using System.Text;
using w4c_workflows.Services.Nodes.Binary;
using Xunit;

namespace w4c_workflows.Tests;

/// <summary>
/// Unit tests for the content-addressed filesystem binary store.
/// </summary>
public class FileSystemBinaryStoreTests
{
    private static async Task<byte[]> ReadAllAsync(Stream stream)
    {
        using var buffer = new MemoryStream();
        await stream.CopyToAsync(buffer);
        return buffer.ToArray();
    }

    [Fact]
    public async Task Save_then_open_round_trips_bytes_and_metadata()
    {
        var store = BinaryTestData.Store();
        var bytes = Encoding.UTF8.GetBytes("hello binary");

        var attachment = await store.SaveAsync(
            new MemoryStream(bytes), "greeting.txt", "text/plain");

        Assert.StartsWith("sha256:", attachment.AssetId);
        Assert.Equal("greeting.txt", attachment.FileName);
        Assert.Equal("text/plain", attachment.MimeType);
        Assert.Equal(bytes.Length, attachment.SizeBytes);

        await using var opened = await store.OpenAsync(attachment.AssetId);
        Assert.NotNull(opened);
        Assert.Equal(bytes, await ReadAllAsync(opened!));

        var described = await store.DescribeAsync(attachment.AssetId);
        Assert.Equal(attachment, described);
    }

    [Fact]
    public async Task Identical_content_is_content_addressed_to_one_asset()
    {
        var store = BinaryTestData.Store();
        var bytes = Encoding.UTF8.GetBytes("same bytes");

        var first = await store.SaveAsync(new MemoryStream(bytes), "a.bin", "application/octet-stream");
        var second = await store.SaveAsync(new MemoryStream(bytes), "b.bin", "application/octet-stream");

        Assert.Equal(first.AssetId, second.AssetId);
    }

    [Fact]
    public async Task Different_content_yields_different_assets()
    {
        var store = BinaryTestData.Store();

        var first = await store.SaveAsync(new MemoryStream([1, 2, 3]), "a.bin", null);
        var second = await store.SaveAsync(new MemoryStream([4, 5, 6]), "b.bin", null);

        Assert.NotEqual(first.AssetId, second.AssetId);
    }

    [Fact]
    public async Task Open_can_be_called_more_than_once()
    {
        var store = BinaryTestData.Store();
        var bytes = Encoding.UTF8.GetBytes("repeatable");
        var attachment = await store.SaveAsync(new MemoryStream(bytes), null, null);

        await using var first = await store.OpenAsync(attachment.AssetId);
        await using var second = await store.OpenAsync(attachment.AssetId);

        Assert.Equal(bytes, await ReadAllAsync(first!));
        Assert.Equal(bytes, await ReadAllAsync(second!));
    }

    [Theory]
    [InlineData("")]
    [InlineData("not-a-sha")]
    [InlineData("sha256:../../etc/passwd")]
    [InlineData("sha256:zzzz")]
    public async Task Malformed_ids_are_rejected(string assetId)
    {
        var store = BinaryTestData.Store();

        Assert.Null(await store.OpenAsync(assetId));
        Assert.Null(await store.DescribeAsync(assetId));
    }

    [Fact]
    public async Task Valid_but_unknown_id_returns_null()
    {
        var store = BinaryTestData.Store();
        var id = FileSystemBinaryStore.BuildAssetId(new string('a', 64));

        Assert.Null(await store.OpenAsync(id));
        Assert.Null(await store.DescribeAsync(id));
    }

    [Fact]
    public async Task Save_rejects_payload_over_the_cap()
    {
        var store = BinaryTestData.Store(o => o.MaxBytes = 3);

        await Assert.ThrowsAsync<InvalidOperationException>(() =>
            store.SaveAsync(new MemoryStream(Encoding.UTF8.GetBytes("four")), "x", null));
    }

    [Fact]
    public async Task Blank_name_and_mime_are_normalised_to_null()
    {
        var store = BinaryTestData.Store();

        var attachment = await store.SaveAsync(new MemoryStream([9]), "  ", " ");

        Assert.Null(attachment.FileName);
        Assert.Null(attachment.MimeType);
    }

    [Fact]
    public void Constructor_sweeps_stale_temp_files_and_keeps_fresh_ones()
    {
        var root = Directory.CreateTempSubdirectory("w4c-binary-sweep-").FullName;
        try
        {
            var stalePayload = Path.Combine(root, "tmp-stale");
            var staleMeta = Path.Combine(root, "ab", "deadbeef.json.tmp-stale");
            var freshPayload = Path.Combine(root, "tmp-fresh");
            Directory.CreateDirectory(Path.Combine(root, "ab"));
            File.WriteAllText(stalePayload, "x");
            File.WriteAllText(staleMeta, "x");
            File.WriteAllText(freshPayload, "x");

            var old = DateTime.UtcNow.AddHours(-12);
            File.SetLastWriteTimeUtc(stalePayload, old);
            File.SetLastWriteTimeUtc(staleMeta, old);

            // Constructing the store runs the startup sweep.
            _ = new FileSystemBinaryStore(new BinaryStoreOptions { RootPath = root });

            Assert.False(File.Exists(stalePayload));
            Assert.False(File.Exists(staleMeta));
            Assert.True(File.Exists(freshPayload));
        }
        finally
        {
            try { Directory.Delete(root, recursive: true); } catch (IOException) { }
        }
    }
}