Koa

CONSTAIA_API_KEY=ck_test_...
CONSTAIA_WEBHOOK_SECRET=whsec_...

import {
  AuthenticationError,
  Constaia,
  ConstaiaError,
  InsufficientCreditsError,
  InvalidRequestError,
  PermissionError,
  RateLimitError,
  type Analysis,
  type WebhookEvent,
} from "@constaia/sdk";

// Reads CONSTAIA_API_KEY from the environment.
export const constaia = new Constaia();

// What you send back to the browser (and what the widget renders): no extracted fields.
export function publicResult(analysis: Analysis) {
  const { id, object, status, document, verdict, warnings } = analysis;
  return { id, object, status, document, verdict, warnings };
}

export type HttpError = {
  status: number;
  body: { error: { code: string; message: string } };
  retryAfter?: number;
};

const httpError = (status: number, code: string, message: string, retryAfter?: number): HttpError => ({
  status,
  body: { error: { code, message } },
  retryAfter,
});

export function toHttpError(error: unknown): HttpError {
  if (error instanceof InvalidRequestError) {
    // Unreadable file, unsupported format, too many pages…: the user can fix it.
    return httpError(error.status === 413 ? 413 : 422, error.code ?? "invalid_request", error.message);
  }
  if (error instanceof RateLimitError) {
    const wait = Math.ceil(error.retryAfter ?? 1);
    return httpError(429, "rate_limited", "Too many requests. Try again in a few seconds.", wait);
  }
  if (error instanceof InsufficientCreditsError) {
    console.error("[constaia] Out of credits. Top up at https://app.constaia.com", error.requestId);
    return httpError(503, "unavailable", "Document validation is temporarily unavailable.");
  }
  if (error instanceof AuthenticationError || error instanceof PermissionError) {
    console.error("[constaia] Check CONSTAIA_API_KEY", error.code, error.requestId);
    return httpError(500, "misconfigured", "Server configuration error.");
  }
  if (error instanceof ConstaiaError) {
    // APIError (5xx), APIConnectionError, APITimeoutError
    console.error("[constaia]", error.name, error.code, error.requestId);
    return httpError(502, "upstream_error", "The document could not be analysed. Please try again.");
  }
  console.error(error);
  return httpError(500, "internal_error", "Internal error.");
}

// Dedupe by webhook-id. In production, use a table with a unique key.
const processed = new Set<string>();
export const alreadyProcessed = (webhookId: string) => processed.has(webhookId);
export const markProcessed = (webhookId: string) => void processed.add(webhookId);

export async function handleEvent(event: WebhookEvent) {
  switch (event.type) {
    case "analysis.completed":
      // event.data is the full analysis (with fields). Store it by event.data.id.
      console.log("analysis.completed", event.data.id, event.data.verdict?.status);
      break;
    case "analysis.review_required":
      console.log("Needs manual review", event.data.id);
      break;
    case "analysis.failed":
      console.warn("analysis.failed", event.data.id, event.data.error?.code);
      break;
    case "credits.low":
      console.warn("Credits running low: top up at https://app.constaia.com");
      break;
  }
}

import Koa from "koa";
import Router from "@koa/router";
import multer from "@koa/multer";
import getRawBody from "raw-body";
import { WebhookVerificationError } from "@constaia/sdk";
import {
  alreadyProcessed,
  constaia,
  handleEvent,
  markProcessed,
  publicResult,
  toHttpError,
} from "./constaia.js";

const app = new Koa();
const router = new Router();
const upload = multer({
  storage: multer.memoryStorage(),
  limits: { fileSize: 20 * 1024 * 1024, files: 1 },
});

app.use(async (ctx, next) => {
  try {
    await next();
  } catch (error) {
    if ((error as { code?: string }).code === "LIMIT_FILE_SIZE") {
      ctx.status = 413;
      ctx.body = { error: { code: "file_too_large", message: "20 MB maximum." } };
      return;
    }
    throw error;
  }
});

// Put your authentication here: only signed-in users should spend credits.
router.post("/api/verify-dni", upload.single("file"), async (ctx) => {
  const file = ctx.file;
  if (!file) {
    ctx.status = 400;
    ctx.body = { error: { code: "missing_file", message: "No file received." } };
    return;
  }
  // Even better: the authenticated user's name, not the form's.
  const fields = (ctx.request.body ?? {}) as Record<string, unknown>;
  const fullName = String(fields.full_name ?? "").trim();

  try {
    const analysis = await constaia.analyze(file.buffer, {
      filename: file.originalname,
      expect: "es_dni",
      checks: { notExpired: true, ...(fullName ? { holder: { fullName } } : {}) },
      storage: "none",
      language: "en",
    });
    // Store analysis.id and analysis.verdict in your database.
    ctx.status = analysis.status === "completed" ? 200 : 202;
    ctx.body = publicResult(analysis);
  } catch (error) {
    const { status, body, retryAfter } = toHttpError(error);
    if (retryAfter) ctx.set("Retry-After", String(retryAfter));
    ctx.status = status;
    ctx.body = body;
  }
});

router.post("/webhooks/constaia", async (ctx) => {
  const rawBody = await getRawBody(ctx.req, { limit: "1mb", encoding: "utf8" });

  let event;
  try {
    event = await constaia.webhooks.verify(rawBody, ctx.headers, process.env.CONSTAIA_WEBHOOK_SECRET!);
  } catch (error) {
    if (!(error instanceof WebhookVerificationError)) throw error;
    ctx.status = 400;
    ctx.body = "Invalid signature";
    return;
  }

  const webhookId = ctx.get("webhook-id");
  if (!alreadyProcessed(webhookId)) {
    await handleEvent(event);
    markProcessed(webhookId);
  }
  ctx.status = 204;
});

app.use(router.routes()).use(router.allowedMethods());

const server = app.listen(Number(process.env.PORT ?? 3000));
server.requestTimeout = 120_000;

npx tsx --env-file=.env src/server.ts

{
  "id": "an_01J…",
  "object": "analysis",
  "status": "completed",
  "document": { "type": "es_dni", "label": "Spanish ID card (DNI)", "confidence": 0.97, "side": "both", "country": "ESP" },
  "verdict": {
    "expected": ["es_dni"],
    "match": true,
    "status": "valid",
    "reasons": [
      { "code": "type_match", "severity": "info", "message": "The document is Spanish ID card (DNI)." },
      { "code": "not_expired", "severity": "info", "message": "Valid until 12/03/2031." },
      { "code": "holder", "severity": "info", "message": "…" }
    ]
  },
  "warnings": []
}

curl -F "file=@dni_valid.jpg" -F "full_name=María García López" http://localhost:3000/api/verify-dni

import { signWebhook } from "@constaia/sdk";

const body = JSON.stringify({
  type: "analysis.completed",
  created_at: new Date().toISOString(),
  data: { id: "an_test", object: "analysis", status: "completed", verdict: { status: "valid", reasons: [] } },
});
const headers = await signWebhook(body, process.env.CONSTAIA_WEBHOOK_SECRET!);

const res = await fetch("http://localhost:3000/webhooks/constaia", {
  method: "POST",
  headers: { ...headers, "content-type": "application/json" },
  body,
});
console.log(res.status); // 204