feat: implement a basic backend (#1)

Reviewed-on: https://git.reya.su/reya/signed/pulls/1

crates/signed_state/src/backend.rs

@@ -0,0 +1,504 @@
+use std::time::Duration;
+
+use anyhow::{Error, anyhow};
+use gpui::{App, AppContext, Context, Entity, EventEmitter, Global, Task};
+use nostr_connect::prelude::*;
+use nostr_sdk::prelude::*;
+use signed_core::filters;
+use signed_nostr::{NostrBackend, SignedAuthUrlHandler, UniversalSigner, Update};
+
+/// Keyring entry holding the user credential (`nsec1...` or `bunker://...`).
+pub const USER_KEYRING: &str = "su.reya.signed#user";
+/// Keyring entry holding the locally generated key for NIP-46 sessions.
+pub const MASTER_KEYRING: &str = "su.reya.signed#master";
+/// Timeout for NIP-46 signer responses.
+pub const NOSTR_CONNECT_TIMEOUT: u64 = 60;
+
+/// Relays connected at startup, before any user-specific relay config is known.
+pub const BOOTSTRAP_RELAYS: [&str; 4] = [
+    "wss://relay.primal.net",
+    "wss://relay.ditto.pub",
+    "wss://index.ngit.dev",
+    "wss://profiles.nostr1.com",
+];
+
+/// Relays used for indexing user's relay list (NIP-65).
+pub const INDEXER_RELAYS: [&str; 3] = [
+    "wss://indexer.coracle.social",
+    "wss://purplepag.es",
+    "wss://user.kindpag.es",
+];
+
+#[derive(Debug, Clone)]
+pub enum BackendEvent {
+    /// User has no signer configured.
+    SignerRequired,
+    /// The signer has changed (login/logout/account switch).
+    SignerChanged,
+    /// Relay bootstrap finished.
+    Connected,
+    /// A new event was received from a relay and stored in the database.
+    NostrUpdate(Update),
+    /// An event built locally was signed, broadcast and stored.
+    Published(Box<Event>),
+    /// An error occurred.
+    Error(String),
+}
+
+impl BackendEvent {
+    pub fn error<T>(error: T) -> Self
+    where
+        T: Into<String>,
+    {
+        Self::Error(error.into())
+    }
+}
+
+/// Global backend entity: owns the nostr client, the signer and the
+/// notification pump. Stores subscribe to [`BackendEvent`] and re-query the
+/// local database when relevant updates arrive.
+pub struct Backend {
+    inner: NostrBackend,
+    current_user: Option<PublicKey>,
+    tasks: Vec<Task<Result<(), Error>>>,
+}
+
+struct GlobalBackend(Entity<Backend>);
+
+impl Global for GlobalBackend {}
+
+impl EventEmitter<BackendEvent> for Backend {}
+
+impl Backend {
+    /// Retrieve the global backend.
+    pub fn global(cx: &App) -> Entity<Self> {
+        cx.global::<GlobalBackend>().0.clone()
+    }
+
+    pub(crate) fn set_global(entity: Entity<Self>, cx: &mut App) {
+        cx.set_global(GlobalBackend(entity));
+    }
+
+    pub(crate) fn new(inner: NostrBackend, cx: &mut Context<Self>) -> Self {
+        let client = inner.client();
+
+        let pump = cx.spawn(async move |this, cx| {
+            let mut notifications = client.notifications();
+
+            while let Some(notification) = notifications.next().await {
+                let ClientNotification::Event { event, .. } = notification else {
+                    continue;
+                };
+
+                let update = Update::from_event(&event);
+
+                if this
+                    .update(cx, |_, cx| cx.emit(BackendEvent::NostrUpdate(update)))
+                    .is_err()
+                {
+                    break;
+                }
+            }
+
+            Ok(())
+        });
+
+        let mut this = Self {
+            inner,
+            current_user: None,
+            tasks: vec![pump],
+        };
+
+        this.bootstrap(cx);
+        this
+    }
+
+    /// Bootstrap the client: connect to the default relays (indexers as
+    /// discovery-only) and restore the saved session, if any.
+    fn bootstrap(&mut self, cx: &mut Context<Self>) {
+        let backend = self.inner.clone();
+
+        let task = cx.background_spawn(async move {
+            for url in BOOTSTRAP_RELAYS {
+                backend.add_relay(url).await?;
+            }
+            for url in INDEXER_RELAYS {
+                backend.add_discovery_relay(url).await?;
+            }
+            backend.connect().await;
+            Ok::<(), Error>(())
+        });
+
+        self.tasks.push(cx.spawn(async move |this, cx| {
+            match task.await {
+                Ok(()) => {
+                    this.update(cx, |_this, cx| cx.emit(BackendEvent::Connected))?;
+                }
+                Err(e) => {
+                    this.update(cx, |_this, cx| cx.emit(BackendEvent::error(e.to_string())))?;
+                }
+            }
+            Ok(())
+        }));
+
+        self.restore_session(cx);
+    }
+
+    /// Restore the saved session from the keyring. Emits
+    /// [`BackendEvent::SignerRequired`] if no credential is stored.
+    pub fn restore_session(&mut self, cx: &mut Context<Self>) {
+        if cfg!(target_arch = "wasm32") {
+            cx.emit(BackendEvent::SignerRequired);
+            return;
+        }
+
+        let user = cx.read_credentials(USER_KEYRING);
+        let master = self.master_key(cx);
+
+        self.tasks.push(cx.spawn(async move |this, cx| {
+            let content = match user.await {
+                Ok(Some((_username, secret))) => String::from_utf8(secret)?,
+                _ => {
+                    this.update(cx, |_, cx| cx.emit(BackendEvent::SignerRequired))?;
+                    return Ok(());
+                }
+            };
+
+            let result = async {
+                if content.starts_with("nsec1") {
+                    let keys = Keys::new(SecretKey::parse(&content)?);
+                    this.update(cx, |this, cx| this.set_signer(keys, cx))?;
+                } else if content.starts_with("bunker://") {
+                    let uri = NostrConnectUri::parse(&content)?;
+                    let mut signer = NostrConnect::new(
+                        uri,
+                        master.await,
+                        Duration::from_secs(NOSTR_CONNECT_TIMEOUT),
+                        None,
+                    )?;
+                    signer.auth_url_handler(SignedAuthUrlHandler);
+                    this.update(cx, |this, cx| this.set_signer(signer, cx))?;
+                } else {
+                    this.update(cx, |_, cx| cx.emit(BackendEvent::SignerRequired))?;
+                }
+
+                Ok::<_, Error>(())
+            }
+            .await;
+
+            if let Err(e) = result {
+                this.update(cx, |_, cx| {
+                    cx.emit(BackendEvent::error(e.to_string()));
+                    cx.emit(BackendEvent::SignerRequired);
+                })?;
+            }
+
+            Ok(())
+        }));
+    }
+
+    /// Login with an `nsec1...` secret key. The credential is verified by
+    /// the signer flow and persisted in the keyring.
+    pub fn login_with_nsec(&mut self, nsec: &str, cx: &mut Context<Self>) {
+        let nsec = nsec.trim().to_owned();
+
+        let keys = match SecretKey::parse(&nsec) {
+            Ok(secret) => Keys::new(secret),
+            Err(e) => {
+                cx.emit(BackendEvent::error(e.to_string()));
+                return;
+            }
+        };
+
+        let write =
+            cx.write_credentials(USER_KEYRING, &keys.public_key().to_hex(), nsec.as_bytes());
+
+        self.tasks.push(cx.spawn(async move |this, cx| {
+            if let Err(e) = write.await {
+                this.update(cx, |_, cx| cx.emit(BackendEvent::error(e.to_string())))?;
+                return Ok(());
+            }
+
+            this.update(cx, |this, cx| this.set_signer(keys, cx))?;
+            Ok(())
+        }));
+    }
+
+    /// Login with a `bunker://...` URI (NIP-46). The auth URL, if any, is
+    /// opened in the default browser. The credential is persisted in the
+    /// keyring after the signer proves reachable.
+    pub fn login_with_bunker(&mut self, uri: &str, cx: &mut Context<Self>) {
+        let uri_string = uri.trim().to_owned();
+
+        let connect_uri = match NostrConnectUri::parse(&uri_string) {
+            Ok(uri) => uri,
+            Err(e) => {
+                cx.emit(BackendEvent::error(e.to_string()));
+                return;
+            }
+        };
+
+        let master = self.master_key(cx);
+        let write = cx.write_credentials(USER_KEYRING, "bunker", uri_string.as_bytes());
+
+        self.tasks.push(cx.spawn(async move |this, cx| {
+            let result = async {
+                let mut signer = NostrConnect::new(
+                    connect_uri,
+                    master.await,
+                    Duration::from_secs(NOSTR_CONNECT_TIMEOUT),
+                    None,
+                )?;
+                signer.auth_url_handler(SignedAuthUrlHandler);
+
+                // Verify the signer before persisting the credential.
+                signer.get_public_key_async().await?;
+                write.await?;
+
+                this.update(cx, |this, cx| this.set_signer(signer, cx))?;
+
+                Ok::<_, Error>(())
+            }
+            .await;
+
+            if let Err(e) = result {
+                this.update(cx, |_, cx| cx.emit(BackendEvent::error(e.to_string())))?;
+            }
+
+            Ok(())
+        }));
+    }
+
+    /// Remove the saved credential and reset to an anonymous session.
+    pub fn logout(&mut self, cx: &mut Context<Self>) {
+        let delete = cx.delete_credentials(USER_KEYRING);
+
+        self.tasks.push(cx.spawn(async move |this, cx| {
+            delete.await.ok();
+
+            this.update(cx, |this, cx| {
+                this.inner.signer().swap_inner(Keys::generate());
+                this.current_user = None;
+                cx.emit(BackendEvent::SignerChanged);
+                cx.emit(BackendEvent::SignerRequired);
+                cx.notify();
+            })?;
+
+            Ok(())
+        }));
+    }
+
+    /// Get (or generate and persist) the key used for NIP-46 sessions.
+    fn master_key(&self, cx: &App) -> Task<Keys> {
+        let task = cx.read_credentials(MASTER_KEYRING);
+
+        cx.spawn(async move |cx| {
+            let (keys, new_key) = match task.await {
+                Ok(Some((_user, secret))) => match SecretKey::from_slice(&secret) {
+                    Ok(secret_key) => (Keys::new(secret_key), false),
+                    _ => (Keys::generate(), true),
+                },
+                _ => (Keys::generate(), true),
+            };
+
+            if new_key {
+                let username = keys.public_key().to_hex();
+                let password = keys.secret_key().to_secret_bytes();
+
+                cx.update(|cx| {
+                    let task = cx.write_credentials(MASTER_KEYRING, &username, &password);
+                    cx.background_spawn(async move { task.await.ok() }).detach();
+                });
+            }
+
+            keys
+        })
+    }
+
+    /// Fetch the user's grasp list (kind `10317`) and add the listed grasp
+    /// servers as relays.
+    fn bootstrap_user(&mut self, public_key: PublicKey, cx: &mut Context<Self>) {
+        let backend = self.inner.clone();
+
+        self.tasks.push(cx.spawn(async move |this, cx| {
+            let result = async {
+                let events = backend
+                    .client()
+                    .fetch_events(filters::grasp_list(public_key))
+                    .await?;
+
+                let urls: Vec<String> = events
+                    .into_iter()
+                    .max_by_key(|e| e.created_at)
+                    .map(|e| {
+                        e.tags
+                            .iter()
+                            .filter(|t| t.kind() == "g")
+                            .filter_map(|t| t.content().map(str::to_owned))
+                            .collect()
+                    })
+                    .unwrap_or_default();
+
+                for url in urls {
+                    backend.add_relay(&url).await.ok();
+                }
+                backend.connect().await;
+
+                Ok::<_, Error>(())
+            }
+            .await;
+
+            if let Err(e) = result {
+                this.update(cx, |_, cx| cx.emit(BackendEvent::error(e.to_string())))?;
+            }
+
+            Ok(())
+        }));
+    }
+
+    /// Get the nostr client.
+    pub fn client(&self) -> Client {
+        self.inner.client()
+    }
+
+    /// Get the current signer.
+    pub fn signer(&self) -> UniversalSigner {
+        self.inner.signer()
+    }
+
+    /// Get the current user's public key.
+    pub fn current_user(&self) -> Option<PublicKey> {
+        self.current_user
+    }
+
+    /// Update the signer (any type implementing the async signer traits,
+    /// e.g. `Keys`, `NostrConnect`, a browser extension proxy).
+    pub fn set_signer<T>(&mut self, new_signer: T, cx: &mut Context<Self>)
+    where
+        T: AsyncGetPublicKey + AsyncSignEvent + AsyncNip44 + 'static,
+        <T as AsyncGetPublicKey>::Error: std::error::Error + Send + Sync + 'static,
+        <T as AsyncSignEvent>::Error: std::error::Error + Send + Sync + 'static,
+        <T as AsyncNip44>::Error: std::error::Error + Send + Sync + 'static,
+    {
+        let task = cx.spawn(async move |this, cx| {
+            match new_signer.get_public_key_async().await {
+                Ok(public_key) => {
+                    this.update(cx, |this, cx| {
+                        this.inner.signer().swap_inner(new_signer);
+                        this.current_user = Some(public_key);
+                        this.bootstrap_user(public_key, cx);
+                        cx.emit(BackendEvent::SignerChanged);
+                        cx.notify();
+                    })?;
+                }
+                Err(e) => {
+                    this.update(cx, |_this, cx| {
+                        cx.emit(BackendEvent::error(e.to_string()));
+                    })?;
+                }
+            }
+
+            Ok(())
+        });
+        self.tasks.push(task);
+    }
+
+    /// Add relays and connect to them.
+    pub fn add_relays(&mut self, urls: Vec<String>, cx: &mut Context<Self>) {
+        let backend = self.inner.clone();
+
+        let task = cx.background_spawn(async move {
+            for url in urls {
+                backend.add_relay(&url).await?;
+            }
+            backend.connect().await;
+            Ok::<(), Error>(())
+        });
+
+        self.tasks.push(cx.spawn(async move |this, cx| {
+            match task.await {
+                Ok(()) => {
+                    this.update(cx, |_this, cx| cx.emit(BackendEvent::Connected))?;
+                }
+                Err(e) => {
+                    this.update(cx, |_this, cx| cx.emit(BackendEvent::error(e.to_string())))?;
+                }
+            }
+            Ok(())
+        }));
+    }
+
+    /// Add relays used only for discovery (e.g. NIP-65 indexers) and
+    /// connect to them. No subscriptions or writes are routed through them.
+    pub fn add_discovery_relays(&mut self, urls: Vec<String>, cx: &mut Context<Self>) {
+        let backend = self.inner.clone();
+
+        let task = cx.background_spawn(async move {
+            for url in urls {
+                backend.add_discovery_relay(&url).await?;
+            }
+            backend.connect().await;
+            Ok::<(), Error>(())
+        });
+
+        self.tasks.push(cx.spawn(async move |this, cx| {
+            if let Err(e) = task.await {
+                this.update(cx, |_this, cx| cx.emit(BackendEvent::error(e.to_string())))?;
+            }
+            Ok(())
+        }));
+    }
+
+    /// Start a persistent subscription. Matching events are stored in the
+    /// database automatically and surface as [`BackendEvent::NostrUpdate`].
+    pub fn subscribe(&mut self, filter: Filter, cx: &mut Context<Self>) {
+        let backend = self.inner.clone();
+
+        let task = cx.background_spawn(async move { backend.subscribe(filter).await.map(|_| ()) });
+
+        self.tasks.push(cx.spawn(async move |this, cx| {
+            if let Err(e) = task.await {
+                this.update(cx, |_this, cx| cx.emit(BackendEvent::error(e.to_string())))?;
+            }
+            Ok(())
+        }));
+    }
+
+    /// Sign, broadcast and locally store an event. Emits
+    /// [`BackendEvent::Published`] on success so stores can refresh.
+    ///
+    /// The returned receiver yields the outcome of this specific action,
+    /// so callers can show inline progress/errors instead of relying on
+    /// the global [`BackendEvent::Error`].
+    pub fn send(
+        &mut self,
+        builder: EventBuilder,
+        cx: &mut Context<Self>,
+    ) -> flume::Receiver<Result<Event, Error>> {
+        let (tx, rx) = flume::bounded(1);
+
+        let backend = self.inner.clone();
+        let task = cx.background_spawn(async move { backend.send(builder).await });
+
+        self.tasks.push(cx.spawn(async move |this, cx| {
+            let result = task.await;
+
+            match &result {
+                Ok(event) => {
+                    this.update(cx, |_this, cx| {
+                        cx.emit(BackendEvent::Published(Box::new(event.clone())));
+                    })?;
+                }
+                Err(e) => {
+                    this.update(cx, |_this, cx| cx.emit(BackendEvent::error(e.to_string())))?;
+                }
+            }
+
+            tx.send_async(result)
+                .await
+                .map_err(|_| anyhow!("action result receiver dropped"))
+        }));
+
+        rx
+    }
+}