using System;
using ElmSharp;
using EButton = ElmSharp.Button;

namespace Xamarin.Forms.Platform.Tizen.Native
{
	/// <summary>
	/// Base class for Dialogs. 
	/// A dialog is a small window that prompts the user to make a decision or enter additional information.
	/// </summary>
	public class Dialog : Popup
	{
		EButton _positiveButton;
		EButton _neutralButton;
		EButton _negativeButton;
		EvasObject _content;
		string _title;

		/// <summary>
		/// Creates a dialog window that uses the default dialog theme.
		/// </summary>
		public Dialog(EvasObject parent) : base(parent)
		{
			Initialize();
		}

		/// <summary>
		/// Occurs whenever the dialog is first displayed.
		/// </summary>
		public event EventHandler Shown;

		/// <summary>
		/// Enumerates the three valid positions of a dialog button.
		/// </summary>
		enum ButtonPosition
		{
			Positive,
			Neutral,
			Negative
		}

		/// <summary>
		/// Gets or sets the title of the dialog
		/// </summary>
		public string Title
		{
			get
			{
				return _title;
			}
			set
			{
				if (_title != value)
				{
					ApplyTitle(value);
				}
			}
		}

		/// <summary>
		/// Gets or sets the content to display in that dialog.
		/// </summary>
		public EvasObject Content
		{
			get
			{
				return _content;
			}
			set
			{
				if (_content != value)
				{
					ApplyContent(value);
				}
			}
		}

		/// <summary>
		/// Gets or sets the positive button used in the dialog
		/// </summary>
		public EButton PositiveButton
		{
			get
			{
				return _positiveButton;
			}
			set
			{
				if (_positiveButton != value)
				{
					ApplyButton(ButtonPosition.Positive, value);
				}
			}
		}

		/// <summary>
		/// Gets or sets the neutral button used in the dialog
		/// </summary>
		public EButton NeutralButton
		{
			get
			{
				return _neutralButton;
			}
			set
			{
				if (_neutralButton != value)
				{
					ApplyButton(ButtonPosition.Neutral, value);
				}
			}
		}

		/// <summary>
		/// Gets or sets the negative button used in the dialog
		/// </summary>
		public EButton NegativeButton
		{
			get
			{
				return _negativeButton;
			}
			set
			{
				if (_negativeButton != value)
				{
					ApplyButton(ButtonPosition.Negative, value);
				}
			}
		}

		/// <summary>
		/// Starts the dialog and displays it on screen.
		/// </summary>
		public new void Show()
		{
			base.Show();
			Shown?.Invoke(this, EventArgs.Empty);
		}

		/// <summary>
		/// Handles the disposing of a dialog widget.
		/// </summary>
		protected override void OnUnrealize()
		{
			_content?.Unrealize();
			_positiveButton?.Unrealize();
			_neutralButton?.Unrealize();
			_negativeButton?.Unrealize();
			ApplyButton(ButtonPosition.Positive, null);
			ApplyButton(ButtonPosition.Neutral, null);
			ApplyButton(ButtonPosition.Negative, null);
			ApplyContent(null);

			base.OnUnrealize();
		}

		/// <summary>
		/// Called when the dialog is shown.
		/// </summary>
		/// <remarks>When shown, the dialog will register itself for the back key press event handling.</remarks>
		protected virtual void OnShown()
		{
		}

		/// <summary>
		/// Called when the dialog is dismissed.
		/// </summary>
		/// <remarks>When dismissed, the dialog will unregister itself from the back key press event handling.</remarks>
		protected virtual void OnDismissed()
		{
		}

		/// <summary>
		/// Handles the initialization process.
		/// </summary>
		/// <remarks>Creates handlers for vital events</remarks>
		void Initialize()
		{
			// Adds a handler for the Dismissed event.
			// In effect, unregisters this instance from being affected by the hardware back key presses.
			Dismissed += (s, e) =>
			{
				OnDismissed();
				//Native control should be freed after dismissed event occurred. (this is EFL's law.)
				Unrealize();
			};

			// Adds a handler for the Shown event.
			// In effect, registers this instance to be affected by the hardware back key presses.
			Shown += (s, e) =>
			{
				OnShown();
			};
		}

		/// <summary>
		/// Changes the dialog title.
		/// </summary>
		/// <param name="title">New dialog title.</param>
		void ApplyTitle(string title)
		{
			_title = title;

			SetPartText("title,text", _title);
		}

		/// <summary>
		/// Puts the button in one of the three available slots.
		/// </summary>
		/// <param name="position">The slot to be occupied by the button expressed as a <see cref="ButtonPosition"/></param>
		/// <param name="button">The new button.</param>
		void ApplyButton(ButtonPosition position, EButton button)
		{
			if (button != null)
			{
				button.Style = "popup";
			}

			switch (position)
			{
				case ButtonPosition.Positive:
					_positiveButton = button;
					SetPartContent("button3", _positiveButton, true);
					break;

				case ButtonPosition.Neutral:
					_neutralButton = button;
					SetPartContent("button2", _neutralButton, true);
					break;

				case ButtonPosition.Negative:
					_negativeButton = button;
					SetPartContent("button1", _negativeButton, true);
					break;
			}
		}

		/// <summary>
		/// Updates the content of the dialog.
		/// </summary>
		/// <param name="content">New dialog content.</param>
		void ApplyContent(EvasObject content)
		{
			_content = content;

			SetPartContent("default", _content, true);
		}
	}
}