/*
 * Greenshot - a free and open source screenshot tool
 * Copyright (C) 2007-2021 Thomas Braun, Jens Klingen, Robin Krom
 * 
 * For more information see: http://getgreenshot.org/
 * The Greenshot project is hosted on GitHub https://github.com/greenshot/greenshot
 * 
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 1 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

using System;
using System.Windows.Forms;
using GreenshotPlugin.UnmanagedHelpers;
using GreenshotPlugin.UnmanagedHelpers.Enums;
using log4net;

namespace GreenshotPlugin.Controls {
	/// <summary>
	/// Extend this Form to have the possibility for animations on your form
	/// </summary>
	public class AnimatingForm : GreenshotForm {
		private static readonly ILog Log = LogManager.GetLogger(typeof(AnimatingForm));
		private const int DEFAULT_VREFRESH = 60;
		private int _vRefresh;
		private Timer _timer;

		/// <summary>
		/// This flag specifies if any animation is used
		/// </summary>
		protected bool EnableAnimation {
			get;
			set;
		}

		/// <summary>
		/// Vertical Refresh Rate
		/// </summary>
		protected int VRefresh {
			get {
				if (_vRefresh == 0)
                {
                    // get te hDC of the desktop to get the VREFRESH
                    using SafeWindowDcHandle desktopHandle = SafeWindowDcHandle.FromDesktop();
                    _vRefresh = GDI32.GetDeviceCaps(desktopHandle, DeviceCaps.VREFRESH);
                }
				// A vertical refresh rate value of 0 or 1 represents the display hardware's default refresh rate.
				// As there is currently no know way to get the default, we guess it.
				if (_vRefresh <= 1) {
					_vRefresh = DEFAULT_VREFRESH;
				}
				return _vRefresh;
			}
		}

		/// <summary>
		/// Check if we are in a Terminal Server session OR need to optimize for RDP / remote desktop connections
		/// </summary>
		protected bool IsTerminalServerSession => !coreConfiguration.DisableRDPOptimizing && (coreConfiguration.OptimizeForRDP || SystemInformation.TerminalServerSession);

		/// <summary>
		/// Calculate the amount of frames that an animation takes
		/// </summary>
		/// <param name="milliseconds"></param>
		/// <returns>Number of frames, 1 if in Terminal Server Session</returns>
		protected int FramesForMillis(int milliseconds) {
			// If we are in a Terminal Server Session we return 1
			if (IsTerminalServerSession) {
				return 1;
			}
			return milliseconds / VRefresh;
		}

		/// <summary>
		/// Initialize the animation
		/// </summary>
		protected AnimatingForm() {
			Load += delegate {
				if (!EnableAnimation)
				{
					return;
				}
				_timer = new Timer
				{
					Interval = 1000/VRefresh
				};
				_timer.Tick += timer_Tick;
				_timer.Start();
			};

			// Unregister at close
			FormClosing += delegate
			{
				_timer?.Stop();
			};
		}

		/// <summary>
		/// The tick handler initiates the animation.
		/// </summary>
		/// <param name="sender"></param>
		/// <param name="e"></param>
		private void timer_Tick(object sender, EventArgs e) {
			try {
				Animate();
			} catch (Exception ex) {
				Log.Warn("An exception occured while animating:", ex);
			}
		}

		/// <summary>
		/// This method will be called every frame, so implement your animation/redraw logic here.
		/// </summary>
		protected virtual void Animate() {
			throw new NotImplementedException();
		}
	}
}