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ts/utils/utils.etag.ts

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+/**
+ * ETag generation utilities
+ */
+
+import type * as plugins from '../plugins.js';
+
+/**
+ * Generate ETag from file stats
+ * Uses weak ETag format: W/"size-mtime"
+ */
+export function generateETag(stat: { size: number; mtime: Date }): string {
+  const mtime = stat.mtime.getTime().toString(16);
+  const size = stat.size.toString(16);
+  return `W/"${size}-${mtime}"`;
+}
+
+/**
+ * Generate strong ETag from content
+ * Uses hash of content
+ */
+export async function generateStrongETag(content: Uint8Array): Promise<string> {
+  const hashBuffer = await crypto.subtle.digest('SHA-256', content as unknown as ArrayBuffer);
+  const hashArray = Array.from(new Uint8Array(hashBuffer));
+  const hashHex = hashArray.map(b => b.toString(16).padStart(2, '0')).join('');
+  return `"${hashHex.slice(0, 32)}"`;
+}
+
+/**
+ * Check if ETag matches
+ */
+export function matchesETag(etag: string, ifNoneMatch: string | null): boolean {
+  if (!ifNoneMatch) return false;
+
+  // Handle multiple ETags
+  const etags = ifNoneMatch.split(',').map(e => e.trim());
+
+  // Wildcard match
+  if (etags.includes('*')) return true;
+
+  // Weak comparison (ignore W/ prefix)
+  const normalizeETag = (e: string) => e.replace(/^W\//, '');
+  const normalizedETag = normalizeETag(etag);
+
+  return etags.some(e => normalizeETag(e) === normalizedETag);
+}