// 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 UnityEngine.EventSystems;
using UnityEngine.VR;
using System.Collections;

/// Helper functions to perform common math operations for Gvr.
public static class GvrMathHelpers {
  private static Vector2 sphericalCoordinatesResult;

  public static Vector3 GetIntersectionPosition(Camera cam, RaycastResult raycastResult) {
    // Check for camera
    if (cam == null) {
      return Vector3.zero;
    }

    float intersectionDistance = raycastResult.distance + cam.nearClipPlane;
    Vector3 intersectionPosition = cam.transform.position + cam.transform.forward * intersectionDistance;
    return intersectionPosition;
  }

  public static Vector2 GetViewportCenter() {
    int viewportWidth = Screen.width;
    int viewportHeight = Screen.height;
    if (UnityEngine.XR.XRSettings.enabled) {
      viewportWidth = UnityEngine.XR.XRSettings.eyeTextureWidth;
      viewportHeight = UnityEngine.XR.XRSettings.eyeTextureHeight;
    }

    return new Vector2(0.5f * viewportWidth, 0.5f * viewportHeight);
  }

  public static Vector2 NormalizedCartesianToSpherical(Vector3 cartCoords) {
    cartCoords.Normalize();

    if (cartCoords.x == 0) {
      cartCoords.x = Mathf.Epsilon;
    }

    float outPolar = Mathf.Atan(cartCoords.z / cartCoords.x);

    if (cartCoords.x < 0) {
      outPolar += Mathf.PI;
    }

    float outElevation = Mathf.Asin(cartCoords.y);

    sphericalCoordinatesResult.x = outPolar;
    sphericalCoordinatesResult.y = outElevation;
    return sphericalCoordinatesResult;
  }

  public static float EaseOutCubic(float min, float max, float value) {
    if (min > max) {
      Debug.LogError("Invalid values passed to EaseOutCubic, max must be greater than min. " +
        "min: " + min + ", max: " + max);
      return value;
    }

    value = Mathf.Clamp01(value);
    value -= 1.0f;
    float delta = max - min;
    float result = delta * (value * value * value + 1.0f) + min;
    return result;
  }

  /// Converts a float array of length 16 into a column-major 4x4 matrix.
  public static Matrix4x4 ConvertFloatArrayToMatrix(float[] floatArray) {
    Matrix4x4 result = new Matrix4x4();

    if (floatArray == null || floatArray.Length != 16) {
      throw new System.ArgumentException("floatArray must not be null and have a length of 16.");
    }

    result[0, 0] = floatArray[0];
    result[1, 0] = floatArray[1];
    result[2, 0] = floatArray[2];
    result[3, 0] = floatArray[3];
    result[0, 1] = floatArray[4];
    result[1, 1] = floatArray[5];
    result[2, 1] = floatArray[6];
    result[3, 1] = floatArray[7];
    result[0, 2] = floatArray[8];
    result[1, 2] = floatArray[9];
    result[2, 2] = floatArray[10];
    result[3, 2] = floatArray[11];
    result[0, 3] = floatArray[12];
    result[1, 3] = floatArray[13];
    result[2, 3] = floatArray[14];
    result[3, 3] = floatArray[15];

    return result;
  }
}