using System.Collections.ObjectModel;
using System.Drawing;
using Mindmagma.Curses;

namespace SCI.CursesWrapper;

public class Window {
	public const int InnerPadding = 1;

	/// <summary>
	/// Gets or sets the window position on the screen
	/// </summary>
	private Point _position;
	public Point Position {
		get {
			return _position;
		}
		set {
			if (ParentWindow is not null) {
				int addedPadding = ParentWindow.BorderEnabled?
					InnerPadding + 1 : 0;

				NCurses.WindowMove (
					WindowId,
					ParentWindow.Position.Y + value.Y + addedPadding,
					ParentWindow.Position.X + value.X + addedPadding
				);
			} else {
				NCurses.WindowMove (
					WindowId,
					value.Y,
					value.X
				);
			}
			_position = value;
		}
	}

	/// <summary>
	/// Gets or sets the width and height of the window
	/// </summary>
	private Size _windowSize;
	public Size WindowSize {
		get {
			return _windowSize;
		}
		set {
			_windowSize = value;
		}
	}

	/// <summary>
	/// Gets or sets the window background color pair
	/// </summary>
	private uint _backgroundColorId;
	public uint BackgroundColorId {
		get {
			return _backgroundColorId;
		}
		set {
			NCurses.WindowBackground (WindowId, value);
			Draw ();
			_backgroundColorId = value;
		}
	}

	private bool _borderEnabled;
	public bool BorderEnabled {
		get {
			return _borderEnabled;
		}
		set {
			SetBorder (value);
			Draw ();
			_borderEnabled = value;
		}
	}

	/// <summary>
	/// Sets the parent window
	/// </summary>
	private Window? _parentWindow;
	public Window?  ParentWindow { get { return _parentWindow; }}

	/// <summary>
	/// Holds a list of children windows this window posesses
	/// </summary>
	private List<Window> _childWindows = new List<Window> ();
	public ReadOnlyCollection<Window> ChildWindows { get { return _childWindows.AsReadOnly (); }}

	/// <summary>
	/// Holds the pointer for this window
	/// </summary>
	private nint _windowId;
	public nint WindowId { get { return _windowId; }}

	/// <summary>
	/// Input handler assigned to this window
	/// </summary>
	protected InputHandler? _targetInputHandler;
	public InputHandler? TargetInputHandler { get { return _targetInputHandler; }}

	/// <summary>
	/// Event handler called when this window is active and a key is pressed
	/// </summary>
	public event InputHandler.KeypressEventHandler? OnKeyPress;

	/// <summary>
	/// Create new window by specifying X/Y and Width/Height geometry
	/// </summary>
	/// <param name="x"></param>
	/// <param name="y"></param>
	/// <param name="width"></param>
	/// <param name="height"></param>
	/// <param name="parentWindow"></param>
	public Window (int x, int y, int width, int height, Window? parentWindow = null) {
		_Initialize (new Point (x, y), new Size (width, height), parentWindow);
	}

	/// <summary>
	/// Create new window by specifying geometry through Point and Size objects
	/// </summary>
	/// <param name="position"></param>
	/// <param name="windowSize"></param>
	/// <param name="parentWindow"></param>
	public Window (Point position, Size windowSize, Window? parentWindow = null) {
		_Initialize (position, windowSize, parentWindow);
	}

	/// <summary>
	/// Create new window by specifying X/Y and Width/Height geometry
	/// </summary>
	/// <param name="x"></param>
	/// <param name="y"></param>
	/// <param name="width"></param>
	/// <param name="height"></param>
	/// <param name="targetInputHandler"></param>
	/// <param name="parentWindow"></param>
	public Window (int x, int y, int width, int height, InputHandler targetInputHandler, Window? parentWindow = null) {
		_Initialize (new Point (x, y), new Size (width, height), parentWindow);
		RegisterInputHandler (targetInputHandler);
		SetWindowActive ();
	}

	/// <summary>
	/// Create new window by specifying geometry through Point and Size objects
	/// </summary>
	/// <param name="position"></param>
	/// <param name="windowSize"></param>
	/// <param name="targetInputHandler"></param>
	/// <param name="parentWindow"></param>
	public Window (Point position, Size windowSize, InputHandler targetInputHandler, Window? parentWindow = null) {
		_Initialize (position, windowSize, parentWindow);
		RegisterInputHandler (targetInputHandler);
		SetWindowActive ();
	}

	/// <summary>
	/// Actual initialization function for this class
	/// </summary>
	/// <param name="position"></param>
	/// <param name="windowSize"></param>
	/// <param name="parentWindow"></param>
	private void _Initialize (Point position, Size windowSize, Window? parentWindow = null) {
		if (parentWindow is not null) {
			int addedPadding = parentWindow.BorderEnabled?
				InnerPadding + 1 : 0;

			_windowId = NCurses.DeriveWindow (
				parentWindow.WindowId,
				windowSize.Height, windowSize.Width,
				position.Y + addedPadding, position.X + addedPadding
			);

			parentWindow.AddChildWindow (this);
		} else {
			_windowId = NCurses.NewWindow (
				windowSize.Height, windowSize.Width,
				position.Y, position.X
			);
		}

		_position = position;
		_windowSize = windowSize;
		_parentWindow = parentWindow;

		NCurses.Keypad (WindowId, true);

		Draw ();
	}

	/// <summary>
	/// Destroys the window and its sub-windows when the Window object is destroyed
	/// </summary>
	~Window () {
		Destroy ();
	}

	/// <summary>
	/// Adds a child window to this window
	/// </summary>
	/// <param name="child"></param>
	public void AddChildWindow (Window child) {
		if (_childWindows.Contains (child)) return;
		_childWindows.Add (child);
	}

	/// <summary>
	/// Removes a child window from this window
	/// </summary>
	/// <param name="child"></param>
	public void RemoveChildWindow (Window child) {
		_childWindows.Remove (child);
	}

	/// <summary>
	/// Discards all optimization options about drawn parts of this window.
	/// Call before drawing a sub window
	/// </summary>
	public void TouchWin () {
		NCurses.TouchWindow (WindowId);
	}

	/// <summary>
	/// Draws this window and all sub windows
	/// </summary>
	public void Draw () {
		NCurses.Refresh (); // TODO: Necessary?

		foreach (var window in ChildWindows) {
			window.Draw ();
		}

		if (ParentWindow is not null) ParentWindow.TouchWin ();
		NCurses.WindowRefresh (WindowId);
	}

	/// <summary>
	/// Destroys this window and all children windows
	/// </summary>
	public void Destroy () {
		// Catch double destroy calls
		if (WindowId == -1) throw new Exception ("Destroy called twice on object");

		foreach (var window in _childWindows.ToList ()) {
			window.Destroy ();
		}

		UnregisterInputHandler ();

		// Prepare for screen clear
		NCurses.WindowBackground (WindowId, NCurses.ColorPair (-1));
		SetBorder (false);

		// Clear window and redraw
		NCurses.ClearWindow (WindowId);
		Draw ();

		NCurses.DeleteWindow (WindowId);
		_windowId = -1;

		// Ensures sure the parent is updated too
		if (ParentWindow is not null) {
			ParentWindow.RemoveChildWindow (this);
			ParentWindow.Draw ();
		}
	}

	/// <summary>
	/// Register an input handler for this window to attach to OnKeyPress events
	/// </summary>
	/// <param name="targetInputHandler">InputHandler to register</param>
	public void RegisterInputHandler (InputHandler inputHandler) {
		if (TargetInputHandler is not null) throw new Exception (
			"Another input handler is already registered"
		);

		_targetInputHandler = inputHandler;
		TargetInputHandler!.OnKeyPress += KeyPressHandler;
	}

	/// <summary>
	/// Detach from all OnKeyPress events and unset input handler
	/// </summary>
	public void UnregisterInputHandler () {
		if (TargetInputHandler is null) return;

		if (TargetInputHandler.ActiveWindow == this) TargetInputHandler.ActiveWindow = null;
		TargetInputHandler.OnKeyPress -= KeyPressHandler;
	}

	/// <summary>
	/// Handle key press events from the input handler
	/// </summary>
	/// <param name="sender"></param>
	/// <param name="e"></param>
	private void KeyPressHandler (object sender, NCursesKeyPressEventArgs e) {
		if (e.SourceWindow != this) return;

		if (OnKeyPress is not null) {
			OnKeyPress (this, e);
		}
	}

	/// <summary>
	/// Tells the input handler this window is active
	/// </summary>
	public void SetWindowActive () {
		if (TargetInputHandler is null) return;

		TargetInputHandler.ActiveWindow = this;
		Draw ();
	}

	/// <summary>
	/// Enables or disables a border around this window
	/// </summary>
	/// <param name="enabled">Sets the status of the border</param>
	/// <param name="horizontalChar">If specified, uses this character as the top and bottom border</param>
	/// <param name="verticalChar">If specified, uses this character as the left and right border</param>
	public void SetBorder (bool enabled, char? horizontalChar = null, char? verticalChar = null) {
		if (horizontalChar is null) horizontalChar = (char) 0;
		if (verticalChar   is null) verticalChar   = (char) 0;
		
		if (enabled) {
			NCurses.Box (WindowId, (char) horizontalChar, (char) verticalChar);
		} else {
			NCurses.Box (WindowId, ' ', ' ');
		}
	}

	/// <summary>
	/// Calcaulates the usable inner width of this window
	/// </summary>
	/// <returns>Usable inner width of window in columns</returns>
	public int GetUsableWidth () {
		if (BorderEnabled) {
			return WindowSize.Width - 1 - InnerPadding;
		} else {
			return WindowSize.Width;
		}
	}

	/// <summary>
	/// Calcaulates the usable inner height of this window
	/// </summary>
	/// <returns>Usable inner height of window in rows</returns>
	public int GetUsableHeight () {
		if (BorderEnabled) {
			return WindowSize.Height - 1 - InnerPadding;
		} else {
			return WindowSize.Height;
		}
	}
}