const bech32CharValues = 'qpzry9x8gf2tvdw0s3jn54khce6mua7l';
module.exports = {
decode: function(paymentRequest) {
let input = paymentRequest.toLowerCase();
let splitPosition = input.lastIndexOf('1');
let humanReadablePart = input.substring(0, splitPosition);
let data = input.substring(splitPosition + 1, input.length - 6);
let checksum = input.substring(input.length - 6, input.length);
if (!this.verify_checksum(humanReadablePart, this.bech32ToFiveBitArray(data + checksum))) {
return 'error';
}
return {
'human_readable_part': this.decodeHumanReadablePart(humanReadablePart),
'data': this.decodeData(data, humanReadablePart),
'checksum': checksum
}
},
decodeHumanReadablePart: function(humanReadablePart) {
let prefixes = ['lnbc', 'lntb', 'lnbcrt'];
let prefix;
prefixes.forEach(value => {
if (humanReadablePart.substring(0, value.length) === value) {
prefix = value;
}
});
if (prefix == null) return 'error'; // A reader MUST fail if it does not understand the prefix.
let amount = this.decodeAmount(humanReadablePart.substring(prefix.length, humanReadablePart.length));
return {
'prefix': prefix,
'amount': amount
}
},
decodeData: function(data, humanReadablePart) {
let date32 = data.substring(0, 7);
let dateEpoch = this.bech32ToInt(date32);
let signature = data.substring(data.length - 104, data.length);
let tagData = data.substring(7, data.length - 104);
let decodedTags = this.decodeTags(tagData);
let value = this.bech32ToFiveBitArray(date32 + tagData);
value = this.fiveBitArrayTo8BitArray(value, true);
value = this.textToHexString(humanReadablePart).concat(this.byteArrayToHexString(value));
return {
'time_stamp': dateEpoch,
'tags': decodedTags,
'signature': this.decodeSignature(signature),
'signing_data': value
}
},
decodeSignature: function(signature) {
let data = this.fiveBitArrayTo8BitArray(this.bech32ToFiveBitArray(signature));
let recoveryFlag = data[data.length - 1];
let r = this.byteArrayToHexString(data.slice(0, 32));
let s = this.byteArrayToHexString(data.slice(32, data.length - 1));
return {
'r': r,
's': s,
'recovery_flag': recoveryFlag
}
},
decodeAmount: function(str) {
let multiplier = str.charAt(str.length - 1);
let amount = str.substring(0, str.length - 1);
if (amount.substring(0, 1) === '0') {
return 'error';
}
amount = Number(amount);
if (amount < 0 || !Number.isInteger(amount)) {
return 'error';
}
switch (multiplier) {
case '':
return 'Any amount'; // A reader SHOULD indicate if amount is unspecified
case 'p':
return amount / 10;
case 'n':
return amount * 100;
case 'u':
return amount * 100000;
case 'm':
return amount * 100000000;
default:
// A reader SHOULD fail if amount is followed by anything except a defined multiplier.
return 'error';
}
},
decodeTags: function(tagData) {
let tags = this.extractTags(tagData);
let decodedTags = [];
tags.forEach(value => decodedTags.push(this.decodeTag(value.type, value.length, value.data)));
return decodedTags;
},
extractTags: function(str) {
let tags = [];
while (str.length > 0) {
let type = str.charAt(0);
let dataLength = this.bech32ToInt(str.substring(1, 3));
let data = str.substring(3, dataLength + 3);
tags.push({
'type': type,
'length': dataLength,
'data': data
});
str = str.substring(3 + dataLength, str.length);
}
return tags;
},
decodeTag: function(type, length, data) {
switch (type) {
case 'p':
if (length !== 52) break; // A reader MUST skip over a 'p' field that does not have data_length 52
return {
'type': type,
'length': length,
'description': 'payment_hash',
'value': this.byteArrayToHexString(this.fiveBitArrayTo8BitArray(this.bech32ToFiveBitArray(data)))
};
case 'd':
return {
'type': type,
'length': length,
'description': 'description',
'value': this.bech32ToUTF8String(data)
};
case 'n':
if (length !== 53) break; // A reader MUST skip over a 'n' field that does not have data_length 53
return {
'type': type,
'length': length,
'description': 'payee_public_key',
'value': this.byteArrayToHexString(this.fiveBitArrayTo8BitArray(this.bech32ToFiveBitArray(data)))
};
case 'h':
if (length !== 52) break; // A reader MUST skip over a 'h' field that does not have data_length 52
return {
'type': type,
'length': length,
'description': 'description_hash',
'value': data
};
case 'x':
return {
'type': type,
'length': length,
'description': 'expiry',
'value': this.bech32ToInt(data)
};
case 'c':
return {
'type': type,
'length': length,
'description': 'min_final_cltv_expiry',
'value': this.bech32ToInt(data)
};
case 'f':
let version = this.bech32ToFiveBitArray(data.charAt(0))[0];
if (version < 0 || version > 18) break; // a reader MUST skip over an f field with unknown version.
data = data.substring(1, data.length);
return {
'type': type,
'length': length,
'description': 'fallback_address',
'value': {
'version': version,
'fallback_address': data
}
};
case 'r':
data = this.fiveBitArrayTo8BitArray(this.bech32ToFiveBitArray(data));
let pubkey = data.slice(0, 33);
let shortChannelId = data.slice(33, 41);
let feeBaseMsat = data.slice(41, 45);
let feeProportionalMillionths = data.slice(45, 49);
let cltvExpiryDelta = data.slice(49, 51);
return {
'type': type,
'length': length,
'description': 'routing_information',
'value': {
'public_key': this.byteArrayToHexString(pubkey),
'short_channel_id': this.byteArrayToHexString(shortChannelId),
'fee_base_msat': this.byteArrayToInt(feeBaseMsat),
'fee_proportional_millionths': this.byteArrayToInt(feeProportionalMillionths),
'cltv_expiry_delta': this.byteArrayToInt(cltvExpiryDelta)
}
};
default:
// reader MUST skip over unknown fields
}
},
polymod: function(values) {
let GEN = [0x3b6a57b2, 0x26508e6d, 0x1ea119fa, 0x3d4233dd, 0x2a1462b3];
let chk = 1;
values.forEach((value) => {
let b = (chk >> 25);
chk = (chk & 0x1ffffff) << 5 ^ value;
for (let i = 0; i < 5; i++) {
if (((b >> i) & 1) === 1) {
chk ^= GEN[i];
} else {
chk ^= 0;
}
}
});
return chk;
},
expand: function(str) {
let array = [];
for (let i = 0; i < str.length; i++) {
array.push(str.charCodeAt(i) >> 5);
}
array.push(0);
for (let i = 0; i < str.length; i++) {
array.push(str.charCodeAt(i) & 31);
}
return array;
},
verify_checksum: function(hrp, data) {
hrp = this.expand(hrp);
let all = hrp.concat(data);
let bool = this.polymod(all);
return bool === 1;
},
byteArrayToInt: function(byteArray) {
let value = 0;
for (let i = 0; i < byteArray.length; ++i) {
value = (value << 8) + byteArray[i];
}
return value;
},
bech32ToInt: function(str) {
let sum = 0;
for (let i = 0; i < str.length; i++) {
sum = sum * 32;
sum = sum + bech32CharValues.indexOf(str.charAt(i));
}
return sum;
},
bech32ToFiveBitArray: function(str) {
let array = [];
for (let i = 0; i < str.length; i++) {
array.push(bech32CharValues.indexOf(str.charAt(i)));
}
return array;
},
fiveBitArrayTo8BitArray: function(int5Array, includeOverflow) {
let count = 0;
let buffer = 0;
let byteArray = [];
int5Array.forEach((value) => {
buffer = (buffer << 5) + value;
count += 5;
if (count >= 8) {
byteArray.push(buffer >> (count - 8) & 255);
count -= 8;
}
});
if (includeOverflow && count > 0) {
byteArray.push(buffer << (8 - count) & 255);
}
return byteArray;
},
bech32ToUTF8String: function(str) {
let int5Array = this.bech32ToFiveBitArray(str);
let byteArray = this.fiveBitArrayTo8BitArray(int5Array);
let utf8String = '';
for (let i = 0; i < byteArray.length; i++) {
utf8String += '%' + ('0' + byteArray[i].toString(16)).slice(-2);
}
return decodeURIComponent(utf8String);
},
byteArrayToHexString: function(byteArray) {
return Array.prototype.map.call(byteArray, function (byte) {
return ('0' + (byte & 0xFF).toString(16)).slice(-2);
}).join('');
},
textToHexString: function(text) {
let hexString = '';
for (let i = 0; i < text.length; i++) {
hexString += text.charCodeAt(i).toString(16);
}
return hexString;
},
epochToDate: function(int) {
let date = new Date(int * 1000);
return date.toUTCString();
}
}