Use once_cell to keep the configuration

In order to keep the configuration globally available use
`once_cell`. Also check for a valid email address in the part which is
receiving the data from the api.

src/api.rs

@@ -7,6 +7,7 @@ use axum::{
     Json,
 };
 use diesel::prelude::*;
+use lettre::message::Mailbox;
 use serde::Deserialize;
 use time::OffsetDateTime;
 use tracing::{error, trace};
@@ -35,7 +36,7 @@ pub struct Reminder {
     planned: OffsetDateTime,
     title: String,
     message: String,
-    receiver: String,
+    receiver: Mailbox,
 }
 
 #[allow(clippy::unused_async)]
@@ -48,7 +49,7 @@ pub async fn create_reminder(
         planned: data.planned,
         title: &data.title,
         message: &data.message,
-        receiver: &data.receiver,
+        receiver: &data.receiver.to_string(),
     };
 
     trace!(?data, "received data");

src/config.rs

@@ -1,4 +1,6 @@
-use anyhow::{bail, Error, Result};
+use anyhow::{anyhow, bail, Error, Result};
+use lettre::{message::Mailbox, Address};
+use once_cell::sync::OnceCell;
 use serde::Deserialize;
 use std::{
     env, fs,
@@ -7,6 +9,8 @@ use std::{
 };
 use tracing::{error, info, trace, warn};
 
+static CONFIG: OnceCell<Config> = OnceCell::new();
+
 fn default_database_host() -> String {
     "localhost".to_string()
 }
@@ -75,15 +79,42 @@ impl Default for Server {
     }
 }
 
+fn default_email_from() -> Mailbox {
+    Mailbox::new(
+        Some(env!("CARGO_BIN_NAME").to_string()),
+        Address::new(env!("CARGO_BIN_NAME"), "localhost").unwrap(),
+    )
+}
+
+#[derive(Debug, Deserialize)]
+#[serde(deny_unknown_fields)]
+pub struct Email {
+    /// Address the notification emails are sent from
+    #[serde(default = "default_email_from")]
+    pub from: Mailbox,
+}
+
+impl Default for Email {
+    fn default() -> Self {
+        Self {
+            from: default_email_from(),
+        }
+    }
+}
+
 #[derive(Debug, Deserialize)]
 #[serde(deny_unknown_fields)]
 pub struct Config {
     /// Database configuration
     pub database: Database,
 
-    /// server configuration
+    /// Server configuration
     #[serde(default)]
     pub server: Server,
+
+    /// Email configuration
+    #[serde(default)]
+    pub email: Email,
 }
 
 impl Config {
@@ -130,4 +161,15 @@ impl Config {
             Ok(Self::try_paths()?)
         }
     }
+
+    pub fn init(file: Option<PathBuf>) -> Result<()> {
+        CONFIG
+            .set(Self::load_config(file)?)
+            .map_err(|_| anyhow!("configuration already initialized"))?;
+        Ok(())
+    }
+
+    pub fn get() -> &'static Self {
+        CONFIG.get().expect("config is not initialized")
+    }
 }

src/main.rs

@@ -51,14 +51,14 @@ fn remind(
         .load::<Reminder>(&mut db_pool.get()?)?;
 
     if result.is_empty() {
-        info!("no reminders present, parking indefinitely");
+        info!("no reminders present, waiting for new reminder");
         std::thread::park();
     } else {
         for reminder in result {
             trace!(?reminder, "checking reminder");
             if reminder.planned <= OffsetDateTime::now_utc() {
                 let email = Message::builder()
-                    .from(format!("{}@localhost", env!("CARGO_BIN_NAME")).parse()?)
+                    .from(Config::get().email.from.clone())
                     .to(reminder.receiver.parse()?)
                     .subject(&reminder.title)
                     .body(reminder.message.to_string())?;
@@ -105,8 +105,9 @@ async fn main() -> Result<()> {
         env!("CARGO_PKG_VERSION")
     );
 
-    let config = Config::load_config(args.config)?;
-    let mut db_pool = get_connection_pool(&config)?;
+    Config::init(args.config)?;
+
+    let mut db_pool = get_connection_pool(Config::get())?;
     trace!(migrations = ?db_pool
         .get()?
         .run_pending_migrations(MIGRATIONS)
@@ -120,7 +121,7 @@ async fn main() -> Result<()> {
         }
     });
 
-    let db_pool = get_connection_pool(&config)?;
+    let db_pool = get_connection_pool(Config::get())?;
     let app = Router::new()
         .route("/v1/reminder", post(api::create_reminder))
         .layer(ServiceBuilder::new().layer(TraceLayer::new_for_http()))
@@ -129,7 +130,7 @@ async fn main() -> Result<()> {
             db_pool,
             reminder: Arc::new(reminder),
         });
-    let addr = SocketAddr::from((config.server.address, config.server.port));
+    let addr = SocketAddr::from((Config::get().server.address, Config::get().server.port));
 
     info!("{} listening on {}", env!("CARGO_PKG_NAME"), addr);