using System;
using System.Collections;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Text;
using System.Threading.Tasks;

namespace HC
{
    public class TrieNode
    {
        private Dictionary<char, TrieNode> children = new();
        private bool _isEndOfWord;

        public void AddWord(string word)
        {
            if (string.IsNullOrEmpty(word))
            {
                throw new ArgumentException("Word cannot be null or empty.");
            }

            if (this == null)
            {
                throw new NullReferenceException("TrieNode instance is null.");
            }

            var currentNode = this;

            foreach (var c in word)
            {
                if (!currentNode.HasChildNode(c))
                {
                    var newNode = new TrieNode();
                    currentNode.AddChildNode(c, newNode);
                }

                currentNode = currentNode.GetChildNode(c);
            }

            currentNode._isEndOfWord = true;
        }

        private TrieNode GetChildNode(char c)
        {
            return children.TryGetValue(c, out var childNode) ? childNode : null;
        }

        private void AddChildNode(char c, TrieNode childNode)
        {
            children.Add(c, childNode);
        }

        private bool HasChildNode(char c)
        {
            return children.ContainsKey(c);
        }

        public IEnumerator Initialize(IEnumerable<string> sensitiveWords, Action callback)
        {
            var count = 0;

            foreach (var word in sensitiveWords)
            {
                AddWord(word.Trim());
                count++;

                if (count % 10000 == 0)
                {
                    yield return null; // 暂停协程一帧
                }
            }

            callback?.Invoke();
        }

        public string FilterText(string inputText)
        {
            var inputChars = inputText.ToCharArray();
            var length = inputChars.Length;
            var resultBuilder = new StringBuilder();

            for (var startIndex = 0; startIndex < length; startIndex++)
            {
                var currentNode = this;
                var currentIndex = startIndex;
                var matchedIndex = -1;

                while (currentIndex < length)
                {
                    var currentChar = inputChars[currentIndex];

                    if (currentNode.HasChildNode(currentChar))
                    {
                        currentNode = currentNode.GetChildNode(currentChar);

                        if (currentNode._isEndOfWord)
                        {
                            matchedIndex = currentIndex;
                        }

                        currentIndex++;
                    }
                    else
                    {
                        break;
                    }
                }

                if (matchedIndex != -1)
                {
                    for (var i = startIndex; i <= matchedIndex; i++)
                    {
                        inputChars[i] = '*';
                    }

                    startIndex = matchedIndex;
                }
            }

            resultBuilder.Append(inputChars);
            return resultBuilder.ToString();
        }
    }
}