//-----------------------------------------------------------------------
// <copyright file="GvrTooltip.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.Collections;
using UnityEngine;
using UnityEngine.UI;

/// <summary>
/// A tooltip for displaying control schemes overlaying the controller visual using a Unity Canvas.
/// </summary>
/// <remarks>
/// Automatically changes what side of the controller the tooltip is shown on depending on the
/// handedness setting for the player.  Automatically fades out when the controller visual is too
/// close or too far away from the player's head.  Look at the prefab GvrControllerPointer to see an
/// example of how to use this script.
/// </remarks>
[RequireComponent(typeof(CanvasGroup))]
[RequireComponent(typeof(RectTransform))]
[ExecuteInEditMode]
[HelpURL("https://developers.google.com/vr/reference/unity/class/GvrTooltip")]
public class GvrTooltip : MonoBehaviour, IGvrArmModelReceiver
{
    /// <summary>
    /// Y Position for touch pad tooltips based on the standard controller visual.
    /// </summary>
    protected const float TOUCH_PAD_Y_POSITION_METERS = 0.0385f;

    /// <summary>
    /// Y position for app button tooltips based on the standard controller visual.
    /// </summary>
    protected const float APP_BUTTON_Y_POSITION_METERS = 0.0105f;

    /// <summary>Z position for all tooltips based on the standard controller visual.</summary>
    protected const float TOOLTIP_Z_POSITION_METERS = 0.0098f;

    /// <summary>
    /// Rotation for a tooltip when it is displayed on the right side of the controller visual.
    /// </summary>
    protected static readonly Quaternion RIGHT_SIDE_ROTATION = Quaternion.Euler(0.0f, 0.0f, 0.0f);

    /// <summary>
    /// Rotation for a tooltip when it is displayed on the left side of the controller visual.
    /// </summary>
    protected static readonly Quaternion LEFT_SIDE_ROTATION = Quaternion.Euler(0.0f, 0.0f, 180.0f);

    /// <summary>
    /// Anchor point for a tooltip, used for controlling what side the tooltip is on.
    /// </summary>
    protected static readonly Vector2 SQUARE_CENTER = new Vector2(0.5f, 0.5f);

    /// <summary>
    /// Pivot point for a tooltip, used for controlling what side the tooltip is on.
    /// </summary>
    protected static readonly Vector2 PIVOT = new Vector2(-0.5f, 0.5f);

    [Tooltip("The location to display the tooltip at relative to the controller visual.")]
    [SerializeField]
    private Location location;

    [Tooltip("The text field for this tooltip.")]
    [SerializeField]
    private Text text;

    [Tooltip(
        "Determines if the tooltip is always visible regardless of the controller's location.")]
    [SerializeField]
    private bool alwaysVisible;

    private bool isOnLeft = false;
    private RectTransform rectTransform;
    private CanvasGroup canvasGroup;

    /// <summary>Options for where the controller should be displayed.</summary>
    /// <remarks>
    /// If set to custom, then the manually set localPosition of the tooltip is used.  This is
    /// useful when displaying a tooltip for a non-standard controller visual.
    /// </remarks>
    internal enum Location
    {
        TouchPadOutside,
        TouchPadInside,
        AppButtonOutside,
        AppButtonInside,
        Custom
    }

    /// <summary>Gets the text field for this tooltip.</summary>
    /// <value>The tooltip text.</value>
    public Text TooltipText
    {
        get { return text; }
    }

    /// <summary>Gets or sets the arm model reference.</summary>
    /// <value>The arm model reference.</value>
    public GvrBaseArmModel ArmModel { get; set; }

    /// <summary>
    /// Returns `true` if this tooltip is set to display on the inside of the controller.
    /// </summary>
    /// <returns>Returns `true` if this instance is tooltip inside; otherwise, `false`.</returns>
    public bool IsTooltipInside()
    {
        switch (location)
        {
            case Location.TouchPadInside:
            case Location.AppButtonInside:
            case Location.Custom:
                return true;
            case Location.TouchPadOutside:
            case Location.AppButtonOutside:
            default:
                return false;
        }
    }

    /// <summary>
    /// Returns `true` if the tooltip should display on the left side of the controller.
    /// </summary>
    /// <remarks>
    /// This will change based on the handedness of the controller, as well as if the tooltip is set
    /// to display inside or outside.
    /// </remarks>
    /// <returns>Returns `true` if this instance is tooltip on left; otherwise, `false`.</returns>
    public bool IsTooltipOnLeft()
    {
        bool isInside = IsTooltipInside();
        GvrSettings.UserPrefsHandedness handedness = GvrSettings.Handedness;

        if (handedness == GvrSettings.UserPrefsHandedness.Left)
        {
            return !isInside;
        }
        else
        {
            return isInside;
        }
    }

    /// <summary>
    /// Refreshes how the tooltip is being displayed based on what side it is being shown on.
    /// </summary>
    /// <remarks>Override to add custom display functionality.</remarks>
    /// <param name="IsLocationOnLeft">Whether the location is on the left.</param>
    protected virtual void OnSideChanged(bool IsLocationOnLeft)
    {
        transform.localRotation = isOnLeft ? LEFT_SIDE_ROTATION : RIGHT_SIDE_ROTATION;

        if (text != null)
        {
            text.transform.localRotation =
                IsLocationOnLeft ? LEFT_SIDE_ROTATION : RIGHT_SIDE_ROTATION;

            text.alignment = IsLocationOnLeft ? TextAnchor.MiddleRight : TextAnchor.MiddleLeft;
        }
    }

    /// <summary>Gets the meters-to-canvas scale.</summary>
    /// <returns>The meters-to-canvas scale.</returns>
    protected float GetMetersToCanvasScale()
    {
        return GvrUIHelpers.GetMetersToCanvasScale(transform);
    }

    private void Awake()
    {
        rectTransform = GetComponent<RectTransform>();
        canvasGroup = GetComponent<CanvasGroup>();
        isOnLeft = IsTooltipOnLeft();
        RefreshTooltip();
    }

    private void OnEnable()
    {
        // Update using OnPostControllerInputUpdated.
        // This way, the position and rotation will be correct for the entire frame
        // so that it doesn't matter what order Updates get called in.
        if (Application.isPlaying)
        {
            GvrControllerInput.OnPostControllerInputUpdated += OnPostControllerInputUpdated;
        }
    }

    private void OnDisable()
    {
        GvrControllerInput.OnPostControllerInputUpdated -= OnPostControllerInputUpdated;
    }

    private void OnPostControllerInputUpdated()
    {
        CheckTooltipSide();

        if (canvasGroup != null && ArmModel != null)
        {
            canvasGroup.alpha = alwaysVisible ? 1.0f : ArmModel.TooltipAlphaValue;
        }
    }

    private void OnValidate()
    {
        rectTransform = GetComponent<RectTransform>();
        RefreshTooltip();
    }

#if UNITY_EDITOR
    private void OnRenderObject()
    {
        if (!Application.isPlaying)
        {
            CheckTooltipSide();
        }
    }
#endif  // UNITY_EDITOR

    private Vector3 GetLocalPosition()
    {
        float metersToCanvasScale = GetMetersToCanvasScale();

        // Return early if we didn't find a valid metersToCanvasScale.
        if (metersToCanvasScale == 0.0f)
        {
            return rectTransform.anchoredPosition3D;
        }

        float tooltipZPosition = TOOLTIP_Z_POSITION_METERS / metersToCanvasScale;
        switch (location)
        {
            case Location.TouchPadOutside:
            case Location.TouchPadInside:
                float touchPadYPosition = TOUCH_PAD_Y_POSITION_METERS / metersToCanvasScale;
                return new Vector3(0.0f, touchPadYPosition, tooltipZPosition);
            case Location.AppButtonOutside:
            case Location.AppButtonInside:
                float appButtonYPosition = APP_BUTTON_Y_POSITION_METERS / metersToCanvasScale;
                return new Vector3(0.0f, appButtonYPosition, tooltipZPosition);
            case Location.Custom:
            default:
                return rectTransform.anchoredPosition3D;
        }
    }

    private void CheckTooltipSide()
    {
        // If handedness changes, the tooltip will switch sides.
        bool newIsOnLeft = IsTooltipOnLeft();
        if (newIsOnLeft != isOnLeft)
        {
            isOnLeft = newIsOnLeft;
            RefreshTooltip();
        }
    }

    private void RefreshTooltip()
    {
        rectTransform.anchorMax = SQUARE_CENTER;
        rectTransform.anchorMax = SQUARE_CENTER;
        rectTransform.pivot = PIVOT;
        rectTransform.anchoredPosition3D = GetLocalPosition();
        OnSideChanged(isOnLeft);
    }
}