// Reference: golang/nats-server/server/filestore_test.go
// Tests ported from: TestFileStorePurge, TestFileStoreCompact,
//                    TestFileStoreCompactLastPlusOne, TestFileStoreCompactMsgCountBug,
//                    TestFileStorePurgeExWithSubject, TestFileStorePurgeExKeepOneBug,
//                    TestFileStorePurgeExNoTombsOnBlockRemoval,
//                    TestFileStoreStreamTruncate

using System.Text;
using NATS.Server.JetStream.Storage;

namespace NATS.Server.Tests.JetStream.Storage;

public sealed class FileStorePurgeTests : IDisposable
{
    private readonly string _dir;

    public FileStorePurgeTests()
    {
        _dir = Path.Combine(Path.GetTempPath(), $"nats-js-fs-purge-{Guid.NewGuid():N}");
        Directory.CreateDirectory(_dir);
    }

    public void Dispose()
    {
        if (Directory.Exists(_dir))
            Directory.Delete(_dir, recursive: true);
    }

    private FileStore CreateStore(string subdirectory, FileStoreOptions? options = null)
    {
        var dir = Path.Combine(_dir, subdirectory);
        var opts = options ?? new FileStoreOptions();
        opts.Directory = dir;
        return new FileStore(opts);
    }

    // Go: TestFileStorePurge server/filestore_test.go:709
    [Fact]
    public async Task Purge_removes_all_messages()
    {
        await using var store = CreateStore("purge-all");

        for (var i = 0; i < 100; i++)
            await store.AppendAsync("foo", new byte[128], default);

        (await store.GetStateAsync(default)).Messages.ShouldBe((ulong)100);

        await store.PurgeAsync(default);

        var state = await store.GetStateAsync(default);
        state.Messages.ShouldBe((ulong)0);
        state.Bytes.ShouldBe((ulong)0);
    }

    // Go: TestFileStorePurge server/filestore_test.go:740
    [Fact]
    public async Task Purge_recovers_same_state_after_restart()
    {
        var subDir = "purge-restart";

        await using (var store = CreateStore(subDir))
        {
            for (var i = 0; i < 50; i++)
                await store.AppendAsync("foo", "Hello"u8.ToArray(), default);

            await store.PurgeAsync(default);
        }

        await using (var store = CreateStore(subDir))
        {
            var state = await store.GetStateAsync(default);
            state.Messages.ShouldBe((ulong)0);
            state.Bytes.ShouldBe((ulong)0);
        }
    }

    // Go: TestFileStorePurge server/filestore_test.go:776
    [Fact]
    public async Task Store_after_purge_works()
    {
        await using var store = CreateStore("purge-then-store");

        for (var i = 0; i < 20; i++)
            await store.AppendAsync("foo", "Hello"u8.ToArray(), default);

        await store.PurgeAsync(default);

        // New messages after purge.
        for (var i = 0; i < 10; i++)
        {
            var seq = await store.AppendAsync("foo", "After purge"u8.ToArray(), default);
            seq.ShouldBeGreaterThan((ulong)0);
        }

        var state = await store.GetStateAsync(default);
        state.Messages.ShouldBe((ulong)10);
    }

    // Go: TestFileStoreCompact server/filestore_test.go:822
    [Fact(Skip = "Compact not yet implemented in .NET FileStore")]
    public async Task Compact_removes_messages_below_sequence()
    {
        await Task.CompletedTask;
    }

    // Go: TestFileStoreCompact server/filestore_test.go:851
    [Fact(Skip = "Compact not yet implemented in .NET FileStore")]
    public async Task Compact_beyond_last_seq_resets_first()
    {
        await Task.CompletedTask;
    }

    // Go: TestFileStoreCompact server/filestore_test.go:862
    [Fact(Skip = "Compact not yet implemented in .NET FileStore")]
    public async Task Compact_recovers_after_restart()
    {
        await Task.CompletedTask;
    }

    // Go: TestFileStoreCompactLastPlusOne server/filestore_test.go:875
    [Fact(Skip = "Compact not yet implemented in .NET FileStore")]
    public async Task Compact_last_plus_one_clears_all()
    {
        await Task.CompletedTask;
    }

    // Go: TestFileStoreCompactMsgCountBug server/filestore_test.go:916
    [Fact(Skip = "Compact not yet implemented in .NET FileStore")]
    public async Task Compact_with_prior_deletes_counts_correctly()
    {
        await Task.CompletedTask;
    }

    // Go: TestFileStoreStreamTruncate server/filestore_test.go:991
    [Fact(Skip = "Truncate not yet implemented in .NET FileStore")]
    public async Task Truncate_removes_messages_after_sequence()
    {
        await Task.CompletedTask;
    }

    // Go: TestFileStoreStreamTruncate server/filestore_test.go:1025
    [Fact(Skip = "Truncate not yet implemented in .NET FileStore")]
    public async Task Truncate_with_interior_deletes()
    {
        await Task.CompletedTask;
    }

    // Go: TestFileStorePurgeExWithSubject server/filestore_test.go:3743
    [Fact(Skip = "PurgeEx not yet implemented in .NET FileStore")]
    public async Task PurgeEx_with_subject_removes_matching()
    {
        await Task.CompletedTask;
    }

    // Go: TestFileStorePurgeExKeepOneBug server/filestore_test.go:3382
    [Fact(Skip = "PurgeEx not yet implemented in .NET FileStore")]
    public async Task PurgeEx_keep_one_preserves_last()
    {
        await Task.CompletedTask;
    }

    // Go: TestFileStorePurgeExNoTombsOnBlockRemoval server/filestore_test.go:3823
    [Fact(Skip = "PurgeEx not yet implemented in .NET FileStore")]
    public async Task PurgeEx_no_tombstones_on_block_removal()
    {
        await Task.CompletedTask;
    }

    // Go: TestFileStorePurge server/filestore_test.go:709
    [Fact]
    public async Task Purge_then_list_returns_empty()
    {
        await using var store = CreateStore("purge-list");

        for (var i = 0; i < 10; i++)
            await store.AppendAsync("foo", "data"u8.ToArray(), default);

        await store.PurgeAsync(default);

        var messages = await store.ListAsync(default);
        messages.Count.ShouldBe(0);
    }

    // Go: TestFileStorePurge server/filestore_test.go:709
    [Fact]
    public async Task Multiple_purges_are_safe()
    {
        await using var store = CreateStore("multi-purge");

        for (var i = 0; i < 5; i++)
            await store.AppendAsync("foo", "data"u8.ToArray(), default);

        await store.PurgeAsync(default);
        await store.PurgeAsync(default); // Double purge should not error.

        (await store.GetStateAsync(default)).Messages.ShouldBe((ulong)0);
    }

    // Go: TestFileStorePurge server/filestore_test.go:709
    [Fact]
    public async Task Purge_empty_store_is_safe()
    {
        await using var store = CreateStore("purge-empty");

        await store.PurgeAsync(default);

        (await store.GetStateAsync(default)).Messages.ShouldBe((ulong)0);
    }

    // Go: TestFileStorePurge server/filestore_test.go:709
    [Fact]
    public async Task Purge_with_prior_removes()
    {
        await using var store = CreateStore("purge-prior-rm");

        for (var i = 0; i < 10; i++)
            await store.AppendAsync("foo", "data"u8.ToArray(), default);

        // Remove some messages first.
        await store.RemoveAsync(2, default);
        await store.RemoveAsync(4, default);
        await store.RemoveAsync(6, default);

        (await store.GetStateAsync(default)).Messages.ShouldBe((ulong)7);

        await store.PurgeAsync(default);

        var state = await store.GetStateAsync(default);
        state.Messages.ShouldBe((ulong)0);
        state.Bytes.ShouldBe((ulong)0);
    }

    // Go: TestFileStorePurge server/filestore_test.go:776
    [Fact]
    public async Task Purge_then_store_then_purge_again()
    {
        await using var store = CreateStore("purge-cycle");

        for (var i = 0; i < 5; i++)
            await store.AppendAsync("foo", "data"u8.ToArray(), default);

        await store.PurgeAsync(default);

        for (var i = 0; i < 3; i++)
            await store.AppendAsync("foo", "new data"u8.ToArray(), default);

        (await store.GetStateAsync(default)).Messages.ShouldBe((ulong)3);

        await store.PurgeAsync(default);
        (await store.GetStateAsync(default)).Messages.ShouldBe((ulong)0);
    }

    // Go: TestFileStorePurge server/filestore_test.go:709
    [Fact]
    public async Task Purge_data_file_is_deleted()
    {
        var subDir = "purge-file";
        var dir = Path.Combine(_dir, subDir);

        await using (var store = CreateStore(subDir))
        {
            for (var i = 0; i < 10; i++)
                await store.AppendAsync("foo", "data"u8.ToArray(), default);

            await store.PurgeAsync(default);
        }

        // The data file should be cleaned up or empty after purge.
        var dataFile = Path.Combine(dir, "messages.jsonl");
        if (File.Exists(dataFile))
        {
            var content = File.ReadAllText(dataFile);
            content.Trim().ShouldBeEmpty();
        }
    }
}