namespace SQLInsight.Core.Data;

/// <summary>
/// Sessions that were blocked, and the sessions blocking them, at the moment of collection.
/// </summary>
public sealed record BlockingSnapshot
{
    public required DateTimeOffset CapturedAt { get; init; }
    public required IReadOnlyList<SessionInfo> Sessions { get; init; }

    /// <summary>Sessions that block others without being blocked themselves.</summary>
    public IEnumerable<SessionInfo> HeadBlockers
    {
        get
        {
            var blocked = Sessions.Where(s => s.BlockingSessionId is > 0).Select(s => s.SessionId).ToHashSet();
            var blockers = Sessions.Where(s => s.BlockingSessionId is > 0).Select(s => s.BlockingSessionId!.Value).ToHashSet();
            return Sessions.Where(s => blockers.Contains(s.SessionId) && !blocked.Contains(s.SessionId));
        }
    }

    public IEnumerable<SessionInfo> BlockedBy(int sessionId) => Sessions.Where(s => s.BlockingSessionId == sessionId);
}

public sealed record SessionInfo
{
    public required int SessionId { get; init; }

    /// <summary>The session this one is waiting on, or <see langword="null"/>.</summary>
    public int? BlockingSessionId { get; init; }

    /// <summary>running, runnable, suspended, sleeping …</summary>
    public string? Status { get; init; }

    public string? WaitType { get; init; }
    public long? WaitTimeMs { get; init; }
    public string? WaitResource { get; init; }
    public string? DatabaseName { get; init; }
    public string? LoginName { get; init; }
    public string? HostName { get; init; }
    public string? ProgramName { get; init; }
    public int OpenTransactionCount { get; init; }

    /// <summary>The current or last statement, truncated. Never includes parameter values.</summary>
    public string? SqlText { get; init; }

    public DateTime? LastRequestEndTime { get; init; }
}