using System.Text.Json;
using System.Text.Json.Serialization;

namespace StellaOps.Bench.LinkNotMerge;

internal sealed record BenchmarkConfig(
    double? ThresholdMs,
    double? MinThroughputPerSecond,
    double? MinInsertThroughputPerSecond,
    double? MaxAllocatedMb,
    int? Iterations,
    IReadOnlyList<LinkNotMergeScenarioConfig> Scenarios)
{
    public static async Task<BenchmarkConfig> LoadAsync(string path)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(path);

        var resolved = Path.GetFullPath(path);
        if (!File.Exists(resolved))
        {
            throw new FileNotFoundException($"Benchmark configuration '{resolved}' was not found.", resolved);
        }

        await using var stream = File.OpenRead(resolved);
        var model = await JsonSerializer.DeserializeAsync<BenchmarkConfigModel>(
            stream,
            new JsonSerializerOptions(JsonSerializerDefaults.Web)
            {
                PropertyNameCaseInsensitive = true,
                ReadCommentHandling = JsonCommentHandling.Skip,
                AllowTrailingCommas = true,
            }).ConfigureAwait(false);

        if (model is null)
        {
            throw new InvalidOperationException($"Benchmark configuration '{resolved}' could not be parsed.");
        }

        if (model.Scenarios.Count == 0)
        {
            throw new InvalidOperationException($"Benchmark configuration '{resolved}' does not contain any scenarios.");
        }

        foreach (var scenario in model.Scenarios)
        {
            scenario.Validate();
        }

        return new BenchmarkConfig(
            model.ThresholdMs,
            model.MinThroughputPerSecond,
            model.MinInsertThroughputPerSecond,
            model.MaxAllocatedMb,
            model.Iterations,
            model.Scenarios);
    }

    private sealed class BenchmarkConfigModel
    {
        [JsonPropertyName("thresholdMs")]
        public double? ThresholdMs { get; init; }

        [JsonPropertyName("minThroughputPerSecond")]
        public double? MinThroughputPerSecond { get; init; }

        [JsonPropertyName("minInsertThroughputPerSecond")]
        public double? MinInsertThroughputPerSecond { get; init; }

        [JsonPropertyName("maxAllocatedMb")]
        public double? MaxAllocatedMb { get; init; }

        [JsonPropertyName("iterations")]
        public int? Iterations { get; init; }

        [JsonPropertyName("scenarios")]
        public List<LinkNotMergeScenarioConfig> Scenarios { get; init; } = new();
    }
}

internal sealed class LinkNotMergeScenarioConfig
{
    private const int DefaultObservationCount = 5_000;
    private const int DefaultAliasGroups = 500;
    private const int DefaultPurlsPerObservation = 4;
    private const int DefaultCpesPerObservation = 2;
    private const int DefaultReferencesPerObservation = 3;
    private const int DefaultTenants = 4;
    private const int DefaultBatchSize = 500;
    private const int DefaultSeed = 42_022;

    [JsonPropertyName("id")]
    public string? Id { get; init; }

    [JsonPropertyName("label")]
    public string? Label { get; init; }

    [JsonPropertyName("observations")]
    public int? Observations { get; init; }

    [JsonPropertyName("aliasGroups")]
    public int? AliasGroups { get; init; }

    [JsonPropertyName("purlsPerObservation")]
    public int? PurlsPerObservation { get; init; }

    [JsonPropertyName("cpesPerObservation")]
    public int? CpesPerObservation { get; init; }

    [JsonPropertyName("referencesPerObservation")]
    public int? ReferencesPerObservation { get; init; }

    [JsonPropertyName("tenants")]
    public int? Tenants { get; init; }

    [JsonPropertyName("batchSize")]
    public int? BatchSize { get; init; }

    [JsonPropertyName("seed")]
    public int? Seed { get; init; }

    [JsonPropertyName("iterations")]
    public int? Iterations { get; init; }

    [JsonPropertyName("thresholdMs")]
    public double? ThresholdMs { get; init; }

    [JsonPropertyName("minThroughputPerSecond")]
    public double? MinThroughputPerSecond { get; init; }

    [JsonPropertyName("minInsertThroughputPerSecond")]
    public double? MinInsertThroughputPerSecond { get; init; }

    [JsonPropertyName("maxAllocatedMb")]
    public double? MaxAllocatedMb { get; init; }

    public string ScenarioId => string.IsNullOrWhiteSpace(Id) ? "linknotmerge" : Id!.Trim();

    public string DisplayLabel => string.IsNullOrWhiteSpace(Label) ? ScenarioId : Label!.Trim();

    public int ResolveObservationCount() => Observations.HasValue && Observations.Value > 0
        ? Observations.Value
        : DefaultObservationCount;

    public int ResolveAliasGroups() => AliasGroups.HasValue && AliasGroups.Value > 0
        ? AliasGroups.Value
        : DefaultAliasGroups;

    public int ResolvePurlsPerObservation() => PurlsPerObservation.HasValue && PurlsPerObservation.Value > 0
        ? PurlsPerObservation.Value
        : DefaultPurlsPerObservation;

    public int ResolveCpesPerObservation() => CpesPerObservation.HasValue && CpesPerObservation.Value >= 0
        ? CpesPerObservation.Value
        : DefaultCpesPerObservation;

    public int ResolveReferencesPerObservation() => ReferencesPerObservation.HasValue && ReferencesPerObservation.Value >= 0
        ? ReferencesPerObservation.Value
        : DefaultReferencesPerObservation;

    public int ResolveTenantCount() => Tenants.HasValue && Tenants.Value > 0
        ? Tenants.Value
        : DefaultTenants;

    public int ResolveBatchSize() => BatchSize.HasValue && BatchSize.Value > 0
        ? BatchSize.Value
        : DefaultBatchSize;

    public int ResolveSeed() => Seed.HasValue && Seed.Value > 0
        ? Seed.Value
        : DefaultSeed;

    public int ResolveIterations(int? defaultIterations)
    {
        var iterations = Iterations ?? defaultIterations ?? 3;
        if (iterations <= 0)
        {
            throw new InvalidOperationException($"Scenario '{ScenarioId}' requires iterations > 0.");
        }

        return iterations;
    }

    public void Validate()
    {
        if (ResolveObservationCount() <= 0)
        {
            throw new InvalidOperationException($"Scenario '{ScenarioId}' requires observations > 0.");
        }

        if (ResolveAliasGroups() <= 0)
        {
            throw new InvalidOperationException($"Scenario '{ScenarioId}' requires aliasGroups > 0.");
        }

        if (ResolvePurlsPerObservation() <= 0)
        {
            throw new InvalidOperationException($"Scenario '{ScenarioId}' requires purlsPerObservation > 0.");
        }

        if (ResolveTenantCount() <= 0)
        {
            throw new InvalidOperationException($"Scenario '{ScenarioId}' requires tenants > 0.");
        }

        if (ResolveBatchSize() > ResolveObservationCount())
        {
            throw new InvalidOperationException($"Scenario '{ScenarioId}' batchSize cannot exceed observations.");
        }
    }
}