feat: add presence-gated session leases (#7)

Closes #7

src/FinalFactory.Rendezvous.Server/State/EphemeralStateContracts.cs

@@ -53,6 +53,12 @@ internal sealed record EphemeralStoreOptions
         RequireDuration(ReplayLifetime, TimeSpan.FromSeconds(30), nameof(ReplayLifetime));
         RequireDuration(IdempotencyLifetime, TimeSpan.FromMinutes(10), nameof(IdempotencyLifetime));
         RequireDuration(GracefulDrainLifetime, TimeSpan.FromSeconds(30), nameof(GracefulDrainLifetime));
+        if (IdempotencyLifetime < LeaseLifetime || IdempotencyLifetime < JoinAttemptLifetime)
+        {
+            throw new ArgumentOutOfRangeException(
+                nameof(IdempotencyLifetime),
+                "Idempotency retention must cover every idempotent resource lifetime.");
+        }
     }
 
     private static void RequirePositive(int value, string name)
@@ -74,8 +80,10 @@ internal sealed record EphemeralStoreOptions
 
 internal readonly record struct TenantScope(GameId GameId, EnvironmentId EnvironmentId);
 
-internal readonly record struct SecretFingerprint
+internal readonly struct SecretFingerprint : IEquatable<SecretFingerprint>
 {
+    private readonly string? _value;
+
     public SecretFingerprint(string value)
     {
         if (string.IsNullOrWhiteSpace(value) || value.Length > 128)
@@ -83,12 +91,33 @@ internal readonly record struct SecretFingerprint
             throw new ArgumentException("Secret fingerprints must contain 1-128 characters.", nameof(value));
         }
 
-        Value = value;
+        _value = value;
     }
 
-    public string Value { get; }
-    public bool IsValid => !string.IsNullOrWhiteSpace(Value) && Value.Length <= 128;
+    public bool IsValid => !string.IsNullOrWhiteSpace(_value) && _value.Length <= 128;
+    public bool Equals(SecretFingerprint other)
+    {
+        ReadOnlySpan<char> left = _value.AsSpan();
+        ReadOnlySpan<char> right = other._value.AsSpan();
+        if (left.Length != right.Length)
+        {
+            return false;
+        }
+
+        int difference = 0;
+        for (int index = 0; index < left.Length; index++)
+        {
+            difference |= left[index] ^ right[index];
+        }
+
+        return difference == 0;
+    }
+
+    public override bool Equals(object? obj) => obj is SecretFingerprint other && Equals(other);
+    public override int GetHashCode() => StringComparer.Ordinal.GetHashCode(_value ?? string.Empty);
     public override string ToString() => "[REDACTED]";
+    public static bool operator ==(SecretFingerprint left, SecretFingerprint right) => left.Equals(right);
+    public static bool operator !=(SecretFingerprint left, SecretFingerprint right) => !left.Equals(right);
 }
 
 internal readonly record struct ObservedEndpoint
@@ -138,6 +167,7 @@ internal sealed record ListingDefinition
     public required SecretFingerprint LeaseFingerprint { get; init; }
     public required MediationHandle HostPresenceHandle { get; init; }
     public required SecretFingerprint HostPresenceFingerprint { get; init; }
+    public required string CapabilityDerivationSalt { get; init; }
 }
 
 internal sealed record StoredListing
@@ -163,12 +193,25 @@ internal sealed record RenewLeaseCommand(
     SessionListingId ListingId,
     LeaseId LeaseId,
     SecretFingerprint LeaseFingerprint,
+    string OwnerSubject,
     long ExpectedVersion);
 
+internal sealed record UpdateListingCommand(
+    SessionListingId ListingId,
+    LeaseId LeaseId,
+    SecretFingerprint LeaseFingerprint,
+    string OwnerSubject,
+    string BuildVersion,
+    string DisplayName,
+    int CurrentPlayers,
+    int MaximumPlayers,
+    IReadOnlyDictionary<string, string> Metadata);
+
 internal sealed record DeleteListingCommand(
     SessionListingId ListingId,
     LeaseId LeaseId,
-    SecretFingerprint LeaseFingerprint);
+    SecretFingerprint LeaseFingerprint,
+    string OwnerSubject);
 
 internal sealed record BindHostPresenceCommand(
     MediationHandle Handle,
@@ -265,6 +308,7 @@ internal interface IEphemeralRendezvousStore
 
     StoreResult<StoredListing> CreateListing(CreateListingCommand command, CancellationToken cancellationToken = default);
     StoreResult<StoredListing> RenewLease(RenewLeaseCommand command, CancellationToken cancellationToken = default);
+    StoreResult<StoredListing> UpdateListing(UpdateListingCommand command, CancellationToken cancellationToken = default);
     StoreResult<bool> DeleteListing(DeleteListingCommand command, CancellationToken cancellationToken = default);
     StoreResult<StoredListing> GetListing(SessionListingId listingId, bool requireFreshPresence, CancellationToken cancellationToken = default);
     StoreResult<IReadOnlyList<StoredListing>> BrowseVisibleListings(VisibleListingQuery query, CancellationToken cancellationToken = default);

src/FinalFactory.Rendezvous.Server/State/InMemoryEphemeralRendezvousStore.cs

@@ -80,7 +80,7 @@ internal sealed class InMemoryEphemeralRendezvousStore : IEphemeralRendezvousSto
             return admission;
         }
 
-        string idempotencyKey = $"listing:{command.Listing.OwnerSubject}:{command.IdempotencyKey}";
+        string idempotencyKey = $"listing:{command.Listing.Scope.GameId}:{command.Listing.Scope.EnvironmentId}:{command.Listing.OwnerSubject}:{command.IdempotencyKey}";
         if (_idempotency.TryGetValue(idempotencyKey, out IdempotencyEntry? previous))
         {
             if (!string.Equals(previous.RequestFingerprint, command.RequestFingerprint, StringComparison.Ordinal))
@@ -151,7 +151,8 @@ internal sealed class InMemoryEphemeralRendezvousStore : IEphemeralRendezvousSto
         }
 
         if (entry.Definition.LeaseId != command.LeaseId
-            || entry.Definition.LeaseFingerprint != command.LeaseFingerprint)
+            || entry.Definition.LeaseFingerprint != command.LeaseFingerprint
+            || !string.Equals(entry.Definition.OwnerSubject, command.OwnerSubject, StringComparison.Ordinal))
         {
             return new(StoreResultCode.NotFound);
         }
@@ -167,6 +168,52 @@ internal sealed class InMemoryEphemeralRendezvousStore : IEphemeralRendezvousSto
         return new(StoreResultCode.Success, Snapshot(entry));
     }, cancellationToken);
 
+    public StoreResult<StoredListing> UpdateListing(
+        UpdateListingCommand command,
+        CancellationToken cancellationToken = default) => Atomic<StoredListing>(_ =>
+    {
+        ArgumentNullException.ThrowIfNull(command);
+        ValidateSubject(command.OwnerSubject, nameof(command.OwnerSubject));
+        if (!ContractValidation.IsBuildVersionValid(command.BuildVersion)
+            || !ContractValidation.IsDisplayNameValid(command.DisplayName)
+            || command.MaximumPlayers is <= 0 or > ContractLimits.SessionCapacityMaxPlayers
+            || command.CurrentPlayers < 0
+            || command.CurrentPlayers > command.MaximumPlayers
+            || !ContractValidation.IsMetadataValid(command.Metadata))
+        {
+            throw new ArgumentException("Listing update invariants are invalid.", nameof(command));
+        }
+
+        if (!_available)
+        {
+            return new(StoreResultCode.ServiceUnavailable);
+        }
+
+        if (_drainDeadline.HasValue)
+        {
+            return new(StoreResultCode.Draining);
+        }
+
+        if (!_listings.TryGetValue(command.ListingId, out ListingEntry? entry)
+            || entry.Definition.LeaseId != command.LeaseId
+            || entry.Definition.LeaseFingerprint != command.LeaseFingerprint
+            || !string.Equals(entry.Definition.OwnerSubject, command.OwnerSubject, StringComparison.Ordinal))
+        {
+            return new(StoreResultCode.NotFound);
+        }
+
+        entry.Definition = StoredListing.Freeze(entry.Definition with
+        {
+            BuildVersion = command.BuildVersion,
+            DisplayName = command.DisplayName,
+            CurrentPlayers = command.CurrentPlayers,
+            MaximumPlayers = command.MaximumPlayers,
+            Metadata = command.Metadata,
+        });
+        entry.Version++;
+        return new(StoreResultCode.Success, Snapshot(entry));
+    }, cancellationToken);
+
     public StoreResult<bool> DeleteListing(
         DeleteListingCommand command,
         CancellationToken cancellationToken = default) => Atomic<bool>(_ =>
@@ -174,7 +221,8 @@ internal sealed class InMemoryEphemeralRendezvousStore : IEphemeralRendezvousSto
         ArgumentNullException.ThrowIfNull(command);
         if (!_listings.TryGetValue(command.ListingId, out ListingEntry? entry)
             || entry.Definition.LeaseId != command.LeaseId
-            || entry.Definition.LeaseFingerprint != command.LeaseFingerprint)
+            || entry.Definition.LeaseFingerprint != command.LeaseFingerprint
+            || !string.Equals(entry.Definition.OwnerSubject, command.OwnerSubject, StringComparison.Ordinal))
         {
             return new(StoreResultCode.NotFound);
         }
@@ -287,7 +335,7 @@ internal sealed class InMemoryEphemeralRendezvousStore : IEphemeralRendezvousSto
             return admission;
         }
 
-        string idempotencyKey = $"attempt:{command.IdempotencyOwner}:{command.IdempotencyKey}";
+        string idempotencyKey = $"attempt:{command.Scope.GameId}:{command.Scope.EnvironmentId}:{command.IdempotencyOwner}:{command.IdempotencyKey}";
         if (_idempotency.TryGetValue(idempotencyKey, out IdempotencyEntry? previous))
         {
             if (!string.Equals(previous.RequestFingerprint, command.RequestFingerprint, StringComparison.Ordinal))
@@ -699,7 +747,8 @@ internal sealed class InMemoryEphemeralRendezvousStore : IEphemeralRendezvousSto
             || listing.CurrentPlayers > listing.MaximumPlayers
             || !ContractValidation.IsMetadataValid(listing.Metadata)
             || !listing.LeaseFingerprint.IsValid
-            || !listing.HostPresenceFingerprint.IsValid)
+            || !listing.HostPresenceFingerprint.IsValid
+            || !IsDerivationSaltValid(listing.CapabilityDerivationSalt))
         {
             throw new ArgumentException("Listing invariants are invalid.", nameof(listing));
         }
@@ -753,6 +802,15 @@ internal sealed class InMemoryEphemeralRendezvousStore : IEphemeralRendezvousSto
     private static bool IsScopeValid(TenantScope scope) =>
         !string.IsNullOrEmpty(scope.GameId.Value) && !string.IsNullOrEmpty(scope.EnvironmentId.Value);
 
+    private static bool IsDerivationSaltValid(string? value) => value is not null
+        && value.Length == 43
+        && value.All(static character =>
+            character is >= 'A' and <= 'Z'
+            or >= 'a' and <= 'z'
+            or >= '0' and <= '9'
+            or '-'
+            or '_');
+
     private static void ValidateSubject(string subject, string parameterName)
     {
         if (string.IsNullOrWhiteSpace(subject) || subject.Length > 256)
@@ -767,7 +825,7 @@ internal sealed class InMemoryEphemeralRendezvousStore : IEphemeralRendezvousSto
         DateTimeOffset wallExpiresAt,
         long version)
     {
-        public ListingDefinition Definition { get; } = definition;
+        public ListingDefinition Definition { get; set; } = definition;
         public TimeSpan LeaseDeadline { get; set; } = leaseDeadline;
         public DateTimeOffset WallExpiresAt { get; set; } = wallExpiresAt;
         public long Version { get; set; } = version;