using System.IO.Compression;
using System.Text.Json;
using Microsoft.Extensions.Logging;
using ZB.MOM.WW.CBDD.Bson;
using ZB.MOM.WW.CBDD.Core.Collections;
using ZB.MOM.WW.CBDD.Core.Compression;
using ZB.MOM.WW.CBDD.Core.Storage;

namespace ZB.MOM.WW.CBDD.Tests.Benchmark;

internal static class PerformanceGateSmoke
{
    private const int CompactionDocumentCount = 2_000;
    private const int CompressionDocumentCount = 1_500;

    /// <summary>
    /// Runs the performance gate smoke probes and writes a report.
    /// </summary>
    /// <param name="logger">The logger.</param>
    public static void Run(ILogger logger)
    {
        var compaction = RunCompactionProbe();
        var compressionOff = RunCompressionGcProbe(enableCompression: false);
        var compressionOn = RunCompressionGcProbe(enableCompression: true);

        var report = new PerformanceGateReport(
            DateTimeOffset.UtcNow,
            compaction,
            compressionOff,
            compressionOn);
        var reportPath = WriteReport(report);

        logger.LogInformation("Performance gate smoke report written to {ReportPath}", reportPath);

        Console.WriteLine("[performance_gate]");
        Console.WriteLine($"report_path={reportPath}");
        Console.WriteLine($"compaction.pre_pages={compaction.PrePages}");
        Console.WriteLine($"compaction.post_pages={compaction.PostPages}");
        Console.WriteLine($"compaction.reclaimed_file_bytes={compaction.ReclaimedFileBytes}");
        Console.WriteLine($"compaction.throughput_bytes_per_sec={compaction.ThroughputBytesPerSecond:F2}");
        Console.WriteLine($"compaction.throughput_pages_per_sec={compaction.ThroughputPagesPerSecond:F2}");
        Console.WriteLine($"compaction.throughput_docs_per_sec={compaction.ThroughputDocumentsPerSecond:F2}");
        Console.WriteLine($"compression_off.gen0_delta={compressionOff.Gen0Delta}");
        Console.WriteLine($"compression_off.gen1_delta={compressionOff.Gen1Delta}");
        Console.WriteLine($"compression_off.gen2_delta={compressionOff.Gen2Delta}");
        Console.WriteLine($"compression_off.alloc_bytes_delta={compressionOff.AllocatedBytesDelta}");
        Console.WriteLine($"compression_on.gen0_delta={compressionOn.Gen0Delta}");
        Console.WriteLine($"compression_on.gen1_delta={compressionOn.Gen1Delta}");
        Console.WriteLine($"compression_on.gen2_delta={compressionOn.Gen2Delta}");
        Console.WriteLine($"compression_on.alloc_bytes_delta={compressionOn.AllocatedBytesDelta}");
    }

    private static CompactionProbeResult RunCompactionProbe()
    {
        var dbPath = NewDbPath("gate_compaction");
        var walPath = Path.ChangeExtension(dbPath, ".wal");

        try
        {
            using var storage = new StorageEngine(dbPath, PageFileConfig.Small);
            using var transactionHolder = new BenchmarkTransactionHolder(storage);
            var collection = new DocumentCollection<Person>(storage, transactionHolder, new PersonMapper());

            var ids = new List<ObjectId>(CompactionDocumentCount);
            for (var i = 0; i < CompactionDocumentCount; i++)
            {
                ids.Add(collection.Insert(CreatePerson(i, includeLargeBio: true)));
            }

            transactionHolder.CommitAndReset();
            storage.Checkpoint();

            for (var i = 0; i < ids.Count; i += 3)
            {
                collection.Delete(ids[i]);
            }

            for (var i = 0; i < ids.Count; i += 5)
            {
                var current = collection.FindById(ids[i]);
                if (current == null)
                    continue;

                current.Bio = BuildBio(i + 10_000);
                current.Age += 1;
                collection.Update(current);
            }

            transactionHolder.CommitAndReset();
            storage.Checkpoint();

            var stats = storage.Compact(new CompactionOptions
            {
                OnlineMode = false,
                DefragmentSlottedPages = true,
                NormalizeFreeList = true,
                EnableTailTruncation = true
            });

            return new CompactionProbeResult(
                stats.PrePageCount,
                stats.PostPageCount,
                stats.ReclaimedFileBytes,
                stats.ThroughputBytesPerSecond,
                stats.ThroughputPagesPerSecond,
                stats.ThroughputDocumentsPerSecond);
        }
        finally
        {
            TryDelete(dbPath);
            TryDelete(walPath);
            TryDelete($"{dbPath}.compact.state");
            TryDelete($"{dbPath}.compact.tmp");
            TryDelete($"{dbPath}.compact.bak");
        }
    }

    private static CompressionGcProbeResult RunCompressionGcProbe(bool enableCompression)
    {
        var dbPath = NewDbPath(enableCompression ? "gate_gc_on" : "gate_gc_off");
        var walPath = Path.ChangeExtension(dbPath, ".wal");
        var compressionOptions = enableCompression
            ? new CompressionOptions
            {
                EnableCompression = true,
                MinSizeBytes = 256,
                MinSavingsPercent = 0,
                Codec = CompressionCodec.Brotli,
                Level = CompressionLevel.Fastest
            }
            : CompressionOptions.Default;

        try
        {
            using var storage = new StorageEngine(dbPath, PageFileConfig.Default, compressionOptions);
            using var transactionHolder = new BenchmarkTransactionHolder(storage);
            var collection = new DocumentCollection<Person>(storage, transactionHolder, new PersonMapper());

            GC.Collect();
            GC.WaitForPendingFinalizers();
            GC.Collect();

            var g0Before = GC.CollectionCount(0);
            var g1Before = GC.CollectionCount(1);
            var g2Before = GC.CollectionCount(2);
            var allocBefore = GC.GetTotalAllocatedBytes(true);

            var ids = new ObjectId[CompressionDocumentCount];
            for (var i = 0; i < CompressionDocumentCount; i++)
            {
                ids[i] = collection.Insert(CreatePerson(i, includeLargeBio: true));
            }

            transactionHolder.CommitAndReset();

            for (var i = 0; i < ids.Length; i += 4)
            {
                var current = collection.FindById(ids[i]);
                if (current == null)
                    continue;

                current.Bio = BuildBio(i + 20_000);
                current.Age += 1;
                collection.Update(current);
            }

            transactionHolder.CommitAndReset();

            var readCount = collection.FindAll().Count();
            transactionHolder.CommitAndReset();

            GC.Collect();
            GC.WaitForPendingFinalizers();
            GC.Collect();

            var g0After = GC.CollectionCount(0);
            var g1After = GC.CollectionCount(1);
            var g2After = GC.CollectionCount(2);
            var allocAfter = GC.GetTotalAllocatedBytes(true);

            return new CompressionGcProbeResult(
                enableCompression,
                readCount,
                g0After - g0Before,
                g1After - g1Before,
                g2After - g2Before,
                allocAfter - allocBefore);
        }
        finally
        {
            TryDelete(dbPath);
            TryDelete(walPath);
            TryDelete($"{dbPath}.compact.state");
            TryDelete($"{dbPath}.compact.tmp");
            TryDelete($"{dbPath}.compact.bak");
        }
    }

    private static string WriteReport(PerformanceGateReport report)
    {
        var outputDirectory = Path.Combine(Directory.GetCurrentDirectory(), "BenchmarkDotNet.Artifacts", "results");
        Directory.CreateDirectory(outputDirectory);

        var reportPath = Path.Combine(outputDirectory, "PerformanceGateSmoke-report.json");
        var json = JsonSerializer.Serialize(report, new JsonSerializerOptions { WriteIndented = true });
        File.WriteAllText(reportPath, json);
        return reportPath;
    }

    private static Person CreatePerson(int i, bool includeLargeBio)
    {
        return new Person
        {
            Id = ObjectId.NewObjectId(),
            FirstName = $"First_{i}",
            LastName = $"Last_{i}",
            Age = 20 + (i % 50),
            Bio = includeLargeBio ? BuildBio(i) : $"bio-{i}",
            CreatedAt = DateTime.UnixEpoch.AddMinutes(i),
            Balance = 100 + i,
            HomeAddress = new Address
            {
                Street = $"{i} Main St",
                City = "Gate City",
                ZipCode = "12345"
            },
            EmploymentHistory =
            [
                new WorkHistory
                {
                    CompanyName = $"Company_{i}",
                    Title = "Engineer",
                    DurationYears = i % 10,
                    Tags = ["csharp", "db", "compression"]
                }
            ]
        };
    }

    private static string BuildBio(int seed)
    {
        var builder = new System.Text.StringBuilder(4500);
        for (var i = 0; i < 150; i++)
        {
            builder.Append("bio-");
            builder.Append(seed.ToString("D6"));
            builder.Append('-');
            builder.Append(i.ToString("D3"));
            builder.Append('|');
        }

        return builder.ToString();
    }

    private static string NewDbPath(string prefix)
        => Path.Combine(Path.GetTempPath(), $"{prefix}_{Guid.NewGuid():N}.db");

    private static void TryDelete(string path)
    {
        if (File.Exists(path))
        {
            File.Delete(path);
        }
    }

    private sealed record PerformanceGateReport(
        DateTimeOffset CapturedAtUtc,
        CompactionProbeResult Compaction,
        CompressionGcProbeResult CompressionOff,
        CompressionGcProbeResult CompressionOn);

    private sealed record CompactionProbeResult(
        uint PrePages,
        uint PostPages,
        long ReclaimedFileBytes,
        double ThroughputBytesPerSecond,
        double ThroughputPagesPerSecond,
        double ThroughputDocumentsPerSecond);

    private sealed record CompressionGcProbeResult(
        bool CompressionEnabled,
        int ReadCount,
        int Gen0Delta,
        int Gen1Delta,
        int Gen2Delta,
        long AllocatedBytesDelta);
}