//
//  WebViewController.swift
//  WebviewDemo
//
//  Created by marco.rossi on 22/09/2019.
//  Copyright © 2019 marco.rossi. All rights reserved.
//

import UIKit
import WebKit

class WebViewController: UIViewController {

    private var webView: WKWebView!

    override func viewDidLoad() {
        super.viewDidLoad()

        let config = WKWebViewConfiguration()
        let userContentController = WKUserContentController()

        userContentController.add(self, name: "camera")
        userContentController.add(self, name: "data")
        config.userContentController = userContentController

        webView = WKWebView(frame: .zero, configuration: config)

        view.addSubview(webView)

        webView.translatesAutoresizingMaskIntoConstraints = false
        webView.leadingAnchor.constraint(equalTo: view.leadingAnchor).isActive = true
        webView.trailingAnchor.constraint(equalTo: view.trailingAnchor).isActive = true
        webView.topAnchor.constraint(equalTo: view.topAnchor).isActive = true
        webView.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true

        if let url = URL(string: "https://demo.morphcast.com/native-app-webview/webview_index.html") {
            webView.load(URLRequest(url: url))
        }
    }

}

extension WebViewController: WKScriptMessageHandler {
    func userContentController(_ userContentController: WKUserContentController, didReceive message: WKScriptMessage) {
        if message.name == "camera", let dict = message.body as? NSDictionary {
            if let maxSize = dict["value"] as? Int {
                onCameraFrame(maxSize: maxSize)
            }
        }
        if message.name == "data", let dict = message.body as? NSDictionary {
            if let type = dict["type"] as? String, let value = dict["value"] as? String {
                onData(type: type, value: value)
            }
        }
    }

    // JS Callbacks
    private func onCameraFrame(maxSize: Int) {
        /*
        App developer shall implement the following behaviour:

        1) Retrieve a frame from camera

        * We suggest to resize frames before passing them to the WebView and to encode them in base64 format
        * Strings are processed faster than binary data through the JavaScript Interface

        2) resize it to maxSize x maxSize (maintaining the aspect ratio)
        3) Convert the frame to Base64
        4) return the Base64 String
        */

        let base64Image = "..."
        let js = "resolveFrame(\(base64Image))"
        webView.evaluateJavaScript(js, completionHandler: nil)
    }

    private func onData(type: String, value: String) {
        /*
         type: String
         ["AGE","GENDER","EMOTION","FEATURES","POSE","AROUSAL_VALENCE","ATTENTION"]
         value: Json-stringified of the result

         App developer can use the values returned from the webview to implement the desired behavior (e.g update the App view, send data to a custom db ...)
        */
    }

}