update wallet example

examples/simpleWallet_example.ts

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+import { CashuMint } from '../src/CashuMint.js';
+import { CashuWallet } from '../src/CashuWallet.js';
+
+import dns from 'node:dns';
+import {
+	MeltQuoteResponse,
+	MeltQuoteState,
+	MintQuoteResponse,
+	MintQuoteState,
+	Proof,
+	Token
+} from '../src/model/types/index.js';
+import { getEncodedTokenV4, sumProofs } from '../src/utils.js';
+dns.setDefaultResultOrder('ipv4first');
+
+const externalInvoice =
+	'lnbc20u1p3u27nppp5pm074ffk6m42lvae8c6847z7xuvhyknwgkk7pzdce47grf2ksqwsdpv2phhwetjv4jzqcneypqyc6t8dp6xu6twva2xjuzzda6qcqzpgxqyz5vqsp5sw6n7cztudpl5m5jv3z6dtqpt2zhd3q6dwgftey9qxv09w82rgjq9qyyssqhtfl8wv7scwp5flqvmgjjh20nf6utvv5daw5h43h69yqfwjch7wnra3cn94qkscgewa33wvfh7guz76rzsfg9pwlk8mqd27wavf2udsq3yeuju';
+
+// const mintUrl = 'https://testnut.cashu.space';
+const mintUrl = 'http://localhost:3338';
+
+// +++++++++++++++++++++ Example of a simple wallet implementation ++++++++++++++++++
+// run the example with the following command: `npx examples/_simpleWallet.ts`
+// a local mint instance should be running on port 3338. Startup command:
+// docker run -d -p 3338:3338 --name nutshell -e MINT_LIGHTNING_BACKEND=FakeWallet -e MINT_INPUT_FEE_PPK=100 -e MINT_LISTEN_HOST=0.0.0.0 -e MINT_LISTEN_PORT=3338 -e MINT_PRIVATE_KEY=TEST_PRIVATE_KEY cashubtc/nutshell:0.16.0 poetry run mint
+
+const mintAmount = 2050;
+
+const runWalletExample = async () => {
+	try {
+		// instantiate a mint. It is used later by the CashuWallet to create api calls to the mint
+		const mint = new CashuMint(mintUrl);
+
+		// create a wallet with the keys loaded from the mint.
+		// The wallet is used as an interface for all cashu specific interactions
+		const wallet = new CashuWallet(mint);
+
+		// In order to load mint keys and other information about the mint, we should call this method
+		await wallet.loadMint();
+
+		//we can store the mint information, in case we later want to initialize the wallet without requesting the mint info again.
+		const mintInfo = wallet.mintInfo;
+		const keys = wallet.keys;
+		const keysets = wallet.keysets;
+
+		// ++++++++ Minting some ecash +++++++++++++
+
+		//First, let's decide on the amount of ecash we want to mint.
+
+		// next we create a place to store the ecash after it has been minted.
+		// Usually, this would be done in a database or somewhere where persistence is guaranteed.
+		// in this example, we will store the ecash in memory to make the example easier to understand.
+		let proofs: Proof[] = [];
+
+		// It's also a good idea to store proofs we've sent: in case the receiver does not claim them, we can receive them back later
+		let sentProofs: Proof[] = [];
+
+		// let's start with minting some ecash!
+		const mintEcash = async function () {
+			// with this command, we can initiate the creation of some ecash.
+			// The mint will return a request, that we have to fullfil in order for the ecash to be issued.
+			// (in most cases this will be a lightning invoice that needs to be paid)
+			console.log('Requesting a mint quote for' + mintAmount + 'satoshis.');
+			const quote = await wallet.createMintQuote(mintAmount);
+
+			console.log('Invoice to pay, in order to fullfill the quote: ' + quote.request);
+
+			//check if an error occurred in the creation of the quote
+			if (quote.error) {
+				console.error(quote.error, quote.code, quote.detail);
+				return;
+			}
+
+			// After some time of waiting, let's ask the mint if the request has been fullfilled.
+			setTimeout(async () => await checkMintQuote(quote), 1000);
+
+			const checkMintQuote = async (q: MintQuoteResponse) => {
+				// with this call, we can check the current status of a given quote
+				console.log('Checking the status of the quote: ' + q.quote);
+				const quote = await wallet.checkMintQuote(q.quote);
+				if (quote.error) {
+					console.error(quote.error, quote.code, quote.detail);
+					return;
+				}
+				if (quote.state === MintQuoteState.PAID) {
+					//if the quote was paid, we can ask the mint to issue the signatures for the ecash
+					const response = await wallet.mintProofs(mintAmount, quote.quote);
+					console.log(`minted proofs: ${response.map((p) => p.amount).join(', ')} sats`);
+
+					// let's store the proofs in the storage we previously created
+					proofs = response;
+
+					// after successfull minting, let's try to send some ecash
+					sendEcash(10);
+				} else if (quote.state === MintQuoteState.ISSUED) {
+					// if the quote has already been issued, we will receive an error if we try to mint again
+					console.error('Quote has already been issued');
+					return;
+				} else {
+					// if the quote has not yet been paid, we will wait some more to get the status of the quote again
+					setTimeout(async () => await checkMintQuote(q), 1000);
+				}
+			};
+		};
+		await mintEcash();
+
+		// ++++++++ Sending some ecash +++++++++++++
+
+		const sendEcash = async (amount: number) => {
+			// to send some ecash, we will call the `send` function
+			// e can provide the proofs we created in the previous step.
+			// If we provide too many proofs, they will be returned by the `keep` array
+			// after that,
+			// If the amount of the accumulated proofs we provide do not match exactly the amount we want to send,
+			// a split will have to be performed.
+			// this will burn the current proofs at the mint, and return a fresh set of proofs, matching the amount we want to send
+			const { keep, send } = await wallet.send(amount, proofs, { includeFees: true });
+
+			console.log(
+				`sending ${send.reduce((a, b) => a + b.amount, 0)} keeping ${keep.reduce(
+					(a, b) => a + b.amount,
+					0
+				)}`
+			);
+			// first, let's update our store with the new proofs
+			proofs = keep;
+
+			sentProofs.push(...send);
+
+			// and now, let's prepare the ecash we want to send as a cashu string
+			// For this, we can use the `Token` type
+			// In there, we set the mint url, and proof we want to send
+			const token: Token = {
+				mint: mintUrl,
+				proofs: send
+			};
+			// and finally, we can encode the token as a cashu string
+			const cashuString = getEncodedTokenV4(token);
+
+			// we can now send the cashu string to someone, and they can receive the ecash! let's try that next
+			console.log(cashuString);
+
+			// let's try to receive the cashu string back to ourselves
+			await receiveEcash(cashuString);
+		};
+
+		// ++++++++ Receiving some ecash +++++++++++++
+
+		const receiveEcash = async (cashuString: string) => {
+			// we can receive a cashu string back with the `receive` method
+			// this step is crucial. It will burn the received proofs, and create new ones,
+			// making sure the sender cannot try to double spend them.
+			const received = await wallet.receive(cashuString);
+			console.log('Received proofs:' + received.reduce((acc, proof) => acc + proof.amount, 0));
+
+			// after receiving, let's not forget to add the proofs back to our storage
+			proofs.push(...received);
+
+			// After receiving back our ecash, let's try to melt it.
+			// Melting ecash means, exchanging it back to the medium it was issued for.
+			// in most cases that would be lightning sats
+			await meltEcash();
+		};
+
+		// ++++++++ Melting some ecash +++++++++++++
+
+		const meltEcash = async () => {
+			// Similar to the minting process, we need to create a melt quote first.
+			// For this, we let the mint know what kind of request we want to be fulfilled.
+			// Usually this would be the payment of a lightning invoice.
+			const quote = await wallet.createMeltQuote(externalInvoice);
+
+			// After creating the melt quote, we can initiate the melting process.
+			const amountToMelt = quote.amount + quote.fee_reserve;
+
+			console.log(`quote amount: ${quote.amount}`);
+			console.log(`fee reserve proofs: ${quote.fee_reserve}`);
+			console.log(`Total quote amount: ${amountToMelt}`);
+
+			// in order to get the correct amount of proofs for the melt request, we can use the `send` function we used before
+			const { keep, send } = await wallet.send(amountToMelt, proofs, { includeFees: true });
+
+			// once again, we update the proofs we have to keep.
+			proofs = keep;
+
+			sentProofs.push(...send);
+
+			// and initiate the melting process with the prepared proofs.
+			const { change } = await wallet.meltProofs(quote, send);
+
+			//in case we overpaid for lightning fees, the mint will return the owed amount in ecash
+			proofs.push(...change);
+
+			if (quote.error) {
+				console.error(quote.error, quote.code, quote.detail);
+				return;
+			}
+
+			// After giving the mint some time to fullfil the melt request,
+			// we can check on the status
+			setTimeout(async () => await checkMeltQuote(quote), 1000);
+
+			const checkMeltQuote = async (q: MeltQuoteResponse) => {
+				// we can check on the status of the quote.
+				const quote = await wallet.checkMeltQuote(q.quote);
+
+				if (quote.error) {
+					console.error(quote.error, quote.code, quote.detail);
+					return;
+				}
+				if (quote.state === MeltQuoteState.PAID) {
+					// if the request has succeeded, we should receive the preimage for the paid invoice.
+					console.log(
+						'success! here is the payment preimage (if its null, the mints lightning backend did not forward the preimage): ',
+						quote.payment_preimage
+					);
+
+					console.log(`Ecash left: ${sumProofs(proofs)}`);
+					console.log(`Spent ecash notes: ${sumProofs(sentProofs)}`);
+
+					// +++++++++++++++++++ THE END +++++++++++++++++++
+					// There are more advanced features that were not touched on in this example.
+					// Take a look at the documentation to learn about features like seed recovery, locking ecash to pubkeys, etc.
+				} else {
+					// if the request has not succeeded, we will ask again
+					setTimeout(async () => await checkMeltQuote(quote), 1000);
+				}
+			};
+		};
+	} catch (error) {
+		console.error(error, 'u-oh something went wrong');
+	}
+};
+
+runWalletExample();