using System.Collections;

using System.Collections.Generic;

using UnityEngine;

namespace DuskModules.ScriptableObjects {

/// <summary> Asset Instance is a scriptable object which is linked to a BehaviourInstance in the scene.

/// By calling the AssetInstance within the AssetDatabase, code can find the scene instance belonging to it and call upon it's code. </summary>

public class AssetInstance<A, B> : ScriptableObject where A : AssetInstance<A, B> where B : BehaviourInstance<B, A> {

/// <summary> Dictionary of all auto instances. Key = prefab, value = instance of that prefab. </summary>

protected static Dictionary<A, B> _instances;

/// <summary> Dictionary of all auto instances. Key = prefab, value = instance of that prefab. </summary>

public static Dictionary<A, B> instances {

get {

if (_instances == null) _instances = new Dictionary<A, B>();

return _instances;

}

}

/// <summary> Upon getting the instance </summary>

public B instance => CreateInstance();

/// <summary> Locates or creates the instance </summary>

public B CreateInstance() {

B instance = null;

A self = (A)this;

if (instances.ContainsKey(self)) {

instance = instances[self];

if (instance == null || instance.gameObject == null) instances.Remove(self);

else return instance;

}

// Not present within dictionary, find or create it.

instance = GetSceneInstance();

if (instance == null)

instance = CreateSceneInstance();

if (instance != null)

instances.Add(self, instance);

return instance;

}

/// <summary> Finds and returns the BehaviourInstance present in the scene </summary>

/// <returns> The scene BehaviourInstance </returns>

protected B GetSceneInstance() {

B[] foundInstances = FindObjectsOfType<B>();

for (int i = 0; i < foundInstances.Length; i++) {

if (foundInstances[i].asset == this) {

return foundInstances[i];

}

}

return null;

}

/// <summary> Creates a new BehaviourInstance within the current scene </summary>

/// <returns> The scene BehaviourInstance </returns>

protected B CreateSceneInstance() {

if (CreationAllowed()) {

B instance = InstantiateInstance();

instance.SetAsset((A)this);

return instance;

}

return null;

}

/// <summary> Actually creates the BehaviourInstance. Can be modified by inheriting code. </summary>

/// <returns> The scene BehaviourInstance </returns>

protected virtual B InstantiateInstance() {

GameObject createdObject = new GameObject(name);

return createdObject.AddComponent<B>();

}

/// <summary> Called when the instance has been destroyed. </summary>

/// <param name="instance"> The instance to remove </param>

public void Remove(B removeInstance) {

if (instance == removeInstance) {

instances.Remove((A)this);

}

}

/// <summary> Whether creation is allowed. If it returns true, a new instance is created if none is found. </summary>

/// <returns> Whether creation is allowed. </returns>

protected virtual bool CreationAllowed() { return true; }

}

}