WaveformView.swift

//
//  WaveformView.swift
//  WaveformSwiftUI
//
//  Created by Adam Bell on 9/4/19.
//  Copyright © 2019 Adam Bell. All rights reserved.
//

import SwiftUI

struct WaveformView: View {
  
  var data: [Float]
  
  var body: some View {
    GeometryReader { geo in
      Path { [data = self.data] path in
        guard data.count > 0 else { return }

        let bounds = geo.frame(in: .local)
        let insetBounds = bounds.insetBy(dx: 20.0, dy: 20.0)

        let width = insetBounds.width
        let height = insetBounds.height
        let halfHeight = height / 2.0

        let yForData = { (value: Float) in
          return insetBounds.minY + halfHeight + (halfHeight * CGFloat(value))
        }

        path.move(to: CGPoint(x: insetBounds.minX, y: yForData(data[0])))

        for i in 1..<data.count {
          let x = insetBounds.minX + (width * (CGFloat(i) / CGFloat(data.count)))
          let y = yForData(data[i])
          path.addLine(to: CGPoint(x: x, y: y))
        }
      }
      .stroke(Color.white, lineWidth: 4.0)
      .background(Color.black)
      .drawingGroup()
    }
  }
}

struct WaveformView_Previews: PreviewProvider {
  static var previews: some View {
    VStack {
      Spacer()
      WaveformView(data: Wavetables.sine)
        .frame(width: nil, height: 280.0, alignment: .center)
      Spacer()
    }
    .background(Color.black)
    .edgesIgnoringSafeArea(.all)
  }
}