Introduce subscription support in the Wallet crate.

The main goal is to add a subscription to CDK Mint updates into the wallet.
This feature will be particularly useful for improving the code whenever loops
hit the mint server to check status changes.

The goal is to add an easy-to-use interface that will hide the fact that we're
connecting to WebSocket and subscribing to events. This will also hide the fact
that the CDK-mint server may not support WebSocket updates.

To be fully backward compatible, the HttpClientMethods traits have a new
method, `subscribe,` which will return an object that implements
`ActiveSubscription.`

In the primary implementation, there is a `SubscriptionClient` that will
attempt to connect through WebSocket and will fall to the HTTP-status pull and
sleep approach (the current approach), but upper stream code will receive
updates as if they come from a stream of updates through WebSocket. This
`SubscriptionClient` struct will also manage reconnections to WebSockets (with
automatic resubscriptions) and all the low-level stuff, providing an
easy-to-use interface and leaving the upper-level code with a nice interface
that is hard to misuse. When `ActiveSubscription` is dropped, it will
automatically unsubscribe.

crates/cdk-axum/src/ws/error.rs

@@ -1,3 +1,4 @@
+use cdk::nuts::nut17::ws::WsErrorBody;
 use serde::{Deserialize, Serialize};
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
@@ -17,3 +18,17 @@ pub enum WsError {
     /// Custom error
     ServerError(i32, String),
 }
+
+impl From<WsError> for WsErrorBody {
+    fn from(val: WsError) -> Self {
+        let (id, message) = match val {
+            WsError::ParseError => (-32700, "Parse error".to_string()),
+            WsError::InvalidRequest => (-32600, "Invalid Request".to_string()),
+            WsError::MethodNotFound => (-32601, "Method not found".to_string()),
+            WsError::InvalidParams => (-32602, "Invalid params".to_string()),
+            WsError::InternalError => (-32603, "Internal error".to_string()),
+            WsError::ServerError(code, message) => (code, message),
+        };
+        WsErrorBody { code: id, message }
+    }
+}

crates/cdk-axum/src/ws/mod.rs

@@ -1,50 +1,32 @@
 use std::collections::HashMap;
 
 use axum::extract::ws::{Message, WebSocket};
+use cdk::nuts::nut17::ws::{
+    NotificationInner, WsErrorBody, WsMessageOrResponse, WsMethodRequest, WsRequest,
+};
 use cdk::nuts::nut17::{NotificationPayload, SubId};
 use futures::StreamExt;
-use handler::{WsHandle, WsNotification};
-use serde::{Deserialize, Serialize};
-use subscribe::Notification;
 use tokio::sync::mpsc;
 
 use crate::MintState;
 
 mod error;
-mod handler;
 mod subscribe;
 mod unsubscribe;
 
-/// JSON RPC version
-pub const JSON_RPC_VERSION: &str = "2.0";
-
-#[derive(Debug, Clone, Serialize, Deserialize)]
-pub struct WsRequest {
-    jsonrpc: String,
-    #[serde(flatten)]
-    method: WsMethod,
-    id: usize,
-}
+async fn process(
+    context: &mut WsContext,
+    body: WsRequest,
+) -> Result<serde_json::Value, serde_json::Error> {
+    let response = match body.method {
+        WsMethodRequest::Subscribe(sub) => subscribe::handle(context, sub).await,
+        WsMethodRequest::Unsubscribe(unsub) => unsubscribe::handle(context, unsub).await,
+    }
+    .map_err(WsErrorBody::from);
 
-#[derive(Debug, Clone, Serialize, Deserialize)]
-#[serde(rename_all = "snake_case", tag = "method", content = "params")]
-pub enum WsMethod {
-    Subscribe(subscribe::Method),
-    Unsubscribe(unsubscribe::Method),
-}
+    let response: WsMessageOrResponse = (body.id, response).into();
 
-impl WsMethod {
-    pub async fn process(
-        self,
-        req_id: usize,
-        context: &mut WsContext,
-    ) -> Result<serde_json::Value, serde_json::Error> {
-        match self {
-            WsMethod::Subscribe(sub) => sub.process(req_id, context),
-            WsMethod::Unsubscribe(unsub) => unsub.process(req_id, context),
-        }
-        .await
-    }
+    serde_json::to_value(response)
 }
 
 pub use error::WsError;
@@ -78,7 +60,10 @@ pub async fn main_websocket(mut socket: WebSocket, state: MintState) {
                     // unsubscribed from the subscription manager, just ignore it.
                     continue;
                 }
-                let notification: WsNotification<Notification> = (sub_id, payload).into();
+                let notification: WsMessageOrResponse= NotificationInner {
+                    sub_id,
+                    payload,
+                }.into();
                 let message = match serde_json::to_string(&notification) {
                     Ok(message) => message,
                     Err(err) => {
@@ -101,7 +86,7 @@ pub async fn main_websocket(mut socket: WebSocket, state: MintState) {
                     }
                 };
 
-                match request.method.process(request.id, &mut context).await {
+                match process(&mut context, request).await {
                     Ok(result) => {
                         if let Err(err) = socket
                             .send(Message::Text(result.to_string()))

crates/cdk-axum/src/ws/subscribe.rs

@@ -1,72 +1,33 @@
-use cdk::nuts::nut17::{NotificationPayload, Params};
-use cdk::pub_sub::SubId;
-
-use super::handler::{WsHandle, WsNotification};
-use super::{WsContext, WsError, JSON_RPC_VERSION};
-
-#[derive(Debug, Clone, serde::Serialize, serde::Deserialize)]
-pub struct Method(Params);
-
-#[derive(Debug, Clone, serde::Serialize)]
-/// The response to a subscription request
-pub struct Response {
-    /// Status
-    status: String,
-    /// Subscription ID
-    #[serde(rename = "subId")]
-    sub_id: SubId,
-}
-
-#[derive(Debug, Clone, serde::Serialize)]
-/// The notification
-///
-/// This is the notification that is sent to the client when an event matches a
-/// subscription
-pub struct Notification {
-    /// The subscription ID
-    #[serde(rename = "subId")]
-    pub sub_id: SubId,
-
-    /// The notification payload
-    pub payload: NotificationPayload,
-}
-
-impl From<(SubId, NotificationPayload)> for WsNotification<Notification> {
-    fn from((sub_id, payload): (SubId, NotificationPayload)) -> Self {
-        WsNotification {
-            jsonrpc: JSON_RPC_VERSION.to_owned(),
-            method: "subscribe".to_string(),
-            params: Notification { sub_id, payload },
-        }
+use cdk::nuts::nut17::ws::{WsResponseResult, WsSubscribeResponse};
+use cdk::nuts::nut17::Params;
+
+use super::{WsContext, WsError};
+
+/// The `handle` method is called when a client sends a subscription request
+pub(crate) async fn handle(
+    context: &mut WsContext,
+    params: Params,
+) -> Result<WsResponseResult, WsError> {
+    let sub_id = params.id.clone();
+    if context.subscriptions.contains_key(&sub_id) {
+        // Subscription ID already exits. Returns an error instead of
+        // replacing the other subscription or avoiding it.
+        return Err(WsError::InvalidParams);
     }
-}
-
-#[async_trait::async_trait]
-impl WsHandle for Method {
-    type Response = Response;
-
-    /// The `handle` method is called when a client sends a subscription request
-    async fn handle(self, context: &mut WsContext) -> Result<Self::Response, WsError> {
-        let sub_id = self.0.id.clone();
-        if context.subscriptions.contains_key(&sub_id) {
-            // Subscription ID already exits. Returns an error instead of
-            // replacing the other subscription or avoiding it.
-            return Err(WsError::InvalidParams);
-        }
 
-        let mut subscription = context.state.mint.pubsub_manager.subscribe(self.0).await;
-        let publisher = context.publisher.clone();
-        context.subscriptions.insert(
-            sub_id.clone(),
-            tokio::spawn(async move {
-                while let Some(response) = subscription.recv().await {
-                    let _ = publisher.send(response).await;
-                }
-            }),
-        );
-        Ok(Response {
-            status: "OK".to_string(),
-            sub_id,
-        })
+    let mut subscription = context.state.mint.pubsub_manager.subscribe(params).await;
+    let publisher = context.publisher.clone();
+    context.subscriptions.insert(
+        sub_id.clone(),
+        tokio::spawn(async move {
+            while let Some(response) = subscription.recv().await {
+                let _ = publisher.send(response).await;
+            }
+        }),
+    );
+    Ok(WsSubscribeResponse {
+        status: "OK".to_string(),
+        sub_id,
     }
+    .into())
 }

crates/cdk-axum/src/ws/unsubscribe.rs

@@ -1,32 +1,18 @@
-use cdk::pub_sub::SubId;
+use cdk::nuts::nut17::ws::{WsResponseResult, WsUnsubscribeRequest, WsUnsubscribeResponse};
 
-use super::handler::WsHandle;
 use super::{WsContext, WsError};
 
-#[derive(Debug, Clone, serde::Serialize, serde::Deserialize)]
-pub struct Method {
-    #[serde(rename = "subId")]
-    pub sub_id: SubId,
-}
-
-#[derive(Debug, Clone, serde::Serialize)]
-pub struct Response {
-    status: String,
-    sub_id: SubId,
-}
-
-#[async_trait::async_trait]
-impl WsHandle for Method {
-    type Response = Response;
-
-    async fn handle(self, context: &mut WsContext) -> Result<Self::Response, WsError> {
-        if context.subscriptions.remove(&self.sub_id).is_some() {
-            Ok(Response {
-                status: "OK".to_string(),
-                sub_id: self.sub_id,
-            })
-        } else {
-            Err(WsError::InvalidParams)
+pub(crate) async fn handle(
+    context: &mut WsContext,
+    req: WsUnsubscribeRequest,
+) -> Result<WsResponseResult, WsError> {
+    if context.subscriptions.remove(&req.sub_id).is_some() {
+        Ok(WsUnsubscribeResponse {
+            status: "OK".to_string(),
+            sub_id: req.sub_id,
         }
+        .into())
+    } else {
+        Err(WsError::InvalidParams)
     }
 }

crates/cdk-cli/src/sub_commands/mint.rs

@@ -1,18 +1,16 @@
 use std::str::FromStr;
 use std::sync::Arc;
-use std::time::Duration;
 
 use anyhow::Result;
 use cdk::amount::SplitTarget;
 use cdk::cdk_database::{Error, WalletDatabase};
 use cdk::mint_url::MintUrl;
-use cdk::nuts::{CurrencyUnit, MintQuoteState};
+use cdk::nuts::{CurrencyUnit, MintQuoteState, NotificationPayload};
 use cdk::wallet::multi_mint_wallet::WalletKey;
-use cdk::wallet::{MultiMintWallet, Wallet};
+use cdk::wallet::{MultiMintWallet, Wallet, WalletSubscription};
 use cdk::Amount;
 use clap::Args;
 use serde::{Deserialize, Serialize};
-use tokio::time::sleep;
 
 #[derive(Args, Serialize, Deserialize)]
 pub struct MintSubCommand {
@@ -59,14 +57,18 @@ pub async fn mint(
 
     println!("Please pay: {}", quote.request);
 
-    loop {
-        let status = wallet.mint_quote_state(&quote.id).await?;
+    let mut subscription = wallet
+        .subscribe(WalletSubscription::Bolt11MintQuoteState(vec![quote
+            .id
+            .clone()]))
+        .await;
 
-        if status.state == MintQuoteState::Paid {
-            break;
+    while let Some(msg) = subscription.recv().await {
+        if let NotificationPayload::MintQuoteBolt11Response(response) = msg {
+            if response.state == MintQuoteState::Paid {
+                break;
+            }
         }
-
-        sleep(Duration::from_secs(2)).await;
     }
 
     let receive_amount = wallet.mint(&quote.id, SplitTarget::default(), None).await?;

crates/cdk-integration-tests/Cargo.toml

@@ -11,7 +11,7 @@ rust-version = "1.63.0"
 
 
 [features]
-
+http_subscription = ["cdk/http_subscription"]
 
 [dependencies]
 axum = "0.6.20"