using System.Collections.Immutable;
using FluentAssertions;
using Xunit;

namespace StellaOps.BinaryIndex.GroundTruth.Abstractions.Tests;

/// <summary>
/// Unit tests for AOC (Aggregation-Only Contract) write guard invariants.
/// </summary>
public class SymbolObservationWriteGuardTests
{
    private readonly SymbolObservationWriteGuard _guard = new();

    #region ValidateWrite Tests

    [Fact]
    public void ValidateWrite_NewObservation_ReturnsProceed()
    {
        // Arrange
        var observation = CreateValidObservation();

        // Act
        var result = _guard.ValidateWrite(observation, existingContentHash: null);

        // Assert
        result.Should().Be(WriteDisposition.Proceed);
    }

    [Fact]
    public void ValidateWrite_IdenticalContentHash_ReturnsSkipIdentical()
    {
        // Arrange
        var observation = CreateValidObservation();
        var existingHash = observation.ContentHash;

        // Act
        var result = _guard.ValidateWrite(observation, existingHash);

        // Assert
        result.Should().Be(WriteDisposition.SkipIdentical);
    }

    [Fact]
    public void ValidateWrite_DifferentContentHash_ReturnsRejectMutation()
    {
        // Arrange
        var observation = CreateValidObservation();
        var existingHash = "sha256:differenthash";

        // Act
        var result = _guard.ValidateWrite(observation, existingHash);

        // Assert
        result.Should().Be(WriteDisposition.RejectMutation);
    }

    [Fact]
    public void ValidateWrite_CaseInsensitiveHashComparison_ReturnsSkipIdentical()
    {
        // Arrange
        var observation = CreateValidObservation();
        var existingHash = observation.ContentHash.ToUpperInvariant();

        // Act
        var result = _guard.ValidateWrite(observation, existingHash);

        // Assert
        result.Should().Be(WriteDisposition.SkipIdentical);
    }

    #endregion

    #region EnsureValid - Required Fields Tests

    [Fact]
    public void EnsureValid_ValidObservation_DoesNotThrow()
    {
        // Arrange
        var observation = CreateValidObservation();

        // Act & Assert
        var act = () => _guard.EnsureValid(observation);
        act.Should().NotThrow();
    }

    [Fact]
    public void EnsureValid_MissingObservationId_ThrowsWithCorrectCode()
    {
        // Arrange
        var observation = CreateValidObservation() with { ObservationId = "" };

        // Act & Assert
        var act = () => _guard.EnsureValid(observation);
        act.Should().Throw<GroundTruthAocGuardException>()
            .Where(ex => ex.Violations.Any(v => v.Code == AocViolationCodes.MissingRequiredField))
            .Where(ex => ex.Violations.Any(v => v.Path == "observationId"));
    }

    [Fact]
    public void EnsureValid_MissingSourceId_ThrowsWithCorrectCode()
    {
        // Arrange
        var observation = CreateValidObservation() with { SourceId = "" };

        // Act & Assert
        var act = () => _guard.EnsureValid(observation);
        act.Should().Throw<GroundTruthAocGuardException>()
            .Where(ex => ex.Violations.Any(v => v.Code == AocViolationCodes.MissingRequiredField))
            .Where(ex => ex.Violations.Any(v => v.Path == "sourceId"));
    }

    [Fact]
    public void EnsureValid_MissingDebugId_ThrowsWithCorrectCode()
    {
        // Arrange
        var observation = CreateValidObservation() with { DebugId = "" };

        // Act & Assert
        var act = () => _guard.EnsureValid(observation);
        act.Should().Throw<GroundTruthAocGuardException>()
            .Where(ex => ex.Violations.Any(v => v.Code == AocViolationCodes.MissingRequiredField))
            .Where(ex => ex.Violations.Any(v => v.Path == "debugId"));
    }

    [Fact]
    public void EnsureValid_MissingBinaryName_ThrowsWithCorrectCode()
    {
        // Arrange
        var observation = CreateValidObservation() with { BinaryName = "" };

        // Act & Assert
        var act = () => _guard.EnsureValid(observation);
        act.Should().Throw<GroundTruthAocGuardException>()
            .Where(ex => ex.Violations.Any(v => v.Code == AocViolationCodes.MissingRequiredField))
            .Where(ex => ex.Violations.Any(v => v.Path == "binaryName"));
    }

    [Fact]
    public void EnsureValid_MissingArchitecture_ThrowsWithCorrectCode()
    {
        // Arrange
        var observation = CreateValidObservation() with { Architecture = "" };

        // Act & Assert
        var act = () => _guard.EnsureValid(observation);
        act.Should().Throw<GroundTruthAocGuardException>()
            .Where(ex => ex.Violations.Any(v => v.Code == AocViolationCodes.MissingRequiredField))
            .Where(ex => ex.Violations.Any(v => v.Path == "architecture"));
    }

    #endregion

    #region EnsureValid - Provenance Tests (GTAOC_001)

    [Fact]
    public void EnsureValid_MissingProvenance_ThrowsWithCorrectCode()
    {
        // Arrange
        var observation = CreateValidObservation() with { Provenance = null! };

        // Act & Assert
        var act = () => _guard.EnsureValid(observation);
        act.Should().Throw<GroundTruthAocGuardException>()
            .Where(ex => ex.Violations.Any(v => v.Code == AocViolationCodes.MissingProvenance));
    }

    [Fact]
    public void EnsureValid_MissingProvenanceSourceId_ThrowsWithCorrectCode()
    {
        // Arrange
        var observation = CreateValidObservation() with
        {
            Provenance = CreateValidProvenance() with { SourceId = "" }
        };

        // Act & Assert
        var act = () => _guard.EnsureValid(observation);
        act.Should().Throw<GroundTruthAocGuardException>()
            .Where(ex => ex.Violations.Any(v => v.Code == AocViolationCodes.MissingProvenance))
            .Where(ex => ex.Violations.Any(v => v.Path == "provenance.sourceId"));
    }

    [Fact]
    public void EnsureValid_MissingProvenanceDocumentUri_ThrowsWithCorrectCode()
    {
        // Arrange
        var observation = CreateValidObservation() with
        {
            Provenance = CreateValidProvenance() with { DocumentUri = "" }
        };

        // Act & Assert
        var act = () => _guard.EnsureValid(observation);
        act.Should().Throw<GroundTruthAocGuardException>()
            .Where(ex => ex.Violations.Any(v => v.Code == AocViolationCodes.MissingProvenance))
            .Where(ex => ex.Violations.Any(v => v.Path == "provenance.documentUri"));
    }

    [Fact]
    public void EnsureValid_MissingProvenanceDocumentHash_ThrowsWithCorrectCode()
    {
        // Arrange
        var observation = CreateValidObservation() with
        {
            Provenance = CreateValidProvenance() with { DocumentHash = "" }
        };

        // Act & Assert
        var act = () => _guard.EnsureValid(observation);
        act.Should().Throw<GroundTruthAocGuardException>()
            .Where(ex => ex.Violations.Any(v => v.Code == AocViolationCodes.MissingProvenance))
            .Where(ex => ex.Violations.Any(v => v.Path == "provenance.documentHash"));
    }

    [Fact]
    public void EnsureValid_DefaultProvenanceFetchedAt_ThrowsWithCorrectCode()
    {
        // Arrange
        var observation = CreateValidObservation() with
        {
            Provenance = CreateValidProvenance() with { FetchedAt = default }
        };

        // Act & Assert
        var act = () => _guard.EnsureValid(observation);
        act.Should().Throw<GroundTruthAocGuardException>()
            .Where(ex => ex.Violations.Any(v => v.Code == AocViolationCodes.MissingProvenance))
            .Where(ex => ex.Violations.Any(v => v.Path == "provenance.fetchedAt"));
    }

    #endregion

    #region EnsureValid - Content Hash Tests (GTAOC_004)

    [Fact]
    public void EnsureValid_InvalidContentHash_ThrowsWithCorrectCode()
    {
        // Arrange
        var observation = CreateValidObservation() with
        {
            ContentHash = "sha256:invalidhash"
        };

        // Act & Assert
        var act = () => _guard.EnsureValid(observation);
        act.Should().Throw<GroundTruthAocGuardException>()
            .Where(ex => ex.Violations.Any(v => v.Code == AocViolationCodes.InvalidContentHash));
    }

    [Fact]
    public void ComputeContentHash_DeterministicForSameInput()
    {
        // Arrange
        var observation = CreateValidObservation();

        // Act
        var hash1 = SymbolObservationWriteGuard.ComputeContentHash(observation);
        var hash2 = SymbolObservationWriteGuard.ComputeContentHash(observation);

        // Assert
        hash1.Should().Be(hash2);
    }

    [Fact]
    public void ComputeContentHash_DifferentForDifferentInput()
    {
        // Arrange
        var observation1 = CreateValidObservation();
        var observation2 = CreateValidObservation() with { DebugId = "different-debug-id" };

        // Act
        var hash1 = SymbolObservationWriteGuard.ComputeContentHash(observation1);
        var hash2 = SymbolObservationWriteGuard.ComputeContentHash(observation2);

        // Assert
        hash1.Should().NotBe(hash2);
    }

    [Fact]
    public void ComputeContentHash_StartsWithSha256Prefix()
    {
        // Arrange
        var observation = CreateValidObservation();

        // Act
        var hash = SymbolObservationWriteGuard.ComputeContentHash(observation);

        // Assert
        hash.Should().StartWith("sha256:");
    }

    #endregion

    #region EnsureValid - Supersession Chain Tests (GTAOC_006)

    [Fact]
    public void EnsureValid_SupersedesItself_ThrowsWithCorrectCode()
    {
        // Arrange
        var observationId = "groundtruth:test-source:build123:1";
        var observation = CreateValidObservation() with
        {
            ObservationId = observationId,
            SupersedesId = observationId
        };

        // Act & Assert
        var act = () => _guard.EnsureValid(observation);
        act.Should().Throw<GroundTruthAocGuardException>()
            .Where(ex => ex.Violations.Any(v => v.Code == AocViolationCodes.InvalidSupersession));
    }

    [Fact]
    public void EnsureValid_ValidSupersession_DoesNotThrow()
    {
        // Arrange
        var observation = CreateValidObservation() with
        {
            ObservationId = "groundtruth:test-source:build123:2",
            SupersedesId = "groundtruth:test-source:build123:1"
        };

        // Act & Assert
        var act = () => _guard.EnsureValid(observation);
        act.Should().NotThrow();
    }

    [Fact]
    public void EnsureValid_NullSupersedes_DoesNotThrow()
    {
        // Arrange
        var observation = CreateValidObservation() with { SupersedesId = null };

        // Act & Assert
        var act = () => _guard.EnsureValid(observation);
        act.Should().NotThrow();
    }

    #endregion

    #region Multiple Violations Tests

    [Fact]
    public void EnsureValid_MultipleViolations_ReportsAll()
    {
        // Arrange
        var observation = CreateValidObservation() with
        {
            ObservationId = "",
            SourceId = "",
            DebugId = ""
        };

        // Act & Assert
        var act = () => _guard.EnsureValid(observation);
        act.Should().Throw<GroundTruthAocGuardException>()
            .Where(ex => ex.Violations.Count >= 3);
    }

    #endregion

    #region AocViolation Record Tests

    [Fact]
    public void AocViolation_RecordEquality()
    {
        // Arrange
        var v1 = new AocViolation(AocViolationCodes.MissingProvenance, "test", "path", AocViolationSeverity.Error);
        var v2 = new AocViolation(AocViolationCodes.MissingProvenance, "test", "path", AocViolationSeverity.Error);
        var v3 = new AocViolation(AocViolationCodes.MissingRequiredField, "test", "path", AocViolationSeverity.Error);

        // Assert
        v1.Should().Be(v2);
        v1.Should().NotBe(v3);
    }

    #endregion

    #region Helper Methods

    private static SymbolObservation CreateValidObservation()
    {
        var provenance = CreateValidProvenance();
        var symbols = ImmutableArray.Create(new ObservedSymbol
        {
            Name = "main",
            Address = 0x1000,
            Size = 100,
            Type = SymbolType.Function,
            Binding = SymbolBinding.Global
        });

        var baseObservation = new SymbolObservation
        {
            ObservationId = "groundtruth:test-source:abcd1234:1",
            SourceId = "test-source",
            DebugId = "abcd1234",
            BinaryName = "test.so",
            Architecture = "x86_64",
            Symbols = symbols,
            SymbolCount = 1,
            Provenance = provenance,
            ContentHash = "", // Will be computed
            CreatedAt = DateTimeOffset.UtcNow
        };

        // Compute and set the correct content hash
        var hash = SymbolObservationWriteGuard.ComputeContentHash(baseObservation);
        return baseObservation with { ContentHash = hash };
    }

    private static ObservationProvenance CreateValidProvenance()
    {
        return new ObservationProvenance
        {
            SourceId = "test-source",
            DocumentUri = "https://example.com/test.elf",
            FetchedAt = DateTimeOffset.UtcNow.AddMinutes(-5),
            RecordedAt = DateTimeOffset.UtcNow,
            DocumentHash = "sha256:abc123",
            SignatureState = SignatureState.None
        };
    }

    #endregion
}