src/tui/lib/external/musicbrainz/daemon/mod.rs

@@ -0,0 +1,224 @@
+use std::{collections::VecDeque, sync::mpsc, thread, time};
+
+use musichoard::collection::{album::AlbumMeta, artist::ArtistMeta, musicbrainz::Mbid};
+
+use crate::tui::{
+    app::MatchStateInfo,
+    event::{Event, EventSender},
+    lib::interface::musicbrainz::api::{Error as ApiError, IMusicBrainz},
+};
+
+pub enum Error {
+    RequestRecv(String),
+    Api(String),
+}
+
+impl From<mpsc::RecvError> for Error {
+    fn from(value: mpsc::RecvError) -> Self {
+        Error::RequestRecv(value.to_string())
+    }
+}
+
+impl From<ApiError> for Error {
+    fn from(value: ApiError) -> Self {
+        Error::Api(value.to_string())
+    }
+}
+
+pub struct MusicBrainzDaemon {
+    api: Box<dyn IMusicBrainz>,
+    request_channel: RequestChannel,
+    job_queue: JobQueue,
+    events: EventSender,
+}
+
+struct JobQueue {
+    foreground_queue: VecDeque<JobInstance>,
+    background_queue: VecDeque<JobInstance>,
+}
+
+impl JobQueue {
+    fn new() -> Self {
+        JobQueue {
+            foreground_queue: VecDeque::new(),
+            background_queue: VecDeque::new(),
+        }
+    }
+
+    fn is_empty(&self) -> bool {
+        self.foreground_queue.is_empty() && self.background_queue.is_empty()
+    }
+
+    fn front_mut(&mut self) -> Option<&mut JobInstance> {
+        self.foreground_queue
+            .front_mut()
+            .or_else(|| self.background_queue.front_mut())
+    }
+
+    fn pop_front(&mut self) -> Option<JobInstance> {
+        self.foreground_queue
+            .pop_front()
+            .or_else(|| self.background_queue.pop_front())
+    }
+
+    fn push_back(&mut self, job: Job) {
+        match job.priority {
+            JobPriority::Foreground => self.foreground_queue.push_back(job.instance),
+            JobPriority::Background => self.background_queue.push_back(job.instance),
+        }
+    }
+}
+
+struct Job {
+    priority: JobPriority,
+    instance: JobInstance,
+}
+
+enum JobPriority {
+    Foreground,
+    Background,
+}
+
+type ReturnSender = mpsc::Sender<Result<MatchStateInfo, ApiError>>;
+struct JobInstance {
+    return_sender: ReturnSender,
+    call_queue: VecDeque<ApiParams>,
+}
+
+enum ApiParams {
+    Search(SearchParams),
+}
+
+enum SearchParams {
+    Artist(SearchArtistParams),
+    ReleaseGroup(SearchReleaseGroupParams),
+}
+
+struct SearchArtistParams {
+    artist: ArtistMeta,
+}
+
+struct SearchReleaseGroupParams {
+    arid: Mbid,
+    album: AlbumMeta,
+}
+
+struct RequestChannel {
+    pub receiver: mpsc::Receiver<Job>,
+    pub sender: mpsc::Sender<Job>,
+}
+
+impl RequestChannel {
+    fn new() -> Self {
+        let (sender, receiver) = mpsc::channel();
+        RequestChannel { receiver, sender }
+    }
+}
+
+impl MusicBrainzDaemon {
+    pub fn run(api: Box<dyn IMusicBrainz>, events: EventSender) {
+        let daemon = MusicBrainzDaemon {
+            api,
+            request_channel: RequestChannel::new(),
+            job_queue: JobQueue::new(),
+            events,
+        };
+        daemon.main();
+    }
+
+    fn wait_for_jobs(&mut self) -> Result<(), Error> {
+        if self.job_queue.is_empty() {
+            self.job_queue
+                .push_back(self.request_channel.receiver.recv()?);
+        }
+        Ok(())
+    }
+
+    fn enqueue_all_pending_jobs(&mut self) -> Result<(), Error> {
+        loop {
+            match self.request_channel.receiver.try_recv() {
+                Ok(job) => self.job_queue.push_back(job),
+                Err(mpsc::TryRecvError::Empty) => return Ok(()),
+                Err(mpsc::TryRecvError::Disconnected) => {
+                    return Err(Error::RequestRecv(
+                        mpsc::TryRecvError::Disconnected.to_string(),
+                    ))
+                }
+            }
+        }
+    }
+
+    fn execute_next_job(&mut self) -> Option<()> {
+        while let Some(instance) = self.job_queue.front_mut() {
+            match instance.execute_next(&mut self.api, &mut self.events) {
+                Some(()) => return Some(()),
+                None => {
+                    self.job_queue.pop_front();
+                }
+            }
+        }
+        None
+    }
+
+    fn main(mut self) -> Result<(), Error> {
+        loop {
+            self.wait_for_jobs()?;
+            self.enqueue_all_pending_jobs()?;
+            if let Some(()) = self.execute_next_job() {
+                // Sleep for one second. Required by MB API rate limiting. Assume all other
+                // processing takes negligible time such that regardless of how much other
+                // processing there is to be done, this one second sleep is necessary.
+                thread::sleep(time::Duration::from_secs(1));
+            }
+        }
+    }
+}
+
+impl JobInstance {
+    fn execute_next(
+        &mut self,
+        api: &mut Box<dyn IMusicBrainz>,
+        events: &mut EventSender,
+    ) -> Option<()> {
+        self.call_queue
+            .pop_front()
+            .map(|api_params| self.execute_call(api, events, api_params))
+    }
+
+    fn execute_call(
+        &mut self,
+        api: &mut Box<dyn IMusicBrainz>,
+        events: &mut EventSender,
+        api_params: ApiParams,
+    ) {
+        match api_params {
+            ApiParams::Search(search) => match search {
+                SearchParams::Artist(params) => {
+                    let result = api.search_artist(&params.artist);
+                    let result = result.map(|list| MatchStateInfo::artist(params.artist, list));
+                    self.return_result(events, result).ok();
+                }
+                SearchParams::ReleaseGroup(params) => {
+                    let result = api.search_release_group(&params.arid, &params.album);
+                    let result = result.map(|list| MatchStateInfo::album(params.album, list));
+                    self.return_result(events, result).ok();
+                }
+            },
+        }
+    }
+
+    fn return_result(
+        &mut self,
+        events: &mut EventSender,
+        result: Result<MatchStateInfo, ApiError>,
+    ) -> Result<(), ()> {
+        // If receiver disconnects just drop the rest.
+        self.return_sender.send(result).map_err(|_| ())?;
+
+        // If this send fails the event listener is dead. Don't panic as this function runs in a
+        // detached thread so this might be happening during normal shut down.
+        events.send(Event::FetchResultReady).map_err(|_| ())?;
+
+        Ok(())
+    }
+}

src/tui/lib/external/musicbrainz/mod.rs

@@ -1 +1,3 @@
 pub mod api;
+pub mod daemon;
+

src/tui/lib/interface/musicbrainz/api/mod.rs

@@ -8,7 +8,7 @@ use musichoard::collection::{album::AlbumMeta, artist::ArtistMeta, musicbrainz::
 /// Trait for interacting with the MusicBrainz API.
 #[cfg_attr(test, automock)]
 pub trait IMusicBrainz {
-    fn search_artist(&mut self, name: &ArtistMeta) -> Result<Vec<Match<ArtistMeta>>, Error>;
+    fn search_artist(&mut self, artist: &ArtistMeta) -> Result<Vec<Match<ArtistMeta>>, Error>;
     fn search_release_group(
         &mut self,
         arid: &Mbid,