Build a Reliable Multi-Step Workflow

import { mkdir, rename, writeFile } from "node:fs/promises";
import { randomUUID } from "node:crypto";

const runsDir = "runs";
await mkdir(runsDir, { recursive: true });

const fixture = {
  product_id: "DEMO-42",
  product_name: "Reusable notebook cover",
  approved_facts: [
    "Available in blue and charcoal",
    "Fits the demo A5 notebook insert"
  ],
  audience: "existing demo-store customers",
  max_characters: 240
};

function validateInput(input) {
  const errors = [];
  if (typeof input.product_id !== "string" || !/^DEMO-\d+$/.test(input.product_id)) errors.push("invalid product_id");
  if (typeof input.product_name !== "string" || !input.product_name.trim() || input.product_name.length > 100) errors.push("missing product_name");
  if (!Array.isArray(input.approved_facts) || input.approved_facts.length < 1 || input.approved_facts.length > 10) errors.push("approved_facts required");
  if (!Number.isInteger(input.max_characters) || input.max_characters < 1 || input.max_characters > 500) errors.push("invalid max_characters");
  if (Array.isArray(input.approved_facts) && input.approved_facts.some(
    (fact) => typeof fact !== "string" || !fact.trim() || fact.length > 500
  )) errors.push("approved_facts must contain short non-empty strings");
  if (errors.length) throw new Error(errors.join("; "));
}

async function save(run) {
  run.updated_at = new Date().toISOString();
  const target = `${runsDir}/${run.run_id}.json`;
  const temporary = `${target}.${randomUUID()}.tmp`;
  await writeFile(temporary, JSON.stringify(run, null, 2), "utf8");
  await rename(temporary, target);
}

// Replace only this adapter when connecting a model.
async function draftAdapter(input) {
  return `${input.product_name}: ${input.approved_facts.join(". ")}.`;
}

function checkDraft(input, draft) {
  const errors = [];
  if (typeof draft !== "string" || !draft.trim()) return ["empty or invalid draft"];
  if (draft.length > input.max_characters) errors.push("draft exceeds character limit");
  for (const fact of input.approved_facts) {
    if (!draft.includes(fact)) errors.push(`approved fact missing: ${fact}`);
  }
  const bannedClaims = ["guaranteed", "best in Pakistan", "limited stock"];
  for (const claim of bannedClaims) {
    if (draft.toLowerCase().includes(claim.toLowerCase())) errors.push(`unsupported claim: ${claim}`);
  }
  return errors;
}

async function start(input) {
  const run = {
    run_id: randomUUID(),
    workflow_version: "1.0.0",
    state: "received",
    created_at: new Date().toISOString(),
    input,
    history: [{ state: "received", at: new Date().toISOString() }]
  };
  await save(run);

  try {
  validateInput(input);
  run.state = "validated";
  run.history.push({ state: "validated", at: new Date().toISOString() });
  await save(run);

  run.draft = await draftAdapter(input);
  run.state = "drafted";
  run.history.push({ state: "drafted", at: new Date().toISOString() });
  await save(run);

  run.check_errors = checkDraft(input, run.draft);
  run.state = run.check_errors.length ? "rejected_by_checks" : "awaiting_approval";
  run.history.push({ state: run.state, at: new Date().toISOString() });
  await save(run);
  } catch {
    run.failed_after = run.state;
    run.failure_code = "STAGE_ERROR";
    run.state = "failed";
    run.history.push({ state: run.state, at: new Date().toISOString() });
    await save(run);
  }
  return run;
}

const result = await start(fixture);
console.log({ run_id: result.run_id, state: result.state, draft: result.draft });
console.log("No customer message was sent. Human approval is still required.");