Add logging for deleted prekeys and other records

Co-authored-by: Scott Nonnenberg <scott@signal.org>

ts/util/groupWhile.ts

@@ -0,0 +1,69 @@
+// Copyright 2023 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+/**
+ * Accepts an array and a predicate function. Returns an array of arrays, where
+ * each time the predicate returns false, a new sub-array is started.
+ *
+ * Useful for grouping sequential items in an array.
+ *
+ * @example
+ * ```ts
+ * groupWhile([1, 2, 3, 4, 5, 6], (item, prev) => {
+ *   return prev + 1 === item
+ * })
+ * // => [[1, 2, 3], [4, 5, 6]]
+ * ```
+ */
+export function groupWhile<T>(
+  array: ReadonlyArray<T>,
+  iteratee: (item: T, prev: T) => boolean
+): Array<Array<T>> {
+  const groups: Array<Array<T>> = [];
+  let cursor = 0;
+  while (cursor < array.length) {
+    const group: Array<T> = [];
+    do {
+      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      group.push(array[cursor]!);
+      cursor += 1;
+      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      if (!iteratee(array[cursor]!, array[cursor - 1]!)) {
+        break;
+      }
+    } while (cursor < array.length);
+    groups.push(group);
+  }
+  return groups;
+}
+
+/**
+ * @example
+ * ```ts
+ * let result = [[1, 2], [4, 5], [7], [9, 10]]
+ * let formatted = formatGroups(result, "-", ", ", String)
+ * // => "1-2, 4-5, 7, 9-10"
+ * ```
+ */
+export function formatGroups<T>(
+  groups: Array<Array<T>>,
+  rangeSeparator: string,
+  groupSeparator: string,
+  formatItem: (value: T) => string
+): string {
+  return groups
+    .map(group => {
+      if (group.length === 0) {
+        return '';
+      }
+      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      const start = formatItem(group.at(0)!);
+      if (group.length === 1) {
+        return start;
+      }
+      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      const end = formatItem(group.at(-1)!);
+      return `${start}${rangeSeparator}${end}`;
+    })
+    .join(groupSeparator);
+}