feat: add race cover image extraction

backend/src/raceCoverImage.ts

@@ -0,0 +1,103 @@
+const IMAGE_META_KEYS = new Set([
+  "og:image",
+  "og:image:url",
+  "twitter:image",
+  "twitter:image:src",
+]);
+
+const FETCH_TIMEOUT_MS = 5_000;
+
+function getAttribute(tag: string, name: string): string | null {
+  const pattern = new RegExp(`${name}\\s*=\\s*["']([^"']+)["']`, "i");
+  return tag.match(pattern)?.[1] ?? null;
+}
+
+function toHttpUrl(value: string, baseUrl: string): string | null {
+  try {
+    const url = new URL(value, baseUrl);
+    return url.protocol === "http:" || url.protocol === "https:" ? url.href : null;
+  } catch {
+    return null;
+  }
+}
+
+function isRuncRunUrl(value: string): boolean {
+  try {
+    const hostname = new URL(value).hostname.toLowerCase();
+    return hostname === "runc.run" || hostname.endsWith(".runc.run");
+  } catch {
+    return false;
+  }
+}
+
+function findRuncIntroImage(html: string, baseUrl: string): string | null {
+  const introMatch = html.match(/<div\b[^>]*class=["'][^"']*\brun-intro__image\b[^"']*["'][^>]*>[\s\S]*?<img\b[^>]*>/i);
+  if (!introMatch) {
+    return null;
+  }
+
+  const src = getAttribute(introMatch[0], "src");
+  return src ? toHttpUrl(src, baseUrl) : null;
+}
+
+function findMetaImage(html: string, baseUrl: string): string | null {
+  const tags = html.match(/<meta\b[^>]*>/gi) ?? [];
+
+  for (const tag of tags) {
+    const key = (getAttribute(tag, "property") || getAttribute(tag, "name") || "").toLowerCase();
+    if (!IMAGE_META_KEYS.has(key)) {
+      continue;
+    }
+
+    const content = getAttribute(tag, "content");
+    if (!content) {
+      continue;
+    }
+
+    const imageUrl = toHttpUrl(content, baseUrl);
+    if (imageUrl) {
+      return imageUrl;
+    }
+  }
+
+  return null;
+}
+
+export function extractRaceCoverImageFromHtml(html: string, pageUrl: string): string | null {
+  if (isRuncRunUrl(pageUrl)) {
+    const runcImage = findRuncIntroImage(html, pageUrl);
+    if (runcImage) {
+      return runcImage;
+    }
+  }
+
+  return findMetaImage(html, pageUrl);
+}
+
+export async function extractRaceCoverImage(officialUrl: string): Promise<string | null> {
+  const normalizedUrl = toHttpUrl(officialUrl, officialUrl);
+  if (!normalizedUrl) {
+    return null;
+  }
+
+  const controller = new AbortController();
+  const timeout = setTimeout(() => controller.abort(), FETCH_TIMEOUT_MS);
+
+  try {
+    const response = await fetch(normalizedUrl, {
+      redirect: "follow",
+      signal: controller.signal,
+    });
+
+    if (!response.ok) {
+      return null;
+    }
+
+    const html = await response.text();
+    return extractRaceCoverImageFromHtml(html, response.url || normalizedUrl);
+  } catch {
+    return null;
+  } finally {
+    clearTimeout(timeout);
+  }
+}