PhysicalConnectivity/src/main/kotlin/net/shadowfacts/phycon/client/screen/ScrollTrackView.kt

package net.shadowfacts.phycon.client.screen

import net.minecraft.util.Identifier
import net.minecraft.util.math.MathHelper
import net.shadowfacts.cacao.geometry.Point
import net.shadowfacts.cacao.geometry.Rect
import net.shadowfacts.cacao.util.MouseButton
import net.shadowfacts.cacao.util.texture.Texture
import net.shadowfacts.cacao.view.TextureView
import net.shadowfacts.cacao.view.View
import net.shadowfacts.phycon.PhysicalConnectivity

/**
 * @author shadowfacts
 */
class ScrollTrackView(
	val scrollPositionChanged: (ScrollTrackView) -> Unit,
): View() {

	companion object {
		private val THUMB = Texture(Identifier(PhysicalConnectivity.MODID, "textures/gui/terminal.png"), 52, 230)
		private const val THUMB_WIDTH = 12.0
		private const val THUMB_HEIGHT = 15.0
	}

	private lateinit var thumbView: TextureView

	private var grabbedY: Double? = null

	/**
	 * The [0,1] normalized position of the scroll thumb.
	 */
	var scrollPosition: Double
		get() = thumbView.frame.top / (frame.height - THUMB_HEIGHT)
		set(value) {
			val newTop = MathHelper.clamp(value, 0.0, 1.0) * (frame.height - THUMB_HEIGHT)
			thumbView.frame = Rect(0.0, newTop, THUMB_WIDTH, THUMB_HEIGHT)
		}

	init {
		respondsToDragging = true
	}

	override fun wasAdded() {
		super.wasAdded()

		thumbView = addSubview(TextureView(THUMB).apply {
			usesConstraintBasedLayout = false
			frame = Rect(0.0, 0.0, THUMB_WIDTH, THUMB_HEIGHT)
		})
	}

	override fun mouseDragged(startPoint: Point, delta: Point, mouseButton: MouseButton): Boolean {
		if (grabbedY == null && startPoint !in thumbView.frame) {
			val newCenter = MathHelper.clamp(startPoint.y, THUMB_HEIGHT / 2, frame.height - THUMB_HEIGHT / 2)
			thumbView.frame = Rect(0.0, newCenter - THUMB_HEIGHT / 2, THUMB_WIDTH, THUMB_HEIGHT)
		}

		if (grabbedY == null) {
			grabbedY = startPoint.y - thumbView.frame.top
		}
		val newTop = MathHelper.clamp(startPoint.y - grabbedY!!, 0.0, frame.height - THUMB_HEIGHT)
		thumbView.frame = Rect(0.0, newTop, THUMB_WIDTH, THUMB_HEIGHT)

		scrollPositionChanged(this)

		return true
	}

	override fun mouseDragEnded(point: Point, mouseButton: MouseButton) {
		grabbedY = null
	}

}