using System;

using UnityEngine;

using Framework.Services;

namespace Framework.Support {

  /// <summary>Adds a margin to the bounds of a mesh</summary>
  public class CullingMarginExtender : ScriptComponent {

    /// <summary>Additional margin that will be added to the bounding boxes</summary>
    public Vector3 AdditionalMargin = new Vector3(4.0f, 4.0f, 4.0f);

    /// <summary>Called once before the game object is updated for the first time</summary>
    public void Start() {
      ExtendCullingMargin();
    }

    /// <summary>Extends the culling margin of all meshes in the game object</summary>
    public void ExtendCullingMargin() {
      Renderer[] meshRenderers = transform.GetComponentsInChildren<Renderer>(
        includeInactive: true
      );
      if((meshRenderers == null) || (meshRenderers.Length == 0)) {
        Debug.LogWarning(
          "Culling margin extender on '" + name + "' has no mesh renderers for " +
          "which it could extend the culling margin. Doing nothing."
        );
        return;
      }

      enlargeBoundingBoxes(meshRenderers);
    }

    /// <summary>Enlarged the bounding boxes of all renderers in the list</summary>
    /// <param name="meshRenderers">Renderers whose bounding boxes will be enlarged</param>
    private void enlargeBoundingBoxes(Renderer[] meshRenderers) {
      for(int index = 0; index < meshRenderers.Length; ++index) {
        var skinnedMeshRenderer = meshRenderers[index] as SkinnedMeshRenderer;
        if(skinnedMeshRenderer != null) {
          Bounds bounds = skinnedMeshRenderer.localBounds;

          Vector3 minimumBounds = bounds.min - this.AdditionalMargin;
          Vector3 maximumBounds = bounds.max + this.AdditionalMargin;
          bounds.SetMinMax(minimumBounds, maximumBounds);

          skinnedMeshRenderer.localBounds = bounds;
          continue;
        }

        Debug.LogWarning(
          "Culling margin extender on '" + name + "' could not find a skinned " +
          "mesh renderer for '" + meshRenderers[index].name + "'. " +
          "Culling will be unchanged for this particular mesh."
        );
      }
    }

  }

} // namespace Framework.Support