feat: offer a merge that keeps the first book, without the workbench

frontend/src/routes/(root)/settings/libraries/[libraryId]/duplicates/+page.svelte

@@ -3,21 +3,23 @@
 	import { resolve } from '$app/paths';
 	import { invalidate } from '$app/navigation';
 	import { toast } from 'svelte-sonner';
-	import { CopyCheck, Fingerprint, Type } from '@lucide/svelte';
+	import { CopyCheck, Fingerprint, GitMerge, SlidersHorizontal, Type } from '@lucide/svelte';
 
 	import * as Card from '$lib/components/ui/card/index.js';
 	import * as Empty from '$lib/components/ui/empty/index.js';
+	import * as DropdownMenu from '$lib/components/ui/dropdown-menu/index.js';
 	import { Badge } from '$lib/components/ui/badge/index.js';
-	import { Button } from '$lib/components/ui/button/index.js';
+	import { Button, buttonVariants } from '$lib/components/ui/button/index.js';
 	import BookImage from '$lib/components/view/book-image.svelte';
 	import GeneratedCover from '$lib/components/view/generated-cover.svelte';
 	import { dismissDuplicateBooks } from '$lib/api/book.remote';
 	import MergeBooks from '$lib/components/forms/merge-books/merge-books.svelte';
+	import { mergeInto } from '$lib/components/forms/merge-books/merge';
 	import type { Book, DuplicateBookGroup } from '$lib/schema';
 
 	let { data }: { data: { groups: DuplicateBookGroup[]; books: Book[] } } = $props();
 
-	// The group being merged, or null when the dialog is closed.
+	// The group open in the workbench, or null when it is closed.
 	let merging = $state<DuplicateBookGroup | null>(null);
 
 	/** The full records behind a group, in the order the group lists them. */
@@ -27,8 +29,33 @@
 			.filter((book): book is Book => book !== undefined);
 	}
 
-	// Which groups are being dismissed, so a slow round trip cannot be started twice.
+	// Which groups have a request in flight — a dismissal or a quick merge — so a
+	// slow round trip cannot be started twice.
 	let dismissing = $state<number[]>([]);
+	let quickMerging = $state<number[]>([]);
+
+	/**
+	 * Merge without opening the workbench, keeping the first book as it stands.
+	 *
+	 * The common case by far: the group is the same book twice, one record is as
+	 * good as the other, and the point is to end up with one. Resolving metadata
+	 * field by field is the other button.
+	 */
+	async function quickMerge(group: DuplicateBookGroup) {
+		const key = keyOf(group);
+		if (quickMerging.includes(key)) return;
+
+		const [survivor, ...folded] = recordsFor(group);
+		if (!survivor || folded.length === 0) return;
+
+		quickMerging = [...quickMerging, key];
+
+		try {
+			await mergeInto(page.params.libraryId!, survivor, folded);
+		} finally {
+			quickMerging = quickMerging.filter((id) => id !== key);
+		}
+	}
 
 	/** A group is named by its lowest book id, which the backend orders it by. */
 	function keyOf(group: DuplicateBookGroup) {
@@ -95,7 +122,8 @@
 		</Empty.Root>
 	{:else}
 		{#each data.groups as group (keyOf(group))}
-			{@const busy = dismissing.includes(keyOf(group))}
+			{@const busy = dismissing.includes(keyOf(group)) || quickMerging.includes(keyOf(group))}
+			{@const records = recordsFor(group)}
 			<Card.Root>
 				<Card.Header>
 					<Card.Title>{group.books.length} books look like the same book</Card.Title>
@@ -108,15 +136,46 @@
 						>
 							Not duplicates
 						</Button>
-						<!-- Disabled until every record in the group came back, so the
-						     dialog can never open on a partial group. -->
-						<Button
-							size="sm"
-							disabled={busy || recordsFor(group).length !== group.books.length}
-							onclick={() => (merging = group)}
-						>
-							Merge…
-						</Button>
+						<!-- A choice rather than a jump straight into the workbench:
+						     most groups are one book twice, where there is nothing to
+						     resolve and the dialog is a step in the way.
+
+						     Disabled until every record in the group came back, so
+						     neither action can run on a partial group. -->
+						<DropdownMenu.Root>
+							<DropdownMenu.Trigger
+								class={buttonVariants({ size: 'sm' })}
+								disabled={busy || records.length !== group.books.length}
+							>
+								Merge…
+							</DropdownMenu.Trigger>
+							<DropdownMenu.Content align="end" class="w-72">
+								<DropdownMenu.Item
+									class="flex-col items-start gap-0.5"
+									onclick={() => quickMerge(group)}
+								>
+									<span class="flex w-full min-w-0 items-center gap-2">
+										<GitMerge class="size-4 shrink-0" />
+										<span class="truncate">Keep “{records[0]?.title}”</span>
+									</span>
+									<span class="pl-6 text-xs text-wrap text-muted-foreground">
+										Files move onto the first book, which keeps its own metadata.
+									</span>
+								</DropdownMenu.Item>
+								<DropdownMenu.Item
+									class="flex-col items-start gap-0.5"
+									onclick={() => (merging = group)}
+								>
+									<span class="flex items-center gap-2">
+										<SlidersHorizontal class="size-4 shrink-0" />
+										Choose what to keep…
+									</span>
+									<span class="pl-6 text-xs text-wrap text-muted-foreground">
+										Pick the record that survives and resolve the metadata field by field.
+									</span>
+								</DropdownMenu.Item>
+							</DropdownMenu.Content>
+						</DropdownMenu.Root>
 					</Card.Action>
 				</Card.Header>
 
@@ -195,7 +254,7 @@
 				(value) => {
 					// Bound, not passed as a bare `true`: the dialog closes itself on an
 					// outside click or Escape, and if that never reaches `merging` the
-					// group stays set — the button then re-assigns the same group,
+					// group stays set — the menu item then re-assigns the same group,
 					// nothing changes, and the workbench never reopens.
 					if (!value) merging = null;
 				}