100 exercises to learn Rust

exercises/07_threads/12_rw_lock/src/lib.rs

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+// TODO: Replace `Mutex` with `RwLock` in the `TicketStore` struct and
+//  all other relevant places to allow multiple readers to access the ticket store concurrently.
+use std::sync::mpsc::{sync_channel, Receiver, SyncSender, TrySendError};
+use std::sync::{Arc, Mutex};
+
+use crate::data::{Ticket, TicketDraft};
+use crate::store::{TicketId, TicketStore};
+
+pub mod data;
+pub mod store;
+
+#[derive(Clone)]
+pub struct TicketStoreClient {
+    sender: SyncSender<Command>,
+}
+
+impl TicketStoreClient {
+    pub fn insert(&self, draft: TicketDraft) -> Result<TicketId, TrySendError<Command>> {
+        let (response_sender, response_receiver) = sync_channel(1);
+        self.sender.try_send(Command::Insert {
+            draft,
+            response_channel: response_sender,
+        })?;
+        Ok(response_receiver.recv().unwrap())
+    }
+
+    pub fn get(&self, id: TicketId) -> Result<Option<Arc<Mutex<Ticket>>>, TrySendError<Command>> {
+        let (response_sender, response_receiver) = sync_channel(1);
+        self.sender.try_send(Command::Get {
+            id,
+            response_channel: response_sender,
+        })?;
+        Ok(response_receiver.recv().unwrap())
+    }
+}
+
+pub fn launch(capacity: usize) -> TicketStoreClient {
+    let (sender, receiver) = sync_channel(capacity);
+    std::thread::spawn(move || server(receiver));
+    TicketStoreClient { sender }
+}
+
+enum Command {
+    Insert {
+        draft: TicketDraft,
+        response_channel: SyncSender<TicketId>,
+    },
+    Get {
+        id: TicketId,
+        response_channel: SyncSender<Option<Arc<Mutex<Ticket>>>>,
+    },
+}
+
+pub fn server(receiver: Receiver<Command>) {
+    let mut store = TicketStore::new();
+    loop {
+        match receiver.recv() {
+            Ok(Command::Insert {
+                draft,
+                response_channel,
+            }) => {
+                let id = store.add_ticket(draft);
+                let _ = response_channel.send(id);
+            }
+            Ok(Command::Get {
+                id,
+                response_channel,
+            }) => {
+                let ticket = store.get(id);
+                let _ = response_channel.send(ticket);
+            }
+            Err(_) => {
+                // There are no more senders, so we can safely break
+                // and shut down the server.
+                break;
+            }
+        }
+    }
+}