WebController.swift

public class WebController: NSObject
{
    @File(name: "gamepad", type: "js", decoder: { String(data: $0, encoding: .utf8) })
    var gamepadScript: String?

    public func setup(webview: WKWebView)
    {
        guard let script = gamepadScript else {
            return
        }

        webview.evaluateJavaScript(script, completionHandler: nil)
    }

    private var controllerData: String {

        guard let controller = GCController.controllers().first,
            let gamepad = controller.extendedGamepad,
            let buttonOptions = gamepad.buttonOptions,
            let buttonHome = gamepad.buttonHome,
            let leftThumbstickButton = gamepad.leftThumbstickButton,
            let rightThumbstickButton = gamepad.rightThumbstickButton else {

            return ""
        }

        let customController = Controller(
            axes: [
                Double(gamepad.leftThumbstick.xAxis.value),
                Double(-1.0 * gamepad.leftThumbstick.yAxis.value),
                Double(gamepad.rightThumbstick.xAxis.value),
                Double(-1.0 * gamepad.rightThumbstick.yAxis.value)
            ],
            buttons: [
                GamePadButton(pressed: gamepad.buttonA.isPressed, value: Double(gamepad.buttonA.value)),
                GamePadButton(pressed: gamepad.buttonB.isPressed, value: Double(gamepad.buttonB.value)),
                GamePadButton(pressed: gamepad.buttonX.isPressed, value: Double(gamepad.buttonX.value)),
                GamePadButton(pressed: gamepad.buttonY.isPressed, value: Double(gamepad.buttonY.value)),
                GamePadButton(pressed: gamepad.leftShoulder.isPressed, value: Double(gamepad.leftShoulder.value)),
                GamePadButton(pressed: gamepad.rightShoulder.isPressed, value: Double(gamepad.rightShoulder.value)),
                GamePadButton(pressed: gamepad.leftTrigger.isPressed, value: Double(gamepad.leftTrigger.value)),
                GamePadButton(pressed: gamepad.rightTrigger.isPressed, value: Double(gamepad.rightTrigger.value)),
                GamePadButton(pressed: buttonOptions.isPressed, value: Double(buttonOptions.value)),
                GamePadButton(pressed: gamepad.buttonMenu.isPressed, value: Double(gamepad.buttonMenu.value)),
                GamePadButton(pressed: leftThumbstickButton.isPressed, value: Double(leftThumbstickButton.value)),
                GamePadButton(pressed: rightThumbstickButton.isPressed, value: Double(rightThumbstickButton.value)),
                GamePadButton(pressed: gamepad.dpad.up.isPressed, value: Double(gamepad.dpad.up.value)),
                GamePadButton(pressed: gamepad.dpad.down.isPressed, value: Double(gamepad.dpad.down.value)),
                GamePadButton(pressed: gamepad.dpad.left.isPressed, value: Double(gamepad.dpad.left.value)),
                GamePadButton(pressed: gamepad.dpad.right.isPressed, value: Double(gamepad.dpad.right.value)),
                GamePadButton(pressed: buttonHome.isPressed, value: Double(buttonHome.value)),
            ],
            connected: true,
            id: "Emulated iOS Controller",
            index: 0,
            mapping: "standard",
            timestamp: 0)

        return customController.jsonString
    }
}

extension WebController: WKScriptMessageHandlerWithReply
{
    public func userContentController(_ userContentController: WKUserContentController, didReceive message: WKScriptMessage, replyHandler: @escaping (Any?, String?) -> Void) {
        replyHandler(controllerData, nil)
    }
}