using System.Collections.Generic;
using System.Diagnostics.Metrics;
using FluentAssertions;
using StellaOps.TestKit.Observability;
using Xunit;

namespace StellaOps.TestKit.Tests;

public sealed partial class ObservabilityContractTests
{
    [Fact]
    public void MetricExists_Present_NoException()
    {
        using var meter = new Meter("TestMeter1");
        using var capture = new MetricsCapture("TestMeter1");

        var counter = meter.CreateCounter<long>("test_requests_total");
        counter.Add(1);

        var act = () => MetricsContractAssert.MetricExists(capture, "test_requests_total");

        act.Should().NotThrow();
    }

    [Fact]
    public void MetricExists_Missing_ThrowsContractViolation()
    {
        using var meter = new Meter("TestMeter2");
        using var capture = new MetricsCapture("TestMeter2");

        var counter = meter.CreateCounter<long>("some_other_metric");
        counter.Add(1);

        var act = () => MetricsContractAssert.MetricExists(capture, "missing_metric");

        act.Should().Throw<ContractViolationException>()
            .WithMessage("*missing_metric*not found*");
    }

    [Fact]
    public void LabelCardinalityBounded_WithinThreshold_NoException()
    {
        using var meter = new Meter("TestMeter3");
        using var capture = new MetricsCapture("TestMeter3");

        var counter = meter.CreateCounter<long>("http_requests_total");
        counter.Add(1, new KeyValuePair<string, object?>("method", "GET"));
        counter.Add(1, new KeyValuePair<string, object?>("method", "POST"));

        var act = () => MetricsContractAssert.LabelCardinalityBounded(
            capture,
            "http_requests_total",
            maxLabels: 10);

        act.Should().NotThrow();
    }

    [Fact]
    public void LabelCardinalityBounded_ExceedsThreshold_ThrowsContractViolation()
    {
        using var meter = new Meter("TestMeter4");
        using var capture = new MetricsCapture("TestMeter4");

        var counter = meter.CreateCounter<long>("requests_by_user");

        for (int i = 0; i < 10; i++)
        {
            counter.Add(1, new KeyValuePair<string, object?>("user_id", $"user-{i}"));
        }

        var act = () => MetricsContractAssert.LabelCardinalityBounded(
            capture,
            "requests_by_user",
            maxLabels: 5);

        act.Should().Throw<ContractViolationException>()
            .WithMessage("*cardinality*exceeds*");
    }
}