SkateSpots/src/hooks/wallet/useCashuEscrow.ts

import { useCallback } from 'react';
import { CashuMint, CashuWallet } from '@cashu/cashu-ts';
import type { WebLNProvider } from '@webbtc/webln-types';
import { useCashu } from './useCashu';
import { useNWC } from '@/hooks/useNWCContext';
import { useCurrentUser } from '@/hooks/useCurrentUser';
import { useAuthor } from '@/hooks/useAuthor';
import { useNostrPublish } from '@/hooks/useNostrPublish';
import { isNativePlatform } from '@/lib/platform';
import {
  createEscrowToken,
  normalizeCashuPubkey,
  parseEscrowToken,
  type EscrowMintWallet,
  type EscrowTokenInfo,
} from '@/lib/cashuEscrow';

/**
 * Cashu escrow — **native-only** (the Cashu wallet is Capacitor-gated).
 *
 * Funds are locked to the seller with a locktime and the buyer as refund key
 * (see `ESCROW.md`). The correctness-critical flow lives in
 * `src/lib/cashuEscrow.ts` (unit-tested); this hook wires it to a real
 * cashu-ts wallet, the NWC/WebLN payment rail, and the coco keyring.
 *
 * EXPERIMENTAL: the mint-touching paths (create/redeem/refund) have not been
 * verified on a device yet — exercise with small amounts first.
 */
export function useCashuEscrow() {
  const { coco, isInitialized, mints } = useCashu();
  const { getActiveConnection, sendPayment } = useNWC();
  const { user } = useCurrentUser();
  const author = useAuthor(user?.pubkey);
  const { mutateAsync: publish } = useNostrPublish();
  const webln = (globalThis as { webln?: WebLNProvider }).webln || null;

  const available = isNativePlatform() && isInitialized && !!coco;

  /** The active mint URL to fund escrow from (first trusted mint). */
  const defaultMintUrl = mints[0]?.url ?? null;

  /**
   * The Cashu keyring pubkey used as the P2PK lock/refund key. Nostr signers
   * can't produce Cashu's raw schnorr witness, so escrow uses the Cashu
   * keyring — not the Nostr key.
   */
  const getEscrowPubkey = useCallback(async (): Promise<string | null> => {
    if (!coco) return null;
    const existing = await coco.keyring.getLatestKeyPair();
    const keypair = existing ?? (await coco.keyring.generateKeyPair(true));
    return normalizeCashuPubkey(keypair.publicKeyHex);
  }, [coco]);

  /** Pay a mint invoice via NWC, then WebLN. */
  const payInvoice = useCallback(
    async (bolt11: string): Promise<void> => {
      const nwc = getActiveConnection();
      if (nwc?.connectionString && nwc.isConnected) {
        await sendPayment(nwc, bolt11);
        return;
      }
      if (webln) {
        if (typeof webln.enable === 'function') await webln.enable();
        await webln.sendPayment(bolt11);
        return;
      }
      throw new Error('No Lightning wallet available to fund escrow — connect NWC or a WebLN wallet.');
    },
    [getActiveConnection, sendPayment, webln],
  );

  const makeMintWallet = useCallback((mintUrl: string): EscrowMintWallet => {
    const wallet = new CashuWallet(new CashuMint(mintUrl), { unit: 'sat' });
    return {
      createMintQuote: (amount) => wallet.createMintQuote(amount),
      checkMintQuote: async (quote) => ({ state: (await wallet.checkMintQuote(quote)).state }),
      mintProofs: (amount, quote, options) =>
        wallet.mintProofs(amount, quote, { p2pk: options.p2pk }),
    };
  }, []);

  /**
   * Create an escrowed token locked to `sellerPubkey` (funded by paying the
   * mint's Lightning invoice). Returns the token to embed in a `31872`.
   */
  const createEscrow = useCallback(
    async ({
      amountSats,
      sellerPubkey,
      lockDays,
      mintUrl,
    }: {
      amountSats: number;
      sellerPubkey: string;
      lockDays?: number;
      mintUrl?: string;
    }): Promise<{ token: string; locktime: number; info: EscrowTokenInfo }> => {
      if (!coco) throw new Error('Cashu wallet is not ready.');

      const buyerPubkey = await getEscrowPubkey();
      if (!buyerPubkey) throw new Error('Could not derive your escrow key.');

      const mint = mintUrl ?? defaultMintUrl;
      if (!mint) throw new Error('No Cashu mint available — add one in your wallet first.');

      const { token, locktime } = await createEscrowToken(
        { wallet: makeMintWallet(mint), payInvoice },
        { mintUrl: mint, amountSats, sellerPubkey, buyerPubkey, lockDays },
      );

      return { token, locktime, info: parseEscrowToken(token) };
    },
    [coco, getEscrowPubkey, defaultMintUrl, makeMintWallet, payInvoice],
  );

  /** Redeem an escrow token (seller on delivery, or buyer after the locktime). */
  const redeemEscrow = useCallback(
    async (token: string): Promise<void> => {
      if (!coco) throw new Error('Cashu wallet is not ready.');
      await coco.wallet.receive(token);
    },
    [coco],
  );

  /**
   * Publish this user's escrow pubkey to their kind 0 profile (`cashu_escrow`)
   * so buyers can lock funds to them.
   */
  const advertiseEscrowKey = useCallback(async (): Promise<string> => {
    if (!user) throw new Error('Log in first.');
    const pubkey = await getEscrowPubkey();
    if (!pubkey) throw new Error('Could not derive your escrow key.');

    const current = (author.data?.metadata ?? {}) as Record<string, unknown>;
    await publish({
      kind: 0,
      content: JSON.stringify({ ...current, cashu_escrow: pubkey }),
    });
    return pubkey;
  }, [user, getEscrowPubkey, author.data?.metadata, publish]);

  return {
    available,
    defaultMintUrl,
    getEscrowPubkey,
    createEscrow,
    redeemEscrow,
    payInvoice,
    advertiseEscrowKey,
  };
}