feat: accept files and folders when uploading books

The picker could only choose folders: webkitdirectory switches the OS dialog
into folder mode rather than filtering, so one input cannot offer both. Adds
a drop zone with two browse buttons behind two inputs.

Dropping a folder never worked either — dataTransfer.files does not descend
into directories, so it arrived as one typeless entry and was rejected. Walks
dataTransfer.items instead.

Also collects skipped files into one expandable line rather than a toast each,
which a folder of covers and notes made unusable, and shows the file count and
total size before uploading.

frontend/src/lib/components/forms/book-drop-zone.svelte

@@ -0,0 +1,223 @@
+<script lang="ts">
+	import { FileUp, Folder, FileText } from '@lucide/svelte';
+
+	import { Button } from '$lib/components/ui/button/index.js';
+	import type { FileRejectedReason } from '$lib/components/ui/file-drop-zone';
+	import { cn } from '$lib/utils';
+
+	let {
+		onUpload,
+		onFileRejected,
+		accept,
+		maxFileSize,
+		disabled = false,
+		class: className
+	}: {
+		onUpload: (files: File[]) => Promise<void> | void;
+		onFileRejected?: (opts: { reason: FileRejectedReason; file: File }) => void;
+		/** Comma separated extensions and/or MIME types, as the `accept` attribute takes. */
+		accept?: string;
+		/** Bytes. */
+		maxFileSize?: number;
+		disabled?: boolean;
+		class?: string;
+	} = $props();
+
+	/**
+	 * Two inputs rather than one.
+	 *
+	 * `webkitdirectory` is not a filter — it switches the picker into folder mode,
+	 * so a single input can offer files or folders but never both. The drop target
+	 * has no such constraint and stays one area.
+	 */
+	let fileInput = $state<HTMLInputElement>();
+	let folderInput = $state<HTMLInputElement>();
+
+	let dragging = $state(false);
+	let busy = $state(false);
+
+	const active = $derived(!disabled && !busy);
+
+	function accepts(file: File): FileRejectedReason | undefined {
+		if (maxFileSize !== undefined && file.size > maxFileSize) return 'Maximum file size exceeded';
+		if (!accept) return undefined;
+
+		const name = file.name.toLowerCase();
+		const type = file.type.toLowerCase();
+
+		const ok = accept
+			.split(',')
+			.map((pattern) => pattern.trim().toLowerCase())
+			.some((pattern) => {
+				// Match on the pattern, not the file's type. Testing `type` here is
+				// what makes MOBI fail: browsers report no MIME type for it, so a
+				// ".mobi" rule never gets compared against the filename.
+				if (pattern.startsWith('.')) return name.endsWith(pattern);
+				if (pattern.endsWith('/*')) return type.startsWith(pattern.slice(0, -1));
+				return type === pattern;
+			});
+
+		return ok ? undefined : 'File type not allowed';
+	}
+
+	/** readEntries hands back at most 100 at a time and signals the end with an empty batch. */
+	function readAll(reader: FileSystemDirectoryReader): Promise<FileSystemEntry[]> {
+		return new Promise((resolve, reject) => {
+			const entries: FileSystemEntry[] = [];
+
+			const next = () =>
+				reader.readEntries((batch) => {
+					if (batch.length === 0) return resolve(entries);
+					entries.push(...batch);
+					next();
+				}, reject);
+
+			next();
+		});
+	}
+
+	/**
+	 * Flattens a dropped entry into files, naming each one with its path inside the
+	 * dropped folder so it matches what the folder picker puts in
+	 * `webkitRelativePath` — which is what the upload form reads to keep structure.
+	 */
+	async function walk(entry: FileSystemEntry, prefix = ''): Promise<File[]> {
+		if (entry.isFile) {
+			const file = await new Promise<File>((resolve, reject) =>
+				(entry as FileSystemFileEntry).file(resolve, reject)
+			);
+			return [new File([file], `${prefix}${file.name}`, { type: file.type })];
+		}
+
+		if (entry.isDirectory) {
+			const entries = await readAll((entry as FileSystemDirectoryEntry).createReader());
+			const nested = await Promise.all(entries.map((e) => walk(e, `${prefix}${entry.name}/`)));
+			return nested.flat();
+		}
+
+		return [];
+	}
+
+	async function handleDrop(event: DragEvent) {
+		event.preventDefault();
+		dragging = false;
+		if (!active) return;
+
+		// Read the entries synchronously: DataTransfer is emptied as soon as this
+		// handler yields, so awaiting first loses everything that was dropped.
+		const entries = Array.from(event.dataTransfer?.items ?? [])
+			.filter((item) => item.kind === 'file')
+			.map((item) => item.webkitGetAsEntry())
+			.filter((entry): entry is FileSystemEntry => entry !== null);
+
+		// Older engines expose no entries; fall back to the flat list, which cannot
+		// contain folders anyway.
+		if (entries.length === 0) {
+			await submit(Array.from(event.dataTransfer?.files ?? []));
+			return;
+		}
+
+		busy = true;
+		try {
+			const nested = await Promise.all(entries.map((entry) => walk(entry)));
+			await submit(nested.flat());
+		} finally {
+			busy = false;
+		}
+	}
+
+	async function handleChange(event: Event) {
+		const input = event.currentTarget as HTMLInputElement;
+		const chosen = Array.from(input.files ?? []);
+		// Reset first so picking the same file twice still fires a change event.
+		input.value = '';
+		await submit(chosen);
+	}
+
+	async function submit(candidates: File[]) {
+		const accepted: File[] = [];
+
+		for (const file of candidates) {
+			const reason = accepts(file);
+			if (reason) onFileRejected?.({ file, reason });
+			else accepted.push(file);
+		}
+
+		if (accepted.length > 0) await onUpload(accepted);
+	}
+</script>
+
+<div
+	role="group"
+	aria-label="Add books"
+	aria-disabled={!active}
+	ondragover={(e) => {
+		e.preventDefault();
+		if (active) dragging = true;
+	}}
+	ondragleave={() => (dragging = false)}
+	ondrop={handleDrop}
+	class={cn(
+		'flex flex-col items-center gap-3 rounded-lg border-2 border-dashed border-border bg-accent/20 p-6 text-center transition-colors',
+		dragging && 'border-primary bg-accent/50',
+		!active && 'opacity-50',
+		className
+	)}
+>
+	<div
+		class="flex size-12 place-items-center justify-center rounded-full border border-dashed border-border text-muted-foreground"
+	>
+		<FileUp class="size-5" />
+	</div>
+
+	<div class="flex flex-col gap-0.5">
+		<span class="font-medium">
+			{busy ? 'Reading folder…' : 'Drop books here'}
+		</span>
+		<span class="text-sm text-muted-foreground">A folder keeps its structure</span>
+	</div>
+
+	<span class="font-mono text-[10px] tracking-widest text-muted-foreground uppercase">or</span>
+
+	<div class="flex flex-wrap justify-center gap-2">
+		<Button
+			type="button"
+			variant="outline"
+			size="sm"
+			disabled={!active}
+			onclick={() => fileInput?.click()}
+		>
+			<FileText class="size-4" />
+			Choose files
+		</Button>
+		<Button
+			type="button"
+			variant="outline"
+			size="sm"
+			disabled={!active}
+			onclick={() => folderInput?.click()}
+		>
+			<Folder class="size-4" />
+			Choose folder
+		</Button>
+	</div>
+
+	<input
+		bind:this={fileInput}
+		type="file"
+		multiple
+		{accept}
+		class="hidden"
+		onchange={handleChange}
+	/>
+	<!-- webkitdirectory is why this needs to be a second input: it turns the
+	     picker into a folder chooser rather than filtering what it accepts. -->
+	<input
+		bind:this={folderInput}
+		type="file"
+		multiple
+		webkitdirectory
+		class="hidden"
+		onchange={handleChange}
+	/>
+</div>

frontend/src/lib/components/forms/books-upload.svelte

@@ -4,17 +4,14 @@
 	import * as Field from '$lib/components/ui/field/index.js';
 	import { Button } from '$lib/components/ui/button';
 	import * as NativeSelect from '$lib/components/ui/native-select/index.js';
-	import {
+	import { displaySize, type FileRejectedReason } from '$lib/components/ui/file-drop-zone';
-		displaySize,
+	import BookDropZone from './book-drop-zone.svelte';
-		FileDropZone,
-		type FileDropZoneProps
-	} from '$lib/components/ui/file-drop-zone';
 	import { X } from '@lucide/svelte';
 	import { toast } from 'svelte-sonner';
 
 	import { Switch } from '$lib/components/ui/switch/index';
 
-	import { tick } from 'svelte';
+	import { tick, untrack } from 'svelte';
 	import { Spinner } from '$lib/components/ui/spinner/index';
 	import { getLibraryState } from '$lib/state/library.svelte';
 	import { uploadBooks } from '$lib/api';
@@ -29,14 +26,20 @@
 		uploadBooks.fields.library_id.set(libraryState.activeLibrary!.id);
 	});
 
-	let files = $derived(uploadBooks.fields.files.value() ?? []);
+	// Narrowed once here rather than asserted at each use in the markup.
+	let files = $derived(
+		(uploadBooks.fields.files.value() ?? []).filter((file): file is File => Boolean(file))
+	);
+	let totalSize = $derived(files.reduce((sum, file) => sum + file.size, 0));
 
 	let autoUploadOnDrop = $state(true);
 	let navigateOnUpload = $state(true);
 	let formEl = $state<HTMLFormElement>();
 
-	const onUpload: FileDropZoneProps['onUpload'] = async (uploadedFiles) => {
+	const onUpload = async (uploadedFiles: File[]) => {
-		// Rename files to use webkitRelativePath so directory structure is preserved through form submission
+		// Rename files to use webkitRelativePath so directory structure is preserved
+		// through form submission. Dropped folders already arrive named that way,
+		// since the drop zone builds the path while walking them.
 		const renamedFiles = uploadedFiles.map(
 			(f) => new File([f], f.webkitRelativePath || f.name, { type: f.type })
 		);
@@ -47,10 +50,29 @@
 		}
 	};
 
-	const onFileRejected: FileDropZoneProps['onFileRejected'] = async ({ reason, file }) => {
+	/**
-		toast.error(`${file.name} failed to upload!`, { description: reason });
+	 * Collected rather than raised one at a time. A folder of a few hundred books
+	 * carries covers and notes alongside them, and a toast per rejected file
+	 * buries the screen.
+	 */
+	let rejected = $state<{ name: string; reason: FileRejectedReason }[]>([]);
+	let showRejected = $state(false);
+
+	const onFileRejected = ({ reason, file }: { reason: FileRejectedReason; file: File }) => {
+		rejected = [...rejected, { name: file.webkitRelativePath || file.name, reason }];
 	};
 
+	// Start each visit clean — a skipped-files list left over from last time reads
+	// as though it applies to what was just chosen.
+	$effect(() => {
+		if (open) {
+			untrack(() => {
+				rejected = [];
+				showRejected = false;
+			});
+		}
+	});
+
 	function navigateToBooks(books: PaginatedResponse<Book>) {
 		open = false;
 		let libraryId = books.items[0].library_id;
@@ -59,7 +81,9 @@
 			goto(resolve('/(root)/(library)/book/[bookId]', { bookId: String(books.items[0].id) }));
 		} else {
 			// The path is resolved; the query string is what the rule cannot see past.
-			const view = resolve('/(root)/(library)/library/[libraryId]/view', { libraryId: String(libraryId) });
+			const view = resolve('/(root)/(library)/library/[libraryId]/view', {
+				libraryId: String(libraryId)
+			});
 			// eslint-disable-next-line svelte/no-navigation-without-resolve
 			goto(`${view}?orderBy=created_at&sortOrder=desc`);
 		}
@@ -81,7 +105,7 @@
 			</Dialog.Header>
 
 			<form
-				{...uploadBooks.enhance(async ({ submit, form }) => {
+				{...uploadBooks.enhance(async ({ submit }) => {
 					try {
 						await submit();
 
@@ -99,6 +123,7 @@
 
 						// Reset the files field
 						uploadBooks.fields.files.set([]);
+						rejected = [];
 						toast.success('Books successfully uploaded!');
 
 						if (navigateOnUpload) {
@@ -116,31 +141,40 @@
 				<!-- Library select field  -->
 				<Field.Label for="library_id">Select Library</Field.Label>
 				<NativeSelect.Root {...uploadBooks.fields.library_id.as('select')} class="w-36">
-					{#each libraryState.libraries as library}
+					{#each libraryState.libraries as library (library.id)}
 						<NativeSelect.Option value={library.id}>
 							{library.name}
 						</NativeSelect.Option>
 					{/each}
 				</NativeSelect.Root>
 
-				<FileDropZone
+				<BookDropZone
 					{onUpload}
 					{onFileRejected}
-					directory={true}
 					accept=".pdf,.epub,.mobi,application/pdf,application/epub+zip,application/x-mobipocket-ebook"
-					sublabel="Only PDF, EPUB, and MOBI files supported"
 				/>
 				<input class="hidden" {...uploadBooks.fields.files.as('file multiple')} />
+
+				{#if files.length > 0}
+					<div class="flex items-baseline justify-between border-b pb-1 text-sm">
+						<span><strong class="tabular-nums">{files.length}</strong> ready to upload</span>
+						<span class="font-mono text-xs text-muted-foreground tabular-nums">
+							{displaySize(totalSize)}
+						</span>
+					</div>
+				{/if}
+
 				<div class="flex max-h-[300px] flex-col gap-2 overflow-y-auto">
-					{#each files as file, idx}
+					{#each files as file, idx (file.name)}
 						<div class="flex place-items-center justify-between gap-2">
-							<div class="flex flex-col">
+							<div class="flex min-w-0 flex-col">
-								<span>{file.name}</span>
+								<span class="truncate" title={file.name}>{file.name}</span>
 								<span class="text-xs text-muted-foreground">{displaySize(file.size)}</span>
 							</div>
 							<Button
 								variant="outline"
 								size="icon"
+								class="shrink-0"
 								onclick={() => {
 									uploadBooks.fields.files.set([
 										...Array.from(files).slice(0, idx),
@@ -149,11 +183,36 @@
 								}}
 							>
 								<X />
+								<span class="sr-only">Remove {file.name}</span>
 							</Button>
 						</div>
 					{/each}
 				</div>
 
+				{#if rejected.length > 0}
+					<div class="rounded-md border border-star/50 bg-star/10 p-2 text-sm">
+						<div class="flex items-center justify-between gap-2">
+							<span>
+								{rejected.length}
+								{rejected.length === 1 ? 'file was' : 'files were'} skipped
+							</span>
+							<Button variant="ghost" size="sm" onclick={() => (showRejected = !showRejected)}>
+								{showRejected ? 'Hide' : 'Show'}
+							</Button>
+						</div>
+						{#if showRejected}
+							<ul class="mt-2 flex max-h-32 flex-col gap-1 overflow-y-auto">
+								{#each rejected as entry (entry.name)}
+									<li class="flex justify-between gap-2 text-xs text-muted-foreground">
+										<span class="truncate" title={entry.name}>{entry.name}</span>
+										<span class="shrink-0">{entry.reason}</span>
+									</li>
+								{/each}
+							</ul>
+						{/if}
+					</div>
+				{/if}
+
 				<div class="flex flex-col gap-2">
 					<div class="flex items-center gap-2">
 						<Switch bind:checked={autoUploadOnDrop} />