NadekoBot/NadekoBot.Core/_Extensions/StringExtensions.cs

using System;
using System.IO;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;

namespace NadekoBot.Extensions
{
    public static class StringExtensions
    {
        public static string StripHTML(this string input)
        {
            return Regex.Replace(input, "<.*?>", String.Empty);
        }

        /// <summary>
        /// Easy use of fast, efficient case-insensitive Contains check with StringComparison Member Types 
        /// CurrentCulture, CurrentCultureIgnoreCase, InvariantCulture, InvariantCultureIgnoreCase, Ordinal, OrdinalIgnoreCase
        /// </summary>    
        public static bool ContainsNoCase(this string str, string contains, StringComparison compare)
        {
            return str.IndexOf(contains, compare) >= 0;
        }

        public static string TrimTo(this string str, int maxLength, bool hideDots = false)
        {
            if (maxLength < 0)
                throw new ArgumentOutOfRangeException(nameof(maxLength), $"Argument {nameof(maxLength)} can't be negative.");
            if (maxLength == 0)
                return string.Empty;
            if (maxLength <= 3)
                return string.Concat(str.Select(c => '.'));
            if (str.Length < maxLength)
                return str;
            return string.Concat(str.Take(maxLength - 3)) + (hideDots ? "" : "...");
        }

        public static string ToTitleCase(this string str)
        {
            var tokens = str.Split(new[] { " " }, StringSplitOptions.RemoveEmptyEntries);
            for (var i = 0; i < tokens.Length; i++)
            {
                var token = tokens[i];
                tokens[i] = token.Substring(0, 1).ToUpper() + token.Substring(1);
            }

            return string.Join(" ", tokens);
        }

        /// <summary>
        /// Removes trailing S or ES (if specified) on the given string if the num is 1
        /// </summary>
        /// <param name="str"></param>
        /// <param name="num"></param>
        /// <param name="es"></param>
        /// <returns>String with the correct singular/plural form</returns>
        public static string SnPl(this string str, int? num, bool es = false)
        {
            if (str == null)
                throw new ArgumentNullException(nameof(str));
            if (num == null)
                throw new ArgumentNullException(nameof(num));
            return num == 1 ? str.Remove(str.Length - 1, es ? 2 : 1) : str;
        }

        //http://www.dotnetperls.com/levenshtein
        public static int LevenshteinDistance(this string s, string t)
        {
            var n = s.Length;
            var m = t.Length;
            var d = new int[n + 1, m + 1];

            // Step 1
            if (n == 0)
            {
                return m;
            }

            if (m == 0)
            {
                return n;
            }

            // Step 2
            for (var i = 0; i <= n; d[i, 0] = i++)
            {
            }

            for (var j = 0; j <= m; d[0, j] = j++)
            {
            }

            // Step 3
            for (var i = 1; i <= n; i++)
            {
                //Step 4
                for (var j = 1; j <= m; j++)
                {
                    // Step 5
                    var cost = (t[j - 1] == s[i - 1]) ? 0 : 1;

                    // Step 6
                    d[i, j] = Math.Min(
                        Math.Min(d[i - 1, j] + 1, d[i, j - 1] + 1),
                        d[i - 1, j - 1] + cost);
                }
            }
            // Step 7
            return d[n, m];
        }

        public static async Task<Stream> ToStream(this string str)
        {
            var ms = new MemoryStream();
            var sw = new StreamWriter(ms);
            await sw.WriteAsync(str);
            await sw.FlushAsync();
            ms.Position = 0;
            return ms;
        }

        private static readonly Regex filterRegex = new Regex(@"(?:discord(?:\.gg|.me|app\.com\/invite)\/(?<id>([\w]{16}|(?:[\w]+-?){3})))", RegexOptions.Compiled | RegexOptions.IgnoreCase);
        public static bool IsDiscordInvite(this string str)
            => filterRegex.IsMatch(str);

        public static string Unmention(this string str) => str.Replace("@", "ම");

        public static string SanitizeMentions(this string str) =>
            str.Replace("@everyone", "@everyοne").Replace("@here", "@һere");

        public static string ToBase64(this string plainText)
        {
            var plainTextBytes = Encoding.UTF8.GetBytes(plainText);
            return Convert.ToBase64String(plainTextBytes);
        }

        public static string GetInitials(this string txt, string glue = "") =>
            string.Join(glue, txt.Split(' ').Select(x => x.FirstOrDefault()));
    }
}