using System.Globalization;
using System.Text.Json;
using Npgsql;
using Xunit.Abstractions;

namespace MeterVault.Integration.Tests.Performance;

/// <summary>
/// Loads the synthetic raw dataset into a database an app has already migrated — the pre-rework app (c0f52db) or the
/// current one — for the page-level before/after comparison (brief §9.10). Nothing derived is written: the next start
/// of that app rebuilds consumption (and, in the new app, rollups and coverage) itself, because the load clears the
/// stored normalization revision. Writes <c>manifest-&lt;label&gt;.json</c> with the meter and type ids the page
/// timings address.
/// </summary>
/// <remarks>
/// <c>METERVAULT_PERF=1 METERVAULT_PERF_LOAD_DB="Host=…;Port=…;Database=metervault;Username=metervault;Password=metervault"
/// dotnet test tests/Integration.Tests --filter "FullyQualifiedName~Performance.SyntheticLoadTests"</c>. The dataset ends at
/// <c>METERVAULT_PERF_NOW</c>, or at the current time, so the pages see recent live data.
/// </remarks>
[Trait("Category", "Performance")]
public sealed class SyntheticLoadTests(ITestOutputHelper output)
{
    [PerfLoadFact]
    public async Task Load_the_synthetic_dataset_into_an_app_migrated_database()
    {
        var settings = PerfSettings.Current;
        using var log = new PerfLog(settings, "load", output);
        var target = settings.LoadDatabase!;

        await using (var connection = new NpgsqlConnection(target))
        {
            await connection.OpenAsync();
            var migrated = await PerfDatabase.ScalarAsync(connection, "SELECT to_regclass('meter') IS NOT NULL AND to_regclass('app_setting') IS NOT NULL");
            Assert.True(migrated is true, "The target database is not migrated: start the app against it once first.");
            var schema = await PerfDatabase.ScalarAsync(connection, "SELECT to_regclass('consumption_rollup') IS NOT NULL") is true ? "analysis rework" : "pre-rework (c0f52db)";
            log.Write($"Target schema: {schema}");
        }

        // The current minute, so the hourly live meters end just before the pages are timed.
        var now = settings.Now ?? DateTimeOffset.UtcNow.AddSeconds(-DateTimeOffset.UtcNow.Second);
        var zone = TimeZoneInfo.FindSystemTimeZoneById("Europe/Berlin");
        var manifest = await SyntheticDataset.LoadAsync(target, now, zone, settings.Scale, log.Write);

        Directory.CreateDirectory(settings.OutputDirectory);
        var path = Path.Combine(settings.OutputDirectory, $"manifest-{settings.Label}.json");
        await File.WriteAllTextAsync(path, JsonSerializer.Serialize(manifest, DatasetManifest.Json));
        log.Write(string.Create(CultureInfo.InvariantCulture, $"Loaded {manifest.MeterCount} meters and {manifest.Readings:N0} readings; manifest {path}"));
    }
}