//-----------------------------------------------------------------------
// <copyright file="GvrAllEventsTrigger.cs" company="Google Inc.">
// 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.
// </copyright>
//-----------------------------------------------------------------------

using System;
using System.Collections;
using UnityEngine;
using UnityEngine.Events;
using UnityEngine.EventSystems;

/// <summary>
/// Exposes events from `GvrEventExecutor` that are fired by `GvrPointerInputModule_`to the editor.
/// </summary>
/// <remarks>Makes it possible to handle `EventSystem` events globally.</remarks>
[HelpURL("https://developers.google.com/vr/unity/reference/class/GvrAllEventsTrigger")]
public class GvrAllEventsTrigger : MonoBehaviour
{
    /// <summary>Event for `OnPointerClick`.</summary>
    [System.Diagnostics.CodeAnalysis.SuppressMessage(
        "UnityRules.LegacyGvrStyleRules",
        "VR1003:FieldsMustBeLowerCamelCase",
        Justification = "Legacy Public API.")]
    public TriggerEvent OnPointerClick;

    /// <summary>Event for `OnPointerDown`.</summary>
    [System.Diagnostics.CodeAnalysis.SuppressMessage(
        "UnityRules.LegacyGvrStyleRules",
        "VR1003:FieldsMustBeLowerCamelCase",
        Justification = "Legacy Public API.")]
    public TriggerEvent OnPointerDown;

    /// <summary>Event for `OnPointerUp`.</summary>
    [System.Diagnostics.CodeAnalysis.SuppressMessage(
        "UnityRules.LegacyGvrStyleRules",
        "VR1003:FieldsMustBeLowerCamelCase",
        Justification = "Legacy Public API.")]
    public TriggerEvent OnPointerUp;

    /// <summary>Event for `OnPointerEnter`.</summary>
    [System.Diagnostics.CodeAnalysis.SuppressMessage(
        "UnityRules.LegacyGvrStyleRules",
        "VR1003:FieldsMustBeLowerCamelCase",
        Justification = "Legacy Public API.")]
    public TriggerEvent OnPointerEnter;

    /// <summary>Event for `OnPointerExit`.</summary>
    [System.Diagnostics.CodeAnalysis.SuppressMessage(
        "UnityRules.LegacyGvrStyleRules",
        "VR1003:FieldsMustBeLowerCamelCase",
        Justification = "Legacy Public API.")]
    public TriggerEvent OnPointerExit;

    /// <summary>Event for `OnScroll`.</summary>
    [System.Diagnostics.CodeAnalysis.SuppressMessage(
        "UnityRules.LegacyGvrStyleRules",
        "VR1003:FieldsMustBeLowerCamelCase",
        Justification = "Legacy Public API.")]
    public TriggerEvent OnScroll;

    private bool listenersAdded;

    private void OnEnable()
    {
        AddListeners();
    }

    private void OnDisable()
    {
        RemoveListeners();
    }

    private void Start()
    {
        // The eventExecutor may not be available during OnEnable when the script is first created.
        AddListeners();
    }

    private void AddListeners()
    {
        GvrEventExecutor eventExecutor = GvrPointerInputModule.FindEventExecutor();
        if (eventExecutor == null)
        {
            return;
        }

        if (listenersAdded)
        {
            return;
        }

        eventExecutor.OnPointerClick += OnPointerClickHandler;
        eventExecutor.OnPointerDown += OnPointerDownHandler;
        eventExecutor.OnPointerUp += OnPointerUpHandler;
        eventExecutor.OnPointerEnter += OnPointerEnterHandler;
        eventExecutor.OnPointerExit += OnPointerExitHandler;
        eventExecutor.OnScroll += OnScrollHandler;

        listenersAdded = true;
    }

    private void RemoveListeners()
    {
        GvrEventExecutor eventExecutor = GvrPointerInputModule.FindEventExecutor();
        if (eventExecutor == null)
        {
            return;
        }

        if (!listenersAdded)
        {
            return;
        }

        eventExecutor.OnPointerClick -= OnPointerClickHandler;
        eventExecutor.OnPointerDown -= OnPointerDownHandler;
        eventExecutor.OnPointerUp -= OnPointerUpHandler;
        eventExecutor.OnPointerEnter -= OnPointerEnterHandler;
        eventExecutor.OnPointerExit -= OnPointerExitHandler;
        eventExecutor.OnScroll -= OnScrollHandler;

        listenersAdded = false;
    }

    private void OnPointerClickHandler(GameObject target, PointerEventData eventData)
    {
        OnPointerClick.Invoke(target, eventData);
    }

    private void OnPointerDownHandler(GameObject target, PointerEventData eventData)
    {
        OnPointerDown.Invoke(target, eventData);
    }

    private void OnPointerUpHandler(GameObject target, PointerEventData eventData)
    {
        OnPointerUp.Invoke(target, eventData);
    }

    private void OnPointerEnterHandler(GameObject target, PointerEventData eventData)
    {
        OnPointerEnter.Invoke(target, eventData);
    }

    private void OnPointerExitHandler(GameObject target, PointerEventData eventData)
    {
        OnPointerExit.Invoke(target, eventData);
    }

    private void OnScrollHandler(GameObject target, PointerEventData eventData)
    {
        OnScroll.Invoke(target, eventData);
    }

    /// <summary>Exposes fired `PointerEventData` events.</summary>
    [Serializable]
    public class TriggerEvent : UnityEvent<GameObject, PointerEventData>
    {
    }
}