import re
from flask import request, jsonify

def validate_email(email):
    """Validate an email address."""
    regex = r"^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+$"
    return re.match(regex, email) is not None

def validate_password(password):
    """Validate a password (at least 8 characters, one uppercase, one number)."""
    if len(password) < 8:
        return False
    if not re.search(r"[A-Z]", password):
        return False
    if not re.search(r"\d", password):
        return False
    return True

def validate_ad_content(content):
    """Validate ad content (non-empty and within length limits)."""
    if not content or len(content) > 1000:
        return False
    return True

def validate_request_json(required_fields):
    """Validate JSON request payload for required fields."""
    data = request.get_json()
    if not data:
        return jsonify({"error": "Request must be JSON"}), 400
    for field in required_fields:
        if field not in data:
            return jsonify({"error": f"Missing required field: {field}"}), 400
    return None