using System;
using System.Collections.Generic;
using System.Text;
using System.Windows.Input;

namespace Sarand.Net.Standard.Base.Core
{
	//=======================================================================
	/// <summary>
	/// Code contract for commands - menu options, button actions, keyboard accelerators etc.
	/// <para></para>
	/// </summary>
	public class SacsCommand : ICommand
	{
		//-------------------------------------------------------------------
		// Definitions.
		public delegate bool CanExecuteFn (object commandParam);
		public delegate void ExecuteFn (object commandParam);

		//-------------------------------------------------------------------
		// Data members.
		private readonly ExecuteFn executeFn;
		private readonly CanExecuteFn canExecuteFn;

		//-------------------------------------------------------------------
		// Construction.
		public SacsCommand (ExecuteFn executeFn, CanExecuteFn canExecuteFn = null)
		{
			this.executeFn = executeFn;
			this.canExecuteFn = canExecuteFn;
		}

		//-------------------------------------------------------------------
		// Properties.
		public String CommandId { get; set; }
		public String Caption { get; set; }

		//-------------------------------------------------------------------
		/// <summary>
		/// CanExecuteChanged event handler.
		/// <para>Unclear when this fires as Command won't know when state changes.</para>
		/// </summary>
		public event EventHandler CanExecuteChanged;
		protected void FireCanExecuteChanged ()
		{
			CanExecuteChanged?.Invoke(this, EventArgs.Empty);
		}

		//-------------------------------------------------------------------
		/// <summary>Determine whether this command can be executed.</summary>
		public virtual bool CanExecute (object commandParam)
		{
			return canExecuteFn?.Invoke(commandParam) ?? false;
		}

		//-------------------------------------------------------------------
		/// <summary>
		/// Execute command.
		/// <para>Only invokes command method if comand can be executed.</para>
		/// </summary>
		public virtual void Execute (object commandParam)
		{
			if (!CanExecute(commandParam)) return;
			executeFn?.Invoke(commandParam);
		}

		//-------------------------------------------------------------------
	}
	//=======================================================================
}