test/Assets/PerfectWorld/Scripts/Chat/UI/ChatPanelUI.cs

using System.Collections.Generic;
using CSNetwork;
using UnityEngine;
using UnityEngine.Pool;
using UnityEngine.UI;

namespace BrewMonster.Scripts.ChatUI
{
    public class ChatPanelUI : MonoBehaviour
    {
        [Header("UI")] public ScrollRect scrollRect;
        public RectTransform content;
        public ChatMessageView messagePrefab;
        //public GameObject newMessageIndicator;

        [Header("Config")] public int maxVisibleMessages = 30;
        public int maxStoredMessages = 2000;

        private List<string> _messages = new();
        private List<ChatMessageView> _visibleViews = new();

        private ObjectPool<ChatMessageView> _pool;

        private bool _userAtBottom = true;

        void Awake()
        {
            EventBus.Subscribe<GameSession.ChatMessageEvent>(
                (x) => AddMessage(x.context));
            _pool = new ObjectPool<ChatMessageView>(
                CreateItem,
                OnGetItem,
                OnReleaseItem,
                OnDestroyItem,
                false,
                10,
                100
            );

            scrollRect.onValueChanged.AddListener(OnScrollChanged);
        }

        ChatMessageView CreateItem()
        {
            var item = Instantiate(messagePrefab);
            item.transform.SetParent(content, false);
            return item;
        }

        void OnGetItem(ChatMessageView item)
        {
            item.gameObject.SetActive(true);
        }

        void OnReleaseItem(ChatMessageView item)
        {
            item.gameObject.SetActive(false);
        }

        void OnDestroyItem(ChatMessageView item)
        {
            Destroy(item.gameObject);
        }

        void OnScrollChanged(Vector2 pos)
        {
            _userAtBottom = scrollRect.verticalNormalizedPosition <= 0.001f;

            if (_userAtBottom)
            {
                //newMessageIndicator.SetActive(false);
            }
        }

        bool IsAtBottom()
        {
            return scrollRect.verticalNormalizedPosition <= 0.001f;
        }

        public void AddMessage(string msg)
        {
            _messages.Add(msg);

            if (_messages.Count > maxStoredMessages)
                _messages.RemoveAt(0);

            RefreshVisible();

            if (_userAtBottom)
            {
                ScrollToBottom();
            }
            else
            {
                //newMessageIndicator.SetActive(true);
            }
        }

        void RefreshVisible()
        {
            foreach (var view in _visibleViews)
                _pool.Release(view);

            _visibleViews.Clear();

            int start = Mathf.Max(0, _messages.Count - maxVisibleMessages);

            for (int i = start; i < _messages.Count; i++)
            {
                var view = _pool.Get();
                view.transform.SetParent(content, false);
                view.Bind(_messages[i]);

                _visibleViews.Add(view);
            }

            Canvas.ForceUpdateCanvases();
        }

        public void ScrollToBottom()
        {
            Canvas.ForceUpdateCanvases();
            scrollRect.verticalNormalizedPosition = 0f;
            //newMessageIndicator.SetActive(false);
        }

        public void ClearChat()
        {
            foreach (var view in _visibleViews)
                _pool.Release(view);

            _visibleViews.Clear();
            _messages.Clear();
        }
    }
}