using System.Diagnostics;
using System.Collections;
using System.Collections.Generic;
using System;
using Godot;


using Rokojori.Extensions;
namespace Rokojori;


public class TimelineRunner
{
  public Timeline timeLine;
  public TimelineManager manager;
  
  public float lastPosition = 0;
  public float position = 0;
  public bool playing = false;
  public float deltaScale = 1;
  public float speed = 1;

  List<TimelineEvent> events = new List<TimelineEvent>();
  List<TimelineSpan> spans = new List<TimelineSpan>(); 
  List<TimelineCallback> callbacks = new List<TimelineCallback>();

  AnimationCurve modulatorCurve;
  float modulatorTime;
  Vector3 modulatorRandomization;
  Action<bool> modulatorOnReady = null;
  float _lastModulation = 1;
  float _currentDelta = 1;
  
  public float modulatedSpeed => (float)( speed * _lastModulation * deltaScale );
  public float currentDelta => _currentDelta;

  public TimelineRunner( Timeline timeLine, TimelineManager manager )
  {
    this.timeLine = timeLine;
    this.manager = manager;
    this.speed = timeLine.startSpeed;

    playing = timeLine.autoStart;
  }

  public void Modulate( AnimationCurve curve, Action<bool> onReady )
  {
    if ( modulatorOnReady != null )
    {
      modulatorOnReady( false );
    }

    modulatorCurve = curve;
    modulatorTime = 0;
    modulatorRandomization = curve.Randomize();
    modulatorOnReady = onReady;
  }

  public void UpdateTimeLine( float realtimeDelta )
  { 
    if ( ! playing || ( manager.paused && ! timeLine.executesInPause ))
    {
      return;
    }

    var modulation = 1f;

    if ( modulatorCurve != null )
    {
      modulation = modulatorCurve.SampleRandomized( modulatorTime, modulatorRandomization );

      _lastModulation = modulation;
      modulatorTime += realtimeDelta;

      if ( modulatorTime >= modulatorCurve.GetRandomizedEndTime( modulatorRandomization ) )
      {
        var mr = modulatorOnReady;
        modulatorOnReady = null;
        modulatorCurve = null;
        modulatorTime = 0;
        modulatorRandomization = Vector3.Zero;

        if ( mr != null )
        {
          mr( true );
        }
        
      }
    }
    else
    {
      _lastModulation = 1;
    }

    _currentDelta = realtimeDelta * deltaScale * speed * modulation;
    lastPosition = position;
    position += _currentDelta;

    var isForward = speed >= 0;

    if ( isForward )
    {
      ProcessForward();
    }
    
  }


  
  void ProcessForward()
  { 
    ProcessEvents();
    ProcessSpans();
    ProcessCallbacks();      
  }

  List<TimelineCallback> _callbackAdditions = new List<TimelineCallback>();

  void ProcessCallbacks()
  {
    if ( _callbackAdditions.Count > 0 )
    {      
      callbacks.AddRange( _callbackAdditions );
      _callbackAdditions.Clear();
    }

    callbacks.ForEach( c => c.callback( c ) );


  }

  void ProcessEvents()
  {
    if ( requestedRemovalIDs.Count > 0 )
    {
      requestedRemovalIDs.Sort();

      RJLog.Log( "Removing:", requestedRemovalIDs, "From:", events );
      //Lists.RemoveIncreasingSortedIndices( events, requestedRemovalIDs );
      events = events.Filter( e => ! requestedRemovalIDs.Contains( e.id ) );
      requestedRemovalIDs.Clear();
    }    

    List<int> eventRemovals = null;

    for ( int  i = 0; i < events.Count; i++ )
    {
      var timelineEvent = events[ i ];

      if ( timelineEvent.looping )
      {
        ProcessLoopingEvent( timelineEvent );
        continue;
      }

      if ( ! RangeDouble.ContainsExclusiveMax( lastPosition, position, timelineEvent.position ) )
      {
        if ( timelineEvent.wasInside )
        {
          eventRemovals = AddRemoval( timelineEvent.persistent, i, eventRemovals );
        }

        continue;
      }

      timelineEvent.callback( timelineEvent );
      timelineEvent.wasInside = true;

    }

    if ( eventRemovals != null )
    {
      ListExtensions.RemoveIncreasingSortedIndices( events, eventRemovals );
    }

    
  }

  // Upper bound of callbacks a single looping event can emit in one frame, so a huge
  // frame spike or a jumped timeline position can't stall the game with catching up.
  const int maxLoopCallbacksPerFrame = 128;

  // Fires once for every loop boundary inside [ lastPosition, position ). Checking for a
  // single boundary dropped the tick completely whenever a frame was longer than the loop
  // duration, which silently stopped loop events at low frame rates. Looping events are
  // only removed by an explicit RemoveEvent, never by elapsing.
  void ProcessLoopingEvent( TimelineEvent timelineEvent )
  {
    if ( timelineEvent.loopDuration <= 0 )
    {
      return;
    }

    var boundary = timelineEvent.GetNextLoopPosition( lastPosition );
    var numCallbacks = 0;

    while ( boundary < position && numCallbacks < maxLoopCallbacksPerFrame )
    {
      timelineEvent.callback( timelineEvent );
      timelineEvent.wasInside = true;

      boundary += timelineEvent.loopDuration;
      numCallbacks ++;
    }
  }

  void ProcessSpans()
  {
    if ( spans.Count == 0 )
    {
      return;
    }

    List<int> spanRemovals  = null;

    var timelineSpan = RangeDouble.Create( lastPosition, position );
    var span = RangeDouble.Create( 0, 1 );
    var isForward = lastPosition < position;

    for ( int  i = 0; i < spans.Count; i++ )
    {
      span.min = spans[ i ].start;
      span.max = spans[ i ].end;

      var overlaps = timelineSpan.Overlaps( span );

      if ( ! overlaps )
      {
        if ( spans[ i ].wasInside )
        {
          spanRemovals = AddRemoval( spans[ i ].persistent, i, spanRemovals );            
        }

        continue;
      }

      var isStart = timelineSpan.ContainsValue( spans[ i ].start );
      var isEnd   = timelineSpan.ContainsValue( spans[ i ].end );

      
      var spanType = TimelineSpanUpdateType.InSpan;

      if ( isStart && isEnd )
      {
        spanType = TimelineSpanUpdateType.CompletelyInside;
      }
      else if ( isStart )
      {
        spanType = TimelineSpanUpdateType.Start;
      }
      else if ( isEnd )
      {
        spanType = TimelineSpanUpdateType.End;
      }

      spans[ i ].wasInside = true;

      spans[ i ].callback( spans[ i ], spanType );        

    }

    if ( spanRemovals != null )
    {
      ListExtensions.RemoveIncreasingSortedIndices( spans, spanRemovals );
    }
  }

  
  List<int> AddRemoval( bool isPersistent, int index, List<int> list )
  {
    if ( isPersistent )
    {
      return list;
    }

    if ( list == null )
    {
      list = new List<int>();
    }

    list.Add( index );

    return list;
  }

  List<int> requestedRemovalIDs = new List<int>();

  public void RemoveEvent( int eventID )
  {
    requestedRemovalIDs.Add( eventID );

    RJLog.Log( "requestedRemovals add:", eventID );
  }

  public TimelineCallback _ScheduleCallback( Action<TimelineCallback> callback, int eventID )
  {
    var tle = new TimelineCallback();
    tle.id = eventID;
    tle.callback = callback;
    tle.timeLine = timeLine;

    _callbackAdditions.Add( tle );

    return tle;
  }

  public TimelineEvent _ScheduleEvent( float position, int eventID, bool isPersistent, Action<TimelineEvent> callback )
  {
    var tle = new TimelineEvent();
    tle.position = position;
    tle.id = eventID;
    tle.persistent = isPersistent;
    tle.callback = callback;
    tle.timeLine = timeLine;

    events.Add( tle );

    return tle;
  }

  public TimelineEvent _ScheduleLoopEvent( float loopDuration, float loopOffset, int eventID, bool isPersistent, Action<TimelineEvent> callback )
  {
    var tle = new TimelineEvent();
    tle.position = loopOffset;
    tle.looping = true;
    tle.loopDuration = loopDuration;
    tle.id = eventID;
    tle.persistent = isPersistent;
    tle.callback = callback;
    tle.timeLine = timeLine;
    events.Add( tle );

    return tle;
  }

  public TimelineSpan _ScheduleSpan( float start, float end, int eventID, bool isPersistent, Action<TimelineSpan, TimelineSpanUpdateType> callback )
  {
    var tse = new TimelineSpan();
    tse.start = start;
    tse.end   = end;
    tse.id = eventID;
    tse.persistent = isPersistent;
    tse.wasInside = false;
    tse.callback = callback;
    tse.timeLine = timeLine;
    
    spans.Add( tse );

    return tse;
  }
}