/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 * All rights reserved.
 *
 * Licensed under the Oculus SDK License Agreement (the "License");
 * you may not use the Oculus SDK except in compliance with the License,
 * which is provided at the time of installation or download, or which
 * otherwise accompanies this software in either electronic or hard copy form.
 *
 * You may obtain a copy of the License at
 *
 * https://developer.oculus.com/licenses/oculussdk/
 *
 * Unless required by applicable law or agreed to in writing, the Oculus SDK
 * 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 System.Collections;
using UnityEngine.EventSystems;
using UnityEngine.UI;

/// <summary>
/// UI pointer driven by gaze input.
/// </summary>
public class OVRGazePointer : OVRCursor {
    private Transform gazeIcon; //the transform that rotates according to our movement

    [Tooltip("Should the pointer be hidden when not over interactive objects.")]
    public bool hideByDefault = true;

    [Tooltip("Time after leaving interactive object before pointer fades.")]
    public float showTimeoutPeriod = 1;

    [Tooltip("Time after mouse pointer becoming inactive before pointer unfades.")]
    public float hideTimeoutPeriod = 0.1f;

    [Tooltip("Keep a faint version of the pointer visible while using a mouse")]
    public bool dimOnHideRequest = true;

    [Tooltip("Angular scale of pointer")]
    public float depthScaleMultiplier = 0.03f;

    public bool matchNormalOnPhysicsColliders;

    /// <summary>
    /// The gaze ray.
    /// </summary>
    public Transform rayTransform;

    /// <summary>
    /// Is gaze pointer current visible
    /// </summary>
    public bool hidden { get; private set; }

    /// <summary>
    /// Current scale applied to pointer
    /// </summary>
    public float currentScale { get; private set; }

    /// <summary>
    /// Current depth of pointer from camera
    /// </summary>
    private float depth;
    private float hideUntilTime;
    /// <summary>
    /// How many times position has been set this frame. Used to detect when there are no position sets in a frame.
    /// </summary>
    private int positionSetsThisFrame = 0;
    /// <summary>
    /// Last time code requested the pointer be shown. Usually when pointer passes over interactive elements.
    /// </summary>
    private float lastShowRequestTime;
    /// <summary>
    /// Last time pointer was requested to be hidden. Usually mouse pointer activity.
    /// </summary>
    private float lastHideRequestTime;

    // Optionally present GUI element displaying progress when using gaze-to-select mechanics
    private OVRProgressIndicator progressIndicator;

    private static OVRGazePointer _instance;
    public static OVRGazePointer instance
    {
        // If there's no GazePointer already in the scene, instanciate one now.
        get
        {
            if (_instance == null)
            {
                Debug.Log(string.Format("Instanciating GazePointer", 0));
                _instance = (OVRGazePointer)GameObject.Instantiate((OVRGazePointer)Resources.Load("Prefabs/GazePointerRing", typeof(OVRGazePointer)));
            }
            return _instance;
        }

    }


    /// <summary>
    /// Used to determine alpha level of gaze cursor. Could also be used to determine cursor size, for example, as the cursor fades out.
    /// </summary>
    public float visibilityStrength
    {
        get
        {
            // It's possible there are reasons to show the cursor - such as it hovering over some UI - and reasons to hide
            // the cursor - such as another input method (e.g. mouse) being used. We take both of these in to account.


            float strengthFromShowRequest;
            if (hideByDefault)
            {
                // fade the cursor out with time
                strengthFromShowRequest =  Mathf.Clamp01(1 - (Time.time - lastShowRequestTime) / showTimeoutPeriod);
            }
            else
            {
                // keep it fully visible
                strengthFromShowRequest = 1;
            }

            // Now consider factors requesting pointer to be hidden
            float strengthFromHideRequest;

            strengthFromHideRequest = (lastHideRequestTime + hideTimeoutPeriod > Time.time) ? (dimOnHideRequest ? 0.1f : 0) : 1;


            // Hide requests take priority
            return Mathf.Min(strengthFromShowRequest, strengthFromHideRequest);
        }
    }

    public float SelectionProgress
    {
        get
        {
            return progressIndicator ? progressIndicator.currentProgress : 0;
        }
        set
        {
            if (progressIndicator)
                progressIndicator.currentProgress = value;
        }
    }

    public void Awake()
    {
        currentScale = 1;
        // Only allow one instance at runtime.
        if (_instance != null && _instance != this)
        {
            enabled = false;
            DestroyImmediate(this);
            return;
        }

        _instance = this;

		gazeIcon = transform.Find("GazeIcon");
        progressIndicator = transform.GetComponent<OVRProgressIndicator>();
    }

    void Update ()
    {
		if (rayTransform == null && Camera.main != null)
			rayTransform = Camera.main.transform;

        // Move the gaze cursor to keep it in the middle of the view
        transform.position = rayTransform.position + rayTransform.forward * depth;

        // Should we show or hide the gaze cursor?
        if (visibilityStrength == 0 && !hidden)
        {
            Hide();
        }
        else if (visibilityStrength > 0 && hidden)
        {
            Show();
        }
    }

    /// <summary>
    /// Set position and orientation of pointer
    /// </summary>
    /// <param name="pos"></param>
    /// <param name="normal"></param>
    public override void SetCursorStartDest(Vector3 _, Vector3 pos, Vector3 normal)
    {
        transform.position = pos;

        if (!matchNormalOnPhysicsColliders) normal = rayTransform.forward;

        // Set the rotation to match the normal of the surface it's on.
        Quaternion newRot = transform.rotation;
        newRot.SetLookRotation(normal, rayTransform.up);
        transform.rotation = newRot;

        // record depth so that distance doesn't pop when pointer leaves an object
        depth = (rayTransform.position - pos).magnitude;

        //set scale based on depth
        currentScale = depth * depthScaleMultiplier;
        transform.localScale = new Vector3(currentScale, currentScale, currentScale);

        positionSetsThisFrame++;
        RequestShow();
    }

    public override void SetCursorRay(Transform ray)
    {
        // We don't do anything here, because we already set this properly by default in Update.
    }

    void LateUpdate()
    {
        // This happens after all Updates so we know that if positionSetsThisFrame is zero then nothing set the position this frame
        if (positionSetsThisFrame == 0)
        {
            // No geometry intersections, so gazing into space. Make the cursor face directly at the camera
            Quaternion newRot = transform.rotation;
            newRot.SetLookRotation(rayTransform.forward, rayTransform.up);
            transform.rotation = newRot;
        }

        Quaternion iconRotation = gazeIcon.rotation;
		iconRotation.SetLookRotation(transform.rotation * new Vector3(0, 0, 1));
		gazeIcon.rotation = iconRotation;

		positionSetsThisFrame = 0;
    }

    /// <summary>
    /// Request the pointer be hidden
    /// </summary>
    public void RequestHide()
    {
        if (!dimOnHideRequest)
        {
            Hide();
        }
        lastHideRequestTime = Time.time;
    }

    /// <summary>
    /// Request the pointer be shown. Hide requests take priority
    /// </summary>
    public void RequestShow()
    {
        Show();
        lastShowRequestTime = Time.time;
    }


    // Disable/Enable child elements when we show/hide the cursor. For performance reasons.
    void Hide()
    {
        var cachedTransform = transform;
        for (int i = 0; i < cachedTransform.childCount; i++)
        {
	        cachedTransform.GetChild(i).gameObject.SetActive(false);
        }
        if (GetComponent<Renderer>())
            GetComponent<Renderer>().enabled = false;
        hidden = true;
    }

    void Show()
    {
        var cachedTransform = transform;
        for (int i = 0; i < cachedTransform.childCount; i++)
        {
	        cachedTransform.GetChild(i).gameObject.SetActive(true);
        }
        if (GetComponent<Renderer>())
            GetComponent<Renderer>().enabled = true;
        hidden = false;
    }

}