is-a-dev/utils/functions.js

module.exports.expandIPv6 = function (ip) {
    // Split into segments by ":"
    let segments = ip.split(":");

    // Count the number of segments that are empty due to "::" shorthand
    const emptyIndex = segments.indexOf("");
    if (emptyIndex !== -1) {
        // Calculate how many "0000" segments are missing
        const nonEmptySegments = segments.filter((seg) => seg !== "");
        const missingSegments = 8 - nonEmptySegments.length;
        
        // Insert the missing "0000" segments into the position of the empty segment
        segments = [...nonEmptySegments.slice(0, emptyIndex), ...Array(missingSegments).fill("0000"), ...nonEmptySegments.slice(emptyIndex)];
    }

    // Expand each segment to 4 characters, padding with leading zeros
    const expandedSegments = segments.map((segment) => segment.padStart(4, "0"));

    // Join the segments back together
    return expandedSegments.join(":");
};

module.exports.isPublicIPv4 = function (ip, proxied) {
    const parts = ip.split('.').map(Number);

    // Validate IPv4 address format
    if (parts.length !== 4 || parts.some(part => isNaN(part) || part < 0 || part > 255)) {
        return false;
    }

    // Exception for 192.0.2.1, assuming the domain is proxied
    if (ip === "192.0.2.1" && proxied) {
        return true;
    }

    // Check for private and reserved IPv4 ranges
    return !(
        // Private ranges
        parts[0] === 10 ||
        (parts[0] === 172 && parts[1] >= 16 && parts[1] <= 31) ||
        (parts[0] === 192 && parts[1] === 168) ||

        // Reserved or special-use ranges
        (parts[0] === 100 && parts[1] >= 64 && parts[1] <= 127) ||    // Carrier-grade NAT
        (parts[0] === 169 && parts[1] === 254) ||                     // Link-local
        (parts[0] === 192 && parts[1] === 0 && parts[2] === 0) ||     // IETF Protocol Assignments
        (parts[0] === 192 && parts[1] === 0 && parts[2] === 2) ||     // Documentation (TEST-NET-1)
        (parts[0] === 198 && parts[1] === 18) ||                      // Network Interconnect Devices
        (parts[0] === 198 && parts[1] === 51 && parts[2] === 100) ||  // Documentation (TEST-NET-2)
        (parts[0] === 203 && parts[1] === 0 && parts[2] === 113) ||   // Documentation (TEST-NET-3)
        (parts[0] >= 224)                                             // Multicast and reserved ranges
    );
};

module.exports.isPublicIPv6 = function (ip) {
    const normalizedIP = ip.toLowerCase();

    // Check for private or special-use IPv6 ranges
    return !(
        normalizedIP.startsWith("fc") ||     // Unique Local Address (ULA)
        normalizedIP.startsWith("fd") ||     // Unique Local Address (ULA)
        normalizedIP.startsWith("fe80") ||   // Link-local
        normalizedIP.startsWith("::1") ||    // Loopback address (::1)
        normalizedIP.startsWith("2001:db8")  // Documentation range
    );
};