using System;
using System.Collections.Generic;
using System.Text.Json;

namespace Learn.Archives.Core.Common
{
    public static class JsonExtractor
    {
        /// <summary>
        /// 提取json字符串
        /// </summary>
        /// <param name="input"></param>
        /// <returns></returns>
        public static List<string> ExtractJsonStrings(this string input)
        {
            List<string> jsonList = new List<string>();
            int index = 0;
            while (index < input.Length)
            {
                if (input[index] == '{' || input[index] == '[')
                {
                    int? endIndex = FindMatchingBracket(input, index);
                    if (endIndex.HasValue)
                    {
                        string candidate = input.Substring(index, endIndex.Value - index + 1);
                        if (IsValidJson(candidate))
                        {
                            jsonList.Add(candidate);
                            index = endIndex.Value + 1;
                            continue;
                        }
                    }
                }
                index++;
            }
            return jsonList;
        }

        private static int? FindMatchingBracket(string str, int start)
        {
            Stack<char> stack = new Stack<char>();
            bool inString = false;
            bool inEscape = false;

            for (int i = start; i < str.Length; i++)
            {
                char c = str[i];

                if (inEscape)
                {
                    inEscape = false;
                }
                else if (inString)
                {
                    if (c == '\\')
                        inEscape = true;
                    else if (c == '"')
                        inString = false;
                }
                else
                {
                    switch (c)
                    {
                        case '{':
                        case '[':
                            stack.Push(c);
                            break;
                        case '}':
                            if (stack.Count == 0 || stack.Peek() != '{')
                                return null;
                            stack.Pop();
                            break;
                        case ']':
                            if (stack.Count == 0 || stack.Peek() != '[')
                                return null;
                            stack.Pop();
                            break;
                        case '"':
                            inString = true;
                            break;
                    }
                }

                if (stack.Count == 0)
                    return i;
            }
            return null; // 括号未完全匹配
        }

        public static bool IsValidJson(string candidate)
        {
            if (string.IsNullOrEmpty(candidate))
                return false;
            try
            {
                JsonDocument.Parse(candidate);
                return true;
            }
            catch (Exception)
            {
                return false;
            }
        }
    }
}