using FluentAssertions;
using StellaOps.Policy.Engine.DeterminismGuard;
using Xunit;

namespace StellaOps.Policy.Engine.Tests.DeterminismGuard;

public sealed class DeterminismGuardTests
{
    #region ProhibitedPatternAnalyzer Tests

    [Fact]
    public void AnalyzeSource_DetectsDateTimeNow()
    {
        // Arrange
        var analyzer = new ProhibitedPatternAnalyzer();
        var source = """
            public class Test
            {
                public DateTime GetTime() => DateTime.Now;
            }
            """;

        // Act
        var result = analyzer.AnalyzeSource(source, "test.cs", DeterminismGuardOptions.Default);

        // Assert
        result.Passed.Should().BeFalse();
        result.Violations.Should().ContainSingle(v =>
            v.ViolationType == "DateTime.Now" &&
            v.Category == DeterminismViolationCategory.WallClock);
    }

    [Fact]
    public void AnalyzeSource_DetectsDateTimeUtcNow()
    {
        var analyzer = new ProhibitedPatternAnalyzer();
        var source = "var now = DateTime.UtcNow;";

        var result = analyzer.AnalyzeSource(source, "test.cs", DeterminismGuardOptions.Default);

        result.Violations.Should().ContainSingle(v =>
            v.ViolationType == "DateTime.UtcNow");
    }

    [Fact]
    public void AnalyzeSource_DetectsRandomClass()
    {
        var analyzer = new ProhibitedPatternAnalyzer();
        var source = "var rng = new Random();";

        var result = analyzer.AnalyzeSource(source, "test.cs", DeterminismGuardOptions.Default);

        result.Violations.Should().ContainSingle(v =>
            v.ViolationType == "Random" &&
            v.Category == DeterminismViolationCategory.RandomNumber);
    }

    [Fact]
    public void AnalyzeSource_DetectsGuidNewGuid()
    {
        var analyzer = new ProhibitedPatternAnalyzer();
        var source = "var id = Guid.NewGuid();";

        var result = analyzer.AnalyzeSource(source, "test.cs", DeterminismGuardOptions.Default);

        result.Violations.Should().ContainSingle(v =>
            v.ViolationType == "Guid.NewGuid" &&
            v.Category == DeterminismViolationCategory.GuidGeneration);
    }

    [Fact]
    public void AnalyzeSource_DetectsHttpClient()
    {
        var analyzer = new ProhibitedPatternAnalyzer();
        var source = "private readonly HttpClient _client = new();";

        var result = analyzer.AnalyzeSource(source, "test.cs", DeterminismGuardOptions.Default);

        result.Violations.Should().ContainSingle(v =>
            v.ViolationType == "HttpClient" &&
            v.Category == DeterminismViolationCategory.NetworkAccess &&
            v.Severity == DeterminismViolationSeverity.Critical);
    }

    [Fact]
    public void AnalyzeSource_DetectsFileOperations()
    {
        var analyzer = new ProhibitedPatternAnalyzer();
        var source = """
            var content = File.ReadAllText("test.txt");
            File.WriteAllText("out.txt", content);
            """;

        var result = analyzer.AnalyzeSource(source, "test.cs", DeterminismGuardOptions.Default);

        result.Violations.Should().HaveCount(2);
        result.Violations.Should().Contain(v => v.ViolationType == "File.Read");
        result.Violations.Should().Contain(v => v.ViolationType == "File.Write");
    }

    [Fact]
    public void AnalyzeSource_DetectsEnvironmentVariableAccess()
    {
        var analyzer = new ProhibitedPatternAnalyzer();
        var source = "var path = Environment.GetEnvironmentVariable(\"PATH\");";

        var result = analyzer.AnalyzeSource(source, "test.cs", DeterminismGuardOptions.Default);

        result.Violations.Should().ContainSingle(v =>
            v.ViolationType == "Environment.GetEnvironmentVariable");
    }

    [Fact]
    public void AnalyzeSource_IgnoresComments()
    {
        var analyzer = new ProhibitedPatternAnalyzer();
        var source = """
            // DateTime.Now is not allowed
            /* DateTime.UtcNow either */
            * Random comment
            """;

        var result = analyzer.AnalyzeSource(source, "test.cs", DeterminismGuardOptions.Default);

        result.Violations.Should().BeEmpty();
        result.Passed.Should().BeTrue();
    }

    [Fact]
    public void AnalyzeSource_RespectsExcludePatterns()
    {
        var analyzer = new ProhibitedPatternAnalyzer();
        var source = "var now = DateTime.Now;";
        var options = DeterminismGuardOptions.Default with
        {
            ExcludePatterns = ["test.cs"]
        };

        var result = analyzer.AnalyzeSource(source, "test.cs", options);

        result.Passed.Should().BeTrue();
        result.Violations.Should().BeEmpty();
    }

    [Fact]
    public void AnalyzeSource_PassesCleanCode()
    {
        var analyzer = new ProhibitedPatternAnalyzer();
        var source = """
            public class PolicyEvaluator
            {
                public bool Evaluate(PolicyContext context)
                {
                    return context.Severity.Score > 7.0m;
                }
            }
            """;

        var result = analyzer.AnalyzeSource(source, "evaluator.cs", DeterminismGuardOptions.Default);

        result.Passed.Should().BeTrue();
        result.Violations.Should().BeEmpty();
    }

    [Fact]
    public void AnalyzeSource_TracksLineNumbers()
    {
        var analyzer = new ProhibitedPatternAnalyzer();
        var source = """
            public class Test
            {
                public void Method()
                {
                    var now = DateTime.Now;
                }
            }
            """;

        var result = analyzer.AnalyzeSource(source, "test.cs", DeterminismGuardOptions.Default);

        result.Violations.Should().ContainSingle(v => v.LineNumber == 5);
    }

    [Fact]
    public void AnalyzeMultiple_AggregatesViolations()
    {
        var analyzer = new ProhibitedPatternAnalyzer();
        var sources = new[]
        {
            ("file1.cs", "var now = DateTime.Now;"),
            ("file2.cs", "var rng = new Random();"),
            ("file3.cs", "var id = Guid.NewGuid();")
        };

        var result = analyzer.AnalyzeMultiple(
            sources.Select(s => (s.Item2, s.Item1)),
            DeterminismGuardOptions.Default);

        result.Violations.Should().HaveCount(3);
        result.Violations.Select(v => v.SourceFile).Should()
            .BeEquivalentTo(["file1.cs", "file2.cs", "file3.cs"]);
    }

    #endregion

    #region DeterminismGuardService Tests

    [Fact]
    public void CreateScope_ReturnsFixedTimestamp()
    {
        var guard = new DeterminismGuardService();
        var timestamp = new DateTimeOffset(2025, 1, 15, 12, 0, 0, TimeSpan.Zero);

        using var scope = guard.CreateScope("test-scope", timestamp);

        scope.GetTimestamp().Should().Be(timestamp);
        scope.EvaluationTimestamp.Should().Be(timestamp);
    }

    [Fact]
    public void CreateScope_TracksViolations()
    {
        var guard = new DeterminismGuardService();
        using var scope = guard.CreateScope("test-scope", DateTimeOffset.UtcNow);

        var violation = new DeterminismViolation
        {
            Category = DeterminismViolationCategory.WallClock,
            ViolationType = "Test",
            Message = "Test violation",
            Severity = DeterminismViolationSeverity.Warning
        };

        scope.ReportViolation(violation);

        scope.GetViolations().Should().ContainSingle(v => v.Message == "Test violation");
    }

    [Fact]
    public void CreateScope_ThrowsOnBlockingViolationWhenEnforcementEnabled()
    {
        var options = new DeterminismGuardOptions
        {
            EnforcementEnabled = true,
            FailOnSeverity = DeterminismViolationSeverity.Error
        };
        var guard = new DeterminismGuardService(options);
        using var scope = guard.CreateScope("test-scope", DateTimeOffset.UtcNow);

        var violation = new DeterminismViolation
        {
            Category = DeterminismViolationCategory.WallClock,
            ViolationType = "Test",
            Message = "Blocking violation",
            Severity = DeterminismViolationSeverity.Error
        };

        var act = () => scope.ReportViolation(violation);

        act.Should().Throw<DeterminismViolationException>()
            .Which.Violation.Should().Be(violation);
    }

    [Fact]
    public void CreateScope_DoesNotThrowWhenEnforcementDisabled()
    {
        var options = new DeterminismGuardOptions
        {
            EnforcementEnabled = false
        };
        var guard = new DeterminismGuardService(options);
        using var scope = guard.CreateScope("test-scope", DateTimeOffset.UtcNow);

        var violation = new DeterminismViolation
        {
            Category = DeterminismViolationCategory.WallClock,
            ViolationType = "Test",
            Message = "Should not throw",
            Severity = DeterminismViolationSeverity.Critical
        };

        var act = () => scope.ReportViolation(violation);

        act.Should().NotThrow();
    }

    [Fact]
    public void Complete_ReturnsAnalysisResult()
    {
        var guard = new DeterminismGuardService();
        using var scope = guard.CreateScope("test-scope", DateTimeOffset.UtcNow);

        scope.ReportViolation(new DeterminismViolation
        {
            Category = DeterminismViolationCategory.RandomNumber,
            ViolationType = "Test",
            Message = "Warning violation",
            Severity = DeterminismViolationSeverity.Warning
        });

        var result = scope.Complete();

        result.Passed.Should().BeTrue(); // Only warnings, no errors
        result.Violations.Should().HaveCount(1);
        result.CountBySeverity.Should().ContainKey(DeterminismViolationSeverity.Warning);
    }

    #endregion

    #region DeterministicTimeProvider Tests

    [Fact]
    public void DeterministicTimeProvider_ReturnsFixedTimestamp()
    {
        var fixedTime = new DateTimeOffset(2025, 6, 15, 10, 30, 0, TimeSpan.Zero);
        var provider = new DeterministicTimeProvider(fixedTime);

        provider.GetUtcNow().Should().Be(fixedTime);
        provider.GetUtcNow().Should().Be(fixedTime); // Same value on repeated calls
    }

    [Fact]
    public void DeterministicTimeProvider_ReturnsUtcTimeZone()
    {
        var provider = new DeterministicTimeProvider(DateTimeOffset.UtcNow);

        provider.LocalTimeZone.Should().Be(TimeZoneInfo.Utc);
    }

    #endregion

    #region GuardedPolicyEvaluator Tests

    [Fact]
    public void Evaluate_ReturnsResultWithViolations()
    {
        var evaluator = new GuardedPolicyEvaluator();
        var timestamp = DateTimeOffset.UtcNow;

        var result = evaluator.Evaluate("test-scope", timestamp, scope =>
        {
            scope.ReportViolation(new DeterminismViolation
            {
                Category = DeterminismViolationCategory.WallClock,
                ViolationType = "Test",
                Message = "Test warning",
                Severity = DeterminismViolationSeverity.Warning
            });
            return 42;
        });

        result.Succeeded.Should().BeTrue();
        result.Result.Should().Be(42);
        result.HasViolations.Should().BeTrue();
        result.Violations.Should().HaveCount(1);
    }

    [Fact]
    public void Evaluate_CapturesBlockingViolation()
    {
        var options = new DeterminismGuardOptions
        {
            EnforcementEnabled = true,
            FailOnSeverity = DeterminismViolationSeverity.Error
        };
        var evaluator = new GuardedPolicyEvaluator(options);

        var result = evaluator.Evaluate("test-scope", DateTimeOffset.UtcNow, scope =>
        {
            scope.ReportViolation(new DeterminismViolation
            {
                Category = DeterminismViolationCategory.NetworkAccess,
                ViolationType = "HttpClient",
                Message = "Network access blocked",
                Severity = DeterminismViolationSeverity.Critical
            });
            return "should not return";
        });

        result.Succeeded.Should().BeFalse();
        result.WasBlocked.Should().BeTrue();
        result.BlockingViolation.Should().NotBeNull();
    }

    [Fact]
    public void ValidatePolicySource_ReturnsViolations()
    {
        var evaluator = new GuardedPolicyEvaluator();
        var source = "var now = DateTime.Now;";

        var result = evaluator.ValidatePolicySource(source, "policy.cs");

        result.Violations.Should().ContainSingle();
    }

    [Fact]
    public async Task EvaluateAsync_WorksWithAsyncCode()
    {
        var evaluator = new GuardedPolicyEvaluator();

        var result = await evaluator.EvaluateAsync("async-scope", DateTimeOffset.UtcNow, async scope =>
        {
            await Task.Delay(1);
            return "async result";
        });

        result.Succeeded.Should().BeTrue();
        result.Result.Should().Be("async result");
    }

    #endregion

    #region DeterminismGuardOptions Tests

    [Fact]
    public void Default_HasEnforcementEnabled()
    {
        DeterminismGuardOptions.Default.EnforcementEnabled.Should().BeTrue();
        DeterminismGuardOptions.Default.FailOnSeverity.Should().Be(DeterminismViolationSeverity.Error);
    }

    [Fact]
    public void Development_HasEnforcementDisabled()
    {
        DeterminismGuardOptions.Development.EnforcementEnabled.Should().BeFalse();
        DeterminismGuardOptions.Development.FailOnSeverity.Should().Be(DeterminismViolationSeverity.Critical);
    }

    #endregion
}