import re
import ipaddress

# Curated IANA timezone list for the dropdown. Validation accepts any entry from this set.
VALID_TIMEZONES = [
    'UTC',
    # Americas
    'America/New_York',
    'America/Detroit',
    'America/Indiana/Indianapolis',
    'America/Chicago',
    'America/Denver',
    'America/Phoenix',
    'America/Los_Angeles',
    'America/Anchorage',
    'America/Adak',
    'Pacific/Honolulu',
    'America/Toronto',
    'America/Vancouver',
    'America/Winnipeg',
    'America/Halifax',
    'America/St_Johns',
    'America/Mexico_City',
    'America/Bogota',
    'America/Lima',
    'America/Santiago',
    'America/Caracas',
    'America/Sao_Paulo',
    'America/Argentina/Buenos_Aires',
    'America/Montevideo',
    # Europe
    'Europe/London',
    'Europe/Dublin',
    'Europe/Lisbon',
    'Europe/Paris',
    'Europe/Berlin',
    'Europe/Amsterdam',
    'Europe/Brussels',
    'Europe/Madrid',
    'Europe/Rome',
    'Europe/Zurich',
    'Europe/Vienna',
    'Europe/Stockholm',
    'Europe/Oslo',
    'Europe/Copenhagen',
    'Europe/Helsinki',
    'Europe/Warsaw',
    'Europe/Prague',
    'Europe/Budapest',
    'Europe/Bucharest',
    'Europe/Athens',
    'Europe/Istanbul',
    'Europe/Moscow',
    'Europe/Kyiv',
    # Africa
    'Africa/Casablanca',
    'Africa/Lagos',
    'Africa/Cairo',
    'Africa/Nairobi',
    'Africa/Johannesburg',
    # Asia
    'Asia/Dubai',
    'Asia/Tbilisi',
    'Asia/Tehran',
    'Asia/Karachi',
    'Asia/Kolkata',
    'Asia/Colombo',
    'Asia/Dhaka',
    'Asia/Yangon',
    'Asia/Bangkok',
    'Asia/Ho_Chi_Minh',
    'Asia/Singapore',
    'Asia/Kuala_Lumpur',
    'Asia/Jakarta',
    'Asia/Shanghai',
    'Asia/Hong_Kong',
    'Asia/Taipei',
    'Asia/Manila',
    'Asia/Seoul',
    'Asia/Tokyo',
    'Asia/Yakutsk',
    'Asia/Vladivostok',
    # Australia / Pacific
    'Australia/Perth',
    'Australia/Darwin',
    'Australia/Adelaide',
    'Australia/Brisbane',
    'Australia/Sydney',
    'Australia/Melbourne',
    'Australia/Hobart',
    'Pacific/Auckland',
    'Pacific/Fiji',
    'Pacific/Guam',
    'Pacific/Honolulu',
]

_TIMEZONE_SET = set(VALID_TIMEZONES)


def _strip(value, pattern, max_len):
    return re.sub(pattern, '', str(value).strip())[:max_len]


def text(value, max_len=200):
    """General description: letters, digits, spaces, basic punctuation. No quotes/braces/brackets/slashes."""
    return _strip(value, r'''["'{}\[\]\\/<>;`^~]''', max_len)

def description(value, max_len=200):
    """Human-readable description: letters, digits, hyphens, parentheses, commas, forward slashes, spaces.
    Whitespace collapsed; no sequential commas or slashes."""
    s = re.sub(r'[^A-Za-z0-9\-()/,\s]', '', str(value))
    s = re.sub(r'\s+', ' ', s)
    s = re.sub(r',{2,}', ',', s)
    s = re.sub(r'/{2,}', '/', s)
    s = re.sub(r'-{2,}', '-', s)
    s = re.sub(r'\({2,}', '(', s)
    s = re.sub(r'\){2,}', ')', s)
    return s.strip()[:max_len]

def name(value, max_len=40):
    """Identifier: lowercase letters, digits, hyphens only. No sequential hyphens."""
    s = re.sub(r'[\s_]+', '-', str(value).strip().lower())
    s = re.sub(r'[^a-z0-9-]', '', s)[:max_len]
    s = re.sub(r'-{2,}', '-', s)
    return s.strip('-')

def domainname(value, max_len=253):
    """Hostname or domain: letters, digits, hyphens, dots. Lowercased."""
    return _strip(value.lower(), r'[^a-z0-9\-.]', max_len)

def domainlist(lines):
    """Sanitize a list of domain name strings, returning only non-empty results."""
    return [h for v in lines if (h := domainname(v))]

def ip(value, max_len=45):
    """IPv4 or IPv6 address. Returns '' if not a valid address."""
    cleaned = _strip(value, r'[^0-9a-fA-F.:]', max_len)
    try:
        ipaddress.ip_address(cleaned)
        return cleaned
    except ValueError:
        return ''

def ip_or_cidr(value, max_len=49):
    """IP address or CIDR subnet. Returns '' if not valid."""
    cleaned = _strip(value, r'[^0-9a-fA-F.:/]', max_len)
    try:
        if '/' in cleaned:
            ipaddress.ip_network(cleaned, strict=False)
        else:
            ipaddress.ip_address(cleaned)
        return cleaned
    except ValueError:
        return ''

def mac(value):
    """MAC address in aa:bb:cc:dd:ee:ff format. Colons required; no other separators accepted.
    Returns lowercase colon-separated MAC if valid, '' otherwise."""
    s = str(value).strip().lower()
    if re.fullmatch(r'([0-9a-f]{2}:){5}[0-9a-f]{2}', s):
        return s
    return ''

def url(value, max_len=500):
    """URL: printable ASCII except quotes, braces, brackets, backslash, spaces."""
    return _strip(value, r'''["'{}\[\]\\ ]''', max_len)

def interface_name(value, max_len=32):
    """Network interface name: letters, digits, hyphens, underscores, dots."""
    return _strip(value, r'[^A-Za-z0-9\-_.]', max_len)

def port(value):
    """Port number string, validated 1-65535. Returns '' if invalid."""
    digits = re.sub(r'[^0-9]', '', str(value))
    try:
        n = int(digits)
        if 1 <= n <= 65535:
            return str(n)
    except (ValueError, TypeError):
        pass
    return ''

def time_24h(value, max_len=5):
    """24-hour time HH:MM: digits and colon only."""
    return _strip(value, r'[^0-9:]', max_len)

def email(value, max_len=254):
    """Email address: letters, digits, @, dot, hyphen, underscore, plus. Lowercased."""
    return _strip(value.lower(), r'[^a-z0-9@.\-_+]', max_len)

def timezone(value):
    """Timezone string: must be in VALID_TIMEZONES list. Returns '' if not found."""
    return value if value in _TIMEZONE_SET else ''

def filterlist(submitted, allowed):
    """Filter a list of submitted values to those present in the allowed set, after sanitizing each."""
    allowed = set(allowed)
    return [n for v in submitted if (n := name(v)) in allowed]

def filtervalue(value, allowed):
    """Return the sanitized value if it exists in the allowed set, otherwise ''."""
    n = name(value)
    return n if n in set(allowed) else ''

_DOTTED_TO_PREFIX = {
    '255.0.0.0': 8, '255.255.0.0': 16, '255.255.255.0': 24,
    '255.255.255.128': 25, '255.255.255.192': 26,
    '255.255.255.224': 27, '255.255.255.240': 28,
    '255.255.255.248': 29, '255.255.255.252': 30,
}

def subnet_mask(value):
    """Subnet prefix length 1-30 (integer). Also accepts legacy dotted notation.
    Returns int on success, None if invalid."""
    s = str(value).strip()
    if s in _DOTTED_TO_PREFIX:
        return _DOTTED_TO_PREFIX[s]
    try:
        n = int(s)
        if 1 <= n <= 30:
            return n
    except (ValueError, TypeError):
        pass
    return None