first commit

2026-06-13 23:23:50 +03:00
commit 23958e8e2c
72 changed files with 6142 additions and 0 deletions
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+namespace SequenceAuth.Lib;
+
+public record SequenceValidationResult(ValidationOutcome Outcome, Option<string> NextSequence, Option<string> UserId, Option<int> RequestsRemaining);
+
+public class SequenceManager(ISequenceStore store)
+{
+    public async Task<SequenceValidationResult> ValidateAndRotateAsync(string currentSequenceId)
+    {
+        var sequenceOpt = await store.GetSequenceAsync(currentSequenceId);
+        
+        return sequenceOpt.State switch
+        {
+            OptionState.None => new SequenceValidationResult(ValidationOutcome.SequenceNotFound, Option<string>.None(), Option<string>.None(), Option<int>.None()),
+            OptionState.Some => await ProcessSequenceAsync(currentSequenceId, sequenceOpt.Value!),
+            _ => new SequenceValidationResult(ValidationOutcome.InternalError, Option<string>.None(), Option<string>.None(), Option<int>.None())
+        };
+    }
+
+    private async Task<SequenceValidationResult> ProcessSequenceAsync(string currentSequenceId, SequenceData data)
+    {
+        return data.State switch
+        {
+            SequenceState.Compromised => new SequenceValidationResult(ValidationOutcome.CompromisedSequenceDetected, Option<string>.None(), Option<string>.None(), Option<int>.None()),
+            SequenceState.Rotated => await HandleRotatedSequenceAsync(data.UserId),
+            SequenceState.Active or SequenceState.Initialized => await HandleActiveSequenceAsync(currentSequenceId, data),
+            _ => new SequenceValidationResult(ValidationOutcome.InternalError, Option<string>.None(), Option<string>.None(), Option<int>.None())
+        };
+    }
+
+    private async Task<SequenceValidationResult> HandleRotatedSequenceAsync(string userId)
+    {
+        await store.InvalidateUserSessionsAsync(userId);
+        return new SequenceValidationResult(ValidationOutcome.CompromisedSequenceDetected, Option<string>.None(), Option<string>.None(), Option<int>.None());
+    }
+
+    private async Task<SequenceValidationResult> HandleActiveSequenceAsync(string currentSequenceId, SequenceData data)
+    {
+        var checkLimit = CheckLimit(data.RequestsRemaining);
+        return checkLimit switch
+        {
+            ValidationOutcome.LimitExceeded => new SequenceValidationResult(ValidationOutcome.LimitExceeded, Option<string>.None(), Option<string>.None(), Option<int>.None()),
+            ValidationOutcome.Success => await RotateSequenceAsync(currentSequenceId, data),
+            _ => new SequenceValidationResult(ValidationOutcome.InternalError, Option<string>.None(), Option<string>.None(), Option<int>.None())
+        };
+    }
+
+    private ValidationOutcome CheckLimit(int requestsRemaining)
+    {
+        return requestsRemaining switch
+        {
+            <= 0 => ValidationOutcome.LimitExceeded,
+            > 0 => ValidationOutcome.Success
+        };
+    }
+
+    private async Task<SequenceValidationResult> RotateSequenceAsync(string currentSequenceId, SequenceData data)
+    {
+        var futureSequenceId = Guid.NewGuid().ToString("N");
+        var oldDataRotated = data with { State = SequenceState.Rotated };
+        await store.SaveSequenceAsync(currentSequenceId, oldDataRotated);
+        
+        var newData = new SequenceData(
+            UserId: data.UserId, 
+            RequestsRemaining: data.RequestsRemaining - 1, 
+            State: SequenceState.Active, 
+            NextSequenceId: futureSequenceId);
+            
+        await store.SaveSequenceAsync(futureSequenceId, newData);
+        
+        return new SequenceValidationResult(ValidationOutcome.Success, Option<string>.Some(futureSequenceId), Option<string>.Some(data.UserId), Option<int>.Some(data.RequestsRemaining - 1));
+    }
+}