using System.Buffers.Binary;
using System.Security.Cryptography;
using WebDrop.Core;
using WebDrop.Storage;

namespace WebDrop.Core.Tests;

public sealed class FakeClock : IClock
{
    public long NowMs { get; set; } = 1_700_000_000_000;
    public void Advance(TimeSpan span) => NowMs += (long)span.TotalMilliseconds;
}

public sealed class RecordingEvents : IChannelEvents
{
    public List<(Id16 Channel, long Seq)> Advances { get; } = [];
    public int Settings, Seats, Deleted;
    public void Advanced(Id16 channelId, long seq) { lock (Advances) Advances.Add((channelId, seq)); }
    public void SettingsChanged(Id16 channelId) => Interlocked.Increment(ref Settings);
    public void SeatsChanged(Id16 channelId) => Interlocked.Increment(ref Seats);
    public void ChannelDeleted(Id16 channelId) => Interlocked.Increment(ref Deleted);
}

/// <summary>一个频道的全部凭据,模拟客户端从 K / A 派生出的令牌。</summary>
public sealed class TestChannel(Id16 id, ChannelMode mode, byte[] read, byte[] write, byte[] owner, byte[] ownerEndpoint)
{
    public Id16 Id { get; } = id;
    public ChannelMode Mode { get; } = mode;
    public byte[] ReadToken { get; } = read;
    public byte[] WriteToken { get; } = write;
    public byte[] OwnerToken { get; } = owner;

    public Credentials Owner(byte[] endpoint) => new(Role.Owner, OwnerToken, endpoint, "owner");
    public Credentials Member(byte[] endpoint) => new(Role.Write, WriteToken, endpoint, endpoint.AsSpan().SequenceEqual(ownerEndpoint) ? "owner" : null);
    public Credentials Reader(byte[] endpoint) => new(Role.Read, ReadToken, endpoint, endpoint.AsSpan().SequenceEqual(ownerEndpoint) ? "owner" : null);
}

public sealed class TestEnv : IDisposable
{
    public string Dir { get; } = Path.Combine(Path.GetTempPath(), "webdrop-tests-" + Guid.NewGuid().ToString("N"));
    public FakeClock Clock { get; } = new();
    public RecordingEvents Events { get; } = new();
    public ServerLimits Limits { get; } = new();
    public SqliteChannelStore Store { get; }
    public DiskBlobStore Blobs { get; }
    public ChannelService Service { get; private set; }

    public TestEnv()
    {
        Directory.CreateDirectory(Dir);
        Store = new SqliteChannelStore(Path.Combine(Dir, "test.db"));
        Blobs = new DiskBlobStore(Path.Combine(Dir, "blobs"));
        Service = new ChannelService(Store, Blobs, Clock, Limits, Events);
    }

    public static byte[] Random(int n) => RandomNumberGenerator.GetBytes(n);
    public static byte[] Endpoint() => TokenHash.Compute(Random(32));
    public static Id16 NewId() => Id16.FromBytes(Random(16));

    public TestChannel Create(
        byte[] ownerEndpoint,
        ChannelMode mode = ChannelMode.Enc,
        ChannelSettings? settings = null,
        bool withWriteHash = true)
    {
        var id = NewId();
        var read = Random(32);
        var write = Random(32);
        var owner = Random(32);

        settings ??= new ChannelSettings();
        settings.Name ??= "Test space";
        Service.CreateChannel(new CreateChannelRequest
        {
            Id = id.ToBase64Url(),
            Mode = mode,
            Settings = settings,
            ReadHash = mode == ChannelMode.Enc ? Codec.Encode(TokenHash.Compute(read)) : null,
            WriteHash = withWriteHash ? Codec.Encode(TokenHash.Compute(write)) : null,
            OwnerHash = Codec.Encode(TokenHash.Compute(owner)),
        }, ownerEndpoint, "owner");

        return new TestChannel(id, mode, read, write, owner, ownerEndpoint);
    }

    /// <summary>构造一个封装。enc 模式的负载长度必须是 档位+16。</summary>
    public static byte[] Frame(Id16 item, uint index, FrameFlags flags, int payloadLength, byte fill = 0x42)
    {
        var bytes = new byte[Envelope.HeaderSize + payloadLength];
        bytes[0] = Envelope.Version;
        bytes[1] = (byte)flags;
        item.WriteTo(bytes.AsSpan(2));
        BinaryPrimitives.WriteUInt32BigEndian(bytes.AsSpan(18), index);
        BinaryPrimitives.WriteUInt32BigEndian(bytes.AsSpan(22), (uint)payloadLength);
        bytes.AsSpan(Envelope.HeaderSize).Fill(fill);
        return bytes;
    }

    public const int EncPayload = 1024 + 16;
    public const FrameFlags SmallEnc = FrameFlags.Final | FrameFlags.Enc;

    public void Dispose()
    {
        Store.Dispose();
        try { Directory.Delete(Dir, recursive: true); } catch (IOException) { }
    }
}