A package that helps you to interact with WebLN providers by providing a FlutterWebln interface for creating Bitcoin Lightning powered web applications.
Features
There are methods to:
- Enable the provider (
FlutterWebln.enable
) - Get information about a users Bitcoin Lightning node (
FlutterWebln.getInfo
) - Send a payment (
FlutterWebln.sendPayment
) - Create an invoice to receive a payment (
FlutterWebln.makeInvoice
) - Request the user to send a keysend payment (
FlutterWebln.keysend
) - Request a signature of an arbitrary message (
FlutterWebln.signMessage
) - Verifies the signature against the raw message (
FlutterWebln.verifyMessage
)
Getting Started
You first need to install WebLN provider in order to use any of the FlutterWebln
methods.
Detecting WebLN support
Before you start using FlutterWebln
you need to check for browser support by checking if the variable FlutterWebln.webln
is defined:
void checkWebln() {
try {
final weblnValue = weblnDecode(FlutterWebln.webln);
if (weblnValue.isEmpty) {
isWallet = false;
} else {
isWallet = true;
}
print('[+] webln value is $weblnValue');
} catch (e) {
print("[!] Error in checkWebln method is $e");
}
}
weblnValue.isEmpty
indicates that the WebLN provider is not installed and the user can’t use any of the FlutterWebln
methods.
Enable WebLN
To begin interacting with FlutterWebln
methods you’ll first need to enable the provider as:
await FlutterWebln.enable()
It will prompt the user for permission to use the WebLN capabilities of the browser. After that you are free to call any of the other FlutterWebln
methods.
Get Info
With FlutterWebln.getInfo
the user gets information about the connected node as:
try {
await FlutterWebln.enable();
await FlutterWebln.getInfo().then(allowInterop((response) {
print('[+] GetInfoResponse: ${weblnDecode(response)}');
}));
} catch (error) {
print('[!] Error in getInfo method is $error');
}
Response
Result: [+] GetInfoResponse: {node: {alias: 🐝 getalby.com}}
Make Invoice
With FlutterWebln.makeInvoice
the user creates an invoice to be used by the web app as:
final invoice = FlutterWebln.requestInvoiceArgs(
amount: 100,
defaultMemo: 'Hello World',
);
try {
await FlutterWebln.makeInvoice(requestInvoiceArgs: invoice)
.then(allowInterop((result) {
print('[+] RequestInvoiceResponse: ${weblnDecode(result)}');
}));
} catch (error) {
print('[!] Error in makeInvoice method is $error');
}
Response
[+] RequestInvoiceResponse: {paymentRequest: lnbc1u1p3jdmdzpp5aehslp0ts0wszr62lwl82qwzcgl6jtqudvg000ez75jx307vpcdqdqjfpjkcmr0yptk7unvvscqzpgxqyz5vqsp5npje0n0mct745acshv8dl5pz5kyznz2z6du45fwpyxgwvxvepdts9qyyssqdynz62hf8xh76pn4qfpswzcz4ezt6k9kj9mccf6lzwzkutm04rwjhzynctgphyk6xc0g2ftn7unjxvmszutzr07xq52h5qeja5mk3sqpqwwx7y, rHash: ee6f0f85eb83dd010f4afbbe7501c2c23fa92c1c6b10f7bf22f52468bfcc0e1a}
Send Payment
With FlutterWebln.sendPayment
the user sends a payment for an invoice. The user needs to provide a BOLT-11 invoice.
try {
await FlutterWebln.sendPayment(invoice: invoiceController.text)
.then(allowInterop((result) {
print('[+] SendPaymentResponse: ${weblnDecode(result)}');
}));
} catch (error) {
print('[!] Error in sendPayment method is $error');
}
Response
[+] SendPaymentResponse: {preimage: 6662313533626135643134626265623164343134363734626261336263306630, paymentHash: ee6f0f85eb83dd010f4afbbe7501c2c23fa92c1c6b10f7bf22f52468bfcc0e1a, route: {total_amt: 100, total_fees: 0}}
Keysend
With FlutterWebln.keysend
it request the user to send a keysend payment. This payment only needs a destination public key and amount.
try {
await FlutterWebln.keysend(keysendArgs: keysendArgs)
.then(allowInterop((result) {
print('[+] KeysendPaymentResponse: ${weblnDecode(result)}');
}));
} catch (error) {
print('[!] Error in keysend method is $error');
}
Response:
[+] KeysendPaymentResponse: {preimage: 3965373033306134316666323562396262333332393463653136383634636265, paymentHash: 20594ee7899bee252917bc44ec744309d0593adf0e79469bb067afb67b632ffc, route: {total_amt: 20, total_fees: 0}}
Sign Message
With “FlutterWebln.signMessage` it request that the user signs an arbitrary string message.
try {
await FlutterWebln.signMessage(message: 'Hello World!')
.then(allowInterop((result) {
print('[+] SignMessageResponse: ${weblnDecode(result)}');
}));
} catch (error) {
print('[!] Error in signMessage method is $error');
}
Signed messages can either be verified server-side using the LND RPC method, or by clients with FlutterWebln.verifyMessage
.
Verify Message
With FlutterWebln.verifyMessage
the users’s client verifies the signature against the raw message, and let’s the user know if it was valid.
try {
await FlutterWebln.verifyMessage(
signature: signatureController.text,
message: messageController.text,
).then(allowInterop((result) {
print('[+] VerifyMessageResponse: ${weblnDecode(result)}');
}));
} catch (error) {
print('[!] Error in verifyMessage method is $error');
}
Example Project
The above flutter_webln_integration project can be found here