Add support for LNURL (#68)

New methods:
- `lnurlauth`
- `lnurlpay`
- `lnurlwithdraw`

Note that `paylnaddress` now supports BIP353 and LNURL addresses. It will try with BIP353 first and fallback to LNURL.

src/commonMain/kotlin/fr/acinq/lightning/bin/Api.kt

@@ -5,26 +5,34 @@ import fr.acinq.bitcoin.ByteVector
 import fr.acinq.bitcoin.ByteVector32
 import fr.acinq.bitcoin.Script
 import fr.acinq.bitcoin.utils.Either
+import fr.acinq.bitcoin.utils.Try
 import fr.acinq.bitcoin.utils.toEither
 import fr.acinq.lightning.BuildVersions
 import fr.acinq.lightning.Lightning.randomBytes32
 import fr.acinq.lightning.NodeParams
 import fr.acinq.lightning.bin.db.SqlitePaymentsDb
 import fr.acinq.lightning.bin.db.WalletPaymentId
 import fr.acinq.lightning.bin.json.ApiType.*
-import fr.acinq.lightning.bin.json.ApiType.IncomingPayment
-import fr.acinq.lightning.bin.json.ApiType.OutgoingPayment
+import fr.acinq.lightning.bin.payments.AddressResolver
 import fr.acinq.lightning.bin.payments.Parser
 import fr.acinq.lightning.bin.payments.PayDnsAddress
+import fr.acinq.lightning.bin.payments.lnurl.LnurlHandler
+import fr.acinq.lightning.bin.payments.lnurl.helpers.LnurlParser
+import fr.acinq.lightning.bin.payments.lnurl.models.Lnurl
+import fr.acinq.lightning.bin.payments.lnurl.models.LnurlAuth
+import fr.acinq.lightning.bin.payments.lnurl.models.LnurlPay
+import fr.acinq.lightning.bin.payments.lnurl.models.LnurlWithdraw
 import fr.acinq.lightning.blockchain.fee.FeeratePerByte
 import fr.acinq.lightning.blockchain.fee.FeeratePerKw
 import fr.acinq.lightning.channel.ChannelCommand
 import fr.acinq.lightning.channel.states.ChannelStateWithCommitments
 import fr.acinq.lightning.channel.states.Closed
 import fr.acinq.lightning.channel.states.Closing
 import fr.acinq.lightning.channel.states.ClosingFeerates
+import fr.acinq.lightning.crypto.LocalKeyManager
 import fr.acinq.lightning.io.Peer
 import fr.acinq.lightning.io.WrappedChannelCommand
+import fr.acinq.lightning.logging.LoggerFactory
 import fr.acinq.lightning.payment.Bolt11Invoice
 import fr.acinq.lightning.utils.*
 import fr.acinq.lightning.wire.OfferTypes
@@ -51,12 +59,22 @@ import kotlinx.serialization.json.Json
 import okio.ByteString.Companion.encodeUtf8
 import kotlin.time.Duration.Companion.seconds
 
-class Api(private val nodeParams: NodeParams, private val peer: Peer, private val eventsFlow: SharedFlow<ApiEvent>, private val password: String, private val webhookUrl: Url?, private val webhookSecret: String) {
+class Api(
+    private val nodeParams: NodeParams,
+    private val peer: Peer,
+    private val eventsFlow: SharedFlow<ApiEvent>,
+    private val password: String,
+    private val webhookUrl: Url?,
+    private val webhookSecret: String,
+    private val loggerFactory: LoggerFactory,
+) {
 
     @OptIn(ExperimentalSerializationApi::class)
     fun Application.module() {
 
         val payDnsAddress = PayDnsAddress()
+        val lnurlHandler = LnurlHandler(loggerFactory, nodeParams.keyManager as LocalKeyManager)
+        val addressResolver = AddressResolver(payDnsAddress, lnurlHandler)
 
         val json = Json {
             prettyPrint = true
@@ -212,20 +230,31 @@ class Api(private val nodeParams: NodeParams, private val peer: Peer, private va
                 }
                 post("paylnaddress") {
                     val formParameters = call.receiveParameters()
-                    val overrideAmount = formParameters["amountSat"]?.let { it.toLongOrNull() ?: invalidType("amountSat", "integer") }?.sat?.toMilliSatoshi()
+                    val amount = formParameters.getLong("amountSat").sat.toMilliSatoshi()
                     val (username, domain) = formParameters.getEmailLikeAddress("address")
-                    val offer = payDnsAddress.resolveBip353Offer(username, domain)
-                    when (offer) {
-                        null -> call.respond("no valid offer found for that address")
-                        else -> {
-                            val amount = (overrideAmount ?: offer.amount) ?: missing("amountSat")
-                            val note = formParameters["message"]
-                            when (val event = peer.payOffer(amount, offer, payerKey = nodeParams.defaultOffer(peer.walletParams.trampolineNode.id).second, payerNote = note, fetchInvoiceTimeout = 30.seconds)) {
-                                is fr.acinq.lightning.io.PaymentSent -> call.respond(PaymentSent(event))
-                                is fr.acinq.lightning.io.PaymentNotSent -> call.respond(PaymentFailed(event))
-                                is fr.acinq.lightning.io.OfferNotPaid -> call.respond(PaymentFailed(event))
+                    val note = formParameters["message"]
+                    when (val res = addressResolver.resolveAddress(username, domain, amount, note)) {
+                        is Try.Success -> when (val either = res.result) {
+                            is Either.Left -> {
+                                // LNURL
+                                val lnurlInvoice = either.value
+                                when (val event = peer.payInvoice(amount, lnurlInvoice.invoice)) {
+                                    is fr.acinq.lightning.io.PaymentSent -> call.respond(PaymentSent(event))
+                                    is fr.acinq.lightning.io.PaymentNotSent -> call.respond(PaymentFailed(event))
+                                    is fr.acinq.lightning.io.OfferNotPaid -> error("unreachable code")
+                                }
+                            }
+                            is Either.Right -> {
+                                // OFFER
+                                val offer = either.value
+                                when (val event = peer.payOffer(amount, offer, payerKey = nodeParams.defaultOffer(peer.walletParams.trampolineNode.id).second, payerNote = note, fetchInvoiceTimeout = 30.seconds)) {
+                                    is fr.acinq.lightning.io.PaymentSent -> call.respond(PaymentSent(event))
+                                    is fr.acinq.lightning.io.PaymentNotSent -> call.respond(PaymentFailed(event))
+                                    is fr.acinq.lightning.io.OfferNotPaid -> call.respond(PaymentFailed(event))
+                                }
                             }
                         }
+                        is Try.Failure -> error("cannot resolve address: ${res.error.message}")
                     }
                 }
                 post("decodeinvoice") {
@@ -238,6 +267,71 @@ class Api(private val nodeParams: NodeParams, private val peer: Peer, private va
                     val offer = formParameters.getOffer("offer")
                     call.respond(offer)
                 }
+                post("lnurlpay") {
+                    val formParameters = call.receiveParameters()
+                    val overrideAmount = formParameters["amountSat"]?.let { it.toLongOrNull() ?: invalidType("amountSat", "integer") }?.sat?.toMilliSatoshi()
+                    val comment = formParameters["message"]
+                    val request = formParameters.getLnurl("lnurl")
+                    // early abort to avoid executing an invalid url
+                    when (request) {
+                        is LnurlAuth -> badRequest("this is an authentication lnurl")
+                        is Lnurl.Request -> if (request.tag == Lnurl.Tag.Withdraw) badRequest("this is a withdraw lnurl")
+                        else -> Unit
+                    }
+                    try {
+                        val lnurl = lnurlHandler.executeLnurl(request.initialUrl)
+                        when (lnurl) {
+                            is LnurlWithdraw -> badRequest("this is a withdraw lnurl")
+                            is LnurlPay.PaymentParameters -> {
+                                val amount = (overrideAmount ?: lnurl.minSendable)
+                                val invoice = lnurlHandler.getLnurlPayInvoice(lnurl, amount, comment)
+                                when (val event = peer.payInvoice(amount, invoice.invoice)) {
+                                    is fr.acinq.lightning.io.PaymentSent -> call.respond(PaymentSent(event))
+                                    is fr.acinq.lightning.io.PaymentNotSent -> call.respond(PaymentFailed(event))
+                                    is fr.acinq.lightning.io.OfferNotPaid -> error("unreachable code")
+                                }
+                            }
+                            else -> badRequest("invalid [${lnurl::class}] lnurl=${lnurl.initialUrl}")
+                        }
+                    } catch (e: Exception) {
+                        badRequest(e.message ?: e::class.toString())
+                    }
+                }
+                post("lnurlwithdraw") {
+                    val formParameters = call.receiveParameters()
+                    val request = formParameters.getLnurl("lnurl")
+                    // early abort to avoid executing an invalid url
+                    when (request) {
+                        is LnurlAuth -> badRequest("this is an authentication lnurl")
+                        is Lnurl.Request -> if (request.tag == Lnurl.Tag.Pay) badRequest("this is a payment lnurl")
+                        else -> Unit
+                    }
+                    try {
+                        val lnurl = lnurlHandler.executeLnurl(request.initialUrl)
+                        when (lnurl) {
+                            is LnurlPay -> badRequest("this is a payment lnurl")
+                            is LnurlWithdraw -> {
+                                val invoice = peer.createInvoice(randomBytes32(), lnurl.maxWithdrawable, Either.Left(lnurl.defaultDescription))
+                                lnurlHandler.sendWithdrawInvoice(lnurl, invoice)
+                                call.respond(LnurlWithdrawResponse(lnurl, invoice))
+                            }
+                            else -> badRequest("invalid [${lnurl::class}] lnurl=${lnurl.initialUrl}")
+                        }
+                    } catch (e: Exception) {
+                        badRequest(e.message ?: e::class.toString())
+                    }
+                }
+                post("lnurlauth") {
+                    val formParameters = call.receiveParameters()
+                    val request = formParameters.getLnurl("lnurl")
+                    if (request !is LnurlAuth) badRequest("this is a payment or withdraw lnurl")
+                    try {
+                        lnurlHandler.signAndSendAuthRequest(request)
+                        call.respond("authentication success")
+                    } catch (e: Exception) {
+                        badRequest("could not authenticate: ${e.message ?: e::class.toString()}")
+                    }
+                }
                 post("sendtoaddress") {
                     val res = kotlin.runCatching {
                         val formParameters = call.receiveParameters()
@@ -331,4 +425,7 @@ class Api(private val nodeParams: NodeParams, private val peer: Peer, private va
 
     private fun Parameters.getEmailLikeAddress(argName: String): Pair<String, String> = this[argName]?.let { Parser.parseEmailLikeAddress(it) } ?: invalidType(argName, "username@domain")
 
+    private fun Parameters.getLnurl(argName: String): Lnurl = this[argName]?.let { LnurlParser.extractLnurl(it) } ?: missing(argName)
+
+    private fun Parameters.getLnurlAuth(argName: String): LnurlAuth = this[argName]?.let { LnurlParser.extractLnurl(it) as LnurlAuth } ?: missing(argName)
 }

src/commonMain/kotlin/fr/acinq/lightning/bin/Main.kt

@@ -364,7 +364,7 @@ class Phoenixd : CliktCommand() {
                 reuseAddress = true
             },
             module = {
-                Api(nodeParams, peer, eventsFlow, httpPassword, webHookUrl, webHookSecret).run { module() }
+                Api(nodeParams, peer, eventsFlow, httpPassword, webHookUrl, webHookSecret, loggerFactory).run { module() }
             }
         )
         val serverJob = scope.launch {

src/commonMain/kotlin/fr/acinq/lightning/bin/json/JsonSerializers.kt

@@ -20,15 +20,20 @@ import fr.acinq.bitcoin.Satoshi
 import fr.acinq.bitcoin.TxId
 import fr.acinq.lightning.MilliSatoshi
 import fr.acinq.lightning.bin.db.PaymentMetadata
+import fr.acinq.lightning.bin.payments.lnurl.models.Lnurl
+import fr.acinq.lightning.bin.payments.lnurl.models.LnurlWithdraw
 import fr.acinq.lightning.channel.states.ChannelState
 import fr.acinq.lightning.channel.states.ChannelStateWithCommitments
 import fr.acinq.lightning.db.*
 import fr.acinq.lightning.json.JsonSerializers
+import fr.acinq.lightning.payment.Bolt11Invoice
 import fr.acinq.lightning.utils.UUID
+import io.ktor.http.*
 import kotlinx.datetime.Clock
 import kotlinx.serialization.SerialName
 import kotlinx.serialization.Serializable
 import kotlinx.serialization.UseSerializers
+import kotlin.math.ln
 
 sealed class ApiType {
 
@@ -133,4 +138,26 @@ sealed class ApiType {
             createdAt = payment.createdAt,
         )
     }
+
+    @Serializable
+    @SerialName("lnurl_request")
+    data class LnurlRequest(val url: String, val tag: String?) {
+        constructor(lnurl: Lnurl) : this(
+            url = lnurl.initialUrl.toString(),
+            tag = if (lnurl is Lnurl.Request) lnurl.tag?.label else null,
+        )
+    }
+
+    @Serializable
+    @SerialName("lnurl_withdraw")
+    data class LnurlWithdrawResponse(val url: String, val minWithdrawable: MilliSatoshi, val maxWithdrawable: MilliSatoshi, val description: String, val k1: String, val invoice: String) {
+        constructor(lnurl: LnurlWithdraw, invoice: Bolt11Invoice) : this(
+            url = lnurl.initialUrl.toString(),
+            minWithdrawable = lnurl.minWithdrawable,
+            maxWithdrawable = lnurl.maxWithdrawable,
+            description = lnurl.defaultDescription,
+            k1 = lnurl.k1,
+            invoice = invoice.write()
+        )
+    }
 }

src/commonMain/kotlin/fr/acinq/lightning/bin/payments/AddressResolver.kt

@@ -0,0 +1,37 @@
+package fr.acinq.lightning.bin.payments
+
+import fr.acinq.bitcoin.utils.Either
+import fr.acinq.bitcoin.utils.Try
+import fr.acinq.lightning.MilliSatoshi
+import fr.acinq.lightning.bin.payments.lnurl.LnurlHandler
+import fr.acinq.lightning.bin.payments.lnurl.models.LnurlPay
+import fr.acinq.lightning.wire.OfferTypes
+import io.ktor.http.*
+
+class AddressResolver(val dnsAddress: PayDnsAddress, val lnurlHandler: LnurlHandler) {
+
+    suspend fun resolveLnUrl(username: String, domain: String, amount: MilliSatoshi, note: String?): Try<LnurlPay.InvoiceToPay> {
+        val url = Url("https://$domain/.well-known/lnurlp/$username")
+        return try {
+            val lnurl = lnurlHandler.executeLnurl(url)
+            val paymentParameters = lnurl as LnurlPay.PaymentParameters
+            if (amount < paymentParameters.minSendable) throw IllegalArgumentException("amount too small (min=${paymentParameters.minSendable})")
+            if (amount > paymentParameters.maxSendable) throw IllegalArgumentException("amount too big (max=${paymentParameters.maxSendable})")
+            val invoice = lnurlHandler.getLnurlPayInvoice(lnurl, amount, note)
+            Try.Success(invoice)
+        } catch (e: Exception) {
+            Try.Failure(e)
+        }
+    }
+
+    suspend fun resolveAddress(username: String, domain: String, amount: MilliSatoshi, note: String?): Try<Either<LnurlPay.InvoiceToPay, OfferTypes.Offer>> {
+        return when (val offer = dnsAddress.resolveBip353Offer(username, domain)) {
+            null -> when (val lnurl = resolveLnUrl(username, domain, amount, note)) {
+                is Try.Success -> Try.Success(Either.Left(lnurl.result))
+                is Try.Failure -> Try.Failure(lnurl.error)
+            }
+            else -> Try.Success(Either.Right(offer))
+        }
+    }
+
+}