// Copyright 2017 Google Inc. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

using UnityEngine;
using UnityEngine.UI;
using UnityEngine.EventSystems;
using System.Collections;

/// Dropdown UI component that works with the GvrRaycasters.
/// This is a workaround for the fact that the Dropdown component doesn't work with custom raycasters
/// because it internally adds two GraphicRaycasters.
[HelpURL("https://developers.google.com/vr/unity/reference/class/GvrDropdown")]
public class GvrDropdown : Dropdown {
  private GameObject currentBlocker;

  public override void OnPointerClick(PointerEventData eventData) {
    base.OnPointerClick(eventData);
    FixTemplateAndBlockerRaycasters();
  }

  public override void OnSubmit(BaseEventData eventData) {
    base.OnSubmit(eventData);
    FixTemplateAndBlockerRaycasters();
  }

  private void FixTemplateAndBlockerRaycasters() {
    if (template != null) {
      FixRaycaster(template.gameObject, false);
    }
    FixRaycaster(currentBlocker, true);
  }

  protected override GameObject CreateBlocker(Canvas rootCanvas) {
    currentBlocker = base.CreateBlocker(rootCanvas);
    return currentBlocker;
  }

  protected override GameObject CreateDropdownList(GameObject template) {
    GameObject dropdown = base.CreateDropdownList(template);
    FixRaycaster(dropdown, false);
    return dropdown;
  }

  private void FixRaycaster(GameObject go, bool shouldCopyProperties) {
    if (go == null) {
      return;
    }

    GraphicRaycaster oldRaycaster = go.GetComponent<GraphicRaycaster>();
    Destroy(oldRaycaster);

    bool addedRaycaster;
    GvrPointerGraphicRaycaster raycaster;
    raycaster = GetOrAddComponent<GvrPointerGraphicRaycaster>(go, out addedRaycaster);

    if (shouldCopyProperties) {
      GvrPointerGraphicRaycaster templateRaycaster = GetTemplateRaycaster();
      if (addedRaycaster && templateRaycaster != null) {
        CopyRaycasterProperties(templateRaycaster, raycaster);
      }
    }
  }

  private GvrPointerGraphicRaycaster GetTemplateRaycaster() {
    if (template == null) {
      return null;
    }

    return template.GetComponent<GvrPointerGraphicRaycaster>();
  }

  private void CopyRaycasterProperties(GvrPointerGraphicRaycaster source, GvrPointerGraphicRaycaster dest) {
    if (source == null || dest == null) {
      return;
    }

    dest.blockingMask = source.blockingMask;
    dest.blockingObjects = source.blockingObjects;
    dest.ignoreReversedGraphics = source.ignoreReversedGraphics;
  }

  private static T GetOrAddComponent<T>(GameObject go, out bool addedComponent) where T : Component {
    T comp = go.GetComponent<T>();
    addedComponent = false;
    if (!comp) {
      comp = go.AddComponent<T>();
      addedComponent = true;
    }
    return comp;
  }
}