Feat: Extension of Download Features, Batch Select, Error/Retry (#38)

src/features/downloads/lib/downloadQueue.ts

@@ -12,14 +12,51 @@ export function optimisticRemove(queue: DownloadQueueItem[], chapterId: number):
   return queue.filter((i) => i.chapter.id !== chapterId);
 }
 
-export function optimisticToggle(state: string, wasRunning: boolean): string {
-  return wasRunning ? "STOPPED" : "STARTED";
+export function optimisticRemoveMany(queue: DownloadQueueItem[], chapterIds: Set<number>): DownloadQueueItem[] {
+  return queue.filter((i) => !chapterIds.has(i.chapter.id));
 }
 
 export function isRunning(state: string | undefined): boolean {
   return state === "STARTED";
 }
 
+export function getErrored(queue: DownloadQueueItem[]): DownloadQueueItem[] {
+  return queue.filter((i) => i.state === "ERROR");
+}
+
 export function pageProgress(progress: number, pageCount: number): { done: number; total: number } {
   return { done: Math.round(progress * pageCount), total: pageCount };
 }
+
+export interface SpeedSample {
+  ts:       number;
+  progress: number;
+  pages:    number;
+}
+
+export function calcSpeed(prev: SpeedSample | null, current: SpeedSample): number | null {
+  if (!prev) return null;
+  const dt = (current.ts - prev.ts) / 1000;
+  if (dt <= 0) return null;
+  const prevDone = Math.round(prev.progress * prev.pages);
+  const curDone  = Math.round(current.progress * current.pages);
+  const delta    = curDone - prevDone;
+  if (delta <= 0) return null;
+  return delta / dt;
+}
+
+export function estimateEta(pagesPerSec: number, queue: DownloadQueueItem[]): number | null {
+  if (pagesPerSec <= 0 || queue.length === 0) return null;
+  let remaining = 0;
+  for (const item of queue) {
+    const pages = item.chapter.pageCount ?? 0;
+    remaining += pages - Math.round(item.progress * pages);
+  }
+  return remaining / pagesPerSec;
+}
+
+export function formatEta(seconds: number): string {
+  if (seconds < 60)  return `~${Math.ceil(seconds)}s`;
+  if (seconds < 3600) return `~${Math.ceil(seconds / 60)}m`;
+  return `~${(seconds / 3600).toFixed(1)}h`;
+}