feat: pdf reader

frontend/src/utils/pdfAnchor.ts

@@ -0,0 +1,82 @@
+export type PdfRect = [number, number, number, number];
+
+export interface ParsedPdfAnchor {
+  page: number;
+  rects: PdfRect[];
+}
+
+const PDF_ANCHOR_PREFIX = "pdf:v1:";
+
+export function isPdfAnchor(anchor: string): boolean {
+  return anchor.startsWith(PDF_ANCHOR_PREFIX) || anchor.startsWith("pdf:page:");
+}
+
+export function parsePageHref(href: string): number | null {
+  const match = href.match(/^pdf:page:(\d+)$/);
+  if (!match) return null;
+  const page = Number(match[1]);
+  return Number.isFinite(page) && page > 0 ? page : null;
+}
+
+export function serializePdfAnchor(page: number, rects?: PdfRect[]): string {
+  const base = `${PDF_ANCHOR_PREFIX}p=${page}`;
+  if (!rects?.length) return base;
+  return `${base};rects=${encodeURIComponent(JSON.stringify(rects))}`;
+}
+
+export function parsePdfAnchor(anchor: string): ParsedPdfAnchor | null {
+  if (anchor.startsWith("pdf:page:")) {
+    const page = parsePageHref(anchor);
+    return page ? { page, rects: [] } : null;
+  }
+  if (!anchor.startsWith(PDF_ANCHOR_PREFIX)) return null;
+
+  const pageMatch = anchor.match(/p=(\d+)/);
+  if (!pageMatch) return null;
+  const page = Number(pageMatch[1]);
+  if (!Number.isFinite(page) || page < 1) return null;
+
+  const rectsMatch = anchor.match(/rects=([^;]+)/);
+  let rects: PdfRect[] = [];
+  if (rectsMatch) {
+    try {
+      const parsed = JSON.parse(decodeURIComponent(rectsMatch[1])) as unknown;
+      if (Array.isArray(parsed)) {
+        rects = parsed.filter(
+          (r): r is PdfRect =>
+            Array.isArray(r) &&
+            r.length === 4 &&
+            r.every((n) => typeof n === "number" && Number.isFinite(n)),
+        );
+      }
+    } catch {
+      rects = [];
+    }
+  }
+
+  return { page, rects };
+}
+
+export function rectsFromSelection(
+  range: Range,
+  pageElement: HTMLElement,
+): PdfRect[] {
+  const pageRect = pageElement.getBoundingClientRect();
+  if (pageRect.width <= 0 || pageRect.height <= 0) return [];
+
+  const rects: PdfRect[] = [];
+  for (const clientRect of range.getClientRects()) {
+    if (clientRect.width <= 0 || clientRect.height <= 0) continue;
+    const x = (clientRect.left - pageRect.left) / pageRect.width;
+    const y = (clientRect.top - pageRect.top) / pageRect.height;
+    const w = clientRect.width / pageRect.width;
+    const h = clientRect.height / pageRect.height;
+    rects.push([
+      Math.max(0, Math.min(1, x)),
+      Math.max(0, Math.min(1, y)),
+      Math.max(0, Math.min(1, w)),
+      Math.max(0, Math.min(1, h)),
+    ]);
+  }
+  return rects;
+}