antiantiswearingbot/AntiAntiSwearingBot/Language.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;

namespace AntiAntiSwearingBot
{
    public static class Language
    {
        static int min(int a, int b, int c) { return Math.Min(Math.Min(a, b), c); }

        public static int HammingDistance(string a, string b)
        {
            if (string.IsNullOrEmpty(a))
            {
                if (string.IsNullOrEmpty(b))
                    return 0;
                return b.Length;
            }

            int dist = 0;
            int len = Math.Min(a.Length, b.Length);
            int leftover = Math.Max(a.Length, b.Length) - len;
            for (int i = 0; i < len; ++i)
                if (!CharMatch(a[i], b[i]))
                    ++dist;

            return leftover + dist;
        }

        public static int LevenshteinDistance(string a, string b)
        {
            int[] prevRow = new int[b.Length + 1];
            int[] thisRow = new int[b.Length + 1];

            // init thisRow as 
            for (int i = 0; i < prevRow.Length; i++) prevRow[i] = i;

            for (int i = 0; i < a.Length; i++)
            {
                thisRow[0] = i + 1;
                for (int j = 0; j < b.Length; j++)
                {
                    var cost = CharMatch(a[i], b[j]) ? 0 : 1;
                    thisRow[j + 1] = min(thisRow[j] + 1, prevRow[j + 1] + 1, prevRow[j] + cost);
                }

                var t = prevRow;
                prevRow = thisRow;
                thisRow = t;
            }
            return prevRow[b.Length];
        }

        public static bool CharMatch(char a, char b)
            => a == b || !char.IsLetterOrDigit(a) || !char.IsLetterOrDigit(b);

        static readonly Regex MentionRegex = new Regex("^@[a-zA-Z0-9_]+$", RegexOptions.Compiled);
        static readonly Regex EmailPartRegex = new Regex("^\\w+@\\w+$", RegexOptions.Compiled);

        static readonly Regex HashTagRegex = new Regex("^#\\w+$", RegexOptions.Compiled);

        public static bool IsTelegramMention(string word) => MentionRegex.IsMatch(word);

        public static bool IsEmailPart(string word) => EmailPartRegex.IsMatch(word);

        public static bool IsHashTag(string word) => HashTagRegex.IsMatch(word);

        public static bool HasNonWordChars(string arg) => arg.Any(c => !char.IsLetterOrDigit(c));

        public static bool HasWordChars(string arg) => arg.Any(char.IsLetter);


    }
}