#nullable enable
using System.ComponentModel;

namespace Terminal.Gui;

/// <summary>
///     Displays a command, help text, and a key binding. When the key specified by <see cref="Key"/> is pressed, the
///     command will be invoked. Useful for
///     displaying a command in <see cref="Bar"/> such as a
///     menu, toolbar, or status bar.
/// </summary>
/// <remarks>
///     <para>
///         The following user actions will invoke the <see cref="Command.Accept"/>, causing the
///         <see cref="View.Accepting"/> event to be fired:
///         - Clicking on the <see cref="Shortcut"/>.
///         - Pressing the key specified by <see cref="Key"/>.
///         - Pressing the HotKey specified by <see cref="CommandView"/>.
///     </para>
///     <para>
///         If <see cref="KeyBindingScope"/> is <see cref="KeyBindingScope.Application"/>, <see cref="Key"/> will invoke
///         <see cref="Command.Accept"/>
///         regardless of what View has focus, enabling an application-wide keyboard shortcut.
///     </para>
///     <para>
///         By default, a Shortcut displays the command text on the left side, the help text in the middle, and the key
///         binding on the
///         right side. Set <see cref="AlignmentModes"/> to <see cref="AlignmentModes.EndToStart"/> to reverse the order.
///     </para>
///     <para>
///         The command text can be set by setting the <see cref="CommandView"/>'s Text property or by setting
///         <see cref="View.Title"/>.
///     </para>
///     <para>
///         The help text can be set by setting the <see cref="HelpText"/> property or by setting <see cref="View.Text"/>.
///     </para>
///     <para>
///         The key text is set by setting the <see cref="Key"/> property.
///         If the <see cref="Key"/> is <see cref="Key.Empty"/>, the <see cref="Key"/> text is not displayed.
///     </para>
/// </remarks>
public class Shortcut : View, IOrientation, IDesignable
{
    /// <summary>
    ///     Creates a new instance of <see cref="Shortcut"/>.
    /// </summary>
    public Shortcut () : this (Key.Empty, null, null, null) { }

    /// <summary>
    ///     Creates a new instance of <see cref="Shortcut"/>, binding it to <paramref name="targetView"/> and
    ///     <paramref name="command"/>. The Key <paramref name="targetView"/>
    ///     has bound to <paramref name="command"/> will be used as <see cref="Key"/>.
    /// </summary>
    /// <remarks>
    ///     <para>
    ///         This is a helper API that simplifies creation of multiple Shortcuts when adding them to <see cref="Bar"/>-based
    ///         objects, like <see cref="MenuBarv2"/>.
    ///     </para>
    /// </remarks>
    /// <param name="targetView">
    ///     The View that <paramref name="command"/> will be invoked on when user does something that causes the Shortcut's Accept
    ///     event to be raised.
    /// </param>
    /// <param name="command">
    ///     The Command to invoke on <paramref name="targetView"/>. The Key <paramref name="targetView"/>
    ///     has bound to <paramref name="command"/> will be used as <see cref="Key"/>
    /// </param>
    /// <param name="commandText">The text to display for the command.</param>
    /// <param name="helpText">The help text to display.</param>
    public Shortcut (View targetView, Command command, string commandText, string helpText)
        : this (
                targetView?.KeyBindings.GetKeyFromCommands (command)!,
                commandText,
                null,
                helpText)
    {
        _targetView = targetView;
        _command = command;
    }

    /// <summary>
    ///     Creates a new instance of <see cref="Shortcut"/>.
    /// </summary>
    /// <remarks>
    ///     <para>
    ///         This is a helper API that mimics the V1 API for creating StatusItems.
    ///     </para>
    /// </remarks>
    /// <param name="key"></param>
    /// <param name="commandText">The text to display for the command.</param>
    /// <param name="action"></param>
    /// <param name="helpText">The help text to display.</param>
    public Shortcut (Key key, string? commandText, Action? action, string? helpText = null)
    {
        Id = "_shortcut";

        HighlightStyle = HighlightStyle.None;
        CanFocus = true;

        SuperViewRendersLineCanvas = true;
        Border.Settings &= ~BorderSettings.Title;

        Width = GetWidthDimAuto ();
        Height = Dim.Auto (DimAutoStyle.Content, 1);

        _orientationHelper = new (this);
        _orientationHelper.OrientationChanging += (sender, e) => OrientationChanging?.Invoke (this, e);
        _orientationHelper.OrientationChanged += (sender, e) => OrientationChanged?.Invoke (this, e);

        AddCommands ();

        TitleChanged += Shortcut_TitleChanged; // This needs to be set before CommandView is set

        CommandView = new ()
        {
            Id = "CommandView",
            Width = Dim.Auto (),
            Height = Dim.Fill()
        };
        Title = commandText ?? string.Empty;

        HelpView.Id = "_helpView";
        HelpView.CanFocus = false;
        HelpView.Text = helpText ?? string.Empty;

        KeyView.Id = "_keyView";
        KeyView.CanFocus = false;
        key ??= Key.Empty;
        Key = key;

        Action = action;

        SubviewLayout += OnLayoutStarted;

        ShowHide ();
    }

    // Helper to set Width consistently
    internal Dim GetWidthDimAuto ()
    {
        return Dim.Auto (
                         DimAutoStyle.Content,
                         minimumContentDim: Dim.Func (() => _minimumNaturalWidth ?? 0),
                         maximumContentDim: Dim.Func (() => _minimumNaturalWidth ?? 0))!;
}

    private AlignmentModes _alignmentModes = AlignmentModes.StartToEnd | AlignmentModes.IgnoreFirstOrLast;

    // This is used to calculate the minimum width of the Shortcut when Width is NOT Dim.Auto
    // It is calculated by setting Width to DimAuto temporarily and forcing layout.
    // Once Frame.Width gets below this value, LayoutStarted makes HelpView an KeyView smaller.
    private int? _minimumNaturalWidth;

    /// <inheritdoc/>
    protected override bool OnHighlight (CancelEventArgs<HighlightStyle> args)
    {
        if (args.NewValue.HasFlag (HighlightStyle.Hover))
        {
            HasFocus = true;
        }

        return true;
    }

    /// <summary>
    ///     Gets or sets the <see cref="AlignmentModes"/> for this <see cref="Shortcut"/>.
    /// </summary>
    /// <remarks>
    ///     <para>
    ///         The default is <see cref="AlignmentModes.StartToEnd"/>. This means that the CommandView will be on the left,
    ///         HelpView in the middle, and KeyView on the right.
    ///     </para>
    /// </remarks>
    public AlignmentModes AlignmentModes
    {
        get => _alignmentModes;
        set
        {
            _alignmentModes = value;
            SetCommandViewDefaultLayout ();
            SetHelpViewDefaultLayout ();
            SetKeyViewDefaultLayout ();
        }
    }

    // When one of the subviews is "empty" we don't want to show it. So we
    // Use Add/Remove. We need to be careful to add them in the right order
    // so Pos.Align works correctly.
    internal void ShowHide ()
    {
        RemoveAll ();

        if (CommandView.Visible)
        {
            Add (CommandView);
            SetCommandViewDefaultLayout ();
        }

        if (HelpView.Visible && !string.IsNullOrEmpty (HelpView.Text))
        {
            Add (HelpView);
            SetHelpViewDefaultLayout ();
        }

        if (KeyView.Visible && Key != Key.Empty)
        {
            Add (KeyView);
            SetKeyViewDefaultLayout ();
        }

        SetColors ();
    }

    // Force Width to DimAuto to calculate natural width and then set it back
    private void ForceCalculateNaturalWidth ()
    {
        // Get the natural size of each subview
        CommandView.SetRelativeLayout (Application.Screen.Size);
        HelpView.SetRelativeLayout (Application.Screen.Size);
        KeyView.SetRelativeLayout (Application.Screen.Size);

        _minimumNaturalWidth = PosAlign.CalculateMinDimension (0, Subviews, Dimension.Width);

        // Reset our relative layout
        SetRelativeLayout (SuperView?.GetContentSize() ?? Application.Screen.Size);
    }

    // TODO: Enable setting of the margin thickness
    private Thickness GetMarginThickness ()
    {
        return new (1, 0, 1, 0);
    }

    // When layout starts, we need to adjust the layout of the HelpView and KeyView
    private void OnLayoutStarted (object? sender, LayoutEventArgs e)
    {
        ShowHide ();
        ForceCalculateNaturalWidth ();

        if (Width is DimAuto widthAuto)
        {

        } 
        else
        {
            // Frame.Width is smaller than the natural width. Reduce width of HelpView.
            _maxHelpWidth = int.Max (0, GetContentSize ().Width - CommandView.Frame.Width - KeyView.Frame.Width);
            if (_maxHelpWidth < 3)
            {
                Thickness t = GetMarginThickness ();
                switch (_maxHelpWidth)
                {
                    case 0:
                    case 1:
                        // Scrunch it by removing both margins
                        HelpView.Margin.Thickness = new (t.Right - 1, t.Top, t.Left - 1, t.Bottom);

                        break;

                    case 2:

                        // Scrunch just the right margin
                        HelpView.Margin.Thickness = new (t.Right, t.Top, t.Left - 1, t.Bottom);

                        break;
                }
            }
            else
            {
                // Reset to default
                HelpView.Margin.Thickness = GetMarginThickness ();
            }
        }
    }


    #region Accept/Select/HotKey Command Handling

    private readonly View? _targetView; // If set, _command will be invoked

    private readonly Command _command; // Used when _targetView is set

    private void AddCommands ()
    {
        // Accept (Enter key) -
        AddCommand (Command.Accept, DispatchCommand);
        // Hotkey -
        AddCommand (Command.HotKey, DispatchCommand);
        // Select (Space key or click) -
        AddCommand (Command.Select, DispatchCommand);
    }

    private bool? DispatchCommand (CommandContext ctx)
    {
        if (ctx.Data != this)
        {
            // Invoke Select on the command view to cause it to change state if it wants to
            // If this causes CommandView to raise Accept, we eat it
            ctx.Data = this;
            CommandView.InvokeCommand (Command.Select, ctx);
        }

        if (RaiseSelecting (ctx) is true)
        {
            return true;
        }

        // The default HotKey handler sets Focus
        SetFocus ();

        var cancel = false;

        cancel = RaiseAccepting (ctx) is true;

        if (cancel)
        {
            return true;
        }

        if (Action is { })
        {
            Action.Invoke ();

            // Assume if there's a subscriber to Action, it's handled.
            cancel = true;
        }

        if (_targetView is { })
        {
            _targetView.InvokeCommand (_command);
        }

        return cancel;
    }

    /// <summary>
    ///     Gets or sets the action to be invoked when the shortcut key is pressed or the shortcut is clicked on with the
    ///     mouse.
    /// </summary>
    /// <remarks>
    ///     Note, the <see cref="View.Accepting"/> event is fired first, and if cancelled, the event will not be invoked.
    /// </remarks>
    public Action? Action { get; set; }

    #endregion Accept/Select/HotKey Command Handling

    #region IOrientation members

    private readonly OrientationHelper _orientationHelper;

    /// <summary>
    ///     Gets or sets the <see cref="Orientation"/> for this <see cref="Bar"/>. The default is
    ///     <see cref="Orientation.Horizontal"/>.
    /// </summary>
    /// <remarks>
    /// </remarks>
    public Orientation Orientation
    {
        get => _orientationHelper.Orientation;
        set => _orientationHelper.Orientation = value;
    }

    /// <inheritdoc/>
    public event EventHandler<CancelEventArgs<Orientation>>? OrientationChanging;

    /// <inheritdoc/>
    public event EventHandler<EventArgs<Orientation>>? OrientationChanged;

    /// <summary>Called when <see cref="Orientation"/> has changed.</summary>
    /// <param name="newOrientation"></param>
    public void OnOrientationChanged (Orientation newOrientation)
    {
        // TODO: Determine what, if anything, is opinionated about the orientation.
        SetNeedsLayout ();
    }

    #endregion

    #region Command

    private View _commandView = new ();

    /// <summary>
    ///     Gets or sets the View that displays the command text and hotkey.
    /// </summary>
    /// <exception cref="ArgumentNullException"></exception>
    /// <remarks>
    ///     <para>
    ///         By default, the <see cref="View.Title"/> of the <see cref="CommandView"/> is displayed as the Shortcut's
    ///         command text.
    ///     </para>
    ///     <para>
    ///         By default, the CommandView is a <see cref="View"/> with <see cref="View.CanFocus"/> set to
    ///         <see langword="false"/>.
    ///     </para>
    ///     <para>
    ///         Setting the <see cref="CommandView"/> will add it to the <see cref="Shortcut"/> and remove any existing
    ///         <see cref="CommandView"/>.
    ///     </para>
    /// </remarks>
    /// <example>
    ///     <para>
    ///         This example illustrates how to add a <see cref="Shortcut"/> to a <see cref="StatusBar"/> that toggles the
    ///         <see cref="Application.Force16Colors"/> property.
    ///     </para>
    ///     <code>
    ///     var force16ColorsShortcut = new Shortcut
    ///     {
    ///         Key = Key.F6,
    ///         KeyBindingScope = KeyBindingScope.HotKey,
    ///         CommandView = new CheckBox { Text = "Force 16 Colors" }
    ///     };
    ///     var cb = force16ColorsShortcut.CommandView as CheckBox;
    ///     cb.Checked = Application.Force16Colors;
    /// 
    ///     cb.Toggled += (s, e) =>
    ///     {
    ///         var cb = s as CheckBox;
    ///         Application.Force16Colors = cb!.Checked == true;
    ///         Application.Refresh();
    ///     };
    ///     StatusBar.Add(force16ColorsShortcut);
    /// </code>
    /// </example>

    public View CommandView
    {
        get => _commandView;
        set
        {
            ArgumentNullException.ThrowIfNull (value);

            if (value == null)
            {
                throw new ArgumentNullException ();
            }

            // Clean up old 
            _commandView.Selecting -= CommandViewOnSelecting;
            _commandView.Accepting -= CommandViewOnAccepted;
            Remove (_commandView);
            _commandView?.Dispose ();

            // Set new
            _commandView = value;
            _commandView.Id = "_commandView";

            // The default behavior is for CommandView to not get focus. I
            // If you want it to get focus, you need to set it.
            _commandView.CanFocus = false;

            _commandView.HotKeyChanged += (s, e) =>
                                          {
                                              if (e.NewKey != Key.Empty)
                                              {
                                                  // Add it
                                                  AddKeyBindingsForHotKey (e.OldKey, e.NewKey);
                                              }
                                          };

            _commandView.HotKeySpecifier = new ('_');

            Title = _commandView.Text;

            _commandView.Selecting += CommandViewOnSelecting;
            _commandView.Accepting += CommandViewOnAccepted;

            //ShowHide ();
            UpdateKeyBindings (Key.Empty);

            return;

            void CommandViewOnAccepted (object? sender, CommandEventArgs e)
            {
                // Always eat CommandView.Accept
                e.Cancel = true;
            }

            void CommandViewOnSelecting (object? sender, CommandEventArgs e)
            {
                if (e.Context.Data != this)
                {
                    // Forward command to ourselves
                    InvokeCommand (Command.Select, new (Command.Select, null, null, this));
                }

                e.Cancel = true;
            }
        }
    }

    private void SetCommandViewDefaultLayout ()
    {
        CommandView.Margin.Thickness = GetMarginThickness ();
        CommandView.X = Pos.Align (Alignment.End, AlignmentModes);

        CommandView.VerticalTextAlignment = Alignment.Center;
        CommandView.TextAlignment = Alignment.Start;
        CommandView.TextFormatter.WordWrap = false;
        CommandView.HighlightStyle = HighlightStyle.None;
    }

    private void Shortcut_TitleChanged (object? sender, EventArgs<string> e)
    {
        // If the Title changes, update the CommandView text.
        // This is a helper to make it easier to set the CommandView text.
        // CommandView is public and replaceable, but this is a convenience.
        _commandView.Text = Title;
    }

    #endregion Command

    #region Help

    // The maximum width of the HelpView. Calculated in OnLayoutStarted and used in HelpView.Width (Dim.Auto/Func).
    private int _maxHelpWidth = 0;

    /// <summary>
    ///     The subview that displays the help text for the command. Internal for unit testing.
    /// </summary>
    public View HelpView { get; } = new ();

    private void SetHelpViewDefaultLayout ()
    {
        HelpView.Margin.Thickness = GetMarginThickness ();
        HelpView.X = Pos.Align (Alignment.End, AlignmentModes);
        _maxHelpWidth = HelpView.Text.GetColumns ();
        HelpView.Width = Dim.Auto (DimAutoStyle.Text, maximumContentDim: Dim.Func ((() => _maxHelpWidth)));
        HelpView.Height = Dim.Fill ();

        HelpView.Visible = true;
        HelpView.VerticalTextAlignment = Alignment.Center;
        HelpView.TextAlignment = Alignment.Start;
        HelpView.TextFormatter.WordWrap = false;
        HelpView.HighlightStyle = HighlightStyle.None;
    }

    /// <summary>
    ///     Gets or sets the help text displayed in the middle of the Shortcut. Identical in function to <see cref="HelpText"/>
    ///     .
    /// </summary>
    public override string Text
    {
        get => HelpView.Text;
        set
        {
            HelpView.Text = value;
            ShowHide ();
        }
    }

    /// <summary>
    ///     Gets or sets the help text displayed in the middle of the Shortcut.
    /// </summary>
    public string HelpText
    {
        get => HelpView.Text;
        set
        {
            HelpView.Text = value;
            ShowHide ();
        }
    }

    #endregion Help

    #region Key

    private Key _key = Key.Empty;

    /// <summary>
    ///     Gets or sets the <see cref="Key"/> that will be bound to the <see cref="Command.Accept"/> command.
    /// </summary>
    public Key Key
    {
        get => _key;
        set
        {
            ArgumentNullException.ThrowIfNull (value);

            Key oldKey = _key;
            _key = value;

            UpdateKeyBindings (oldKey);

            KeyView.Text = Key == Key.Empty ? string.Empty : $"{Key}";
            ShowHide ();
        }
    }

    private KeyBindingScope _keyBindingScope = KeyBindingScope.HotKey;

    /// <summary>
    ///     Gets or sets the scope for the key binding for how <see cref="Key"/> is bound to <see cref="Command"/>.
    /// </summary>
    public KeyBindingScope KeyBindingScope
    {
        get => _keyBindingScope;
        set
        {
            if (value == _keyBindingScope)
            {
                return;
            }

            if (_keyBindingScope == KeyBindingScope.Application)
            {
                Application.KeyBindings.Remove (Key);
            }

            if (_keyBindingScope is KeyBindingScope.HotKey or KeyBindingScope.Focused)
            {
                KeyBindings.Remove (Key);
            }

            _keyBindingScope = value;

            UpdateKeyBindings (Key.Empty);
        }
    }

    /// <summary>
    ///     Gets the subview that displays the key. Internal for unit testing.
    /// </summary>

    public View KeyView { get; } = new ();

    private int _minimumKeyTextSize;

    /// <summary>
    ///     Gets or sets the minimum size of the key text. Useful for aligning the key text with other <see cref="Shortcut"/>s.
    /// </summary>
    public int MinimumKeyTextSize
    {
        get => _minimumKeyTextSize;
        set
        {
            if (value == _minimumKeyTextSize)
            {
                //return;
            }

            _minimumKeyTextSize = value;
            SetKeyViewDefaultLayout ();

            // TODO: Prob not needed
            CommandView.SetNeedsLayout ();
            HelpView.SetNeedsLayout ();
            KeyView.SetNeedsLayout ();
            SetSubViewNeedsDraw ();
        }
    }


    private void SetKeyViewDefaultLayout ()
    {
        KeyView.Margin.Thickness = GetMarginThickness ();
        KeyView.X = Pos.Align (Alignment.End, AlignmentModes);
        KeyView.Width = Dim.Auto (DimAutoStyle.Text, minimumContentDim: Dim.Func (() => MinimumKeyTextSize));
        KeyView.Height = Dim.Fill ();

        KeyView.Visible = true;

        // Right align the text in the keyview
        KeyView.TextAlignment = Alignment.End;
        KeyView.VerticalTextAlignment = Alignment.Center;
        KeyView.KeyBindings.Clear ();
        HelpView.HighlightStyle = HighlightStyle.None;
    }

    private void UpdateKeyBindings (Key oldKey)
    {
        if (Key.IsValid)
        {
            if (KeyBindingScope.FastHasFlags (KeyBindingScope.Application))
            {
                if (oldKey != Key.Empty)
                {
                    Application.KeyBindings.Remove (oldKey);
                }

                Application.KeyBindings.Remove (Key);
                Application.KeyBindings.Add (Key, this, Command.HotKey);
            }
            else
            {
                if (oldKey != Key.Empty)
                {
                    KeyBindings.Remove (oldKey);
                }

                KeyBindings.Remove (Key);
                KeyBindings.Add (Key, KeyBindingScope | KeyBindingScope.HotKey, Command.HotKey);
            }
        }
    }

    #endregion Key

    #region Focus

    /// <inheritdoc/>
    public override ColorScheme? ColorScheme
    {
        get => base.ColorScheme;
        set
        {
            base.ColorScheme = _nonFocusColorScheme = value;
            SetColors ();
        }
    }

    private ColorScheme? _nonFocusColorScheme;
    /// <summary>
    /// </summary>
    internal void SetColors (bool highlight = false)
    {
        // Border should match superview.
        if (Border is { })
        {
            // Border.ColorScheme = SuperView?.ColorScheme;
        }

        if (HasFocus || highlight)
        {
            if (_nonFocusColorScheme is null)
            {
                _nonFocusColorScheme = base.ColorScheme;
            }

            base.ColorScheme ??= new (Attribute.Default);

            // When we have focus, we invert the colors
            base.ColorScheme = new (base.ColorScheme)
            {
                Normal = base.ColorScheme.Focus,
                HotNormal = base.ColorScheme.HotFocus,
                HotFocus = base.ColorScheme.HotNormal,
                Focus = base.ColorScheme.Normal
            };
        }
        else
        {
            if (_nonFocusColorScheme is { })
            {
                base.ColorScheme = _nonFocusColorScheme;
               //_nonFocusColorScheme = null;
            }
            else
            {
                base.ColorScheme = SuperView?.ColorScheme ?? base.ColorScheme;
            }
        }

        // Set KeyView's colors to show "hot"
        if (IsInitialized && base.ColorScheme is { })
        {
            var cs = new ColorScheme (base.ColorScheme)
            {
                Normal = base.ColorScheme.HotNormal,
                HotNormal = base.ColorScheme.Normal
            };
            KeyView.ColorScheme = cs;
        }
    }

    /// <inheritdoc/>
    protected override void OnHasFocusChanged (bool newHasFocus, View? previousFocusedView, View? view) { SetColors (); }

    #endregion Focus

    /// <inheritdoc/>
    public bool EnableForDesign ()
    {
        Title = "_Shortcut";
        HelpText = "Shortcut help";
        Key = Key.F1;

        return true;
    }

    /// <inheritdoc/>
    protected override void Dispose (bool disposing)
    {
        if (disposing)
        {
            TitleChanged -= Shortcut_TitleChanged;

            if (CommandView?.IsAdded == false)
            {
                CommandView.Dispose ();
            }

            if (HelpView?.IsAdded == false)
            {
                HelpView.Dispose ();
            }

            if (KeyView?.IsAdded == false)
            {
                KeyView.Dispose ();
            }
        }

        base.Dispose (disposing);
    }
}