using System.Net;
using System.Net.Sockets;
using System.Security.Cryptography;
using System.Text;

namespace YMhut.Box.Core.Plugins;

public static class PluginNetworkPolicy
{
    public static bool TryNormalizePublicOrigin(string? value, bool allowWebSocket, out string origin)
    {
        origin = string.Empty;
        if (!Uri.TryCreate(value?.Trim(), UriKind.Absolute, out var uri) ||
            !string.IsNullOrEmpty(uri.UserInfo) ||
            !string.IsNullOrEmpty(uri.Query) ||
            !string.IsNullOrEmpty(uri.Fragment) ||
            uri.AbsolutePath != "/" ||
            (uri.Scheme != Uri.UriSchemeHttps && (!allowWebSocket || uri.Scheme != "wss")) ||
            !IsPublicHostName(uri.Host))
        {
            return false;
        }

        origin = uri.GetLeftPart(UriPartial.Authority).TrimEnd('/').ToLowerInvariant();
        return true;
    }

    public static bool IsAllowed(Uri uri, IReadOnlyList<string>? declaredOrigins, bool allowWebSocket = false)
    {
        if (!TryNormalizePublicOrigin(uri.GetLeftPart(UriPartial.Authority), allowWebSocket, out var candidate))
        {
            return false;
        }

        return (declaredOrigins ?? []).Any(value =>
            TryNormalizePublicOrigin(value, allowWebSocket, out var allowed) &&
            string.Equals(candidate, allowed, StringComparison.OrdinalIgnoreCase));
    }

    public static async Task<bool> ResolvesToPublicAddressAsync(string host, CancellationToken cancellationToken = default)
    {
        if (!IsPublicHostName(host))
        {
            return false;
        }

        if (IPAddress.TryParse(host, out var literal))
        {
            return IsPublicAddress(literal);
        }

        try
        {
            var addresses = await Dns.GetHostAddressesAsync(host, cancellationToken).ConfigureAwait(false);
            return addresses.Length > 0 && addresses.All(IsPublicAddress);
        }
        catch (SocketException)
        {
            return false;
        }
    }

    public static bool IsPublicHostName(string host)
    {
        if (string.IsNullOrWhiteSpace(host) ||
            string.Equals(host, "localhost", StringComparison.OrdinalIgnoreCase) ||
            host.EndsWith(".localhost", StringComparison.OrdinalIgnoreCase) ||
            host.EndsWith(".local", StringComparison.OrdinalIgnoreCase) ||
            host.EndsWith(".internal", StringComparison.OrdinalIgnoreCase) ||
            !host.Contains('.') && !IPAddress.TryParse(host, out _))
        {
            return false;
        }

        return !IPAddress.TryParse(host, out var address) || IsPublicAddress(address);
    }

    public static bool IsPublicAddress(IPAddress address)
    {
        if (IPAddress.IsLoopback(address) || address.Equals(IPAddress.Any) || address.Equals(IPAddress.IPv6Any) ||
            address.Equals(IPAddress.None) || address.Equals(IPAddress.IPv6None))
        {
            return false;
        }

        if (address.AddressFamily == AddressFamily.InterNetworkV6)
        {
            return !address.IsIPv6LinkLocal && !address.IsIPv6SiteLocal && !address.IsIPv6Multicast &&
                !(address.GetAddressBytes()[0] is 0xFC or 0xFD);
        }

        var bytes = address.GetAddressBytes();
        return bytes[0] != 0 && bytes[0] != 10 && bytes[0] != 127 &&
            !(bytes[0] == 100 && bytes[1] is >= 64 and <= 127) &&
            !(bytes[0] == 169 && bytes[1] == 254) &&
            !(bytes[0] == 172 && bytes[1] is >= 16 and <= 31) &&
            !(bytes[0] == 192 && bytes[1] == 168) &&
            !(bytes[0] == 198 && bytes[1] is 18 or 19) &&
            bytes[0] < 224;
    }
}

public static class PluginWebOrigin
{
    public static string Create(string pluginId, string surfaceId)
    {
        var value = $"{PluginIds.Normalize(pluginId)}:{PluginIds.Normalize(surfaceId)}";
        var hash = Convert.ToHexString(SHA256.HashData(Encoding.UTF8.GetBytes(value))).ToLowerInvariant()[..32];
        return $"https://p-{hash}.plugin.ymhut.invalid";
    }
}

public static class PluginExternalWebOrigin
{
    public static string ProtocolName(string pluginId, string surfaceId)
    {
        var value = $"external:{PluginIds.Normalize(pluginId)}:{PluginIds.Normalize(surfaceId)}";
        var hash = Convert.ToHexString(SHA256.HashData(Encoding.UTF8.GetBytes(value))).ToLowerInvariant()[..32];
        return $"p-{hash}";
    }

    public static string Create(string pluginId, string surfaceId)
    {
        return $"https://{ProtocolName(pluginId, surfaceId)}.localhost";
    }
}

public static class PluginResourcePathPolicy
{
    public static bool IsSafeRequestUri(Uri uri)
    {
        var original = uri.OriginalString;
        var authorityStart = original.IndexOf("://", StringComparison.Ordinal);
        var pathStart = authorityStart < 0 ? -1 : original.IndexOf('/', authorityStart + 3);
        var escaped = pathStart < 0 ? string.Empty : original[pathStart..].Split(['?', '#'], 2)[0].TrimStart('/');
        if (escaped.Contains("%25", StringComparison.OrdinalIgnoreCase) ||
            escaped.Contains("%2e", StringComparison.OrdinalIgnoreCase) ||
            escaped.Contains("%5c", StringComparison.OrdinalIgnoreCase) ||
            escaped.Contains("%00", StringComparison.OrdinalIgnoreCase) ||
            escaped.Contains('\\') ||
            escaped.Contains(':'))
        {
            return false;
        }

        string decoded;
        try
        {
            decoded = Uri.UnescapeDataString(escaped).Replace('\\', '/');
        }
        catch (UriFormatException)
        {
            return false;
        }

        return !decoded.StartsWith("/", StringComparison.Ordinal) &&
            decoded.Split('/', StringSplitOptions.RemoveEmptyEntries)
                .All(segment => segment is not "." and not ".." && !Path.IsPathFullyQualified(segment));
    }
}