import SwiftUI

struct MapOpportunities: View {

  let mapSize: CGSize
  let lineWidth: CGFloat
  let vertexSize: CGSize
  let opportunities: [Opportunity]

  let arrowheadSize = CGFloat(10.0)

  var body: some View {
    ForEach(opportunities, id: \.id) { edge in
      Path { path in

        // First we transform edges from percentage to map coordinates
        let origin = CGPoint(x: w(edge.origin.x), y: h(edge.origin.y))
        let destination = CGPoint(x: w(edge.destination.x), y: h(edge.destination.y))

        let multiplier = CGFloat(edge.destination.x > edge.origin.x ? 1.0 : -1.0)
        let upperAngle = -CGFloat.pi / 4.0
        let lowerAngle = CGFloat.pi / 4.0

        let offsetOrigin = CGPoint(x: origin.x + multiplier * (vertexSize.width / 2.0), y: origin.y)
        let offsetDestination = CGPoint(
          x: destination.x - multiplier * (vertexSize.width / 2.0), y: destination.y)

        path.move(to: offsetOrigin)
        path.addLine(to: offsetDestination)

        path.move(to: offsetDestination)
        path.addLine(
          to: CGPoint(
            x: offsetDestination.x - multiplier * arrowheadSize * cos(upperAngle),
            y:
              offsetDestination.y - multiplier * arrowheadSize * sin(upperAngle)))

        path.move(to: offsetDestination)
        path.addLine(
          to: CGPoint(
            x: offsetDestination.x - multiplier * arrowheadSize * cos(lowerAngle),
            y:
              offsetDestination.y - multiplier * arrowheadSize * sin(lowerAngle)))

        path.move(to: offsetDestination)
        path.closeSubpath()
      }.applying(
        CGAffineTransform(translationX: vertexSize.width / 2.0, y: vertexSize.height / 2.0)
      ).strokedPath(StrokeStyle(lineWidth: lineWidth / 4, dash: [10.0])).stroke(Color.map.opportunityColor)
    }
  }

  func h(_ dimension: CGFloat) -> CGFloat {
    max(0.0, min(mapSize.height, dimension * mapSize.height / 100.0))
  }

  func w(_ dimension: CGFloat) -> CGFloat {
    max(0.0, min(mapSize.width, dimension * mapSize.width / 100.0))
  }
}

struct MapOpportunities_Previews: PreviewProvider {
  static var previews: some View {
    MapOpportunities(
      mapSize: CGSize(width: 400.0, height: 400.0), lineWidth: 1.0,
      vertexSize: CGSize(width: 25.0, height: 25.0),
      opportunities: [
        Opportunity(id: 1, origin: CGPoint(x: 2.0, y: 34.0), destination: CGPoint(x: 23.0, y: 76.2))
      ])
  }
}