"""Input validation functions for HAProxy MCP Server."""

import ipaddress
from .config import DOMAIN_PATTERN, BACKEND_NAME_PATTERN, NON_ALNUM_PATTERN


def validate_domain(domain: str) -> bool:
    """Validate domain format.

    Args:
        domain: The domain name to validate

    Returns:
        True if domain is valid, False otherwise
    """
    if not domain or len(domain) > 253:
        return False
    return bool(DOMAIN_PATTERN.match(domain))


def validate_ip(ip: str, allow_empty: bool = False) -> bool:
    """Validate IPv4 or IPv6 address format.

    Args:
        ip: The IP address to validate
        allow_empty: If True, empty string is considered valid

    Returns:
        True if IP is valid, False otherwise
    """
    if not ip:
        return allow_empty
    try:
        ipaddress.ip_address(ip)
        return True
    except ValueError:
        return False


def validate_port(port: str) -> bool:
    """Validate port number is in valid range.

    Args:
        port: Port number as string

    Returns:
        True if port is valid (1-65535), False otherwise
    """
    if not port or not port.isdigit():
        return False
    port_num = int(port)
    return 1 <= port_num <= 65535


def validate_backend_name(name: str) -> bool:
    """Validate backend or server name to prevent command injection.

    Args:
        name: The backend or server name to validate

    Returns:
        True if name contains only safe characters
    """
    if not name or len(name) > 255:
        return False
    return bool(BACKEND_NAME_PATTERN.match(name))


def domain_to_backend(domain: str) -> str:
    """Convert domain to backend name (alphanumeric + underscore only).

    Args:
        domain: The domain name to convert

    Returns:
        Backend name with non-alphanumeric characters replaced by underscores

    Raises:
        ValueError: If resulting name is invalid
    """
    result = NON_ALNUM_PATTERN.sub('_', domain)
    if not validate_backend_name(result):
        raise ValueError(f"Invalid backend name after conversion: {result}")
    return result