nucleic-windows/NucleicApp/ViewModels/SessionDetailViewModel.cs

using System.ComponentModel;
using System.Text.Json;
using NucleicApp.Services;
using NucleicProtocol.Interop;

namespace NucleicApp.ViewModels;

/// Presentation and intent surface for one session detail screen. Transcript rows remain owned
/// by the shared Swift projector; this model forwards only that session's splice diffs.
public sealed class SessionDetailViewModel : ViewModelBase, IDisposable
{
    private readonly RendererStore store;
    private readonly HostConnection connection;
    private ProjectionDiff? lastProjection;
    private bool active;
    private bool disposed;

    public SessionDetailViewModel(
        string sessionId, RendererStore store, HostConnection connection)
    {
        SessionId = sessionId;
        this.store = store;
        this.connection = connection;
        store.PropertyChanged += StoreChanged;
        store.ProjectionChanged += ProjectionChanged;
    }

    public string SessionId { get; }
    public SessionSummary? Session => store.Sessions.FirstOrDefault(item => item.Id == SessionId);
    public IReadOnlyList<ApprovalRequest> PendingApprovals => store.PendingApprovals
        .Where(item => item.SessionId == SessionId).ToArray();
    public ProjectionDiff? LastProjection
    {
        get => lastProjection;
        private set => Set(ref lastProjection, value);
    }

    public ProtocolResult Activate(ulong? sinceSequence = null)
    {
        ObjectDisposedException.ThrowIf(disposed, this);
        if (active) return ProtocolResult.Ok;
        var result = connection.SendIntent(ClientIntents.Subscribe(SessionId, sinceSequence));
        if (result == ProtocolResult.Ok) active = true;
        return result;
    }

    public ProtocolResult SendText(string text)
    {
        ObjectDisposedException.ThrowIf(disposed, this);
        if (string.IsNullOrWhiteSpace(text)) return ProtocolResult.InvalidArgument;
        return connection.SendIntent(ClientIntents.SendInput(SessionId, text));
    }

    public ProtocolResult Allow(ApprovalRequest approval, JsonElement? updatedInput = null) =>
        Respond(approval, ClientIntents.ApprovalAllow(approval.Id, updatedInput));

    public ProtocolResult Deny(ApprovalRequest approval, string? reason = null) =>
        Respond(approval, ClientIntents.ApprovalDeny(approval.Id, reason));

    public ProtocolResult AllowAlways(ApprovalRequest approval, ApprovalAlwaysScope scope) =>
        Respond(approval, ClientIntents.ApprovalAllowAlways(approval.Id, scope));

    public ProtocolResult CancelRun(ApprovalRequest approval) =>
        Respond(approval, ClientIntents.ApprovalCancelRun(approval.Id));

    private ProtocolResult Respond(ApprovalRequest approval, string intent)
    {
        ObjectDisposedException.ThrowIf(disposed, this);
        if (approval.SessionId != SessionId) return ProtocolResult.InvalidArgument;
        return connection.SendIntent(intent);
    }

    private void StoreChanged(object? sender, PropertyChangedEventArgs args)
    {
        if (args.PropertyName == nameof(RendererStore.Sessions)) Raise(nameof(Session));
        else if (args.PropertyName == nameof(RendererStore.PendingApprovals))
            Raise(nameof(PendingApprovals));
    }

    private void ProjectionChanged(ProjectionDiff diff)
    {
        if (diff.Root.TryGetProperty("sessionID", out var session) &&
            session.ValueKind == JsonValueKind.String && session.GetString() == SessionId)
        {
            LastProjection = diff;
        }
    }

    public void Dispose()
    {
        if (disposed) return;
        disposed = true;
        store.PropertyChanged -= StoreChanged;
        store.ProjectionChanged -= ProjectionChanged;
        if (active) _ = connection.SendIntent(ClientIntents.Unsubscribe(SessionId));
        active = false;
    }
}