feat: implement a basic backend (#1)

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

crates/signed_state/src/profile.rs

@@ -0,0 +1,225 @@
+use std::collections::{HashMap, HashSet};
+use std::time::Duration;
+
+use anyhow::Error;
+use gpui::{App, Context, Entity, Global, SharedString, Subscription, Task};
+use nostr_sdk::prelude::*;
+
+use crate::backend::{Backend, BackendEvent};
+
+/// A user profile (kind `0` metadata), as plain data for the UI.
+#[derive(Debug, Clone)]
+pub struct Profile {
+    public_key: PublicKey,
+    metadata: Metadata,
+}
+
+impl Profile {
+    pub fn new(public_key: PublicKey, metadata: Metadata) -> Self {
+        Self {
+            public_key,
+            metadata,
+        }
+    }
+
+    pub fn public_key(&self) -> PublicKey {
+        self.public_key
+    }
+
+    pub fn metadata(&self) -> &Metadata {
+        &self.metadata
+    }
+
+    /// Display name, falling back to `name`, then a shortened npub.
+    pub fn name(&self) -> SharedString {
+        if let Some(display_name) = self.metadata.display_name.as_ref()
+            && !display_name.is_empty()
+        {
+            return SharedString::from(display_name.trim().to_owned());
+        }
+
+        if let Some(name) = self.metadata.name.as_ref()
+            && !name.is_empty()
+        {
+            return SharedString::from(name.trim().to_owned());
+        }
+
+        SharedString::from(shorten_pubkey(self.public_key, 4))
+    }
+
+    /// Avatar URL, if set.
+    pub fn picture(&self) -> Option<SharedString> {
+        self.metadata
+            .picture
+            .as_ref()
+            .filter(|p| !p.is_empty())
+            .map(|p| SharedString::from(p.clone()))
+    }
+}
+
+/// Shorten a [`PublicKey`] to `npub1abc...wxyz` form.
+pub fn shorten_pubkey(public_key: PublicKey, len: usize) -> String {
+    let npub = public_key.to_bech32().unwrap();
+    format!("{}...{}", &npub[..(len + 5)], &npub[npub.len() - len..])
+}
+
+/// Global profile cache. Profiles are fetched in batches and kept as plain
+/// data; the whole store notifies on change.
+pub struct ProfileStore {
+    profiles: HashMap<PublicKey, Profile>,
+    /// Public keys we've already requested this session.
+    seen: HashSet<PublicKey>,
+    /// Public keys queued for the next batched fetch.
+    queued: HashSet<PublicKey>,
+    fetching: bool,
+    tasks: Vec<Task<Result<(), Error>>>,
+    _subscription: Subscription,
+}
+
+struct GlobalProfileStore(Entity<ProfileStore>);
+
+impl Global for GlobalProfileStore {}
+
+impl ProfileStore {
+    /// Retrieve the global profile store.
+    pub fn global(cx: &App) -> Entity<Self> {
+        cx.global::<GlobalProfileStore>().0.clone()
+    }
+
+    pub(crate) fn set_global(entity: Entity<Self>, cx: &mut App) {
+        cx.set_global(GlobalProfileStore(entity));
+    }
+
+    pub(crate) fn new(cx: &mut Context<Self>) -> Self {
+        let backend = Backend::global(cx);
+
+        let subscription = cx.subscribe(&backend, |this, _backend, event, cx| match event {
+            BackendEvent::NostrUpdate(update) if update.kind == Kind::Metadata => {
+                this.apply_author(update.author, cx);
+            }
+            BackendEvent::Published(event) if event.kind == Kind::Metadata => {
+                let metadata = Metadata::from_json(&event.content).unwrap_or_default();
+                this.profiles
+                    .insert(event.pubkey, Profile::new(event.pubkey, metadata));
+                cx.notify();
+            }
+            _ => {}
+        });
+
+        let mut store = Self {
+            profiles: HashMap::new(),
+            seen: HashSet::new(),
+            queued: HashSet::new(),
+            fetching: false,
+            tasks: Vec::new(),
+            _subscription: subscription,
+        };
+
+        store.load(cx);
+        store
+    }
+
+    /// Get a profile. Returns a placeholder (default metadata) and queues a
+    /// fetch if the profile isn't cached yet.
+    pub fn get(&mut self, public_key: PublicKey, cx: &mut Context<Self>) -> Profile {
+        if let Some(profile) = self.profiles.get(&public_key) {
+            return profile.clone();
+        }
+
+        if self.seen.insert(public_key) {
+            self.queued.insert(public_key);
+            self.queue_fetch(cx);
+        }
+
+        Profile::new(public_key, Metadata::default())
+    }
+
+    /// Load recently seen profiles from the local database.
+    fn load(&mut self, cx: &mut Context<Self>) {
+        let client = Backend::global(cx).read(cx).client();
+
+        let task = cx.spawn(async move |this, cx| {
+            let filter = Filter::new().kind(Kind::Metadata).limit(200);
+            let events = client.database().query(filter).await?;
+
+            this.update(cx, |this, cx| {
+                for event in events {
+                    let metadata = Metadata::from_json(&event.content).unwrap_or_default();
+                    this.profiles
+                        .insert(event.pubkey, Profile::new(event.pubkey, metadata));
+                }
+                cx.notify();
+            })?;
+
+            Ok(())
+        });
+
+        self.tasks.push(task);
+    }
+
+    /// Re-read the latest metadata of an author from the local database.
+    fn apply_author(&mut self, public_key: PublicKey, cx: &mut Context<Self>) {
+        let client = Backend::global(cx).read(cx).client();
+
+        let task = cx.spawn(async move |this, cx| {
+            let filter = Filter::new().kind(Kind::Metadata).author(public_key);
+            let events = client.database().query(filter).await?;
+
+            if let Some(event) = events.into_iter().max_by_key(|e| e.created_at) {
+                let metadata = Metadata::from_json(event.content).unwrap_or_default();
+
+                this.update(cx, |this, cx| {
+                    this.profiles
+                        .insert(public_key, Profile::new(public_key, metadata));
+                    cx.notify();
+                })?;
+            }
+
+            Ok(())
+        });
+
+        self.tasks.push(task);
+    }
+
+    /// Drain the queue in a batched fetch, debounced to collect requests.
+    fn queue_fetch(&mut self, cx: &mut Context<Self>) {
+        if self.fetching {
+            return;
+        }
+        self.fetching = true;
+
+        let client = Backend::global(cx).read(cx).client();
+
+        let task = cx.spawn(async move |this, cx| {
+            loop {
+                // Collect more requests before firing the batch.
+                cx.background_executor()
+                    .timer(Duration::from_millis(500))
+                    .await;
+
+                let batch = this.update(cx, |this, _cx| std::mem::take(&mut this.queued))?;
+
+                if batch.is_empty() {
+                    this.update(cx, |this, _cx| {
+                        this.fetching = false;
+                    })?;
+                    break;
+                }
+
+                let filter = Filter::new()
+                    .kind(Kind::Metadata)
+                    .authors(batch.into_iter().collect::<Vec<PublicKey>>());
+
+                // Gossip routes the fetch to each author's relays. Fetched
+                // events land in the database and surface via NostrUpdate.
+                if let Err(e) = client.fetch_events(filter).await {
+                    log::warn!("profile fetch failed: {e}");
+                }
+            }
+
+            Ok(())
+        });
+
+        self.tasks.push(task);
+    }
+}