using HtmlAgilityPack;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
using System.Web;

namespace Beam.Dynamic {
    public static partial class OnlineCleaner {
        [GeneratedRegex("&#x?[\\d\\w]{1,4};")]
        public static partial Regex MochaBlendUnicodeEscapeSequence();

        private static string UnicodeEscapeSequences(string text) {
            return MochaBlendUnicodeEscapeSequence().Replace(text, (x) => {
                int numOfDigits = x.Value.Length - 3;
                int sequence = 0;
                if (x.Value[2] == 'x')
                    sequence = int.Parse(x.Value[3..(3 + (numOfDigits - 1))], System.Globalization.NumberStyles.HexNumber);
                else
                    sequence = int.Parse(x.Value[2..(2 + numOfDigits)]);
                var uni = Encoding.Unicode.GetString(BitConverter.GetBytes(sequence));
                return uni.Length == 1 ? uni : uni[0].ToString();
            });
        }

        public static string Clean(string? onlineText) {
            if (string.IsNullOrWhiteSpace(onlineText))
                return "";
            var decoded = HttpUtility.HtmlDecode(onlineText);
            var escaped = UnicodeEscapeSequences(onlineText);
            return escaped;
        }
    }
}