/// Copyright (c) 2017 Razeware LLC
///
/// Permission is hereby granted, free of charge, to any person obtaining a copy
/// of this software and associated documentation files (the "Software"), to deal
/// in the Software without restriction, including without limitation the rights
/// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
/// copies of the Software, and to permit persons to whom the Software is
/// furnished to do so, subject to the following conditions:
///
/// The above copyright notice and this permission notice shall be included in
/// all copies or substantial portions of the Software.
///
/// Notwithstanding the foregoing, you may not use, copy, modify, merge, publish,
/// distribute, sublicense, create a derivative work, and/or sell copies of the
/// Software in any work that is designed, intended, or marketed for pedagogical or
/// instructional purposes related to programming, coding, application development,
/// or information technology.  Permission for such use, copying, modification,
/// merger, publication, distribution, sublicensing, creation of derivative works,
/// or sale is expressly withheld.
///
/// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
/// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
/// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
/// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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/// THE SOFTWARE.

import UIKit
import CoreML
import Vision

class ViewController: UIViewController {

  @IBOutlet weak var drawView: DrawView!
  @IBOutlet weak var predictLabel: UILabel!

  // DONE: Define lazy var classificationRequest
  lazy var classificationRequest: VNCoreMLRequest = {
    // Load the ML model through its generated class and create a Vision request for it.
    do {
      let model = try VNCoreMLModel(for: MNISTClassifier().model)
      return VNCoreMLRequest(model: model, completionHandler: self.handleClassification)
    } catch {
      fatalError("Can't load Vision ML model: \(error).")
    }
  }()

  func handleClassification(request: VNRequest, error: Error?) {
    guard let observations = request.results as? [VNClassificationObservation]
      else { fatalError("Unexpected result type from VNCoreMLRequest.") }
    guard let best = observations.first
      else { fatalError("Can't get best result.") }

    DispatchQueue.main.async {
      self.predictLabel.text = best.identifier
      self.predictLabel.isHidden = false
    }
  }

  override func viewDidLoad() {
    super.viewDidLoad()
    predictLabel.isHidden = true
  }

  @IBAction func clearTapped() {
    drawView.lines = []
    drawView.setNeedsDisplay()
    predictLabel.isHidden = true
  }

  @IBAction func predictTapped() {
    guard let context = drawView.getViewContext(),
      let inputImage = context.makeImage()
      else { fatalError("Get context or make image failed.") }
    // DONE: Perform request on model
    let ciImage = CIImage(cgImage: inputImage)
    let handler = VNImageRequestHandler(ciImage: ciImage)
    do {
      try handler.perform([classificationRequest])
    } catch {
      print(error)
    }
  }

}

