GameList/Endpoints/EndpointHelpers.cs

using GameList.Data;
using GameList.Domain;
using Microsoft.EntityFrameworkCore;
using System.Net;
using System.Net.Sockets;
using System.Security.Claims;

namespace GameList.Endpoints;

internal static class EndpointHelpers
{
    public static async Task<Player?> GetAuthenticatedPlayer(HttpContext ctx, AppDbContext db)
    {
        if (ctx.User.Identity?.IsAuthenticated != true)
            return null;

        if (ctx.Items.TryGetValue(nameof(Player), out var cached) && cached is Player cachedPlayer)
            return cachedPlayer;

        var idValue = ctx.User.FindFirstValue(ClaimTypes.NameIdentifier);
        if (string.IsNullOrWhiteSpace(idValue) || !Guid.TryParse(idValue, out var playerId))
        {
            // Auth cookie is present but malformed; clear and reject.
            await Infrastructure.PlayerIdentityExtensions.SignOutPlayerAsync(ctx);
            return null;
        }

        var existing = await db.Players.FindAsync(playerId);
        if (existing is null)
        {
            await Infrastructure.PlayerIdentityExtensions.SignOutPlayerAsync(ctx);
            return null;
        }

        ctx.Items[nameof(Player)] = existing;
        return existing;
    }

    public static async Task<Phase> GetCurrentPhaseAsync(AppDbContext db, Guid playerId)
    {
        var playerPhase = await db.Players
            .AsNoTracking()
            .Where(p => p.Id == playerId)
            .Select(p => (Phase?)p.CurrentPhase)
            .FirstOrDefaultAsync();
        if (playerPhase is null)
            return Phase.Suggest;

        var resultsOpen = await db.AppState.AsNoTracking().Select(s => s.ResultsOpen).SingleAsync();
        return GetCurrentPhase(playerPhase.Value, resultsOpen);
    }

    public static Phase GetCurrentPhase(Phase phase, bool resultsOpen)
    {
        var normalized = NormalizePhase(phase);

        if (resultsOpen)
            return Phase.Results;

        return normalized == Phase.Results ? Phase.Vote : normalized;
    }

    public static bool ReconcilePlayerPhase(Player player, bool resultsOpen)
    {
        var changed = false;

        var normalized = NormalizePhase(player.CurrentPhase);
        if (player.CurrentPhase != normalized)
        {
            player.CurrentPhase = normalized;
            changed = true;
        }

        if (resultsOpen && player.CurrentPhase != Phase.Results)
        {
            player.CurrentPhase = Phase.Results;
            changed = true;
        }
        else if (!resultsOpen && player.CurrentPhase == Phase.Results)
        {
            player.CurrentPhase = Phase.Vote;
            player.VotesFinal = false;
            changed = true;
        }

        return changed;
    }

    private static Phase NormalizePhase(Phase phase)
    {
        return phase switch
        {
            Phase.Suggest => Phase.Suggest,
            Phase.Vote => Phase.Vote,
            Phase.Results => Phase.Results,
            _ => Phase.Vote // legacy/invalid phase fallback
        };
    }

    public static IResult PhaseMismatch(Phase required, Phase current) =>
        BadRequestError($"This endpoint is available in the {required} phase. Your current phase is {current}.");

    public static IResult BadRequestError(string detail) => Problem(StatusCodes.Status400BadRequest, "Bad Request", detail);

    public static IResult NotFoundError(string detail) => Problem(StatusCodes.Status404NotFound, "Not Found", detail);

    public static IResult ConflictError(string detail) => Problem(StatusCodes.Status409Conflict, "Conflict", detail);

    public static IResult UnauthorizedError(string detail = "Unauthorized") => Problem(StatusCodes.Status401Unauthorized, "Unauthorized", detail);

    private static IResult Problem(int statusCode, string title, string detail)
    {
        return Results.Problem(
            statusCode: statusCode,
            title: title,
            detail: detail,
            extensions: new Dictionary<string, object?>
            {
                ["error"] = detail
            }
        );
    }

    public static string? TrimTo(string? input, int max) =>
        string.IsNullOrWhiteSpace(input) ? null : input.Trim() is { Length: > 0 } t ? t[..Math.Min(t.Length, max)] : null;

    public static bool IsValidImageUrl(string? url)
    {
        if (string.IsNullOrWhiteSpace(url))
            return true; // empty is acceptable
        if (!Uri.TryCreate(url, UriKind.Absolute, out var uri))
            return false;
        if (uri.Scheme is not ("http" or "https"))
            return false;

        var path = uri.AbsolutePath.ToLowerInvariant();
        return path.EndsWith(".png", StringComparison.Ordinal)
            || path.EndsWith(".jpg", StringComparison.Ordinal)
            || path.EndsWith(".jpeg", StringComparison.Ordinal)
            || path.EndsWith(".gif", StringComparison.Ordinal)
            || path.EndsWith(".webp", StringComparison.Ordinal)
            || path.EndsWith(".avif", StringComparison.Ordinal);
    }

    public static HttpMessageHandler CreateImageValidationHandler()
    {
        return new SocketsHttpHandler
        {
            AllowAutoRedirect = false,
            ConnectCallback = async (context, cancellationToken) =>
            {
                var addresses = await ResolveSafePublicAddressesAsync(context.DnsEndPoint.Host, cancellationToken);
                if (addresses.Count == 0)
                    throw new HttpRequestException("No safe public IPs found for host.");

                foreach (var ip in addresses)
                {
                    var socket = new Socket(ip.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
                    try
                    {
                        await socket.ConnectAsync(new IPEndPoint(ip, context.DnsEndPoint.Port), cancellationToken);
                        return new NetworkStream(socket, ownsSocket: true);
                    }
                    catch
                    {
                        socket.Dispose();
                    }
                }

                throw new HttpRequestException("Unable to connect to validated public IP for host.");
            }
        };
    }

    public static async Task<bool> IsReachableImageAsync(string? url, IHttpClientFactory httpFactory, HttpMessageHandler? handler = null, CancellationToken ct = default)
    {
        if (string.IsNullOrWhiteSpace(url))
            return true;
        if (!Uri.TryCreate(url, UriKind.Absolute, out var uri))
            return false;
        if (uri.Scheme is not ("http" or "https"))
            return false;
        if (handler is null)
        {
            if (!await IsSafePublicHostAsync(uri, ct))
                return false;
        }
        else if (IPAddress.TryParse(uri.Host, out var literal) && IsBlockedAddress(literal))
        {
            return false;
        }

        using var cts = CancellationTokenSource.CreateLinkedTokenSource(ct);
        cts.CancelAfter(TimeSpan.FromSeconds(3));

        using var fallbackClient = handler is null ? null : new HttpClient(handler, disposeHandler: false);
        var client = fallbackClient ?? httpFactory.CreateClient("imageValidation");

        try
        {
            using var head = new HttpRequestMessage(HttpMethod.Head, uri);
            var headResp = await client.SendAsync(head, HttpCompletionOption.ResponseHeadersRead, cts.Token);
            if (WasRedirected(uri, headResp))
                return false;
            if (headResp is { IsSuccessStatusCode: true, StatusCode: not System.Net.HttpStatusCode.Redirect })
            {
                if (headResp.Content.Headers.ContentLength is > MaxImageBytes)
                    return false;

                var ctHeader = headResp.Content.Headers.ContentType?.MediaType;
                if (!string.IsNullOrWhiteSpace(ctHeader) && ctHeader.StartsWith("image/", StringComparison.OrdinalIgnoreCase))
                    return true;
            }
        }
        catch
        {
            /* fallback */
        }

        try
        {
            using var get = new HttpRequestMessage(HttpMethod.Get, uri);
            get.Headers.Range = new System.Net.Http.Headers.RangeHeaderValue(0, 1023);
            var resp = await client.SendAsync(get, HttpCompletionOption.ResponseHeadersRead, cts.Token);
            if (WasRedirected(uri, resp))
                return false;
            if (!resp.IsSuccessStatusCode)
                return false;
            if (resp.StatusCode is System.Net.HttpStatusCode.Redirect)
                return false;
            if (resp.Content.Headers.ContentLength is > MaxImageBytes)
                return false;

            var ctHeader = resp.Content.Headers.ContentType?.MediaType;
            if (!string.IsNullOrWhiteSpace(ctHeader) && ctHeader.StartsWith("image/", StringComparison.OrdinalIgnoreCase))
                return true;

            await using var stream = await resp.Content.ReadAsStreamAsync(cts.Token);
            var rented = new byte[12];
            var read = await stream.ReadAsync(rented.AsMemory(0, rented.Length), cts.Token);
            var sig = new ReadOnlySpan<byte>(rented, 0, read);

            if (IsMagic(sig, "PNG"))
                return true;
            if (IsMagic(sig, [0xFF, 0xD8]))
                return true; // JPEG
            if (IsMagic(sig, "GIF8"))
                return true;
            if (IsRiffWithTag(sig, "WEBP"))
                return true;
            if (ContainsFtyp(sig, "avif"))
                return true;

            return false;
        }
        catch
        {
            return false;
        }
    }

    private const long MaxImageBytes = 5 * 1024 * 1024; // 5 MB guard

    private static bool WasRedirected(Uri requestedUri, HttpResponseMessage response)
    {
        var finalUri = response.RequestMessage?.RequestUri;
        if (finalUri is null)
            return false;

        return !requestedUri.Equals(finalUri);
    }

    private static async Task<bool> IsSafePublicHostAsync(Uri uri, CancellationToken ct)
    {
        try
        {
            var addresses = await ResolveSafePublicAddressesAsync(uri.Host, ct);
            return addresses.Count > 0;
        }
        catch
        {
            return false;
        }
    }

    private static async Task<IReadOnlyList<IPAddress>> ResolveSafePublicAddressesAsync(string host, CancellationToken ct)
    {
        if (!IsSupportedHostType(host))
            return [];

        IPAddress[] resolved;
        if (IPAddress.TryParse(host, out var literal))
        {
            resolved = [literal];
        }
        else
        {
            resolved = await Dns.GetHostAddressesAsync(host, ct);
        }

        var safe = new List<IPAddress>(resolved.Length);
        foreach (var ip in resolved)
        {
            if (!IsBlockedAddress(ip))
                safe.Add(ip);
        }

        return safe.Distinct().ToArray();
    }

    private static bool IsSupportedHostType(string host)
    {
        var type = Uri.CheckHostName(host);
        return type is UriHostNameType.Dns or UriHostNameType.IPv4 or UriHostNameType.IPv6;
    }

    private static bool IsBlockedAddress(IPAddress ip)
    {
        if (IPAddress.IsLoopback(ip))
            return true;

        if (ip.IsIPv4MappedToIPv6)
            return IsBlockedAddress(ip.MapToIPv4());

        if (ip.AddressFamily == AddressFamily.InterNetwork)
            return IsBlockedIpv4(ip);

        if (ip.AddressFamily == AddressFamily.InterNetworkV6)
            return IsBlockedIpv6(ip);

        return true;
    }

    private static bool IsBlockedIpv4(IPAddress ip)
    {
        var b = ip.GetAddressBytes();
        return b[0] switch
        {
            0 => true, // "This network"
            10 => true, // private
            100 when b[1] >= 64 && b[1] <= 127 => true, // CGNAT
            127 => true, // loopback
            169 when b[1] == 254 => true, // link local
            172 when b[1] >= 16 && b[1] <= 31 => true, // private
            192 when b[1] == 0 && b[2] == 0 => true, // IETF protocol assignments
            192 when b[1] == 0 && b[2] == 2 => true, // documentation
            192 when b[1] == 88 && b[2] == 99 => true, // 6to4 relay anycast
            192 when b[1] == 168 => true, // private
            198 when b[1] is 18 or 19 => true, // benchmarking
            198 when b[1] == 51 && b[2] == 100 => true, // documentation
            203 when b[1] == 0 && b[2] == 113 => true, // documentation
            >= 224 => true, // multicast/reserved/broadcast
            _ => false
        };
    }

    private static bool IsBlockedIpv6(IPAddress ip)
    {
        if (ip.Equals(IPAddress.IPv6None))
            return true;
        if (ip.IsIPv6Multicast || ip.IsIPv6LinkLocal || ip.IsIPv6SiteLocal)
            return true;

        var bytes = ip.GetAddressBytes();
        if ((bytes[0] & 0xFE) == 0xFC) // fc00::/7 unique local
            return true;
        if (bytes[0] == 0x20 && bytes[1] == 0x01 && bytes[2] == 0x0D && bytes[3] == 0xB8) // 2001:db8::/32 docs
            return true;

        return false;
    }

    private static bool IsMagic(ReadOnlySpan<byte> data, string ascii)
    {
        var bytes = System.Text.Encoding.ASCII.GetBytes(ascii);
        return data.StartsWith(bytes);
    }

    private static bool IsMagic(ReadOnlySpan<byte> data, ReadOnlySpan<byte> magic) => data.StartsWith(magic);

    private static bool IsRiffWithTag(ReadOnlySpan<byte> data, string tag)
    {
        if (data.Length < 12)
            return false;

        var riff = "RIFF"u8.ToArray();
        if (!data.StartsWith(riff))
            return false;

        var tagBytes = System.Text.Encoding.ASCII.GetBytes(tag);
        return data[8..].StartsWith(tagBytes);
    }

    private static bool ContainsFtyp(ReadOnlySpan<byte> data, string brand)
    {
        if (data.Length < 12)
            return false;

        var ftyp = "ftyp"u8.ToArray();
        if (!data[4..].StartsWith(ftyp))
            return false;

        var brandBytes = System.Text.Encoding.ASCII.GetBytes(brand);
        return data[8..].StartsWith(brandBytes);
    }

    public static bool IsValidHttpUrl(string? url)
    {
        if (string.IsNullOrWhiteSpace(url))
            return true; // empty is allowed
        if (!Uri.TryCreate(url, UriKind.Absolute, out var uri))
            return false;

        return uri.Scheme is "http" or "https";
    }

    public static async Task<bool> IsAdmin(HttpContext ctx, AppDbContext db)
    {
        var player = await GetAuthenticatedPlayer(ctx, db);
        return player?.IsAdmin == true;
    }

    public static AppState NewAppState() => new()
    {
        Id = 1,
        ResultsOpen = false,
        UpdatedAt = DateTimeOffset.UnixEpoch
    };

    public static Dictionary<int, int> BuildLinkRoots(IEnumerable<(int Id, int? ParentId)> items)
    {
        var parentMap = items.ToDictionary(x => x.Id, x => x.ParentId);
        var roots = new Dictionary<int, int>();
        foreach (var id in parentMap.Keys)
        {
            roots[id] = FindRootId(id, parentMap);
        }

        return roots;
    }

    public static int FindRootId(int suggestionId, IReadOnlyDictionary<int, int?> parentMap)
    {
        var current = suggestionId;
        var visited = new HashSet<int>();

        while (parentMap.TryGetValue(current, out var parent) && parent is { } p && !visited.Contains(p))
        {
            visited.Add(current);
            current = p;
        }

        return current;
    }

    public static List<int> LinkedIdsFor(int suggestionId, IReadOnlyDictionary<int, int> rootIndex)
    {
        if (!rootIndex.TryGetValue(suggestionId, out var root))
            return [];

        return rootIndex.Where(kv => kv.Value == root).Select(kv => kv.Key).ToList();
    }
}