetime.datetime.strptime(share['expires_at'], '%Y-%m-%d %H:%M:%S.%f') < datetime.datetime.now():
        conn.close()
        flash('This share link has expired', 'error')
        return redirect(url_for('index'))
    
    # Record download in analytics
    user_id = session.get('user_id')
    conn.execute('''
        INSERT INTO analytics (document_id, action, user_id, ip_address)
        VALUES (?, ?, ?, ?)
    ''', (share['document_id'], 'shared_download', user_id, request.remote_addr))
    
    conn.commit()
    conn.close()
    
    return send_from_directory(app.config['UPLOAD_FOLDER'], share['filename'], 
                              as_attachment=True, download_name=share['original_filename'])

# Error handlers
@app.errorhandler(404)
def page_not_found(e):
    return render_template('error.html', error_code=404, error_message="Page not found"), 404

@app.errorhandler(500)
def internal_server_error(e):
    return render_template('error.html', error_code=500, error_message="Internal server error"), 500

# Initialize database and start app
if __name__ == '__main__':
    init_db()
    app.run(host='0.0.0.0', port=1000, debug=False)
else:
    # For production WSGI servers
    init_db()