From 9e0fbac6d3cb4e11efdb33c339ccf0adbca0bc6c Mon Sep 17 00:00:00 2001
From: ivarlovlie <git@ivarlovlie.no>
Date: Thu, 1 Apr 2021 22:36:59 +0200
Subject: Initial commit

---
 src/IOL.Helpers/SlugGenerator.cs | 108 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 108 insertions(+)
 create mode 100644 src/IOL.Helpers/SlugGenerator.cs

(limited to 'src/IOL.Helpers/SlugGenerator.cs')

diff --git a/src/IOL.Helpers/SlugGenerator.cs b/src/IOL.Helpers/SlugGenerator.cs
new file mode 100644
index 0000000..3f53dd6
--- /dev/null
+++ b/src/IOL.Helpers/SlugGenerator.cs
@@ -0,0 +1,108 @@
+using System.Text;
+
+namespace IOL.Helpers
+{
+	public static class Slug
+	{
+		public static string Generate(bool toLower, params string[] values) {
+			return Create(string.Join("-", values), toLower);
+		}
+
+		/// <summary>
+		/// Creates a slug.
+		/// References:
+		/// http://www.unicode.org/reports/tr15/tr15-34.html
+		/// https://meta.stackexchange.com/questions/7435/non-us-ascii-characters-dropped-from-full-profile-url/7696#7696
+		/// https://stackoverflow.com/questions/25259/how-do-you-include-a-webpage-title-as-part-of-a-webpage-url/25486#25486
+		/// https://stackoverflow.com/questions/3769457/how-can-i-remove-accents-on-a-string
+		/// </summary>
+		/// <param name="value"></param>
+		/// <param name="toLower"></param>
+		/// <returns>Slugified string</returns>
+		public static string Create(string value, bool toLower) {
+			if (string.IsNullOrWhiteSpace(value))
+				return value;
+
+			var normalised = value.Normalize(NormalizationForm.FormKD);
+
+			const int MAXLEN = 80;
+			var len = normalised.Length;
+			var prevDash = false;
+			var sb = new StringBuilder(len);
+
+			for (var i = 0; i < len; i++) {
+				var c = normalised[i];
+				switch (c) {
+					case >= 'a' and <= 'z':
+					case >= '0' and <= '9': {
+						if (prevDash) {
+							sb.Append('-');
+							prevDash = false;
+						}
+
+						sb.Append(c);
+						break;
+					}
+					case >= 'A' and <= 'Z': {
+						if (prevDash) {
+							sb.Append('-');
+							prevDash = false;
+						}
+
+						// Tricky way to convert to lowercase
+						if (toLower)
+							sb.Append((char) (c | 32));
+						else
+							sb.Append(c);
+						break;
+					}
+					case ' ':
+					case ',':
+					case '.':
+					case '/':
+					case '\\':
+					case '-':
+					case '_':
+					case '=': {
+						if (!prevDash && sb.Length > 0) {
+							prevDash = true;
+						}
+
+						break;
+					}
+					default: {
+						var swap = ConvertEdgeCases(c, toLower);
+						if (swap != null) {
+							if (prevDash) {
+								sb.Append('-');
+								prevDash = false;
+							}
+
+							sb.Append(swap);
+						}
+
+						break;
+					}
+				}
+
+				if (sb.Length == MAXLEN)
+					break;
+			}
+
+			return sb.ToString();
+		}
+
+		private static string ConvertEdgeCases(char c, bool toLower) => c switch {
+			'ı' => "i",
+			'ł' => "l",
+			'Ł' => toLower ? "l" : "L",
+			'đ' => "d",
+			'ß' => "ss",
+			'ø' => "o",
+			'å' => "aa",
+			'æ' => "ae",
+			'Þ' => "th",
+			_ => null
+		};
+	}
+}
\ No newline at end of file
-- 
cgit v1.3