feat: rebuild the book page with the jacket layout

frontend/src/lib/utils.ts

@@ -58,6 +58,52 @@ export function formatFileSize(bytes: number, decimals = 1, binary = true) {
 	return `${formattedSize} ${units[exponent]}`;
 }
 
+/**
+ * Presentation for a book identifier.
+ *
+ * The backend stores identifiers as free-form name/value pairs, so this only
+ * decides how to label and link the ones we recognise. Anything unknown falls
+ * back to the stored name and renders as plain text.
+ */
+const IDENTIFIER_TYPES: Record<string, { label: string; url?: (value: string) => string }> = {
+	'isbn-13': { label: 'ISBN-13', url: (v) => `https://openlibrary.org/isbn/${isbnDigits(v)}` },
+	'isbn-10': { label: 'ISBN-10', url: (v) => `https://openlibrary.org/isbn/${isbnDigits(v)}` },
+	isbn: { label: 'ISBN', url: (v) => `https://openlibrary.org/isbn/${isbnDigits(v)}` },
+	doi: { label: 'DOI', url: (v) => `https://doi.org/${encodeURI(v.trim())}` },
+	asin: { label: 'ASIN', url: (v) => `https://www.amazon.com/dp/${encodeURIComponent(v.trim())}` }
+};
+
+/** Order the ones worth reading first; everything else keeps its own order. */
+const IDENTIFIER_ORDER = ['isbn-13', 'isbn-10', 'isbn', 'doi', 'asin'];
+
+function isbnDigits(value: string) {
+	return value.replace(/[^0-9Xx]/g, '');
+}
+
+function identifierKey(name: string) {
+	return name.trim().toLowerCase().replace(/[\s_]+/g, '-');
+}
+
+export function describeIdentifier(name: string, value: string) {
+	const known = IDENTIFIER_TYPES[identifierKey(name)];
+
+	return {
+		label: known?.label ?? name.toUpperCase(),
+		href: known?.url?.(value)
+	};
+}
+
+export function sortIdentifiers(identifiers: Record<string, string>) {
+	return Object.entries(identifiers).sort(([a], [b]) => {
+		const ia = IDENTIFIER_ORDER.indexOf(identifierKey(a));
+		const ib = IDENTIFIER_ORDER.indexOf(identifierKey(b));
+		if (ia === -1 && ib === -1) return 0;
+		if (ia === -1) return 1;
+		if (ib === -1) return -1;
+		return ia - ib;
+	});
+}
+
 export function getFileType(filename: string) {
 	const parts = filename.split('.');
 	if (parts.length < 2) return 'UNKNOWN';