From e14fa6bdce7e5ab857860af2962d89e2ed9a92f4 Mon Sep 17 00:00:00 2001
From: clover caruso <git@paperclover.net>
Date: Sat, 28 Mar 2026 16:03:22 -0700
Subject: [PATCH] feat: expand `string.formatDurationLetters` cases

resolves #100
---
 lib/string.test.ts | 21 ++++++++++++++++++---
 lib/string.ts      | 40 +++++++++++++++++++++++++++++++---------
 2 files changed, 49 insertions(+), 12 deletions(-)

diff --git a/lib/string.test.ts b/lib/string.test.ts
index 8db6f2008103f91af7a2e69b6ba761e6b49d0de7..ddf66e2b99d6320c1e037be33612c70a005df4fd 100644
--- a/lib/string.test.ts
+++ b/lib/string.test.ts
@@ -29,22 +29,37 @@ test("escapeShellArgument", () => {
   assert.equal(string.escapeShellArgument("'string"), "\"'string\"");
   assert.equal(string.escapeShellArgument("'str\"ing"), "\\''str\"ing'");
 });
-test.todo("formatByteSize", () => {
+test("formatByteSize", () => {
   assert.equal(string.formatByteSize(0), "0B");
   assert.equal(string.formatByteSize(1), "1B");
   assert.equal(string.formatByteSize(1000), "1kB");
   assert.equal(string.formatByteSize(-1000), "-1kB");
   assert.equal(string.formatByteSize(1500), "1.5kB");
   assert.equal(string.formatByteSize(1578), "1.58kB");
-  assert.equal(string.formatByteSize(5_100_000), "5.1MB");
+  assert.equal(string.formatByteSize(5_100_000), "5.10MB");
   assert.equal(string.formatByteSize(-7_231_692_881), "-7.23GB");
-  assert.equal(string.formatByteSize(-4_294_967_296), "-7.23GB");
+  assert.equal(string.formatByteSize(-4_294_967_296), "-4.29GB");
 
   assert.equal(string.formatByteSize(53.251), "53.25B");
   assert.equal(string.formatByteSize(Infinity), "Infinity");
   assert.equal(string.formatByteSize(-Infinity), "-Infinity");
   assert.equal(string.formatByteSize(NaN), "NaN");
 });
+test("formatDurationLetters", () => {
+  assert.equal(string.formatDurationLetters(1), "1s");
+  assert.equal(string.formatDurationLetters(1.542), "1.54s");
+  assert.equal(string.formatDurationLetters(1.5), "1.5s");
+  assert.equal(string.formatDurationLetters(60), "1m");
+  assert.equal(string.formatDurationLetters(65), "1m5s");
+  assert.equal(string.formatDurationLetters(10000), "2h46m");
+  assert.equal(string.formatDurationLetters(421321378), "13y131d");
+
+  assert.equal(string.formatDurationLetters(0), "now");
+  assert.equal(string.formatDurationLetters(-3000), "50m ago");
+  assert.equal(string.formatDurationLetters(Infinity), "forever");
+  assert.equal(string.formatDurationLetters(-Infinity), "forever ago");
+  assert.equal(string.formatDurationLetters(NaN), "NaN");
+});
 
 import assert from "node:assert";
 import { test } from "vitest";
diff --git a/lib/string.ts b/lib/string.ts
index e6081cbf57402c3c794008681d9dcb9aa21e9789..c69e3c431548f08b3337c500f8acd5c6641e2a8d 100644
--- a/lib/string.ts
+++ b/lib/string.ts
@@ -53,10 +53,11 @@ export function formatByteSize(bytes: number): string {
     bytes /= 1000;
     unit += 1;
   } while (bytes >= 1000);
-  return prefix
-    + bytes.toFixed(
-      Math.floor(bytes) === bytes || unit === 1 ? 0 : bytes > 100 ? 1 : 2,
-    )
+  return prefix + (unit === 1
+    ? String(+bytes.toFixed(bytes > 100 ? 1 : 2))
+    : bytes.toFixed(
+      Math.floor(bytes) === bytes ? 0 : bytes > 100 ? 1 : 2,
+    ))
     + byteUnits.charAt(unit - 1) + "B";
 }
 
@@ -73,10 +74,31 @@ export function formatBinaryByteSize(bytes: number): string {
     + byteUnits.charAt(unit - 1) + "iB";
 }
 
-// TODO:
 export function formatDurationLetters(seconds: number): string {
-  const minutes = Math.floor(seconds / 60);
-  const remainingSeconds = seconds % 60;
-  if (minutes < 1) return `${remainingSeconds}s`;
-  return `${minutes}m${remainingSeconds}s`;
+  if (seconds === 0) return "now";
+  if (!Number.isFinite(seconds)) {
+    if (seconds === Infinity) return "forever";
+    if (seconds === -Infinity) return "forever ago";
+    return "NaN";
+  }
+  let ago = "";
+  if (seconds < 0) seconds = -seconds, ago = " ago";
+  const units = [
+    [31536000, "y"],
+    [86400, "d"],
+    [3600, "h"],
+    [60, "m"],
+  ] as const;
+  let out = "";
+  let remain = seconds;
+  let u = 0;
+  for (const [size, label] of units) {
+    if (remain < size) continue;
+    const value = Math.floor(remain / size);
+    remain -= value * size;
+    out += `${value}${label}`;
+    if ((u += 1) === 2) return out + ago;
+  }
+  if (remain > 0 || out === "") out += `${+remain.toFixed(2)}s`;
+  return out + ago;
 }
-- 
2.54.0