from datetime import datetime

def timeago(dt):
    """
    Returns a human-readable string representing time difference between now and the given datetime.
    
    For example: "2 minutes ago", "3 hours ago", "5 days ago", etc.
    """
    now = datetime.utcnow()
    diff = now - dt
    
    seconds = diff.total_seconds()
    
    if seconds < 60:
        return "just now"
    elif seconds < 3600:
        minutes = int(seconds / 60)
        return f"{minutes} minute{'s' if minutes != 1 else ''} ago"
    elif seconds < 86400:
        hours = int(seconds / 3600)
        return f"{hours} hour{'s' if hours != 1 else ''} ago"
    elif seconds < 604800:
        days = int(seconds / 86400)
        return f"{days} day{'s' if days != 1 else ''} ago"
    elif seconds < 2592000:
        weeks = int(seconds / 604800)
        return f"{weeks} week{'s' if weeks != 1 else ''} ago"
    elif seconds < 31536000:
        months = int(seconds / 2592000)
        return f"{months} month{'s' if months != 1 else ''} ago"
    else:
        years = int(seconds / 31536000)
        return f"{years} year{'s' if years != 1 else ''} ago"

def init_app(app):
    """Register filters with the Flask app"""
    app.jinja_env.filters['timeago'] = timeago