Honor bread.command.pad.capture via breadpad listen

EVENTS.md

@@ -8,11 +8,11 @@ specifically its "Namespaces" and "Integrating a bread\* app" sections — for
 the general convention this follows.
 
 App id: **`pad`**. Transport: `bread-utils`'s `bread_client` module
-(feature `bread-client`) — the capture popup links it directly. breadpad is
-short-lived (one popup, or one `fire <id>` invocation from the existing
-systemd user timer), so each `emit` is its own short-lived connection.
-There is no long-running breadpad daemon and therefore no command
-subscription.
+(feature `bread-client`) — the capture popup links it directly. One-shot
+popup / `fire <id>` invocations each `emit` on their own short-lived
+connection. Command verbs are only received while `breadpad listen` is
+running — that process holds the `bread.command.pad.**` subscription
+open.
 
 `breadman` (the viewer) does not emit or subscribe. Notes created or edited
 there are not quick-capture, and it is not on the reminder-fire path.
@@ -23,6 +23,8 @@ there are not quick-capture, and it is not on the reminder-fire path.
 |-------|------|------|
 | `bread.pad.captured` | `{ "id": "<note id>" }` | The capture popup saved a note successfully (`Store::save_note` returned `Ok`). Not emitted when the field is empty, the window is dismissed, classification-only preview happens, or the write fails. |
 | `bread.pad.reminder.due` | `{ "id": "<note id>" }` | `breadpad fire <id>` decided the reminder is due (`Scheduler::fire` returned true) and is about to show the reminder window. This is the existing in-process systemd-timer hook (`breadpad-reminder-<id>.timer` → `breadpad fire <id>`), not a new daemon. Not emitted when the note is missing, the fire is outside the missed-grace window, or the reminder window is opened as a `--screenshot` sample. |
+| `bread.pad.capture.done` | `{}` | `bread.command.pad.capture` was received and `breadpad` was spawned. This is the command confirmation, not proof the popup mapped — the spawned process is the same no-args invocation as the capture keybind. |
+| `bread.pad.capture.failed` | `{ "error": "<message>" }` | `bread.command.pad.capture` was received but this binary could not be started. |
 
 Note bodies are never included in the payload — only the local note id.
 Notes stay in `~/.local/share/breadpad/notes.jsonl`; the event bus is for
@@ -31,19 +33,38 @@ content.
 
 ## Commands honored (`bread.command.pad.*`)
 
-None. breadpad has no persistent process that could subscribe, and the
-actions a command verb would map to already exist as local CLI / keybind
-paths (`breadpad` for capture, `breadpad fire <id>` for the reminder
-window, `breadman` for viewing and editing). Stubbing `capture` / `snooze`
-/ `done` on the bus without a subscriber (or inventing a daemon just to
-hold one) would be a no-op dressed up as an API. If breadpad later grows a
-long-running piece that can honor a verb for real, add the verb then.
+These are only received while `breadpad listen` is running. Publishing a
+command with no subscriber is a silent no-op — that is the documented
+bread convention, not a breadpad bug.
+
+| Verb | Data | Effect |
+|------|------|--------|
+| `capture` | none | Same as running `breadpad` with no args: open the capture popup. Emits `bread.pad.capture.done` / `.failed`. |
+
+```lua
+bread.spawn(function()
+    bread.emit("bread.command.pad.capture")
+    bread.wait("bread.pad.capture.done", { timeout = 5000 })
+end)
+```
+
+### Not implemented: extra verbs
+
+There is no `snooze` / `done` / `fire` command verb. Reminder fire
+already exists as `breadpad fire <id>` (systemd user timer), and
+viewing/editing lives in `breadman`. If/when a bus verb maps to real
+extra behavior, add it then — do not stub one as a no-op ahead of it.
 
 ## Fail-safe behavior
 
 - If breadd isn't installed or isn't running, `emit` is a silent no-op
-  (`BreadClient::emit` never blocks or errors the caller). Capture, save,
+  (`BreadClient::emit` never blocks or errors the caller) and the
+  command subscription simply never receives anything. Capture, save,
   systemd timers, and the reminder window are entirely unaffected.
-- There is no command subscription to reconnect. Restarting breadd does
-  not require restarting breadpad; the next real capture or fire will emit
-  again if breadd is reachable at that moment.
+- If breadd restarts, the command subscription reconnects automatically
+  (`BreadClient::subscribe`'s background thread has its own backoff
+  loop); no restart of `breadpad listen` is needed.
+- If `breadpad listen` is not running, commands are a graceful no-op at
+  the bus (no subscriber). One-shot capture / `fire` still emit
+  `bread.pad.captured` / `bread.pad.reminder.due` on their own
+  short-lived connection.

breadpad/src/listen.rs

@@ -0,0 +1,83 @@
+//! Long-running command subscription for `bread.command.pad.*`.
+//!
+//! `breadpad` is still a one-shot capture popup by default. `breadpad listen`
+//! is the optional persistent process that can honor bus commands. See
+//! `EVENTS.md`.
+
+use anyhow::Result;
+use bread_utils::bread_client::{BreadClient, BreadEvent};
+
+/// Sibling-app id in `bread_shared::apps::KNOWN_APPS`.
+const APP_ID: &str = "pad";
+
+/// Subscribe to `bread.command.pad.**` and block until the process is killed.
+///
+/// breadd being absent is not an error: [`BreadClient::subscribe`] reconnects
+/// with backoff, and `on_event` simply isn't called until the daemon is up.
+pub fn run() -> Result<()> {
+    let client = BreadClient::connect(APP_ID);
+    if client.health().is_none() {
+        tracing::warn!("breadd unreachable; command subscription will connect when it comes back");
+    }
+
+    let _commands = client.subscribe("bread.command.pad.**", |event| {
+        handle_command(&event);
+    });
+
+    tracing::info!("listening for bread.command.pad.**");
+    loop {
+        std::thread::park();
+    }
+}
+
+/// Reacts to `bread.command.pad.*` verbs. Only `capture` is honored today —
+/// other verbs are ignored, not stubbed as no-ops that pretend to succeed.
+fn handle_command(event: &BreadEvent) {
+    let Some(verb) = command_verb(&event.event) else {
+        return;
+    };
+    match verb {
+        "capture" => handle_capture(),
+        other => {
+            tracing::debug!("ignoring unrecognized command verb '{other}'");
+        }
+    }
+}
+
+fn handle_capture() {
+    // Same as running `breadpad` with no args: open the capture popup.
+    let result = spawn_self();
+    let client = BreadClient::connect(APP_ID);
+    match result {
+        Ok(_) => client.emit("bread.pad.capture.done", serde_json::json!({})),
+        Err(e) => {
+            tracing::warn!("bread.command.pad.capture failed: {e}");
+            client.emit(
+                "bread.pad.capture.failed",
+                serde_json::json!({ "error": e.to_string() }),
+            );
+        }
+    }
+}
+
+fn spawn_self() -> std::io::Result<std::process::Child> {
+    let exe = std::env::current_exe().unwrap_or_else(|_| std::path::PathBuf::from("breadpad"));
+    std::process::Command::new(exe).spawn()
+}
+
+fn command_verb(event_name: &str) -> Option<&str> {
+    event_name.strip_prefix("bread.command.pad.")
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn command_verb_strips_pad_prefix() {
+        assert_eq!(command_verb("bread.command.pad.capture"), Some("capture"));
+        assert_eq!(command_verb("bread.command.pad.snooze"), Some("snooze"));
+        assert_eq!(command_verb("bread.command.box.open"), None);
+        assert_eq!(command_verb("bread.pad.captured"), None);
+    }
+}

breadpad/src/main.rs

@@ -15,6 +15,7 @@ use std::cell::RefCell;
 use std::rc::Rc;
 use std::sync::{Arc, Once};
 
+mod listen;
 mod screenshot;
 
 /// Sibling-app id in `bread_shared::apps::KNOWN_APPS`. Events are `bread.pad.*`.
@@ -64,6 +65,7 @@ mod args {
         pub output: Option<String>,
         pub width: u32,
         pub height: u32,
+        pub listen: bool,
     }
 
     impl Args {
@@ -99,6 +101,7 @@ mod args {
             output: None,
             width: 1920,
             height: 1080,
+            listen: false,
         };
         let raw: Vec<String> = std::env::args().skip(1).collect();
         let mut i = 0;
@@ -112,6 +115,7 @@ mod args {
                 "--status" => args.status = true,
                 "download-model" => args.download_model = true,
                 "model-info" => args.model_info = true,
+                "listen" => args.listen = true,
                 "fire" => {
                     i += 1;
                     args.fire_id = raw.get(i).cloned();
@@ -165,6 +169,9 @@ fn main() -> Result<()> {
         .init();
 
     let args = args::parse();
+    if args.listen {
+        return listen::run();
+    }
     let cfg = Config::load()?;
 
     if args.status {