1 files changed, 101 insertions, 0 deletions
diff --git a/source/library/fetcher/apq.ts b/source/library/fetcher/apq.ts
new file mode 100644
index 0000000..7f9f3c1
--- /dev/null
+++ b/source/library/fetcher/apq.ts
@@ -0,0 +1,101 @@
+
+
+
+/*** UTILITY ------------------------------------------ ***/
+
+import { buildHeaders, postJson } from "./http-body.ts";
+import type { Fetcher, FetcherOptions } from "./types.ts";
+
+/*** EXPORT ------------------------------------------- ***/
+
+export type ApqOptions = FetcherOptions & {
+  disable?: boolean;
+};
+
+export function createApqFetcher(options: ApqOptions): Fetcher {
+  const cache = new Map<string, string>();
+  const fetchImpl = options.fetch ?? globalThis.fetch;
+
+  return async (req) => {
+    const headers = buildHeaders(options, req);
+    const sha256Hash = await getHash(cache, req.query);
+
+    const extensions = {
+      persistedQuery: {
+        sha256Hash,
+        version: 1
+      }
+    };
+
+    if (options.disable === true) {
+      return await postJson(fetchImpl, options.url, headers, {
+        extensions,
+        operationName: req.operationName,
+        query: req.query,
+        variables: req.variables
+      });
+    }
+
+    const firstResponse = await postJson(fetchImpl, options.url, headers, {
+      extensions,
+      operationName: req.operationName,
+      variables: req.variables
+    });
+
+    if (!isPersistedQueryNotFound(firstResponse))
+      return firstResponse;
+
+    return await postJson(fetchImpl, options.url, headers, {
+      extensions,
+      operationName: req.operationName,
+      query: req.query,
+      variables: req.variables
+    });
+  };
+}
+
+/*** INTERNAL ----------------------------------------- ***/
+
+async function getHash(cache: Map<string, string>, query: string): Promise<string> {
+  const cached = cache.get(query);
+
+  if (cached !== undefined)
+    return cached;
+
+  const hash = await sha256Hex(query);
+  cache.set(query, hash);
+  return hash;
+}
+
+function isPersistedQueryNotFound(response: Record<string, unknown>): boolean {
+  const errors = response.errors;
+
+  if (!Array.isArray(errors))
+    return false;
+
+  for (const entry of errors) {
+    if (entry === null || typeof entry !== "object")
+      continue;
+
+    const err = entry as Record<string, unknown>;
+
+    if (err.message === "PersistedQueryNotFound")
+      return true;
+
+    const ext = err.extensions;
+
+    if (ext !== null && typeof ext === "object") {
+      const code = (ext as Record<string, unknown>).code;
+
+      if (code === "PERSISTED_QUERY_NOT_FOUND")
+        return true;
+    }
+  }
+
+  return false;
+}
+
+async function sha256Hex(input: string): Promise<string> {
+  const buf = await globalThis.crypto.subtle.digest("SHA-256", new TextEncoder().encode(input));
+  return Array.from(new Uint8Array(buf)).map((b) => b.toString(16).padStart(2, "0")).join("");
+}