using System;
using System.Collections;
using System.Collections.Generic;
using System.Text;
using UnityEngine;

[Serializable]
[DisallowMultipleComponent]
public partial class UIdSystem : MonoBehaviour
{
    public bool IsPrefab;
    public ulong Id;

    [SerializeField]
    private List<ComponentIdPair> componentIdPairs = new List<ComponentIdPair>();

    /// <summary>
    /// 为该实体对象和组件重新分配唯一的 Id。
    /// </summary>
    public void CreateId(ulong offset = 0, bool recursive = true)
    {
        this.Id = GUID.NewGuid() - offset;

        var components = this.gameObject.GetComponents<Component>();

        foreach (var component in components)
        {
            var index = GetComponentIndex(component);

            if (index == -1)
            {
                var componentIdPair = new ComponentIdPair(component, GUID.NewGuid() - offset);
                componentIdPairs.Add(componentIdPair);
            }
            else
            {
                var componentIdPair = componentIdPairs[index];
                componentIdPair.Id = GUID.NewGuid() - offset;
            }
        }

        if (recursive)
            CreateIdRecursively(offset);
    }

    /// <summary>
    /// 为该实体对象和组件重新分配唯一 Id，已分配过的组件不会再分配。
    /// </summary>
    public void ReassignId(ulong offset = 0, bool recursive = true)
    {
        this.Id = GUID.NewGuid() - offset;

        var components = this.gameObject.GetComponents<Component>();

        foreach (var component in components)
        {
            var index = GetComponentIndex(component);

            if (index == -1)
            {
                var componentIdPair = new ComponentIdPair(component, GUID.NewGuid() - offset);
                componentIdPairs.Add(componentIdPair);
            }
        }

        if (recursive)
            AssignIdRecursively(offset, true);
    }

    /// <summary>
    /// 为该实体对象和组件更新唯一 Id，已分配过的组件不会再更新。
    /// </summary>
    public void UpdateId(ulong offset = 0, bool recursive = true)
    {
        if (this.Id <= 0)
            this.Id = GUID.NewGuid() - offset;

        var components = this.gameObject.GetComponents<Component>();

        foreach (var component in components)
        {
            var index = GetComponentIndex(component);

            if (index == -1)
            {
                var componentIdPair = new ComponentIdPair(component, GUID.NewGuid() - offset);
                componentIdPairs.Add(componentIdPair);
            }
        }

        if (recursive)
            AssignIdRecursively(offset, false);
    }

    private void AssignIdRecursively(ulong offset, bool reassign)
    {
        foreach (Transform child in transform)
        {
            var entity = child.gameObject;

            var component = entity.GetComponent<UIdSystem>();
            if (component == null)
                component = entity.AddComponent<UIdSystem>();

            component.IsPrefab = this.IsPrefab;

            if (reassign)
                component.ReassignId(offset, true);
            else
                component.UpdateId(offset, true);
        }
    }

    private void CreateIdRecursively(ulong offset)
    {
        foreach (Transform child in transform)
        {
            var entity = child.gameObject;

            var component = entity.GetComponent<UIdSystem>();
            if (component == null)
                component = entity.AddComponent<UIdSystem>();

            component.IsPrefab = this.IsPrefab;
            component.CreateId(offset, true);
        }
    }

    private int GetComponentIndex(Component component)
    {
        return componentIdPairs.FindIndex((componentIdPair) => componentIdPair.Component == component);
    }

    private void Reset()
    {
        IsPrefab = false;

        this.ReassignId();
    }
}