using System;
using System.ComponentModel;
using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using ClaudeDo.Ui.Services;

namespace ClaudeDo.Ui.ViewModels.MissionControl;

/// <summary>
/// Command Center pane hosting an embedded ConPTY terminal for either one task's interactive
/// Claude session, or an ad-hoc/free session in a user-chosen directory (no task, <see cref="TaskId"/>
/// is null — ad-hoc panes are never deduped, unlike task-based ones).
/// </summary>
public sealed partial class ConPtyPaneViewModel : ViewModelBase, IDisposable
{
    public string? TaskId { get; }

    // Only a task-based pane can be submitted for review (an ad-hoc directory session has no task).
    public bool IsTaskBased => TaskId is not null;

    [ObservableProperty] private string _displayTitle;

    [ObservableProperty] private InteractiveTerminalViewModel _terminal = new();

    /// <summary>Set by the host (Mission Control) while a submit-for-review round trip is in
    /// flight, so a rapid double-click can't race two submissions for the same task.</summary>
    [ObservableProperty] private bool _isSubmitPending;

    /// <summary>Raised when the terminal failed to start — the host surfaces this via the footer error strip.</summary>
    public event Action<string>? ErrorReported;

    /// <summary>Set by the host (Mission Control) to remove this pane from its collection.</summary>
    public Action<ConPtyPaneViewModel>? CloseRequested { get; set; }

    /// <summary>Raised when the user submits this task's hand-driven work for review; the host
    /// commits the worktree and moves the task to WaitingForReview.</summary>
    public event Action<string>? SubmitForReviewRequested;

    /// <summary>Raised with <c>(taskId, exitCode)</c> when a task-based session that had been running
    /// dies non-zero. The host reports it to the worker, which decides whether this was a list
    /// handler killed by the usage limit and worth reopening. Ad-hoc panes never raise it — there is
    /// no task to reopen.</summary>
    public event Action<string, int>? SessionDiedAfterStartup;

    /// <summary>Task-based pane — dedup'd by <see cref="TaskId"/>. Pass null for an ad-hoc pane
    /// (no task, never deduped); prefer <see cref="CreateAdHoc"/> at ad-hoc call sites.
    /// <paramref name="descriptorFactory"/> is resolved by the pane itself (in <see cref="Start"/>)
    /// so the tile — and its starting spinner — is visible while the launch spec is still being
    /// fetched. The host must wire its handlers and then call <see cref="Start"/>.</summary>
    public ConPtyPaneViewModel(
        string? taskId,
        string displayTitle,
        Func<System.Threading.Tasks.Task<TerminalLaunchDescriptor>> descriptorFactory)
    {
        TaskId = taskId;
        _displayTitle = displayTitle;
        _descriptorFactory = descriptorFactory;
        Subscribe(Terminal);
    }

    // Terminal is swapped wholesale on Retry, so the handlers follow the property rather than being
    // wired once at construction. (The initial value comes from the field initializer, which never
    // runs through the setter -- hence the explicit Subscribe in the constructor.)
    partial void OnTerminalChanging(InteractiveTerminalViewModel? oldValue, InteractiveTerminalViewModel newValue)
    {
        if (oldValue is not null) Unsubscribe(oldValue);
    }

    partial void OnTerminalChanged(InteractiveTerminalViewModel value) => Subscribe(value);

    private void Subscribe(InteractiveTerminalViewModel terminal)
    {
        terminal.PropertyChanged += OnTerminalPropertyChanged;
        terminal.ExitedAfterStartup += OnTerminalExitedAfterStartup;
    }

    private void Unsubscribe(InteractiveTerminalViewModel terminal)
    {
        terminal.PropertyChanged -= OnTerminalPropertyChanged;
        terminal.ExitedAfterStartup -= OnTerminalExitedAfterStartup;
    }

    private void OnTerminalExitedAfterStartup(int exitCode)
    {
        if (TaskId is { } id) SessionDiedAfterStartup?.Invoke(id, exitCode);
    }

    private readonly Func<System.Threading.Tasks.Task<TerminalLaunchDescriptor>> _descriptorFactory;

    /// <summary>Resolves the launch spec and spawns the session. Call after wiring
    /// <see cref="ErrorReported"/> so a failed launch is not swallowed.</summary>
    public void Start() => _ = StartAsync();

    private async System.Threading.Tasks.Task StartAsync()
    {
        try
        {
            Terminal.Start(await _descriptorFactory());
        }
        catch (Exception ex)
        {
            Terminal.ReportStartFailure(ex.Message);
        }
    }

    /// <summary>Ad-hoc pane — no task, no dedup.</summary>
    public static ConPtyPaneViewModel CreateAdHoc(
        string displayTitle,
        Func<System.Threading.Tasks.Task<TerminalLaunchDescriptor>> descriptorFactory)
        => new(null, displayTitle, descriptorFactory);

    private void OnTerminalPropertyChanged(object? sender, PropertyChangedEventArgs e)
    {
        if (e.PropertyName == nameof(InteractiveTerminalViewModel.StartError) && Terminal.StartError is { Length: > 0 } error)
            ErrorReported?.Invoke(error);

        if (e.PropertyName is nameof(InteractiveTerminalViewModel.IsStarting)
            or nameof(InteractiveTerminalViewModel.StartError)
            or nameof(InteractiveTerminalViewModel.HasExited))
        {
            SubmitForReviewCommand.NotifyCanExecuteChanged();
            RetryCommand.NotifyCanExecuteChanged();
        }
    }

    /// <summary>Types a message into this pane's live session and submits it (the worker's
    /// pre-usage-limit warning). False when the session isn't running.</summary>
    public System.Threading.Tasks.Task<bool> SendLineAsync(string text) => Terminal.SendLineAsync(text);

    [RelayCommand]
    private void Close() => CloseRequested?.Invoke(this);

    private bool CanSubmitForReview() =>
        IsTaskBased && !IsSubmitPending && !Terminal.IsStarting && Terminal.StartError is null && !Terminal.HasExited;

    [RelayCommand(CanExecute = nameof(CanSubmitForReview))]
    private void SubmitForReview()
    {
        if (TaskId is { } id) SubmitForReviewRequested?.Invoke(id);
    }

    partial void OnIsSubmitPendingChanged(bool value) => SubmitForReviewCommand.NotifyCanExecuteChanged();

    // A launch failure permanently occupies the TaskId dedupe slot unless the user can retry —
    // re-opening the same task would otherwise just re-focus a dead tile.
    private bool CanRetry() => Terminal.HasExited && Terminal.StartError is not null;

    [RelayCommand(CanExecute = nameof(CanRetry))]
    private void Retry()
    {
        var dead = Terminal;
        Terminal = new InteractiveTerminalViewModel(); // OnTerminalChanging/Changed move the handlers
        dead.Dispose();
        Start();
    }

    public void Dispose()
    {
        Unsubscribe(Terminal);
        Terminal.Kill();
        Terminal.Dispose();
    }
}