using System;
using System.Collections.Generic;

using UnityEngine;

namespace Framework.Support {

  /// <summary>Contains helper methods for dealign with materials</summary>
  public static class MaterialHelper {

    /// <summary>Returns all materials used by the renderers of a game object</summary>
    /// <param name="actor">Game object whose materials will be returned</param>
    /// <returns>An array containing all materials used in a game object</returns>
    /// <remarks>
    ///   This will include all children with renderers
    /// </remarks>
    public static Material[] GetMeshMaterials(GameObject actor) {
      Renderer[] renderers = actor.GetComponentsInChildren<Renderer>();
      if((renderers == null) || (renderers.Length == 0)) {
        return new Material[0];
      }

      var materialLists = new List<Material[]>(capacity: renderers.Length);
      int materialCount = 0;

      // Count the number of materials so we can avoid garbage production.
      // Under the assumption that querying a renderers materials involves
      // a Mono/Native boundary call, we remember the returned arrays instead
      // of asking for them multiple times. Maybe it's micro-optimization :)
      for(int index = 0; index < renderers.Length; ++index) {
        Material[] materialList = renderers[index].materials;
        if(materialList != null) {
          materialLists.Add(materialList);
          materialCount += materialList.Length;
        }
      }

      // Prepare the final material array for the caller
      var materials = new Material[materialCount];
      int materialIndex = 0;
      for(int index = 0; index < materialLists.Count; ++index) {
        for(int listIndex = 0; listIndex < materialLists[index].Length; ++listIndex) {
          materials[materialIndex] = materialLists[index][listIndex];
          ++materialIndex;
        }
      }

      return materials;
    }

  }

} // namespace Framework.Support