// 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 System;
using System.Collections.Generic;

using Gvr.Internal;

/// Provides mouse-controlled head tracking emulation in the Unity editor.
public class GvrEditorEmulator : MonoBehaviour {
  private const string AXIS_MOUSE_X = "Mouse X";
  private const string AXIS_MOUSE_Y = "Mouse Y";

#if UNITY_EDITOR && UNITY_HAS_GOOGLEVR && (UNITY_ANDROID || UNITY_IOS)
  // Simulated neck model.  Vector from the neck pivot point to the point between the eyes.
  private static readonly Vector3 m_neckOffset = new Vector3(0, 0.075f, 0.08f);

  // Use mouse to emulate head in the editor.
  // These variables must be static so that head pose is maintained between scene changes,
  // as it is on device.
  private static float m_mouseX = 0;
  private static float m_mouseY = 0;
  private static float m_mouseZ = 0;

  private bool m_isRecenterOnlyController = false;
#endif

  [Tooltip("Camera to track")]
  public Camera m_camera;

#if UNITY_EDITOR && UNITY_HAS_GOOGLEVR && (UNITY_ANDROID || UNITY_IOS)
  void Start()
  {
    GvrRecenterOnlyController controllerOnlyRecenter =
      FindObjectOfType<GvrRecenterOnlyController>();
    if (controllerOnlyRecenter != null)
    {
      m_isRecenterOnlyController = true;
    }
    if (m_camera == null)
    {
      m_camera = Camera.main;
    }
  }

  void Update()
  {
    if (GvrController.Recentered)
    {
      Recenter();
    }

    Quaternion rot;
    bool rolled = false;
    if (Input.GetKey(KeyCode.LeftAlt) || Input.GetKey(KeyCode.RightAlt)) {
      m_mouseX += Input.GetAxis(AXIS_MOUSE_X) * 5;
      if (m_mouseX <= -180) {
        m_mouseX += 360;
      } else if (m_mouseX > 180) {
        m_mouseX -= 360;
      }
      m_mouseY -= Input.GetAxis(AXIS_MOUSE_Y) * 2.4f;
      m_mouseY = Mathf.Clamp(m_mouseY, -85, 85);
    } else if (Input.GetKey(KeyCode.LeftControl) || Input.GetKey(KeyCode.RightControl)) {
      rolled = true;
      m_mouseZ += Input.GetAxis(AXIS_MOUSE_X) * 5;
      m_mouseZ = Mathf.Clamp(m_mouseZ, -85, 85);
    }
    if (!rolled) {
      // People don't usually leave their heads tilted to one side for long.
      m_mouseZ = Mathf.Lerp(m_mouseZ, 0, Time.deltaTime / (Time.deltaTime + 0.1f));
    }
    rot = Quaternion.Euler(m_mouseY, m_mouseX, m_mouseZ);
    var neck = (rot * m_neckOffset - m_neckOffset.y * Vector3.up) * m_camera.transform.lossyScale.y;

    Vector3 camPosition = m_camera.transform.position;
    camPosition.y = neck.y;
    m_camera.transform.localPosition = neck;
    m_camera.transform.localRotation = rot;
  }
#endif  // UNITY_EDITOR && UNITY_HAS_GOOGLEVR && (UNITY_ANDROID || UNITY_IOS)

  public void Recenter()
  {
#if UNITY_EDITOR && UNITY_HAS_GOOGLEVR && (UNITY_ANDROID || UNITY_IOS)
    if (m_isRecenterOnlyController)
    {
      return;
    }
    m_mouseX = m_mouseZ = 0;  // Do not reset pitch, which is how it works on the phone.
    m_camera.transform.localPosition = Vector3.zero;
    m_camera.transform.localRotation = new Quaternion(m_mouseX, m_mouseY, m_mouseZ, 1);
#endif  // UNITY_EDITOR && UNITY_HAS_GOOGLEVR && (UNITY_ANDROID || UNITY_IOS)
  }
}