How to implement an asynchronous image-editing API

# Generate once, persist it, and reuse it for any submit retry.
IDEMPOTENCY_KEY="$(uuidgen)"

# Submit one image.
curl -sS -X POST https://api.peelaway.io/api/process \
  -H "Authorization: Bearer $PEELAWAY_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: $IDEMPOTENCY_KEY" \
  -d '{
    "image": "<base64-encoded JPEG, PNG, or WebP>",
    "prompt": "remove the temporary sign",
    "format": "jpeg"
  }'
# -> {"job_id":"...","credits_remaining":24}

# Poll until status is done or error.
curl -sS \
  -H "Authorization: Bearer $PEELAWAY_API_KEY" \
  "https://api.peelaway.io/api/process/status?job_id=<job_id>"
# -> {"status":"pending"}

# After done, fetch the signed result URL.
curl -sS \
  -H "Authorization: Bearer $PEELAWAY_API_KEY" \
  "https://api.peelaway.io/api/process/result?job_id=<job_id>"

import { readFile } from "node:fs/promises";

const apiKey = process.env.PEELAWAY_API_KEY;
if (!apiKey) throw new Error("PEELAWAY_API_KEY is required");

const headers = {
  Authorization: "Bearer " + apiKey,
  "Content-Type": "application/json",
};
const image = (await readFile("input.jpg")).toString("base64");
const submission = await fetch("https://api.peelaway.io/api/process", {
  method: "POST",
  headers: { ...headers, "Idempotency-Key": crypto.randomUUID() },
  body: JSON.stringify({ image, prompt: "remove the temporary sign" }),
});
if (!submission.ok) throw new Error("submit failed: " + submission.status);
const { job_id: jobId } = await submission.json() as { job_id: string };

for (;;) {
  await new Promise((resolve) => setTimeout(resolve, 3_000));
  const statusResponse = await fetch(
    "https://api.peelaway.io/api/process/status?job_id=" + jobId,
    { headers },
  );
  if (!statusResponse.ok) throw new Error("status failed: " + statusResponse.status);
  const { status } = await statusResponse.json() as {
    status: "pending" | "done" | "error";
  };
  if (status === "pending") continue;
  if (status === "error") throw new Error("image edit failed");
  break;
}

const resultResponse = await fetch(
  "https://api.peelaway.io/api/process/result?job_id=" + jobId,
  { headers },
);
if (!resultResponse.ok) throw new Error("result failed: " + resultResponse.status);
const result = await resultResponse.json() as { url: string };
console.log(result.url);