using System;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.EventSystems;

// To use:
// 1. Drag onto your EventSystem game object.
// 2. Disable any other Input Modules (eg: StandaloneInputModule & TouchInputModule) as they will fight over selections.
// 3. Make sure your Canvas is in world space and has a GraphicRaycaster (should by default).
// 4. If you have multiple cameras then make sure to drag your VR (center eye) camera into the canvas.
public class OcculusGazeInputModule : PointerInputModule {
  public RaycastResult CurrentRaycast;

  private PointerEventData pointerEventData;
  private GameObject currentLookAtHandler;

  public override void Process() {
    HandleLook();
    HandleSelection();
  }

  void HandleLook() {
    if (pointerEventData == null) {
      pointerEventData = new PointerEventData(eventSystem);
    }

    // fake a pointer always being at the center of the screen
    pointerEventData.Reset();
    pointerEventData.position = new Vector2(Screen.width / 2f, Screen.height / 2f);
    pointerEventData.delta = Vector2.zero;
    List<RaycastResult> raycastResults = new List<RaycastResult>();
    eventSystem.RaycastAll(pointerEventData, raycastResults);
    CurrentRaycast = pointerEventData.pointerCurrentRaycast = FindFirstRaycast(raycastResults);

    Debug.Log(CurrentRaycast);

    ProcessMove(pointerEventData);
  }

  void HandleSelection() {
    if (pointerEventData.pointerEnter != null) {
      // if the ui receiver has changed, reset the gaze delay timer
      GameObject handler = ExecuteEvents.GetEventHandler<IPointerClickHandler>(pointerEventData.pointerEnter);
      if (currentLookAtHandler != handler) {
        currentLookAtHandler = handler;
      }

      // if we have a handler and it's time to click, do it now
      if (currentLookAtHandler != null && (OVRInput.Get(OVRInput.Button.Start) || OVRInput.Get(OVRInput.Button.One))) {
        ExecuteEvents.ExecuteHierarchy(currentLookAtHandler, pointerEventData, ExecuteEvents.pointerClickHandler);
      }
    }
    else {
      currentLookAtHandler = null;
    }
  }

}