feat(date): add defTimecode() formatter

packages/date/src/format.ts

@@ -175,3 +175,55 @@ export const FMT_hms = defFormat(["h", ":", "mm", ":", "ss", " ", "A"]);
  */
 // prettier-ignore
 export const FMT_yyyyMMdd_HHmmss = defFormat(["yyyy", "MM", "dd", "-", "HH", "mm", "ss"]);
+
+/**
+ * Returns a time formatter for given FPS (frames / second, in [1..100] range),
+ * e.g. `HH:mm:ss:ff`. The returned function takes a single arg (time in
+ * milliseconds) and returns formatted string.
+ *
+ * @remarks
+ * The timecode considers days too, but only includes them in the result if the
+ * day part is non-zero. The 4 separators between each field can be customized
+ * via 2nd arg (default: all `:`).
+ *
+ * @example
+ * ```ts
+ * a = defTimecode(30);
+ * a(HOUR + 2*MINUTE + 3*SECOND + 4*1000/30)
+ * // "01:02:03:04"
+ *
+ * a(DAY);
+ * // "01:00:00:00:00"
+ *
+ * b = defTimecode(30, ["d ", "h ", "' ", '" ']);
+ * b(Day + HOUR + 2*MINUTE + 3*SECOND + 999)
+ * // "01d 01h 02' 03" 29"
+ * ```
+ *
+ * @param fps
+ * @param sep
+ */
+export const defTimecode = (fps: number, sep: ArrayLike<string> = "::::") => {
+    const frame = 1000 / fps;
+    return (t: number) => {
+        const d = (t / DAY) | 0;
+        t -= d * DAY;
+        const h = (t / HOUR) | 0;
+        t -= h * HOUR;
+        const m = (t / MINUTE) | 0;
+        t -= m * MINUTE;
+        const s = (t / SECOND) | 0;
+        t -= s * SECOND;
+        const parts = [
+            Z2(h),
+            sep[1],
+            Z2(m),
+            sep[2],
+            Z2(s),
+            sep[3],
+            Z2((t / frame) | 0),
+        ];
+        d > 0 && parts.unshift(`${Z2(d)}${sep[0]}`);
+        return parts.join("");
+    };
+};