import CoreGraphics
import Foundation

extension Math {
  final class DisplayRadical: DisplayNode {
    var radicand: DisplayList?
    var degree: DisplayList?
    var radicalGlyph: DisplayNode?

    var radicalShift: CGFloat = 0
    var topKern: CGFloat = 0
    var lineThickness: CGFloat = 0

    init(radicand: DisplayList?, glyph: DisplayNode, position: CGPoint, range: NSRange) {
      self.radicand = radicand
      self.radicalGlyph = glyph
      super.init()
      self.position = position
      self.range = range
    }

    func setDegree(_ degree: DisplayList?, fontMetrics: Math.FontMetrics) {
      guard let degree else { return }
      let kernBefore = fontMetrics.radicalKernBeforeDegree
      let kernAfter = fontMetrics.radicalKernAfterDegree
      let raise = fontMetrics.radicalDegreeBottomRaisePercent * (ascent - descent)

      self.degree = degree

      var shift = kernBefore + degree.width + kernAfter
      if shift < 0 {
        shift = 0
      }
      radicalShift = shift

      degree.position = CGPoint(x: position.x + kernBefore, y: position.y + raise)
      width = shift + (radicalGlyph?.width ?? 0) + (radicand?.width ?? 0)
      updateRadicandPosition()
    }

    override var position: CGPoint {
      didSet { updateRadicandPosition() }
    }

    func updateRadicandPosition() {
      guard let radicand, let radicalGlyph else { return }
      radicand.position = CGPoint(
        x: position.x + radicalShift + radicalGlyph.width,
        y: position.y
      )
    }
  }
}