// Copyright 2015 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;

/// Draws a circular reticle in front of any object that the user points at.
/// The circle dilates if the object is clickable.
[AddComponentMenu("GoogleVR/UI/GvrReticlePointer")]
[RequireComponent(typeof(Renderer))]
public class GvrReticlePointer : MonoBehaviour {
  private GvrReticlePointerImpl reticlePointerImpl;

  /// Number of segments making the reticle circle.
  public int reticleSegments = 20;

  /// Growth speed multiplier for the reticle/
  public float reticleGrowthSpeed = 8.0f;

  void Awake() {
    reticlePointerImpl = new GvrReticlePointerImpl();
  }

  void Start() {
    reticlePointerImpl.OnStart();
    reticlePointerImpl.MaterialComp = gameObject.GetComponent<Renderer>().material;
    UpdateReticleProperties();
    CreateReticleVertices();
  }

  void Update() {
    UpdateReticleProperties();
    reticlePointerImpl.UpdateDiameters();
  }

  public void SetAsMainPointer() {
    GvrPointerManager.Pointer = reticlePointerImpl;
  }

  private void CreateReticleVertices() {
    Mesh mesh = new Mesh();
    gameObject.AddComponent<MeshFilter>();
    GetComponent<MeshFilter>().mesh = mesh;

    int segments_count = reticleSegments;
    int vertex_count = (segments_count+1)*2;

    #region Vertices

    Vector3[] vertices = new Vector3[vertex_count];

    const float kTwoPi = Mathf.PI * 2.0f;
    int vi = 0;
    for (int si = 0; si <= segments_count; ++si) {
      // Add two vertices for every circle segment: one at the beginning of the
      // prism, and one at the end of the prism.
      float angle = (float)si / (float)(segments_count) * kTwoPi;

      float x = Mathf.Sin(angle);
      float y = Mathf.Cos(angle);

      vertices[vi++] = new Vector3(x, y, 0.0f); // Outer vertex.
      vertices[vi++] = new Vector3(x, y, 1.0f); // Inner vertex.
    }
    #endregion

    #region Triangles
    int indices_count = (segments_count+1)*3*2;
    int[] indices = new int[indices_count];

    int vert = 0;
    int idx = 0;
    for (int si = 0; si < segments_count; ++si) {
      indices[idx++] = vert+1;
      indices[idx++] = vert;
      indices[idx++] = vert+2;

      indices[idx++] = vert+1;
      indices[idx++] = vert+2;
      indices[idx++] = vert+3;

      vert += 2;
    }
    #endregion

    mesh.vertices = vertices;
    mesh.triangles = indices;
    mesh.RecalculateBounds();
#if !UNITY_5_5_OR_NEWER
    // Optimize() is deprecated as of Unity 5.5.0p1.
    mesh.Optimize();
#endif  // !UNITY_5_5_OR_NEWER
  }


  private void UpdateReticleProperties() {
    if (reticlePointerImpl == null) {
      return;
    }
    reticlePointerImpl.ReticleGrowthSpeed = reticleGrowthSpeed;
    reticlePointerImpl.PointerTransform = transform;
  }
}