Build a Voluntary Carbon Credit Marketplace

import { TokenFactory, IndexerClient } from "@ankarachain/sdk";

export const factory = new TokenFactory({
  network:          "stellar-testnet",
  stellarSecretKey: process.env.STELLAR_SECRET_KEY!,   // the platform's own custody signer
  factoryAddress:   "CBMBI63UU6KJIZ5KUVP6A3FGMBMS4R3OXSY27NQNK5PPLCWJW7DPSEEF",
});

export const indexer = new IndexerClient(process.env.INDEXER_URL!); // e.g. "https://indexer.myapp.com"

import express from "express";
import { AssetRegistry } from "@ankarachain/sdk";
import { factory } from "./config";

export const router = express.Router();
const TREASURY_ADDRESS = process.env.TREASURY_ADDRESS!; // the platform's own custody address

router.post("/api/projects", async (req, res) => {
  const { creditType, verificationBodyRef, vintageYear, quantityCO2e, projectLocation, projectType } = req.body;

  const now = BigInt(Math.floor(Date.now() / 1000));

  const result = await factory.deployCarbonCredit({
    name:        `${projectLocation} ${creditType} Credits`,
    symbol:      "CARB",
    assetId:     `${verificationBodyRef}-${vintageYear}`,
    countryCode: req.body.countryCode,
    metadata: {
      creditType,
      verificationBodyRef,
      vintageYear:         BigInt(vintageYear),
      quantityCO2e:        BigInt(quantityCO2e) * 10n ** 18n, // 1e18 = 1 tCO2e
      projectLocation,
      projectType,
      verificationDocHash: "0x" + "00".repeat(32),
      lastUpdated:         now,
    },
  });

  // Mint the full verified quantity into the platform's own custody treasury —
  // buyers hold an internal balance in your DB rather than an on-chain wallet of their own.
  const registry = new AssetRegistry(factory.adapter, result.tokenAddress, "carbon-credit");
  await registry.mint(TREASURY_ADDRESS, BigInt(quantityCO2e) * 10n ** 18n);

  res.json({ tokenAddress: result.tokenAddress, txHash: result.txHash });
});

router.post("/api/purchase", async (req, res) => {
  const { buyerId, tokenAddress, amountCO2e } = req.body;
  await creditBuyerLedger(buyerId, tokenAddress, amountCO2e); // your DB — no on-chain call needed yet
  res.sendStatus(200);
});

router.post("/api/retire", async (req, res) => {
  const { buyerId, buyerName, tokenAddress, amountCO2e, note } = req.body;

  await debitBuyerLedger(buyerId, tokenAddress, amountCO2e); // your DB — fails if buyer's ledger balance is short

  const registry = new AssetRegistry(factory.adapter, tokenAddress, "carbon-credit");
  const txHash = await registry.retire(
    BigInt(amountCO2e) * 10n ** 18n,
    buyerName,   // beneficiary — a free-text label, not an address
    note         // e.g. "Scope 1 offset — Lagos office, 2025"
  );

  res.json({ txHash });
});

router.get("/api/registry/:tokenAddress", async (req, res) => {
  const registry = new AssetRegistry(factory.adapter, req.params.tokenAddress, "carbon-credit");

  const total  = await registry.getTotalRetired();
  const count  = await registry.getTotalRetirements();
  const records = [];
  for (let i = 0; i < count; i++) {
    records.push(await registry.getRetirement(i));
  }

  res.json({ totalRetired: total.toString(), records });
});

router.post("/api/admin/watch-retirements", async (req, res) => {
  const webhook = await indexer.registerWebhook(
    "https://yourplatform.com/api/hooks/retirements",
    ["*"] // subscribe to all event types; filter by payload shape in your handler below
  );

  await saveWebhookSecret(webhook.id, webhook.secret!); // shown only once — store it now
  res.json({ webhookId: webhook.id });
});

router.post("/api/hooks/retirements", express.raw({ type: "*/*" }), async (req, res) => {
  // Verify req.headers["x-ankara-signature"] against your stored secret first —
  // see the signature verification example in the IndexerClient reference.
  const event = JSON.parse(req.body.toString());

  if (event.data && "beneficiary" in event.data) {
    await broadcastToRegistryFeed(event); // push to your public live feed (WebSocket, SSE, etc.)
  }

  res.sendStatus(200);
});