// -----------------------------------------------------------------------------
// GraphQueryDeterminismTests.cs
// Sprint: SPRINT_5100_0010_0002_graph_timeline_tests
// Task: GRAPH-5100-005
// Description: S1 Query determinism tests (same input → same result ordering)
// -----------------------------------------------------------------------------

using System.Security.Cryptography;
using System.Text;
using FluentAssertions;
using Microsoft.Extensions.Logging.Abstractions;
using MicrosoftOptions = Microsoft.Extensions.Options;
using StellaOps.Graph.Indexer.Storage.Postgres.Repositories;
using Xunit;

namespace StellaOps.Graph.Indexer.Storage.Postgres.Tests;

/// <summary>
/// S1 Storage Layer Tests: Query Determinism Tests
/// Task GRAPH-5100-005: Query determinism (same input → same result ordering)
/// </summary>
[Collection(GraphIndexerPostgresCollection.Name)]
public sealed class GraphQueryDeterminismTests : IAsyncLifetime
{
    private readonly GraphIndexerPostgresFixture _fixture;
    private readonly PostgresIdempotencyStore _idempotencyStore;

    public GraphQueryDeterminismTests(GraphIndexerPostgresFixture fixture)
    {
        _fixture = fixture;

        var options = fixture.Fixture.CreateOptions();
        options.SchemaName = fixture.SchemaName;
        var dataSource = new GraphIndexerDataSource(MicrosoftOptions.Options.Create(options), NullLogger<GraphIndexerDataSource>.Instance);
        _idempotencyStore = new PostgresIdempotencyStore(dataSource, NullLogger<PostgresIdempotencyStore>.Instance);
    }

    public async Task InitializeAsync()
    {
        await _fixture.TruncateAllTablesAsync();
    }

    public Task DisposeAsync() => Task.CompletedTask;

    #region Result Ordering Determinism

    [Fact]
    public async Task MultipleIdempotencyQueries_ReturnSameOrder()
    {
        // Arrange - Insert multiple tokens
        var tokens = Enumerable.Range(1, 100)
            .Select(i => $"seq-determinism-{i:D4}")
            .ToList();

        foreach (var token in tokens)
        {
            await _idempotencyStore.MarkSeenAsync(token, CancellationToken.None);
        }

        // Act - Query multiple times
        var results1 = new List<bool>();
        var results2 = new List<bool>();
        var results3 = new List<bool>();

        foreach (var token in tokens)
        {
            results1.Add(await _idempotencyStore.HasSeenAsync(token, CancellationToken.None));
        }
        foreach (var token in tokens)
        {
            results2.Add(await _idempotencyStore.HasSeenAsync(token, CancellationToken.None));
        }
        foreach (var token in tokens)
        {
            results3.Add(await _idempotencyStore.HasSeenAsync(token, CancellationToken.None));
        }

        // Assert - All results should be identical
        results1.Should().BeEquivalentTo(results2, "First and second query should return identical results");
        results2.Should().BeEquivalentTo(results3, "Second and third query should return identical results");
        results1.Should().AllBeEquivalentTo(true, "All tokens should be marked as seen");
    }

    [Fact]
    public async Task ConcurrentQueries_ProduceDeterministicResults()
    {
        // Arrange
        var token = $"seq-concurrent-{Guid.NewGuid():N}";
        await _idempotencyStore.MarkSeenAsync(token, CancellationToken.None);

        // Act - Run concurrent queries
        var tasks = Enumerable.Range(1, 50)
            .Select(_ => _idempotencyStore.HasSeenAsync(token, CancellationToken.None))
            .ToList();

        var results = await Task.WhenAll(tasks);

        // Assert - All concurrent queries should return the same result
        results.Should().AllBeEquivalentTo(true, "All concurrent queries should return identical result");
    }

    #endregion

    #region Input Stability

    [Fact]
    public async Task SameInput_ProducesSameHash()
    {
        // Arrange
        var input = "determinism-test-input";
        
        // Act
        var hash1 = ComputeHash(input);
        var hash2 = ComputeHash(input);
        var hash3 = ComputeHash(input);

        // Assert
        hash1.Should().Be(hash2, "Same input should produce same hash");
        hash2.Should().Be(hash3, "Hash should be stable across multiple computations");
    }

    [Fact]
    public async Task ShuffledInputs_ProduceSameCanonicalOrdering()
    {
        // Arrange
        var originalOrder = new[] { "node-a", "node-b", "node-c", "node-d", "node-e" };
        var shuffledOrder = new[] { "node-c", "node-a", "node-e", "node-b", "node-d" };

        // Act - Sort both to canonical order
        var canonical1 = originalOrder.OrderBy(x => x).ToList();
        var canonical2 = shuffledOrder.OrderBy(x => x).ToList();

        // Assert
        canonical1.Should().BeEquivalentTo(canonical2, options => options.WithStrictOrdering(),
            "Shuffled inputs should produce identical canonical ordering");
    }

    [Fact]
    public async Task Timestamps_DoNotAffectOrdering()
    {
        // Arrange - Insert tokens at "different" times (same logical batch)
        var tokens = Enumerable.Range(1, 10)
            .Select(i => $"seq-timestamp-{i:D3}")
            .ToList();

        // Insert in reverse order
        foreach (var token in tokens.AsEnumerable().Reverse())
        {
            await _idempotencyStore.MarkSeenAsync(token, CancellationToken.None);
        }

        // Act - Query in original order
        var results = new List<(string Token, bool Seen)>();
        foreach (var token in tokens)
        {
            results.Add((token, await _idempotencyStore.HasSeenAsync(token, CancellationToken.None)));
        }

        // Assert - All should be seen regardless of insertion order
        results.Should().AllSatisfy(r => r.Seen.Should().BeTrue());
    }

    #endregion

    #region Cross-Tenant Isolation with Determinism

    [Fact]
    public async Task CrossTenant_QueriesRemainIsolated()
    {
        // Arrange - Create tokens that could collide without tenant isolation
        var baseToken = "seq-shared-token";
        var tenant1Token = $"tenant1:{baseToken}";
        var tenant2Token = $"tenant2:{baseToken}";

        await _idempotencyStore.MarkSeenAsync(tenant1Token, CancellationToken.None);

        // Act
        var tenant1Seen = await _idempotencyStore.HasSeenAsync(tenant1Token, CancellationToken.None);
        var tenant2Seen = await _idempotencyStore.HasSeenAsync(tenant2Token, CancellationToken.None);

        // Assert
        tenant1Seen.Should().BeTrue("Tenant 1 token was marked as seen");
        tenant2Seen.Should().BeFalse("Tenant 2 token was not marked as seen");
    }

    #endregion

    #region Helpers

    private static string ComputeHash(string input)
    {
        var bytes = Encoding.UTF8.GetBytes(input);
        var hash = SHA256.HashData(bytes);
        return Convert.ToHexString(hash).ToLowerInvariant();
    }

    #endregion
}