zpay32: move the BOLT-11 compatible invoice format to zpay32 namespace

zpay32/amountunits.go

@@ -0,0 +1,158 @@
+package zpay32
+
+import (
+	"fmt"
+	"strconv"
+
+	"github.com/lightningnetwork/lnd/lnwire"
+)
+
+var (
+	// toMSat is a map from a unit to a function that converts an amount
+	// of that unit to millisatoshis.
+	toMSat = map[byte]func(uint64) (lnwire.MilliSatoshi, error){
+		'm': mBtcToMSat,
+		'u': uBtcToMSat,
+		'n': nBtcToMSat,
+		'p': pBtcToMSat,
+	}
+
+	// fromMSat is a map from a unit to a function that converts an amount
+	// in millisatoshis to an amount of that unit.
+	fromMSat = map[byte]func(lnwire.MilliSatoshi) (uint64, error){
+		'm': mSatToMBtc,
+		'u': mSatToUBtc,
+		'n': mSatToNBtc,
+		'p': mSatToPBtc,
+	}
+)
+
+// mBtcToMSat converts the given amount in milliBTC to millisatoshis.
+func mBtcToMSat(m uint64) (lnwire.MilliSatoshi, error) {
+	return lnwire.MilliSatoshi(m) * 100000000, nil
+}
+
+// uBtcToMSat converts the given amount in microBTC to millisatoshis.
+func uBtcToMSat(u uint64) (lnwire.MilliSatoshi, error) {
+	return lnwire.MilliSatoshi(u * 100000), nil
+}
+
+// nBtcToMSat converts the given amount in nanoBTC to millisatoshis.
+func nBtcToMSat(n uint64) (lnwire.MilliSatoshi, error) {
+	return lnwire.MilliSatoshi(n * 100), nil
+}
+
+// pBtcToMSat converts the given amount in picoBTC to millisatoshis.
+func pBtcToMSat(p uint64) (lnwire.MilliSatoshi, error) {
+	if p < 10 {
+		return 0, fmt.Errorf("minimum amount is 10p")
+	}
+	if p%10 != 0 {
+		return 0, fmt.Errorf("amount %d pBTC not expressible in msat",
+			p)
+	}
+	return lnwire.MilliSatoshi(p / 10), nil
+}
+
+// mSatToMBtc converts the given amount in millisatoshis to milliBTC.
+func mSatToMBtc(msat lnwire.MilliSatoshi) (uint64, error) {
+	if msat%100000000 != 0 {
+		return 0, fmt.Errorf("%d msat not expressible "+
+			"in mBTC", msat)
+	}
+	return uint64(msat / 100000000), nil
+}
+
+// mSatToUBtc converts the given amount in millisatoshis to microBTC.
+func mSatToUBtc(msat lnwire.MilliSatoshi) (uint64, error) {
+	if msat%100000 != 0 {
+		return 0, fmt.Errorf("%d msat not expressible "+
+			"in uBTC", msat)
+	}
+	return uint64(msat / 100000), nil
+}
+
+// mSatToNBtc converts the given amount in millisatoshis to nanoBTC.
+func mSatToNBtc(msat lnwire.MilliSatoshi) (uint64, error) {
+	if msat%100 != 0 {
+		return 0, fmt.Errorf("%d msat not expressible in nBTC", msat)
+	}
+	return uint64(msat / 100), nil
+}
+
+// mSatToPBtc converts the given amount in milllisatoshis to picoBTC.
+func mSatToPBtc(msat lnwire.MilliSatoshi) (uint64, error) {
+	return uint64(msat * 10), nil
+}
+
+// decodeAmount returns the amount encoded by the provided string in
+// milllisatoshi.
+func decodeAmount(amount string) (lnwire.MilliSatoshi, error) {
+	if len(amount) < 1 {
+		return 0, fmt.Errorf("amount must be non-empty")
+	}
+
+	// If last character is a digit, then the amount can just be
+	// interpreted as BTC.
+	char := amount[len(amount)-1]
+	digit := char - '0'
+	if digit >= 0 && digit <= 9 {
+		btc, err := strconv.ParseUint(amount, 10, 64)
+		if err != nil {
+			return 0, err
+		}
+		return lnwire.MilliSatoshi(btc) * mSatPerBtc, nil
+	}
+
+	// If not a digit, it must be part of the known units.
+	conv, ok := toMSat[char]
+	if !ok {
+		return 0, fmt.Errorf("unknown multiplier %c", char)
+	}
+
+	// Known unit.
+	num := amount[:len(amount)-1]
+	if len(num) < 1 {
+		return 0, fmt.Errorf("number must be non-empty")
+	}
+
+	am, err := strconv.ParseUint(num, 10, 64)
+	if err != nil {
+		return 0, err
+	}
+
+	return conv(am)
+}
+
+// encodeAmount encodes the provided millisatoshi amount using as few characters
+// as possible.
+func encodeAmount(msat lnwire.MilliSatoshi) (string, error) {
+	// If possible to express in BTC, that will always be the shortest
+	// representation.
+	if msat%mSatPerBtc == 0 {
+		return strconv.FormatInt(int64(msat/mSatPerBtc), 10), nil
+	}
+
+	// Should always be expressible in pico BTC.
+	pico, err := fromMSat['p'](msat)
+	if err != nil {
+		return "", fmt.Errorf("unable to express %d msat as pBTC: %v",
+			msat, err)
+	}
+	shortened := strconv.FormatUint(pico, 10) + "p"
+	for unit, conv := range fromMSat {
+		am, err := conv(msat)
+		if err != nil {
+			// Not expressible using this unit.
+			continue
+		}
+
+		// Save the shortest found representation.
+		str := strconv.FormatUint(am, 10) + string(unit)
+		if len(str) < len(shortened) {
+			shortened = str
+		}
+	}
+
+	return shortened, nil
+}