Funkin/source/funkin/play/notes/SustainTrail.hx

package funkin.play.notes;

import funkin.play.notes.NoteDirection;
import funkin.play.song.SongData.SongNoteData;
import flixel.util.FlxDirectionFlags;
import flixel.FlxSprite;
import flixel.graphics.FlxGraphic;
import flixel.graphics.tile.FlxDrawTrianglesItem;
import flixel.math.FlxMath;
import funkin.ui.PreferencesMenu;

/**
 * This is based heavily on the `FlxStrip` class. It uses `drawTriangles()` to clip a sustain note
 * trail at a certain time.
 * The whole `FlxGraphic` is used as a texture map. See the `NOTE_hold_assets.fla` file for specifics
 * on how it should be constructed.
 *
 * @author MtH
 */
class SustainTrail extends FlxSprite
{
  /**
   * The triangles corresponding to the hold, followed by the endcap.
   * `top left, top right, bottom left`
   * `top left, bottom left, bottom right`
   */
  static final TRIANGLE_VERTEX_INDICES:Array<Int> = [0, 1, 2, 1, 2, 3, 4, 5, 6, 5, 6, 7];

  public var strumTime:Float = 0; // millis
  public var noteDirection:NoteDirection = 0;
  public var sustainLength(default, set):Float = 0; // millis
  public var fullSustainLength:Float = 0;
  public var noteData:SongNoteData;

  public var cover:NoteHoldCover = null;

  /**
   * Set to `true` if the user hit the note and is currently holding the sustain.
   * Should display associated effects.
   */
  public var hitNote:Bool = false;

  /**
   * Set to `true` if the user missed the note or released the sustain.
   * Should make the trail transparent.
   */
  public var missedNote:Bool = false;

  // maybe BlendMode.MULTIPLY if missed somehow, drawTriangles does not support!

  /**
   * A `Vector` of floats where each pair of numbers is treated as a coordinate location (an x, y pair).
   */
  public var vertices:DrawData<Float> = new DrawData<Float>();

  /**
   * A `Vector` of integers or indexes, where every three indexes define a triangle.
   */
  public var indices:DrawData<Int> = new DrawData<Int>();

  /**
   * A `Vector` of normalized coordinates used to apply texture mapping.
   */
  public var uvtData:DrawData<Float> = new DrawData<Float>();

  private var processedGraphic:FlxGraphic;

  private var zoom:Float = 1;

  /**
   * What part of the trail's end actually represents the end of the note.
   * This can be used to have a little bit sticking out.
   */
  public var endOffset:Float = 0.5; // 0.73 is roughly the bottom of the sprite in the normal graphic!

  /**
   * At what point the bottom for the trail's end should be clipped off.
   * Used in cases where there's an extra bit of the graphic on the bottom to avoid antialiasing issues with overflow.
   */
  public var bottomClip:Float = 0.9;

  /**
   * Normally you would take strumTime:Float, noteData:Int, sustainLength:Float, parentNote:Note (?)
   * @param NoteData
   * @param SustainLength Length in milliseconds.
   * @param fileName
   */
  public function new(noteDirection:NoteDirection, sustainLength:Float, fileName:String)
  {
    super(0, 0, fileName);

    antialiasing = true;

    // TODO: Why does this reference pixel stuff?
    if (fileName == "arrowEnds")
    {
      endOffset = bottomClip = 1;
      antialiasing = false;
      zoom = 6;
    }
    // BASIC SETUP
    this.sustainLength = sustainLength;
    this.fullSustainLength = sustainLength;
    this.noteDirection = noteDirection;

    zoom *= 0.7;

    // CALCULATE SIZE
    width = graphic.width / 8 * zoom; // amount of notes * 2
    height = sustainHeight(sustainLength, PlayState.instance.currentChart.scrollSpeed);
    // instead of scrollSpeed, PlayState.SONG.speed

    flipY = PreferencesMenu.getPref('downscroll');

    // alpha = 0.6;
    alpha = 1.0;
    // calls updateColorTransform(), which initializes processedGraphic!
    updateColorTransform();

    updateClipping();
    indices = new DrawData<Int>(12, true, TRIANGLE_VERTEX_INDICES);
  }

  /**
   * Calculates height of a sustain note for a given length (milliseconds) and scroll speed.
   * @param	susLength	The length of the sustain note in milliseconds.
   * @param	scroll		The current scroll speed.
   */
  public static inline function sustainHeight(susLength:Float, scroll:Float)
  {
    return (susLength * 0.45 * scroll);
  }

  function set_sustainLength(s:Float)
  {
    if (s < 0) s = 0;

    height = sustainHeight(s, PlayState.instance.currentChart.scrollSpeed);
    updateColorTransform();
    updateClipping();
    return sustainLength = s;
  }

  /**
   * Sets up new vertex and UV data to clip the trail.
   * If flipY is true, top and bottom bounds swap places.
   * @param songTime	The time to clip the note at, in milliseconds.
   */
  public function updateClipping(songTime:Float = 0):Void
  {
    var clipHeight:Float = FlxMath.bound(sustainHeight(sustainLength - (songTime - strumTime), PlayState.instance.currentChart.scrollSpeed), 0, height);
    if (clipHeight == 0)
    {
      visible = false;
      return;
    }
    else
      visible = true;

    var bottomHeight:Float = graphic.height * zoom * endOffset;
    var partHeight:Float = clipHeight - bottomHeight;

    // ===HOLD VERTICES==
    // Top left
    vertices[0 * 2] = 0.0; // Inline with left side
    vertices[0 * 2 + 1] = flipY ? clipHeight : height - clipHeight;

    // Top right
    vertices[1 * 2] = width;
    vertices[1 * 2 + 1] = vertices[0 * 2 + 1]; // Inline with top left vertex

    // Bottom left
    vertices[2 * 2] = 0.0; // Inline with left side
    vertices[2 * 2 + 1] = if (partHeight > 0)
    {
      // flipY makes the sustain render upside down.
      flipY ? 0.0 + bottomHeight : vertices[1] + partHeight;
    }
    else
    {
      vertices[0 * 2 + 1]; // Inline with top left vertex (no partHeight available)
    }

    // Bottom right
    vertices[3 * 2] = width;
    vertices[3 * 2 + 1] = vertices[2 * 2 + 1]; // Inline with bottom left vertex

    // ===HOLD UVs===

    // The UVs are a bit more complicated.
    // UV coordinates are normalized, so they range from 0 to 1.
    // We are expecting an image containing 8 horizontal segments, each representing a different colored hold note followed by its end cap.

    uvtData[0 * 2] = 1 / 4 * (noteDirection % 4); // 0%/25%/50%/75% of the way through the image
    uvtData[0 * 2 + 1] = (-partHeight) / graphic.height / zoom; // top bound
    // Top left

    // Top right
    uvtData[1 * 2] = uvtData[0 * 2] + 1 / 8; // 12.5%/37.5%/62.5%/87.5% of the way through the image (1/8th past the top left)
    uvtData[1 * 2 + 1] = uvtData[0 * 2 + 1]; // top bound

    // Bottom left
    uvtData[2 * 2] = uvtData[0 * 2]; // 0%/25%/50%/75% of the way through the image
    uvtData[2 * 2 + 1] = 0.0; // bottom bound

    // Bottom right
    uvtData[3 * 2] = uvtData[1 * 2]; // 12.5%/37.5%/62.5%/87.5% of the way through the image (1/8th past the top left)
    uvtData[3 * 2 + 1] = uvtData[2 * 2 + 1]; // bottom bound

    // === END CAP VERTICES ===
    // Top left
    vertices[4 * 2] = vertices[2 * 2]; // Inline with bottom left vertex of hold
    vertices[4 * 2 + 1] = vertices[2 * 2 + 1]; // Inline with bottom left vertex of hold

    // Top right
    vertices[5 * 2] = vertices[3 * 2]; // Inline with bottom right vertex of hold
    vertices[5 * 2 + 1] = vertices[3 * 2 + 1]; // Inline with bottom right vertex of hold

    // Bottom left
    vertices[6 * 2] = vertices[2 * 2]; // Inline with left side
    vertices[6 * 2 + 1] = flipY ? (graphic.height * (-bottomClip + endOffset) * zoom) : (height + graphic.height * (bottomClip - endOffset) * zoom);

    // Bottom right
    vertices[7 * 2] = vertices[3 * 2]; // Inline with right side
    vertices[7 * 2 + 1] = vertices[6 * 2 + 1]; // Inline with bottom of end cap

    // === END CAP UVs ===
    // Top left
    uvtData[4 * 2] = uvtData[2 * 2] + 1 / 8; // 12.5%/37.5%/62.5%/87.5% of the way through the image (1/8th past the top left of hold)
    uvtData[4 * 2 + 1] = if (partHeight > 0)
    {
      0;
    }
    else
    {
      (bottomHeight - clipHeight) / zoom / graphic.height;
    };

    // Top right
    uvtData[5 * 2] = uvtData[4 * 2] + 1 / 8; // 25%/50%/75%/100% of the way through the image (1/8th past the top left of cap)
    uvtData[5 * 2 + 1] = uvtData[4 * 2 + 1]; // top bound

    // Bottom left
    uvtData[6 * 2] = uvtData[4 * 2]; // 12.5%/37.5%/62.5%/87.5% of the way through the image (1/8th past the top left of hold)
    uvtData[6 * 2 + 1] = bottomClip; // bottom bound

    // Bottom right
    uvtData[7 * 2] = uvtData[5 * 2]; // 25%/50%/75%/100% of the way through the image (1/8th past the top left of cap)
    uvtData[7 * 2 + 1] = uvtData[6 * 2 + 1]; // bottom bound
  }

  @:access(flixel.FlxCamera)
  override public function draw():Void
  {
    if (alpha == 0 || graphic == null || vertices == null) return;

    for (camera in cameras)
    {
      if (!camera.visible || !camera.exists) continue;
      // if (!isOnScreen(camera)) continue; // TODO: Update this code to make it work properly.

      getScreenPosition(_point, camera).subtractPoint(offset);
      camera.drawTriangles(processedGraphic, vertices, indices, uvtData, null, _point, blend, true, antialiasing);
    }
  }

  public override function kill():Void
  {
    super.kill();

    strumTime = 0;
    noteDirection = 0;
    sustainLength = 0;
    fullSustainLength = 0;
    noteData = null;

    hitNote = false;
    missedNote = false;
  }

  override public function destroy():Void
  {
    vertices = null;
    indices = null;
    uvtData = null;
    processedGraphic.destroy();

    super.destroy();
  }

  override function updateColorTransform():Void
  {
    super.updateColorTransform();
    if (processedGraphic != null) processedGraphic.destroy();
    processedGraphic = FlxGraphic.fromGraphic(graphic, true);
    processedGraphic.bitmap.colorTransform(processedGraphic.bitmap.rect, colorTransform);
  }
}