nip60: wallet.PayBolt11()

nip60/pay.go

@@ -0,0 +1,96 @@
+package nip60
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"github.com/elnosh/gonuts/cashu"
+	"github.com/elnosh/gonuts/cashu/nuts/nut05"
+	"github.com/nbd-wtf/go-nostr/nip60/client"
+)
+
+func (w *Wallet) PayBolt11(ctx context.Context, invoice string, opts ...SendOption) (string, error) {
+	ss := &sendSettings{}
+	for _, opt := range opts {
+		opt(ss)
+	}
+
+	invoiceAmount, err := getSatoshisAmountFromBolt11(invoice)
+	if err != nil {
+		return "", err
+	}
+
+	w.tokensMu.Lock()
+	defer w.tokensMu.Unlock()
+
+	var chosen chosenTokens
+	var meltQuote string
+	var meltAmount uint64
+
+	invoicePct := uint64(99)
+	for range 10 {
+		amount := invoiceAmount * invoicePct / 100
+		var fee uint64
+		chosen, fee, err = w.getProofsForSending(ctx, amount, ss.specificMint)
+		if err != nil {
+			return "", err
+		}
+
+		// request _melt_ quote (ask the mint how much will it cost to pay a bolt11 invoice)
+		meltResp, err := client.PostMeltQuoteBolt11(ctx, chosen.mint, nut05.PostMeltQuoteBolt11Request{
+			Request: invoice,
+			Unit:    cashu.Sat.String(),
+		})
+		if err != nil {
+			return "", fmt.Errorf("error requesting melt quote from %s: %w", chosen.mint, err)
+		}
+
+		// if amount in proofs is not sufficient to pay for the melt request,
+		// increase the amount and get proofs again  (because of lighting fees)
+		if meltResp.Amount+meltResp.FeeReserve+fee > chosen.proofs.Amount() {
+			invoicePct--
+		} else {
+			meltQuote = meltResp.Quote
+			meltAmount = meltResp.Amount
+			goto meltworked
+		}
+	}
+
+	return "", fmt.Errorf("stop trying to do the melt because the mint part is too expensive")
+
+meltworked:
+	// swap our proofs so we get the exact amount for paying the invoice
+	principal, change, err := w.SwapProofs(ctx, chosen.mint, chosen.proofs, meltAmount)
+	if err != nil {
+		return "", fmt.Errorf("failed to swap at %s into the exact melt amount: %w", chosen.mint, err)
+	}
+
+	if err := w.saveChangeAndDeleteUsedTokens(ctx, chosen.mint, change, chosen.tokenIndexes); err != nil {
+		return "", err
+	}
+
+	// request from mint to _melt_ into paying the invoice
+	delay := 200 * time.Millisecond
+	// this request will block until the invoice is paid or it fails
+	// (but the API also says it can return "pending" so we handle both)
+	meltStatus, err := client.PostMeltBolt11(ctx, chosen.mint, nut05.PostMeltBolt11Request{
+		Quote:  meltQuote,
+		Inputs: principal,
+	})
+inspectmeltstatusresponse:
+	if err != nil || meltStatus.State == nut05.Unpaid {
+		return "", fmt.Errorf("error melting token: %w", err)
+	} else if meltStatus.State == nut05.Unknown {
+		return "", fmt.Errorf("we don't know what happened with the melt at %s: %v", chosen.mint, meltStatus)
+	} else if meltStatus.State == nut05.Pending {
+		for {
+			time.Sleep(delay)
+			delay *= 2
+			meltStatus, err = client.GetMeltQuoteState(ctx, chosen.mint, meltStatus.Quote)
+			goto inspectmeltstatusresponse
+		}
+	}
+
+	return meltStatus.Preimage, nil
+}