Chore: Port over Settings (Barely Works)

src/lib/state/tracking.svelte.ts

@@ -1,4 +1,6 @@
-import type { Tracker } from '$lib/types'
+import type { Tracker, TrackRecord } from '$lib/types'
+import type { Chapter } from '$lib/types/chapter'
+import type { MangaPrefs } from '$lib/types/settings'
 
 export const trackingState = $state({
   trackers:       [] as Tracker[],
@@ -13,4 +15,42 @@ export const trackingState = $state({
   searchResults:  [] as unknown[],
   searchLoading:  false,
   searchError:    null as string | null,
-})
+})
+
+export async function syncBackFromTracker(
+  records: TrackRecord[],
+  chapters: Chapter[],
+  opts: {
+    threshold:              number | null
+    respectScanlatorFilter: boolean
+    chapterPrefs:           Partial<MangaPrefs>
+  },
+  markChaptersRead: (ids: string[], read: boolean) => Promise<void>,
+): Promise<Chapter[]> {
+  const marked: Chapter[] = []
+
+  const activeScanlators: string[] | null =
+    opts.respectScanlatorFilter && opts.chapterPrefs.scanlatorFilter?.length
+      ? opts.chapterPrefs.scanlatorFilter
+      : null
+
+  for (const record of records) {
+    const lastRead = record.lastChapterRead ?? 0
+    if (lastRead <= 0) continue
+
+    const toMark = chapters.filter(ch => {
+      if (ch.read) return false
+      if (activeScanlators && ch.scanlator && !activeScanlators.includes(ch.scanlator)) return false
+      return opts.threshold !== null
+        ? ch.chapterNumber <= lastRead && ch.chapterNumber >= lastRead - opts.threshold
+        : ch.chapterNumber <= lastRead
+    })
+
+    if (toMark.length === 0) continue
+
+    await markChaptersRead(toMark.map(ch => String(ch.id)), true)
+    marked.push(...toMark)
+  }
+
+  return marked
+}