package funkin;

import flixel.util.FlxSignal;
import funkin.SongLoad.SwagSong;
import funkin.play.song.Song.SongDifficulty;
import funkin.play.song.SongData.SongTimeChange;

typedef BPMChangeEvent =
{
  var stepTime:Int;
  var songTime:Float;
  var bpm:Float;
}

class Conductor
{
  /**
   * The list of time changes in the song.
   * There should be at least one time change (at the beginning of the song) to define the BPM.
   */
  static var timeChanges:Array<SongTimeChange> = [];

  /**
   * The current time change.
   */
  static var currentTimeChange:SongTimeChange;

  /**
   * The current position in the song in milliseconds.
   * Updated every frame based on the audio position.
   */
  public static var songPosition:Float;

  /**
   * Beats per minute of the current song at the current time.
   */
  public static var bpm(get, null):Float;

  static function get_bpm():Float
  {
    if (bpmOverride != null) return bpmOverride;

    if (currentTimeChange == null) return 100;

    return currentTimeChange.bpm;
  }

  static var bpmOverride:Null<Float> = null;

  // OLD, replaced with timeChanges.
  public static var bpmChangeMap:Array<BPMChangeEvent> = [];

  /**
   * Duration of a beat in millisecond. Calculated based on bpm.
   */
  public static var crochet(get, null):Float;

  static function get_crochet():Float
  {
    return ((60 / bpm) * 1000);
  }

  /**
   * Duration of a step (quarter) in milliseconds. Calculated based on bpm.
   */
  public static var stepCrochet(get, null):Float;

  static function get_stepCrochet():Float
  {
    return crochet / timeSignatureNumerator;
  }

  public static var timeSignatureNumerator(get, null):Int;

  static function get_timeSignatureNumerator():Int
  {
    if (currentTimeChange == null) return 4;

    return currentTimeChange.timeSignatureNum;
  }

  public static var timeSignatureDenominator(get, null):Int;

  static function get_timeSignatureDenominator():Int
  {
    if (currentTimeChange == null) return 4;

    return currentTimeChange.timeSignatureDen;
  }

  /**
   * Current position in the song, in beats.
  **/
  public static var currentBeat(default, null):Int;

  /**
   * Current position in the song, in steps.
   */
  public static var currentStep(default, null):Int;

  /**
   * Current position in the song, in steps and fractions of a step.
   */
  public static var currentStepTime(default, null):Float;

  public static var beatHit(default, null):FlxSignal = new FlxSignal();
  public static var stepHit(default, null):FlxSignal = new FlxSignal();

  public static var lastSongPos:Float;
  public static var visualOffset:Float = 0;
  public static var audioOffset:Float = 0;
  public static var offset:Float = 0;

  // TODO: Add code to update this.
  public static var beatsPerMeasure(get, null):Int;

  static function get_beatsPerMeasure():Int
  {
    return timeSignatureNumerator;
  }

  public static var stepsPerMeasure(get, null):Int;

  static function get_stepsPerMeasure():Int
  {
    // Is this always x4?
    return timeSignatureNumerator * 4;
  }

  function new() {}

  public static function getLastBPMChange()
  {
    var lastChange:BPMChangeEvent =
      {
        stepTime: 0,
        songTime: 0,
        bpm: 0
      }
    for (i in 0...Conductor.bpmChangeMap.length)
    {
      if (Conductor.songPosition >= Conductor.bpmChangeMap[i].songTime) lastChange = Conductor.bpmChangeMap[i];

      if (Conductor.songPosition < Conductor.bpmChangeMap[i].songTime) break;
    }
    return lastChange;
  }

  /**
   * Forcibly defines the current BPM of the song.
   * Useful for things like the chart editor that need to manipulate BPM in real time.
   * 
   * Set to null to reset to the BPM defined by the timeChanges.
   * 
   * WARNING: Avoid this for things like setting the BPM of the title screen music,
   * you should have a metadata file for it instead.
   */
  public static function forceBPM(?bpm:Float = null)
  {
    if (bpm != null) trace('[CONDUCTOR] Forcing BPM to ' + bpm);
    else
      trace('[CONDUCTOR] Resetting BPM to default');
    Conductor.bpmOverride = bpm;
  }

  /**
   * Update the conductor with the current song position.
   * BPM, current step, etc. will be re-calculated based on the song position.
   * 
   * @param	songPosition The current position in the song in milliseconds.
   *        Leave blank to use the FlxG.sound.music position.
   */
  public static function update(songPosition:Float = null)
  {
    if (songPosition == null) songPosition = (FlxG.sound.music != null) ? FlxG.sound.music.time + Conductor.offset : 0.0;

    var oldBeat = currentBeat;
    var oldStep = currentStep;

    Conductor.songPosition = songPosition;
    // Conductor.bpm = Conductor.getLastBPMChange().bpm;

    currentTimeChange = timeChanges[0];
    for (i in 0...timeChanges.length)
    {
      if (songPosition >= timeChanges[i].timeStamp) currentTimeChange = timeChanges[i];

      if (songPosition < timeChanges[i].timeStamp) break;
    }

    if (currentTimeChange == null && bpmOverride == null && FlxG.sound.music != null)
    {
      trace('WARNING: Conductor is broken, timeChanges is empty.');
    }
    else if (currentTimeChange != null)
    {
      currentStepTime = (currentTimeChange.beatTime * 4) + (songPosition - currentTimeChange.timeStamp) / stepCrochet;
      currentStep = Math.floor(currentStepTime);
      currentBeat = Math.floor(currentStep / 4);
    }
    else
    {
      // Assume a constant BPM equal to the forced value.
      currentStepTime = (songPosition / stepCrochet);
      currentStep = Math.floor(currentStepTime);
      currentBeat = Math.floor(currentStep / 4);
    }

    // FlxSignals are really cool.
    if (currentStep != oldStep)
    {
      stepHit.dispatch();
    }

    if (currentBeat != oldBeat)
    {
      beatHit.dispatch();
    }
  }

  @:deprecated // Switch to TimeChanges instead.
  public static function mapBPMChanges(song:SwagSong)
  {
    bpmChangeMap = [];

    var curBPM:Float = song.bpm;
    var totalSteps:Int = 0;
    var totalPos:Float = 0;
    for (i in 0...SongLoad.getSong().length)
    {
      if (SongLoad.getSong()[i].changeBPM && SongLoad.getSong()[i].bpm != curBPM)
      {
        curBPM = SongLoad.getSong()[i].bpm;
        var event:BPMChangeEvent =
          {
            stepTime: totalSteps,
            songTime: totalPos,
            bpm: curBPM
          };
        bpmChangeMap.push(event);
      }

      var deltaSteps:Int = SongLoad.getSong()[i].lengthInSteps;
      totalSteps += deltaSteps;
      totalPos += ((60 / curBPM) * 1000 / 4) * deltaSteps;
    }
  }

  public static function mapTimeChanges(songTimeChanges:Array<SongTimeChange>)
  {
    timeChanges = [];

    for (currentTimeChange in songTimeChanges)
    {
      timeChanges.push(currentTimeChange);
    }

    trace('Done mapping time changes: ' + timeChanges);

    // Done.
  }

  /**
   * Given a time in milliseconds, return a time in steps.
   */
  public static function getTimeInSteps(ms:Float):Int
  {
    if (timeChanges.length == 0)
    {
      // Assume a constant BPM equal to the forced value.
      return Math.floor(ms / stepCrochet);
    }
    else
    {
      var resultStep:Int = 0;

      var lastTimeChange:SongTimeChange = timeChanges[0];
      for (timeChange in timeChanges)
      {
        if (ms >= timeChange.timeStamp)
        {
          lastTimeChange = timeChange;
          resultStep = lastTimeChange.beatTime * 4;
        }
        else
        {
          // This time change is after the requested time.
          break;
        }
      }

      resultStep += Math.floor((ms - lastTimeChange.timeStamp) / stepCrochet);

      return resultStep;
    }
  }
}