Move over to new lexicographic string sorting

src/utils/stringOrderField.ts

@@ -0,0 +1,56 @@
+/*
+Copyright 2021 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+export const ALPHABET_START = 0x20;
+export const ALPHABET_END = 0x7E;
+export const ALPHABET = new Array(1 + ALPHABET_END - ALPHABET_START)
+    .fill(undefined)
+    .map((_, i) => String.fromCharCode(ALPHABET_START + i))
+    .join("");
+
+export const baseToString = (base: number, alphabet = ALPHABET): string => {
+    base = Math.floor(base);
+    if (base < alphabet.length) return alphabet[base];
+    return baseToString(Math.floor(base / alphabet.length), alphabet) + alphabet[base % alphabet.length];
+};
+
+export const stringToBase = (str: string, alphabet = ALPHABET): number => {
+    let result = 0;
+    for (let i = str.length - 1, j = 0; i >= 0; i--, j++) {
+        result += (str.charCodeAt(i) - alphabet.charCodeAt(0)) * (alphabet.length ** j);
+    }
+    return result;
+};
+
+const pad = (str: string, length: number, alphabet = ALPHABET): string => str.padEnd(length, alphabet[0]);
+
+export const averageBetweenStrings = (a: string, b: string, alphabet = ALPHABET): string => {
+    const n = Math.max(a.length, b.length);
+    const aBase = stringToBase(pad(a, n, alphabet), alphabet);
+    const bBase = stringToBase(pad(b, n, alphabet), alphabet);
+    return baseToString((aBase + bBase) / 2, alphabet);
+};
+
+export const midPointsBetweenStrings = (a: string, b: string, count: number, alphabet = ALPHABET): string[] => {
+    const n = Math.max(a.length, b.length);
+    const aBase = stringToBase(pad(a, n, alphabet), alphabet);
+    const bBase = stringToBase(pad(b, n, alphabet), alphabet);
+    const step = (bBase - aBase) / (count + 1);
+    if (step < 1) {
+        return [];
+    }
+    return Array(count).fill(undefined).map((_, i) => baseToString(aBase + step + (i * step), alphabet));
+};