//-----------------------------------------------------------------------
//-----------------------------------------------------------------------
//     file="ShowViewPort.cs"
//     Project: StepVisualizer
//     AuthorGroup: Nitload Space
//     Copyright (c) Nitload Space. All rights reserved.
//     
//     Permission is hereby granted, free of charge, to any person 
//     obtaining a copy of this software and associated documentation 
//     files (the “Software”), to deal in the Software without restriction, 
//     including without limitation the rights to use, copy, modify, merge,
//     publish, distribute, sublicense, and/or sell copies of the Software, 
//     and to permit persons to whom the Software is furnished to do so, 
//     subject to the following conditions:
//     
//     The above copyright notice and 
//     this permission notice shall be included in all copies 
//     or substantial portions of the Software.
//     
//     THE SOFTWARE IS PROVIDED “AS IS”, 
//     WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, 
//     INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
//     FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. 
//     IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, 
//     DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 
//     ARISING FROM, OUT OF OR IN CONNECTION WITH 
//     THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//     
//-----------------------------------------------------------------------
//-----------------------------------------------------------------------
using StgSharp.Controls;
using StgSharp.Graphics;
using StgSharp.MVVM;
using StgSharp.Threading;
using StgSharp.Timing;

using System;
using System.Collections.Generic;
using System.Text;
using System.Threading;

namespace StgSharp.MVVM.ViewModel
{
    public abstract partial class ViewModelBase
    {

        private volatile bool _closed = true;
        private ViewBase _nextView, _currentView;

        protected ViewBase CurrentView
        {
            get => _currentView;
            set => _nextView = value;
        }

        /// <summary>
        ///   CustomizeInit this form and render it on screen, and respond with operation
        /// </summary>
        public unsafe void UseViewModel( string viewEntryName )
        {
            CustomizeInitialize();
            UseViewInNextFrame( viewEntryName );
            TimeSpanAwaitingToken fpsCountingToken = fpsCountProvider.ParticipantSpanAwaiting( 1 );
            fpsCountingToken.TimeSpanRefreshed += CountFps;
            fpsCountingToken.MissTimeSpanRefreshed += CountFps;
            if( _nextView != _currentView ) {
                Interlocked.Exchange( ref _currentView, _nextView );
            }
            Thread renderThread = new Thread(
                ( token ) => {
                    try
                    {
                        ProcessFrameWithoutEvent();
                    }
                    catch( Exception ex )
                    {
                        InternalIO.InternalWriteLog(
                            $"Critical error when rendering:\n" + $"{ex}", LogType.Error );
                        ShouldClose = true;
                        throw;
                    }
                } );
            renderThread.Start();
            /**/
            using( TimeSpanAwaitingToken eventAwaitingToken = frameTimeProvider.ParticipantSpanAwaiting(
                1 ) )
            {
                while( _closed )
                {
                    if( _nextView != _currentView ) {
                        Interlocked.Exchange( ref _currentView, _nextView );
                    }
                    InternalIO.glfwPollEvents();
                    eventAwaitingToken.WaitNextSpan();
                    _closed = !ShouldClose;
                }
            }
            /**/
            renderThread.Join();
            fpsCountingToken.Dispose();
            fpsCountProvider.StopSpanProviding();
            frameTimeProvider.StopSpanProviding();
        }

        protected void UseViewInNextFrame( string name )
        {
            if( !allView.TryGetValue( name, out ViewBase v ) ) {
                throw new KeyNotFoundException(
                    $"{$"Cannot find View named {name} "}{$"in current View Model of {GetType().FullName}"}" );
            }
            CurrentView = v;
        }

        private void CountFps( object sender, EventArgs e )
        {
            Interlocked.Exchange( ref _frameSpeed, _frameCount );
            Interlocked.Exchange( ref _frameCount, 0 );
        }

        private unsafe void PrivateShow()
        {
            if( 0 == InternalIO.glfwWindowShouldClose( this.viewPortDisplay.ViewPortHandle ) )
            {
                CurrentView.Use();
                RenderStream.PollEvents();
            }
        }

        private void ProcessFrameWithoutEvent()
        {
            using( TimeSpanAwaitingToken renderAwaitingToken = frameTimeProvider.ParticipantSpanAwaiting(
                1 ) )
            {
                renderAwaitingToken.TimeSpanRefreshed += ( _, _ ) => { };
                while( _closed )
                {
                    foreach( ViewPort context in CurrentView.Render ) {
                        context.FlushSize();
                    }
                    CurrentView.Use();
                    renderAwaitingToken.WaitNextSpan();
                    Interlocked.Add( ref _frameCount, 1 );
                }
            }
        }

    }
}