import ipaddress
import logging
import socket

logger = logging.getLogger(__name__)


def is_private_ip(hostname: str) -> bool:
    """
    Check if a hostname resolves to a private/internal IP address.
    Protects against SSRF attacks by blocking access to internal networks.
    """
    try:
        # Try to parse as IP address directly
        ip = ipaddress.ip_address(hostname)
        return ip.is_private or ip.is_loopback or ip.is_link_local or ip.is_reserved
    except ValueError:
        # Not a direct IP, try to resolve hostname
        try:
            # Get all IP addresses for this hostname
            addr_info = socket.getaddrinfo(hostname, None)
            for info in addr_info:
                ip_str = info[4][0]
                ip = ipaddress.ip_address(ip_str)
                # Block if ANY resolved IP is private/internal
                if ip.is_private or ip.is_loopback or ip.is_link_local or ip.is_reserved:
                    return True
            return False
        except (socket.gaierror, socket.error):
            # Cannot resolve.
            # Fail securely: block unresolved domains to prevent DNS rebinding
            # and SSRF bypasses via unresolvable addresses.
            logger.warning(f"Could not resolve hostname (blocking securely): {hostname}")
            return True


def join_url(base: str, *parts: str) -> str:
    """
    Safely join a base URL and multiple path parts.
    Handles double slashes while preserving the protocol '://'.
    """
    url = "/".join([base, *parts])
    url = url.replace("://", "$PLACEHOLDER$")
    while "//" in url:
        url = url.replace("//", "/")
    url = url.replace("$PLACEHOLDER$", "://")
    return url