namespace WebDrop.Core;

public interface IClock
{
    long NowMs { get; }
}

public sealed class SystemClock : IClock
{
    public long NowMs => DateTimeOffset.UtcNow.ToUnixTimeMilliseconds();
}

/// <summary>大帧的字节存储。键由服务生成,实现不得解析。</summary>
public interface IBlobStore
{
    ValueTask PutAsync(string key, ReadOnlyMemory<byte> data, CancellationToken ct = default);
    ValueTask<byte[]?> ReadAsync(string key, CancellationToken ct = default);
    void Delete(string key);
    void DeletePrefix(string prefix);
    IEnumerable<(string Key, DateTimeOffset LastWrite)> Enumerate();
}

/// <summary>
/// 创建频道前的人机/滥用校验(Cap 的 PoW 验证码)。验证码本身不属于本项目:
/// 校验失败抛 CaptchaRequired,验证服务不可用抛 CaptchaUnavailable(两者对用户的含义不同)。
/// </summary>
public interface ICaptchaVerifier
{
    bool Enabled { get; }
    Task VerifyAsync(string? token, CancellationToken ct);
}

/// <summary>不启用验证码(开发和小型自托管)。</summary>
public sealed class NullCaptchaVerifier : ICaptchaVerifier
{
    public bool Enabled => false;
    public Task VerifyAsync(string? token, CancellationToken ct) => Task.CompletedTask;
}

/// <summary>服务提交后发出的通知,传输层据此唤醒订阅者。</summary>
public interface IChannelEvents
{
    void Advanced(Id16 channelId, long seq);
    void SettingsChanged(Id16 channelId);
    void SeatsChanged(Id16 channelId);
    void ChannelDeleted(Id16 channelId);
}

public sealed class NullChannelEvents : IChannelEvents
{
    public void Advanced(Id16 channelId, long seq) { }
    public void SettingsChanged(Id16 channelId) { }
    public void SeatsChanged(Id16 channelId) { }
    public void ChannelDeleted(Id16 channelId) { }
}

/// <summary>频道和分享资源共用的读写事务入口。Write 串行执行,抛出异常即回滚。</summary>
public interface IResourceStore
{
    T Read<T>(Func<IResourceTx, T> action);
    T Write<T>(Func<IResourceTx, T> action);
}

/// <summary>单个数据库事务内的频道、分享与帧操作。</summary>
public interface IResourceTx
{
    // 便捷分享
    Share? GetShare(Id16 id);
    void InsertShare(Share share);
    void UpdateShare(Share share);
    IReadOnlyList<Id16> ListExpiredShares(long now, int limit);
    bool HasResourceId(Id16 id);
    int CountShareVisitors(Id16 id);
    bool HasShareVisitor(Id16 id, ReadOnlySpan<byte> endpointHash);
    void InsertShareVisitor(Id16 id, ReadOnlySpan<byte> endpointHash, long joinedAt);
    void DeleteShareRows(Id16 id);
    IReadOnlyList<ShareItem> ListShareItems(Id16 id);
    int CountShareItems(Id16 id);
    void AddShareBytes(Id16 id, long delta);
    IReadOnlyList<ShareItem> ListExpiredShareItems(long now, int limit);
    ShareItem? GetShareItem(Id16 shareId, Id16 itemId);
    void InsertShareItem(ShareItem item);
    void UpdateShareItem(ShareItem item);
    void DeleteShareItemRows(Id16 shareId, Id16 itemId);
    bool HasDownloadGrant(Id16 resourceId, Id16 itemId, ReadOnlySpan<byte> endpointHash);
    void AddDownloadGrant(Id16 resourceId, Id16 itemId, ReadOnlySpan<byte> endpointHash);
    ShareFrame? GetShareFrame(Id16 shareId, Id16 itemId, uint index);
    void InsertShareFrame(ShareFrame frame);
    IReadOnlyList<ShareFrame> ListShareFrames(Id16 shareId, Id16 itemId, uint fromIndex, int limit);

    // 频道
    Channel? GetChannel(Id16 id);
    void InsertChannel(Channel channel);
    void UpdateChannel(Id16 id, ChannelSettings settings, long expiresAt);
    void TouchChannel(Id16 id, long expiresAt);
    void AddChannelBytes(Id16 id, long delta);
    void SetCompactedThrough(Id16 id, long seq);
    long NextSeq(Id16 id);
    void DeleteChannelRows(Id16 id);
    IReadOnlyList<Id16> ListExpiredChannels(long now, int limit);

    // 席位
    Seat? GetSeat(Id16 channelId, ReadOnlySpan<byte> endpointHash);
    int CountSeats(Id16 channelId);
    void InsertSeat(Id16 channelId, Seat seat);
    bool DeleteSeat(Id16 channelId, ReadOnlySpan<byte> endpointHash);
    void SetSeatLabel(Id16 channelId, ReadOnlySpan<byte> endpointHash, byte[] label);
    IReadOnlyList<Seat> ListSeats(Id16 channelId);

    // 条目
    Item? GetItem(Id16 channelId, Id16 itemId);
    void InsertItem(Item item);
    void UpdateItem(Item item);
    void DeleteItemRows(Id16 channelId, Id16 itemId);
    int CountItems(Id16 channelId);
    IReadOnlyList<Item> ListOldestItems(Id16 channelId, int limit);
    Item? FindSnapshotItem(Id16 channelId, Id16 excludeItemId);
    IReadOnlyList<Item> ListExpiredItems(long now, int limit);

    // 帧
    StoredFrame? GetFrame(Id16 channelId, Id16 itemId, uint index);
    void InsertFrame(StoredFrame frame);
    IReadOnlyList<StoredFrame> ListFrames(Id16 channelId, Id16 itemId, uint fromIndex, int limit);
    bool BlobKeyExists(string blobKey);

    // 日志
    void InsertLog(Id16 channelId, LogEntry entry);
    IReadOnlyList<LogEntry> ReadLog(Id16 channelId, long fromSeq, int limit);
    long PruneTombstones(Id16 channelId, long olderThanMs);
}