First working POC

src/lib/utils/playbackUnits.ts

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+/**
+ * Playback unit conversion utilities
+ *
+ * Jellyfin uses "ticks" for time values where 10 million ticks = 1 second.
+ * This module provides type-safe conversion functions to eliminate magic numbers
+ * and prevent conversion bugs across the codebase.
+ */
+
+/**
+ * Number of Jellyfin ticks per second (10 million)
+ */
+export const TICKS_PER_SECOND = 10_000_000;
+
+/**
+ * Convert seconds to Jellyfin ticks
+ * @param seconds - Time in seconds (e.g., 90.5 for 1 minute 30.5 seconds)
+ * @returns Time in Jellyfin ticks
+ */
+export function secondsToTicks(seconds: number): number {
+  return Math.floor(seconds * TICKS_PER_SECOND);
+}
+
+/**
+ * Convert Jellyfin ticks to seconds
+ * @param ticks - Time in Jellyfin ticks
+ * @returns Time in seconds
+ */
+export function ticksToSeconds(ticks: number): number {
+  return ticks / TICKS_PER_SECOND;
+}
+
+/**
+ * Convert normalized volume (0-1) to percentage (0-100)
+ * Used when sending volume to Jellyfin remote sessions
+ * @param volume - Normalized volume (0.0 to 1.0)
+ * @returns Volume as percentage (0 to 100)
+ */
+export function volumeToPercent(volume: number): number {
+  return Math.floor(Math.max(0, Math.min(1, volume)) * 100);
+}
+
+/**
+ * Convert percentage volume (0-100) to normalized (0-1)
+ * Used when receiving volume from Jellyfin remote sessions
+ * @param percent - Volume as percentage (0 to 100)
+ * @returns Normalized volume (0.0 to 1.0)
+ */
+export function percentToVolume(percent: number): number {
+  return Math.max(0, Math.min(100, percent)) / 100;
+}
+
+/**
+ * Format time in seconds to MM:SS display string
+ * @param seconds - Time in seconds
+ * @returns Formatted string like "3:45" or "12:09"
+ */
+export function formatTime(seconds: number): string {
+  const mins = Math.floor(seconds / 60);
+  const secs = Math.floor(seconds % 60);
+  return `${mins}:${secs.toString().padStart(2, "0")}`;
+}
+
+/**
+ * Format time in seconds to HH:MM:SS display string (for longer content)
+ * @param seconds - Time in seconds
+ * @returns Formatted string like "1:23:45" or "0:03:45"
+ */
+export function formatTimeLong(seconds: number): string {
+  const hours = Math.floor(seconds / 3600);
+  const mins = Math.floor((seconds % 3600) / 60);
+  const secs = Math.floor(seconds % 60);
+
+  if (hours > 0) {
+    return `${hours}:${mins.toString().padStart(2, "0")}:${secs.toString().padStart(2, "0")}`;
+  }
+  return `${mins}:${secs.toString().padStart(2, "0")}`;
+}
+
+/**
+ * Calculate progress percentage
+ * @param position - Current position in seconds
+ * @param duration - Total duration in seconds
+ * @returns Progress as percentage (0 to 100)
+ */
+export function calculateProgress(position: number, duration: number): number {
+  if (duration <= 0) return 0;
+  return Math.min(100, Math.max(0, (position / duration) * 100));
+}