//-----------------------------------------------------------------------
// <copyright file="GvrLaserPointer.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>
//-----------------------------------------------------------------------

// The controller is not available for versions of Unity without the
// GVR native integration.

using UnityEngine;
using UnityEngine.EventSystems;

/// <summary>Implementation of GvrBasePointer for a laser pointer visual.</summary>
/// <remarks>
/// This script should be attached to the controller object. The laser visual is important to help
/// users locate their cursor when its not directly in their field of view.
/// </remarks>
[RequireComponent(typeof(GvrLaserVisual))]
[HelpURL("https://developers.google.com/vr/reference/unity/class/GvrLaserPointer")]
public class GvrLaserPointer : GvrBasePointer
{
    /// <summary>Maximum distance from the pointer that raycast hits will be detected.</summary>
    [Tooltip("Distance from the pointer that raycast hits will be detected.")]
    public float maxPointerDistance = 20.0f;

    /// <summary>
    /// Distance from the pointer that the reticle will be drawn at when hitting nothing.
    /// </summary>
    [Tooltip("Distance from the pointer that the reticle will be drawn at when hitting nothing.")]
    public float defaultReticleDistance = 20.0f;

    /// <summary>
    /// By default, the length of the laser is used as the CameraRayIntersectionDistance.
    /// </summary>
    /// <remarks>Set this field to a non-zero value to override it.</remarks>
    [Tooltip("By default, the length of the laser is used as the CameraRayIntersectionDistance. " +
    "Set this field to a non-zero value to override it.")]
    public float overrideCameraRayIntersectionDistance;

    /// <summary>The percentage of the reticle mesh that shows the reticle.</summary>
    /// <remarks>The rest of the reticle mesh is transparent.</remarks>
    private const float RETICLE_VISUAL_RATIO = 0.1f;

    private bool isHittingTarget;

    /// <summary>Gets the visual object for the laser beam.</summary>
    /// <value>The visual object for the laser beam.</value>
    public GvrLaserVisual LaserVisual { get; private set; }

    /// <inheritdoc/>
    public override float MaxPointerDistance
    {
        get
        {
            return maxPointerDistance;
        }
    }

    /// <inheritdoc/>
    public override float CameraRayIntersectionDistance
    {
        get
        {
            if (overrideCameraRayIntersectionDistance != 0.0f)
            {
                return overrideCameraRayIntersectionDistance;
            }

            return LaserVisual != null ?
                                  LaserVisual.maxLaserDistance :
                                  overrideCameraRayIntersectionDistance;
        }
    }

    /// <inheritdoc/>
    public override void OnPointerEnter(RaycastResult raycastResult, bool isInteractive)
    {
        LaserVisual.SetDistance(raycastResult.distance);
        isHittingTarget = true;
    }

    /// <inheritdoc/>
    public override void OnPointerHover(RaycastResult raycastResult, bool isInteractive)
    {
        LaserVisual.SetDistance(raycastResult.distance);
        isHittingTarget = true;
    }

    /// <inheritdoc/>
    public override void OnPointerExit(GameObject previousObject)
    {
        // Don't set the distance immediately.
        // If we exit/enter an object on the same frame, then SetDistance
        // will be called twice which could cause an issue with lerping the reticle.
        // If we don't re-enter a new object, the distance will be set in Update.
        isHittingTarget = false;
    }

    /// <inheritdoc/>
    public override void OnPointerClickDown()
    {
    }

    /// <inheritdoc/>
    public override void OnPointerClickUp()
    {
    }

    /// <inheritdoc/>
    public override void GetPointerRadius(out float enterRadius, out float exitRadius)
    {
        if (LaserVisual.reticle != null)
        {
            float reticleScale = LaserVisual.reticle.transform.localScale.x;

            // Fixed size for enter radius to avoid flickering.
            // This will cause some slight variability based on the distance of the object
            // from the camera, and is optimized for the average case.
            enterRadius = LaserVisual.reticle.sizeMeters * 0.5f * RETICLE_VISUAL_RATIO;

            // Dynamic size for exit radius.
            // Always correct because we know the intersection point of the object and can
            // therefore use the correct radius based on the object's distance from the camera.
            exitRadius =
                reticleScale * LaserVisual.reticle.ReticleMeshSizeMeters * RETICLE_VISUAL_RATIO;
        }
        else
        {
            enterRadius = 0.0f;
            exitRadius = 0.0f;
        }
    }

    /// @endcond
    /// @cond
    /// <inheritdoc/>
    protected override void Start()
    {
        base.Start();
        LaserVisual.GetPointForDistanceFunction = GetPointAlongPointer;
        LaserVisual.SetDistance(defaultReticleDistance, true);
    }

    /// @cond
    /// <summary>This MonoBehavior's Awake method.</summary>
    private void Awake()
    {
        LaserVisual = GetComponent<GvrLaserVisual>();
    }

    /// @endcond
    /// <summary>This MonoBehavior's Update method.</summary>
    private void Update()
    {
        if (isHittingTarget)
        {
            return;
        }

        LaserVisual.SetDistance(defaultReticleDistance);
    }
}