using System;
using UnityEngine;
using Object = UnityEngine.Object;

namespace BitGames.Terrain
{
  [RequireComponent(typeof(MeshRenderer), typeof(MeshFilter))]
  [DisallowMultipleComponent]
  public class TerrainFloorRenderer : MonoBehaviour, ITerrainMaterialUser
  {
    public TerrainAsset Asset;

    private MeshRenderer _renderer;
    private MeshFilter _meshFilter;
    private Material _instancedMaterial;

    private void Awake()
    {
      LinkMaterial();
      ActivateAsset();
      UpdateMesh();
    }

    private void UpdateMesh()
    {
      VerifyComponents();

      transform.localScale = (Asset != null ? Asset.Size : 32) * RuntimeGlobals.TILE_SIZE * Vector3.one;
      transform.position = Vector3.zero;
      transform.rotation = Quaternion.Euler(90, 0, 0);
      GetComponent<MeshFilter>().sharedMesh = Resources.GetBuiltinResource<Mesh>("Quad.fbx");
    }

    private void LinkMaterial()
    {
      VerifyComponents();

      if (_instancedMaterial == null)
      {
        _instancedMaterial = RuntimeGlobals.RegisterMaterialUser(this);
      }

      _renderer.sharedMaterial = _instancedMaterial;
    }

    private void UnlinkMaterial()
    {
      RuntimeGlobals.RemoveMaterialUser(this);
    }

    private void ActivateAsset()
    {
      if(Asset != null)
        RuntimeGlobals.ActivateAsset(Asset);
    }

#if UNITY_EDITOR
    internal void OnValidate()
    {
      UpdateMesh();
      LinkMaterial();
      ActivateAsset();
    }

    internal void HideMeshFilterRenderer()
    {
      VerifyComponents();
      const HideFlags flags = HideFlags.HideInInspector; // Hide mesh renderer and filter
      _renderer.hideFlags = flags;
      _meshFilter.hideFlags = flags;
    }
#endif

    private void VerifyComponents()
    {
      EnsureComponent(ref _renderer);
      EnsureComponent(ref _meshFilter);
    }

    private void EnsureComponent<T>(ref T component) where T : Component
    {
      if(component == null)
        component = gameObject.TryGetComponent(out T found) ? found : gameObject.AddComponent<T>();
    }

    private void OnDestroy()
    {
      UnlinkMaterial();
    }
  }
}