using System;

using NUnit.Framework;

using System.Collections.Generic;

using System.Linq;

public class Programm

{

    public static string FormatJson(string json, string indent = "  ")

    {

        var indentation = 0;

        var quoteCount = 0;

        var escapeCount = 0;

        var result =

            from ch in json ?? string.Empty

            let escaped = (ch == '\\' ? escapeCount++ : escapeCount > 0 ? escapeCount-- : escapeCount) > 0

            let quotes = ch == '"' && !escaped ? quoteCount++ : quoteCount

                let unquoted = quotes % 2 == 0

                let colon = ch == ':' && unquoted ? ": " : null

                    let nospace = char.IsWhiteSpace(ch) && unquoted ? string.Empty : null

                    let lineBreak = ch == ',' && unquoted ? ch + Environment.NewLine + string.Concat(Enumerable.Repeat(indent, indentation)) : null

                    let openChar = (ch == '{' || ch == '[') && unquoted ? ch + Environment.NewLine + string.Concat(Enumerable.Repeat(indent, ++indentation)) : ch.ToString()

                    let closeChar = (ch == '}' || ch == ']') && unquoted ? Environment.NewLine + string.Concat(Enumerable.Repeat(indent, --indentation)) + ch : ch.ToString()

                    select colon ?? nospace ?? lineBreak ?? (

                    openChar.Length > 1 ? openChar : closeChar

                );

        return string.Concat(result);

    }

    public void Main()

    {

        Console.WriteLine(FormatJson("{\"hallo\": [1,2,3,4,5,6,7,8]}"));

    }

}