support async command execution

src/commands.rs

@@ -1,3 +1,7 @@
+use std::sync::Arc;
+
+use tokio::sync::Mutex;
+
 use crate::{context::save_context, Context, Error};
 
 #[poise::command(prefix_command)]
@@ -8,22 +12,44 @@ pub async fn register(ctx: Context<'_>) -> Result<(), Error> {
 
 #[poise::command(prefix_command, slash_command)]
 pub async fn calc(ctx: Context<'_>, expr: String) -> Result<(), Error> {
-    let mut data = ctx.data().context.lock().await;
+    ctx.defer().await.unwrap();
+
     let author = ctx.author().id.get();
 
-    if !data.contains_key(&author) {
-        let mut context = fend_core::Context::new();
-        context.set_random_u32_fn(rand::random);
-        data.insert(author, fend_core::Context::new());
+    let context = {
+        let mut data = ctx.data().context.lock().await;
+
+        if !data.contains_key(&author) {
+            let mut context = fend_core::Context::new();
+            context.set_random_u32_fn(rand::random);
+            data.insert(author, fend_core::Context::new());
+        }
+        data.get(&ctx.author().id.get()).unwrap().clone()
+    };
+    let context = Arc::new(Mutex::new(context));
+
+    let result = tokio::task::spawn_blocking({
+        let context = context.clone();
+        let expr = expr.clone();
+        move || async move {
+            let mut context = context.lock().await;
+            let eval_result = fend_core::evaluate(&expr, &mut context).unwrap();
+            let main_result = eval_result.get_main_result().to_string();
+            main_result
+        }
+    })
+    .await?
+    .await;
+
+    ctx.reply(format!("> {}\n{}", expr, result)).await.unwrap();
+
+    {
+        let mut data = ctx.data().context.lock().await;
+        let context = context.lock().await;
+        data.insert(author, context.clone());
+
+        save_context(&context, author);
     }
-    let mut context = data.get_mut(&ctx.author().id.get()).unwrap();
-
-    let result = fend_core::evaluate(&expr, &mut context).unwrap();
-    let result = result.get_main_result();
-
-    ctx.reply(result).await.unwrap();
-
-    save_context(context, author);
 
     Ok(())
 }