wavehunter: add QMDL storage

Instead of reading/writing to a single QMDL file, we now can manage
a directory of several files, and have the ability to start/stop writing
to them on the fly.

This commit also adds graceful exiting to the server, so we can perform
cleanup steps when the server's exiting.

wavehunter/src/diag.rs

@@ -0,0 +1,99 @@
+use std::sync::Arc;
+
+use axum::extract::State;
+use axum::http::StatusCode;
+use orca::diag_device::DiagDevice;
+use orca::diag_reader::DiagReader;
+use tokio::sync::RwLock;
+use tokio::sync::mpsc::{Receiver, self};
+use orca::qmdl::QmdlWriter;
+use log::{debug, info};
+use tokio::sync::mpsc::error::TryRecvError;
+use tokio::task::JoinHandle;
+use tokio_util::task::TaskTracker;
+
+use crate::error::WavehunterError;
+use crate::qmdl_store::QmdlStore;
+use crate::server::ServerState;
+
+pub enum DiagDeviceCtrlMessage {
+    StopRecording,
+    StartRecording(QmdlWriter<std::fs::File>),
+    Exit,
+}
+
+pub fn run_diag_read_thread(task_tracker: &TaskTracker, mut dev: DiagDevice, mut qmdl_file_rx: Receiver<DiagDeviceCtrlMessage>, qmdl_store_lock: Arc<RwLock<QmdlStore>>) -> JoinHandle<Result<(), WavehunterError>> {
+    let (tx, mut rx) = mpsc::channel::<(usize, usize)>(1);
+    let qmdl_store_lock_clone = qmdl_store_lock.clone();
+    task_tracker.spawn(async move {
+        while let Some((entry_idx, new_size)) = rx.recv().await {
+            let mut qmdl_store = qmdl_store_lock_clone.write().await;
+            qmdl_store.update_entry_size(entry_idx, new_size).await
+                .expect("failed to update qmdl file size");
+        }
+        info!("QMDL store size updater thread exiting...");
+    });
+
+    task_tracker.spawn_blocking(move || {
+        loop {
+            match qmdl_file_rx.try_recv() {
+                Ok(DiagDeviceCtrlMessage::StartRecording(qmdl_writer)) => {
+                    dev.qmdl_writer = Some(qmdl_writer);
+                },
+                Ok(DiagDeviceCtrlMessage::StopRecording) => dev.qmdl_writer = None,
+                Ok(DiagDeviceCtrlMessage::Exit) | Err(TryRecvError::Disconnected) => {
+                    info!("Diag reader thread exiting...");
+                    return Ok(())
+                },
+                // empty just means there's no message for us, so continue as normal
+                Err(TryRecvError::Empty) => {},
+            }
+
+            // remember the QmdlStore current entry index so we can update its size later
+            let qmdl_store_index = qmdl_store_lock.blocking_read().current_entry;
+
+            // TODO: once we're actually doing analysis, we'll wanna use the messages
+            // returned here. Until then, the DiagDevice has already written those messages
+            // to the QMDL file, so we can just ignore them.
+            debug!("reading response from diag device...");
+            let _messages = dev.read_response().map_err(WavehunterError::DiagReadError)?;
+            debug!("got diag response ({} messages)", _messages.len());
+
+            // keep track of how many bytes were written to the QMDL file so we can read
+            // a valid block of data from it in the HTTP server
+            if let Some(qmdl_writer) = dev.qmdl_writer.as_ref() {
+                debug!("total QMDL bytes written: {}, sending update...", qmdl_writer.total_written);
+                let index = qmdl_store_index.expect("DiagDevice had qmdl_writer, but QmdlStore didn't have current entry???");
+                tx.blocking_send((index, qmdl_writer.total_written)).unwrap();
+                debug!("done!");
+            } else {
+                debug!("no qmdl_writer set, continuing...");
+            }
+        }
+    })
+}
+
+pub async fn start_recording(State(state): State<Arc<ServerState>>) -> Result<(StatusCode, String), (StatusCode, String)> {
+    if state.readonly_mode {
+        return Err((StatusCode::FORBIDDEN, format!("server is in readonly mode")));
+    }
+    let mut qmdl_store = state.qmdl_store_lock.write().await;
+    let qmdl_file = qmdl_store.new_entry().await
+        .map_err(|e| (StatusCode::INTERNAL_SERVER_ERROR, format!("couldn't create new qmdl entry: {}", e)))?;
+    let qmdl_writer = QmdlWriter::new(qmdl_file.into_std().await);
+    state.diag_device_ctrl_sender.send(DiagDeviceCtrlMessage::StartRecording(qmdl_writer)).await
+        .map_err(|e| (StatusCode::INTERNAL_SERVER_ERROR, format!("couldn't send stop recording message: {}", e)))?;
+    Ok((StatusCode::ACCEPTED, format!("ok")))
+}
+
+pub async fn stop_recording(State(state): State<Arc<ServerState>>) -> Result<(StatusCode, String), (StatusCode, String)> {
+    if state.readonly_mode {
+        return Err((StatusCode::FORBIDDEN, format!("server is in readonly mode")));
+    }
+    let mut qmdl_store = state.qmdl_store_lock.write().await;
+    qmdl_store.close_current_entry().await
+        .map_err(|e| (StatusCode::INTERNAL_SERVER_ERROR, format!("couldn't close current qmdl entry: {}", e)))?;
+    state.diag_device_ctrl_sender.send(DiagDeviceCtrlMessage::StopRecording).await
+        .map_err(|e| (StatusCode::INTERNAL_SERVER_ERROR, format!("couldn't send stop recording message: {}", e)))?;
+    Ok((StatusCode::ACCEPTED, format!("ok")))
+}