using System.Text.Json;
using System.Text.Json.Serialization;
using StellaOps.Bench.ScannerAnalyzers.Baseline;

namespace StellaOps.Bench.ScannerAnalyzers.Reporting;

internal static class BenchmarkJsonWriter
{
    private static readonly JsonSerializerOptions SerializerOptions = new(JsonSerializerDefaults.Web)
    {
        WriteIndented = true,
        DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull
    };

    public static async Task WriteAsync(
        string path,
        BenchmarkJsonMetadata metadata,
        IReadOnlyList<BenchmarkScenarioReport> reports,
        CancellationToken cancellationToken)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(path);
        ArgumentNullException.ThrowIfNull(metadata);
        ArgumentNullException.ThrowIfNull(reports);

        var resolved = Path.GetFullPath(path);
        var directory = Path.GetDirectoryName(resolved);
        if (!string.IsNullOrEmpty(directory))
        {
            Directory.CreateDirectory(directory);
        }

        var document = new BenchmarkJsonDocument(
            metadata.SchemaVersion,
            metadata.CapturedAtUtc,
            metadata.Commit,
            metadata.Environment,
            reports.Select(CreateScenario).ToArray());

        await using var stream = new FileStream(resolved, FileMode.Create, FileAccess.Write, FileShare.None);
        await JsonSerializer.SerializeAsync(stream, document, SerializerOptions, cancellationToken).ConfigureAwait(false);
        await stream.FlushAsync(cancellationToken).ConfigureAwait(false);
    }

    private static BenchmarkJsonScenario CreateScenario(BenchmarkScenarioReport report)
    {
        var baseline = report.Baseline;
        return new BenchmarkJsonScenario(
            report.Result.Id,
            report.Result.Label,
            report.Result.Iterations,
            report.Result.SampleCount,
            report.Result.MeanMs,
            report.Result.P95Ms,
            report.Result.MaxMs,
            report.Result.ThresholdMs,
            baseline is null
                ? null
                : new BenchmarkJsonScenarioBaseline(
                    baseline.Iterations,
                    baseline.SampleCount,
                    baseline.MeanMs,
                    baseline.P95Ms,
                    baseline.MaxMs),
            new BenchmarkJsonScenarioRegression(
                report.MaxRegressionRatio,
                report.MeanRegressionRatio,
                report.RegressionLimit,
                report.RegressionBreached));
    }

    private sealed record BenchmarkJsonDocument(
        string SchemaVersion,
        DateTimeOffset CapturedAt,
        string? Commit,
        string? Environment,
        IReadOnlyList<BenchmarkJsonScenario> Scenarios);

    private sealed record BenchmarkJsonScenario(
        string Id,
        string Label,
        int Iterations,
        int SampleCount,
        double MeanMs,
        double P95Ms,
        double MaxMs,
        double ThresholdMs,
        BenchmarkJsonScenarioBaseline? Baseline,
        BenchmarkJsonScenarioRegression Regression);

    private sealed record BenchmarkJsonScenarioBaseline(
        int Iterations,
        int SampleCount,
        double MeanMs,
        double P95Ms,
        double MaxMs);

    private sealed record BenchmarkJsonScenarioRegression(
        double? MaxRatio,
        double? MeanRatio,
        double Limit,
        bool Breached);
}

internal sealed record BenchmarkJsonMetadata(
    string SchemaVersion,
    DateTimeOffset CapturedAtUtc,
    string? Commit,
    string? Environment);