flutter_webln

Description:

flutter webln

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");
}
}
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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()
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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');
}
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Response
Result: [+] GetInfoResponse: {node: {alias: 🐝 getalby.com}}
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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');
}
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Response
[+] RequestInvoiceResponse: {paymentRequest: lnbc1u1p3jdmdzpp5aehslp0ts0wszr62lwl82qwzcgl6jtqudvg000ez75jx307vpcdqdqjfpjkcmr0yptk7unvvscqzpgxqyz5vqsp5npje0n0mct745acshv8dl5pz5kyznz2z6du45fwpyxgwvxvepdts9qyyssqdynz62hf8xh76pn4qfpswzcz4ezt6k9kj9mccf6lzwzkutm04rwjhzynctgphyk6xc0g2ftn7unjxvmszutzr07xq52h5qeja5mk3sqpqwwx7y, rHash: ee6f0f85eb83dd010f4afbbe7501c2c23fa92c1c6b10f7bf22f52468bfcc0e1a}
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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');
}
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Response
[+] SendPaymentResponse: {preimage: 6662313533626135643134626265623164343134363734626261336263306630, paymentHash: ee6f0f85eb83dd010f4afbbe7501c2c23fa92c1c6b10f7bf22f52468bfcc0e1a, route: {total_amt: 100, total_fees: 0}}
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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');
}
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Response:
[+] KeysendPaymentResponse: {preimage: 3965373033306134316666323562396262333332393463653136383634636265, paymentHash: 20594ee7899bee252917bc44ec744309d0593adf0e79469bb067afb67b632ffc, route: {total_amt: 20, total_fees: 0}}
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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');
}
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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');
}
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Example Project #

The above flutter_webln_integration project can be found here
Reference #

WebLN Guide
WebLN Dev
TLV record registry