Simplenote Tag Hashing Functions - generate tag entity id from tag name

tag-hasher.java

import java.io.UnsupportedEncodingException;
import java.net.URLEncoder;
import java.text.Normalizer;
import java.util.Locale;

class TagHasher {
  public static String tagHash(String tagName) {
    try {
      String normalized = Normalizer.normalize(tagName, Normalizer.Form.NFC);
      String lowercased = normalized.toLowerCase(Locale.ENGLISH);
      String encoded = URLEncoder.encode(lowercased, "UTF-8");

      return encoded.replace("*", "%2A").replace("+", "%20");
    } catch (UnsupportedEncodingException e) {
      // @TODO handle this with a custom UTF-8 encoder
      return tagName;
    }
  }
}

tag-hasher.m

#import <Foundation/Foundation.h>

NSString *tagHash(NSString *tagName) {
        NSString *normalized = [tagName precomposedStringWithCanonicalMapping];
        NSString *lowercased = [normalized lowercaseStringWithLocale:[NSLocale localeWithLocaleIdentifier:@"en-US"]];
        NSString *encoded = [lowercased stringByAddingPercentEncodingWithAllowedCharacters:[NSCharacterSet alphanumericCharacterSet]];

        return encoded;
}

tag-hasher.swift

import Foundation

func tagHash(tagName: String) -> String {
  let normalized = (tagName as NSString).precomposedStringWithCanonicalMapping
  let lowercased = normalized.lowercased(with: Locale(identifier: "en-US"))
  if let encoded = lowercased.addingPercentEncoding(withAllowedCharacters:CharacterSet.alphanumerics) {
    return encoded
  }

  // @TODO: handle failure with custom encoder
  return tagName
}

tag-hasher.ts

export const tagHash = (tagName: string): string => {
  const normalized = tagName.normalize('NFC');
  const lowercased = normalized.toLocaleLowerCase('en-US');
  const encoded = encodeURIComponent(lowercased);

  return encoded.replace(/[!'()*]/g, c => '%' + c.charCodeAt(0).toString(16).toUpperCase())
}