feat(backend): support smtp

apps/backend/.env.example

@@ -1,3 +1,8 @@
 database_url=postgresql://username:password@host:port/db_name
 redis_url=redis://127.0.0.1:6379
 sentry_dsn=
+smtp_host=smtp.example.com
+smtp_port=587
+smtp_username=your_smtp_username
+smtp_password=your_smtp_password
+smtp_from=no-reply@example.com

apps/backend/Cargo.toml

@@ -44,3 +44,4 @@ rand = "0.10"
 subtle = "2.4"
 strum = { version = "0.28.0", features = ["derive"] }
 strum_macros = "0.28"
+lettre = { version = "0.11", default-features = false, features = ["builder", "hostname", "smtp-transport","tokio1", "tokio1-rustls-tls"] }

apps/backend/src/lib.rs

@@ -1,4 +1,7 @@
-use crate::{settings::Settings, utils::redis::RedisConnection};
+use crate::{
+    settings::Settings,
+    utils::{redis::RedisConnection, smtp::SmtpClient},
+};
 use sea_orm::DatabaseConnection;
 
 pub mod dto;
@@ -17,4 +20,5 @@ pub struct AppState {
     pub settings: Settings,
     pub db: DatabaseConnection,
     pub redis_client: RedisConnection,
+    pub smtp_client: SmtpClient,
 }

apps/backend/src/main.rs

@@ -1,4 +1,4 @@
-use backend::{AppState, server::run};
+use backend::{AppState, server::run, utils::smtp::SmtpClient};
 
 #[tokio::main]
 async fn main() -> Result<(), Box<dyn std::error::Error>> {
@@ -19,12 +19,24 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
         .sync(&db)
         .await?;
 
+    let smtp_client = SmtpClient::new(
+        &settings.smtp_host,
+        settings.smtp_port,
+        &settings.smtp_username,
+        &settings.smtp_password,
+         )
+     .map_err(|err| {
+         std::io::Error::other(format!(
+             "SMTP client initialization failed. If email is required in this environment, check smtp_host/smtp_port/smtp_username/smtp_password. Underlying error: {err}"
+         ))
+     })?;
     let redis_client = backend::utils::redis::RedisConnection::new(&settings.redis_url);
     redis_client.ping().await?;
     let state = AppState {
         settings,
         db,
         redis_client,
+        smtp_client,
     };
     run(state).await?;
 

apps/backend/src/settings.rs

@@ -1,13 +1,18 @@
 use config::{Config, Environment};
 use serde::Deserialize;
 
-#[derive(Clone, Debug, Deserialize)]
+#[derive(Clone, Deserialize)]
 pub struct Settings {
     pub database_url: String,
     pub redis_url: String,
     pub sentry_dsn: Option<String>,
     #[serde(default = "default_allow_origin")]
     pub allow_origin: String,
+    pub smtp_host: String,
+    pub smtp_port: u16,
+    pub smtp_username: String,
+    pub smtp_password: String,
+    pub smtp_from: String,
 }
 
 fn default_allow_origin() -> String {

apps/backend/src/utils/auth.rs

@@ -1,6 +1,9 @@
 use argon2::{
     Argon2,
-    password_hash::{PasswordHash, PasswordHasher, PasswordVerifier, SaltString, rand_core::{OsRng, RngCore}},
+    password_hash::{
+        PasswordHash, PasswordHasher, PasswordVerifier, SaltString,
+        rand_core::{OsRng, RngCore},
+    },
 };
 
 use axum::{

apps/backend/src/utils/mod.rs

@@ -1,2 +1,3 @@
 pub mod auth;
 pub mod redis;
+pub mod smtp;

apps/backend/src/utils/smtp.rs

@@ -0,0 +1,110 @@
+//! SMTPクライアントを提供するモジュール
+
+use lettre::Tokio1Executor;
+use lettre::message::{Mailbox, Message, MultiPart, SinglePart};
+use lettre::{AsyncSmtpTransport, AsyncTransport, transport::smtp::authentication::Credentials};
+use std::time::Duration;
+use tokio::time::timeout;
+
+/// SMTP送信タイムアウト（秒）
+const SMTP_SEND_TIMEOUT_SECS: u64 = 30;
+
+/// SMTPクライアントの構造体
+#[derive(Clone)]
+pub struct SmtpClient {
+    mailer: AsyncSmtpTransport<Tokio1Executor>,
+}
+
+/// SmtpClientの実装
+impl SmtpClient {
+    /// 新しいSMTPクライアントを作成する関数
+    ///
+    /// # Arguments
+    /// * `smtp_server` - SMTPサーバーのアドレス
+    /// * `smtp_port` - SMTPサーバーのポート番号
+    /// * `username` - SMTPサーバーの認証に使用するユーザー名
+    /// * `password` - SMTPサーバーの認証に使用するパスワード
+    ///
+    ///  # Examples
+    ///
+    ///  ```no_run
+    /// use backend::utils::smtp::SmtpClient;
+    ///
+    /// let smtp_client = SmtpClient::new("smtp.example.com", 587, "user", "pass").unwrap();
+    /// ```
+    pub fn new(
+        smtp_server: &str,
+        smtp_port: u16,
+        username: &str,
+        password: &str,
+    ) -> Result<Self, lettre::transport::smtp::Error> {
+        let creds = Credentials::new(username.to_string(), password.to_string());
+
+        let mailer = AsyncSmtpTransport::<Tokio1Executor>::starttls_relay(smtp_server)?
+            .port(smtp_port)
+            .credentials(creds)
+            .build();
+
+        Ok(SmtpClient { mailer })
+    }
+
+    /// メールを送信する関数
+    ///
+    /// # Arguments
+    /// * `from` - 送信元のメールアドレス
+    /// * `to` - 送信先のメールアドレス
+    /// * `subject` - メールの件名
+    /// * `body_text` - メールのテキスト形式の本文
+    /// * `body_html` - メールのHTML形式の本文（オプション）
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use backend::utils::smtp::SmtpClient;
+    ///
+    /// # #[tokio::main]
+    /// # async fn main() -> Result<(), Box<dyn std::error::Error>> {
+    /// let client = SmtpClient::new("smtp.example.com", 587, "user", "pass")?;
+    /// client.send_email(
+    ///     "sender@example.com",
+    ///     "receiver@example.com",
+    ///     "Hello from Async Rust!",
+    ///     "This is a test email sent asynchronously.",
+    ///     Some("<p>This is a <b>test</b> email sent asynchronously.</p>"),
+    /// ).await?;
+    /// # Ok(())
+    /// # }
+    /// ```
+    pub async fn send_email(
+        &self,
+        from: &str,
+        to: &str,
+        subject: &str,
+        body_text: &str,
+        body_html: Option<&str>,
+    ) -> Result<(), Box<dyn std::error::Error>> {
+        let builder = Message::builder()
+            .from(from.parse::<Mailbox>()?)
+            .to(to.parse::<Mailbox>()?)
+            .subject(subject);
+
+        let email = match body_html {
+            Some(html) => builder.multipart(
+                MultiPart::alternative()
+                    .singlepart(SinglePart::plain(body_text.to_string()))
+                    .singlepart(SinglePart::html(html.to_string())),
+            )?,
+            None => builder.singlepart(SinglePart::plain(body_text.to_string()))?,
+        };
+
+        // 送信処理にタイムアウトを30秒に設定
+        timeout(
+            Duration::from_secs(SMTP_SEND_TIMEOUT_SECS),
+            self.mailer.send(email),
+        )
+        .await
+        .map_err(|_| "SMTP send timeout")??;
+
+        Ok(())
+    }
+}