using System.Collections.Generic;
using UnityEngine;

namespace NanoBrain {

    /// <summary>
    /// The Unity ScriptableObject to implement re-usable Cluster Prefabs
    /// </summary>
    [CreateAssetMenu(menuName = "Passer/Cluster")]
    public class ClusterPrefab : ScriptableObject {
        /// The nuclei in this cluster
        [SerializeReference]
        public List<Nucleus> nuclei = new();

        /// <summary>
        /// The output of this cluster
        /// </summary>
        /// <deprecated>This only returens the first(default) nucleus. Use outputs[0] instead</deprecated>
        public virtual Nucleus output => this.nuclei[0] as Nucleus;

        /// <summary>
        /// The nuclei in this cluster which are meant for receiving signals from outside the cluster
        /// </summary>
        /// <remark>This is currently the nuclei which do not have any incoming synapse</remark>
        public List<Nucleus> _inputs = null;
        public virtual List<Nucleus> inputs {
            get {
                if (this._inputs == null) {
                    this._inputs = new();
                    foreach (Nucleus receptor in this.nuclei) {
                        if (receptor is Nucleus nucleus) {
                            // inputs have no incoming synapses yet.
                            if (nucleus.synapses.Count == 0)
                                this._inputs.Add(nucleus);
                        }
                    }
                }
                return this._inputs;
            }
        }
        /// <summary>
        /// The nuclei in this cluster which are meant for sending signals onward
        /// </summary>
        private List<Nucleus> _outputs = null;
        public List<Nucleus> outputs {
            get {
                if (this._outputs == null)
                    RefreshOutputs();
                return this._outputs;
            }
        }
        /// <summary>
        /// Redetermine the outpus in the cluster
        /// </summary>
        public void RefreshOutputs() {
            this._outputs = new();
            foreach (Nucleus nucleus in this.nuclei) {
                if (nucleus is Neuron neuron && neuron.receivers.Count == 0)
                    this._outputs.Add(nucleus);
            }
        }

        /// <summary>
        /// Retrieve a nucleus in this cluster
        /// </summary>
        /// <param name="nucleusName">The name of the nucleus</param>
        /// <returns>The Nucleus with the given name or null if no such Nucleus could be found</returns>
        public Nucleus GetNucleus(string nucleusName) {
            foreach (Nucleus nucleus in this.nuclei) {
                if (nucleus.name == nucleusName)
                    return nucleus;
            }
            return null;
        }

        // Call this function to ensure that there is at least one nucleus
        // This is an invariant and should be ensured before the nucleus is used
        // because output requires it.
        public void EnsureInitialization() {
            nuclei ??= new List<Nucleus>();
            if (nuclei.Count == 0)
                new Neuron(this, "Output"); // Every cluster should have at least 1 neuron
        }

        public void GarbageCollection() {
            HashSet<Nucleus> visitedNuclei = new();
            foreach (Nucleus output in this.outputs)
                MarkNuclei(visitedNuclei, output);
            //Debug.Log($"Garbage collection found {visitedNuclei.Count} Nuclei");
            this.nuclei.RemoveAll(nucleus => visitedNuclei.Contains(nucleus) == false);
        }

        public void MarkNuclei(HashSet<Nucleus> visitedNuclei, Nucleus nucleus) {
            if (nucleus is null)
                return;

            if (nucleus.parent != null && nucleus.parent.prefab != this)
                visitedNuclei.Add(nucleus.parent);
            else
                visitedNuclei.Add(nucleus);
            if (nucleus.synapses != null) {
                HashSet<Synapse> visitedSynapses = new();
                foreach (Synapse synapse in nucleus.synapses) {
                    if (synapse != null && synapse.neuron != null) {
                        visitedSynapses.Add(synapse);
                        if (synapse.neuron is Nucleus synapse_nucleus)
                            MarkNuclei(visitedNuclei, synapse_nucleus);
                    }
                }
                nucleus.synapses.RemoveAll(synapse => visitedSynapses.Contains(synapse) == false);
            }
            if (nucleus is Neuron neuron && neuron.receivers != null) {
                HashSet<Nucleus> visitedReceivers = new();
                foreach (Nucleus receiver in neuron.receivers) {
                    if (receiver != null && receiver != null) {
                        visitedReceivers.Add(receiver);
                        visitedNuclei.Add(receiver);
                    }
                }
                neuron.receivers.RemoveAll(receiver => visitedReceivers.Contains(receiver) == false);
            }
        }

        public virtual void UpdateNuclei() {
            foreach (Nucleus nucleus in this.nuclei)
                nucleus.UpdateNuclei();
        }

        public int GetNucleusIndex(Nucleus receiver) {
            int ix = 0;
            foreach (Nucleus nucleus in this.nuclei) {
                if (receiver == nucleus)
                    return ix;
                ix++;
            }
            return -1;
        }
    }

}