using System;

using UnityEngine;

namespace Framework.Support {

  /// <summary>Provides helper methods for dealing with game objects</summary>
  public static class GameObjectHelper {

    /// <summary>Looks up a child of the specified game object by its name</summary>
    /// <param name="parent">Parent of which a child will be looked up</param>
    /// <param name="name">Name of the child that will be lookd up</param>
    /// <returns>The child, if found, or null if no child with that name existed</returns>
    public static GameObject GetChildByName(GameObject parent, string name) {
      Transform childTransform = parent.transform.Find(name);
      if(childTransform == null) {
        return null;
      } else {
        return childTransform.gameObject;
      }
    }

    /// <summary>Adds one game object as child to another</summary>
    /// <param name="parent">Parent the child will be added to</param>
    /// <param name="child">Game object that will become a child</param>
    public static void SetAsChild(GameObject parent, GameObject child) {
      if(parent == null) {
        child.transform.SetParent(null, worldPositionStays: false);
      } else {
        child.transform.SetParent(parent.transform, worldPositionStays: false);
      }
    }

    /// <summary>Looks for a component in a game object and its parents</summary>
    /// <typeparam name="T">Type of component that should be looked up</typeparam>
    /// <param name="gameObject">Game object in which the component will be searched</param>
    /// <returns>The component of the specified type, if found, or null</returns>
    public static T GetComponentInParents<T>(GameObject gameObject) where T : MonoBehaviour {
      if(GameObjectHelper.IsNullOrDestroyed(gameObject)) {
        return null;
      }

      Transform current = gameObject.transform;
      while(current != null) {
        T component = current.GetComponent<T>();
        if(component != null) {
          return component;
        }

        current = current.parent;
      }

      return null;
    }

    /// <summary>Checks whether a game object is null or destroyed already</summary>
    /// <param name="gameObject">Game object reference that will be checked</param>
    /// <returns>True if the reference is null or the game object has been destroyed</returns>
    public static bool IsNullOrDestroyed(GameObject gameObject) {
      if(ReferenceEquals(gameObject, null)) {
        return true;
      } else {
        return (gameObject == null); // Wrapper call - could be slow
      }
    }

  }

} // namespace Framework.Support