Added support for custom SMTP Server (#2)

README.md

@@ -29,23 +29,24 @@
 
 To run this project, you will need to add the following environment variables
 
-- `CONTACT_FORM_CONFIGS_FOLDER`
-- `MAIL_CONFIGS_FOLDER`
-- `TEMPLATES_FOLDER`
-- `GOOGLE_RECAPTCHA_SECRET`
-- `SENDGRID_API_KEY`
+- `CONTACT_FORM_CONFIGS_FOLDER`: An existing folder in your file system where the contact form configs will be stored.
+- `MAIL_CONFIGS_FOLDER`: An existing folder in your file system where the email configs will be stored.
+- `TEMPLATES_FOLDER`: An existing folder in your file system where the email templates will be stored.
+- `GOOGLE_RECAPTCHA_SECRET`: A Google ReCaptcha secret (required only when using forms).
 
 ## Documentation
 
 ### Supported Mail Providers
 
 - ~~[Sendgrid](https://sendgrid.com/)~~ Removed due to lack of support for batch emails requests
 - [Resend](https://resend.io/)
+- Custom SMTP server, that can be configured in the email & contact form configs
 
 ### Contact Form
 
 #### Example of `CONTACT_FORM_CONFIGS_FOLDER` configuration files
 
+**Resend-based config**
 ```json
 {
     "id": "UUID",
@@ -56,7 +57,25 @@ To run this project, you will need to add the following environment variables
     "lang": "fr", // ISO 639-1
     "subjectTemplate": "New mail from {{form.firstName}}",
     "provider": "RESEND",
-    "apiKey": ""
+    "apiKey": "<YOUR_RESEND_API_KEY>"
+}
+```
+
+**SMTP-based config**
+```json
+{
+    "id": "UUID",
+    "dailyLimit": 10,
+    "destination": "[email protected]",
+    "sender": "[email protected]",
+    "threshold": 0.5, // Recapthca score thresold
+    "lang": "fr", // ISO 639-1
+    "subjectTemplate": "New mail from {{form.firstName}}",
+    "provider": "SMTP",
+    "username": "<SMTP_USERNAME>",
+    "password": "<SMTP_PASSWORD>",
+    "smtpHost": "<SMTP_SERVER_IP>",
+    "smtpPort": "<SMTP_SERVER_PORT>"
 }
 ```
 
@@ -66,13 +85,28 @@ Filename does not have to respect any convention.
 
 #### Example of `MAIL_CONFIGS_FOLDER` configuration files
 
+**Resend-based config**
 ```json
 {
     "id": "UUID",
     "sender": "[email protected]",
     "subjectTemplate": "New mail from {{form.firstName}}",
     "provider": "RESEND",
-    "apiKey": ""
+    "apiKey": "<YOUR_RESEND_API_KEY>"
+}
+```
+
+**SMTP-based config**
+```json
+{
+    "id": "UUID",
+    "sender": "[email protected]",
+    "subjectTemplate": "New mail from {{form.firstName}}",
+    "provider": "SMTP",
+    "username": "<SMTP_USERNAME>",
+    "password": "<SMTP_PASSWORD>",
+    "smtpHost": "<SMTP_SERVER_IP>",
+    "smtpPort": "<SMTP_SERVER_PORT>"
 }
 ```
 

build.gradle.kts

@@ -56,6 +56,8 @@ dependencies {
 
     implementation("org.jetbrains.kotlinx:kotlinx-serialization-json:$kotlinx_serialization_version")
 
+    implementation("com.sun.mail:javax.mail:1.6.2")
+
     testImplementation("io.ktor:ktor-server-tests-jvm")
     testImplementation("org.jetbrains.kotlin:kotlin-test-junit:$kotlin_version")
 }

src/main/kotlin/com/vandeas/dto/configs/Config.kt

@@ -1,6 +1,50 @@
 package com.vandeas.dto.configs
 
+import com.vandeas.service.Mailer
+import com.vandeas.service.impl.mailer.ResendMailer
+import com.vandeas.service.impl.mailer.SMTPMailer
+import kotlinx.serialization.Serializable
+
+const val RESEND_SERIAL_NAME = "RESEND"
+const val SMTP_SERIAL_NAME = "SMTP"
+
 interface Config {
     val id: String
-    val apiKey: String
+
+    /**
+     * Instantiates a new [Mailer] using this config.
+     */
+    fun toMailer(): Mailer
+
+    /**
+     * @return a string that uniquely identifies this config based on the credentials.
+     */
+    fun identifierFromCredentials(): String
+}
+
+@Serializable
+abstract class ResendProvider: Config {
+    protected abstract val apiKey: String
+
+    override fun toMailer() = ResendMailer(apiKey = apiKey)
+
+    override fun identifierFromCredentials() = apiKey
+
+}
+
+@Serializable
+abstract class SMTPProvider: Config {
+    protected abstract val username: String
+    protected abstract val password: String
+    protected abstract val smtpHost: String
+    protected abstract val smtpPort: Int
+
+    override fun toMailer() = SMTPMailer(
+        username = username,
+        password = password,
+        host = smtpHost,
+        port = smtpPort
+    )
+
+    override fun identifierFromCredentials() = "smtp://${username}:${password}@$smtpHost:$smtpPort"
 }

src/main/kotlin/com/vandeas/dto/configs/ContactFormConfig.kt

@@ -1,23 +1,47 @@
 package com.vandeas.dto.configs
 
-import com.vandeas.dto.enums.Providers
-import com.vandeas.dto.enums.toMailer
-import com.vandeas.service.Mailer
+import kotlinx.serialization.ExperimentalSerializationApi
+import kotlinx.serialization.SerialName
 import kotlinx.serialization.Serializable
+import kotlinx.serialization.json.JsonClassDiscriminator
 
+@OptIn(ExperimentalSerializationApi::class)
 @Serializable
-data class ContactFormConfig(
+@JsonClassDiscriminator("provider")
+sealed interface ContactFormConfig : Config {
+    val dailyLimit: Int
+    val destination: String
+    val sender: String
+    val threshold: Double
+    val lang: String
+    val subjectTemplate: String
+}
+
+@Serializable
+@SerialName(RESEND_SERIAL_NAME)
+data class ResendContactFormConfig(
     override val id: String,
-    val dailyLimit: Int,
-    val destination: String,
-    val sender: String,
-    val threshold: Double,
-    val lang: String,
-    val subjectTemplate: String,
-    val provider: Providers,
-    override val apiKey: String,
-): Config
+    override val dailyLimit: Int,
+    override val destination: String,
+    override val sender: String,
+    override val threshold: Double,
+    override val lang: String,
+    override val subjectTemplate: String,
+    override val apiKey: String
+) : ContactFormConfig, ResendProvider()
 
-fun ContactFormConfig.toMailer(): Mailer {
-    return provider.toMailer(apiKey)
-}
+@Serializable
+@SerialName(SMTP_SERIAL_NAME)
+data class SMTPContactFormConfig(
+    override val id: String,
+    override val dailyLimit: Int,
+    override val destination: String,
+    override val sender: String,
+    override val threshold: Double,
+    override val lang: String,
+    override val subjectTemplate: String,
+    override val username: String,
+    override val password: String,
+    override val smtpHost: String,
+    override val smtpPort: Int = 587
+) : ContactFormConfig, SMTPProvider()

src/main/kotlin/com/vandeas/dto/configs/MailConfig.kt

@@ -1,19 +1,37 @@
 package com.vandeas.dto.configs
 
-import com.vandeas.dto.enums.Providers
-import com.vandeas.dto.enums.toMailer
-import com.vandeas.service.Mailer
+import com.vandeas.service.impl.mailer.ResendMailer
+import com.vandeas.service.impl.mailer.SMTPMailer
+import kotlinx.serialization.ExperimentalSerializationApi
+import kotlinx.serialization.SerialName
 import kotlinx.serialization.Serializable
+import kotlinx.serialization.json.JsonClassDiscriminator
 
+@OptIn(ExperimentalSerializationApi::class)
 @Serializable
-data class MailConfig(
+@JsonClassDiscriminator("provider")
+sealed interface MailConfig : Config {
+    val sender: String
+    val subjectTemplate: String
+}
+
+@Serializable
+@SerialName(RESEND_SERIAL_NAME)
+data class ResendMailConfig(
     override val id: String,
-    val sender: String,
-    val subjectTemplate: String,
-    val provider: Providers,
-    override val apiKey: String,
-): Config
+    override val sender: String,
+    override val subjectTemplate: String,
+    override val apiKey: String
+) : MailConfig, ResendProvider()
 
-fun MailConfig.toMailer(): Mailer {
-    return provider.toMailer(apiKey)
-}
+@Serializable
+@SerialName(SMTP_SERIAL_NAME)
+data class SMTPMailConfig(
+    override val id: String,
+    override val sender: String,
+    override val subjectTemplate: String,
+    override val username: String,
+    override val password: String,
+    override val smtpHost: String,
+    override val smtpPort: Int = 587
+) : MailConfig, SMTPProvider()

src/main/kotlin/com/vandeas/logic/impl/MailLogicImpl.kt

@@ -4,7 +4,6 @@ import com.vandeas.dto.ContactForm
 import com.vandeas.dto.MailInput
 import com.vandeas.dto.configs.ContactFormConfig
 import com.vandeas.dto.configs.MailConfig
-import com.vandeas.dto.configs.toMailer
 import com.vandeas.entities.Mail
 import com.vandeas.exception.RecaptchaFailedException
 import com.vandeas.logic.MailLogic
@@ -43,7 +42,7 @@ class MailLogicImpl(
         val contentTemplate = Template.parse(contactFormConfigHandler.getTemplate(config.id))
         val subjectTemplate = Template.parse(config.subjectTemplate)
 
-        val mailer = mailers[config.apiKey] ?: config.toMailer().also { mailers[config.apiKey] = it }
+        val mailer = mailers[config.identifierFromCredentials()] ?: config.toMailer().also { mailers[config.identifierFromCredentials()] = it }
 
         return mailer.sendEmail(
             from = config.sender,
@@ -58,7 +57,7 @@ class MailLogicImpl(
         val contentTemplate = Template.parse(mailConfigHandler.getTemplate(config.id))
         val subjectTemplate = Template.parse(config.subjectTemplate)
 
-        val mailer = mailers[config.apiKey] ?: config.toMailer().also { mailers[config.apiKey] = it }
+        val mailer = mailers[config.identifierFromCredentials()] ?: config.toMailer().also { mailers[config.identifierFromCredentials()] = it }
 
         return mailer.sendEmail(
             from = config.sender,
@@ -75,7 +74,7 @@ class MailLogicImpl(
 
         mailsByConfigId.entries.map { (config, mails) ->
             async {
-                (mailers[config.apiKey] ?: config.toMailer().also { mailers[config.apiKey] = it }).sendEmails(
+                (mailers[config.identifierFromCredentials()] ?: config.toMailer().also { mailers[config.identifierFromCredentials()] = it }).sendEmails(
                     mails = mails.map { mailInput ->
                         val contentTemplate = Template.parse(mailConfigHandler.getTemplate(config.id))
                         val subjectTemplate = Template.parse(config.subjectTemplate)

src/main/kotlin/com/vandeas/service/Mailer.kt

@@ -3,8 +3,6 @@ package com.vandeas.service
 import com.vandeas.entities.Mail
 
 interface Mailer {
-    val apiKey: String
-
     fun sendEmail(
         to: String,
         from: String,

src/main/kotlin/com/vandeas/service/impl/mailer/ResendMailer.kt

@@ -10,7 +10,7 @@ import com.vandeas.service.Response
 import io.ktor.http.*
 
 class ResendMailer(
-    override val apiKey: String
+    apiKey: String
 ): Mailer {
     private val resend = Resend(apiKey)
     override fun sendEmail(to: String, from: String, subject: String, content: String): Response {

src/main/kotlin/com/vandeas/service/impl/mailer/SMTPMailer.kt

@@ -0,0 +1,61 @@
+package com.vandeas.service.impl.mailer
+
+import com.vandeas.entities.Mail
+import com.vandeas.service.BatchResponse
+import com.vandeas.service.Mailer
+import com.vandeas.service.Response
+import java.util.*
+import javax.mail.Authenticator
+import javax.mail.Message
+import javax.mail.PasswordAuthentication
+import javax.mail.SendFailedException
+import javax.mail.Session
+import javax.mail.Transport
+import javax.mail.internet.InternetAddress
+import javax.mail.internet.MimeMessage
+
+class SMTPMailer(
+	username: String,
+	password: String,
+	host: String,
+	port: Int = 587
+): Mailer {
+
+	private val session: Session = Session.getInstance(
+			Properties().apply {
+				put("mail.smtp.host", host)
+				put("mail.smtp.port", "$port")
+				put("mail.smtp.auth", "true")
+				put("mail.smtp.starttls.enable", "true")
+			},
+			object : Authenticator() {
+				override fun getPasswordAuthentication(): PasswordAuthentication {
+					return PasswordAuthentication(username, password)
+				}
+			},
+		)
+
+	override fun sendEmail(to: String, from: String, subject: String, content: String): Response {
+		val message = MimeMessage(session).apply {
+			setFrom(InternetAddress(from))
+			addRecipient(Message.RecipientType.TO, InternetAddress(to))
+			this.subject = subject
+			setText(content)
+		}
+		return try {
+			Transport.send(message)
+			Response(200, "[$to] ok")
+		} catch (e: SendFailedException) {
+			Response(500, "[$to] ${e.message ?: "Unknown error"}")
+		}
+	}
+
+	override suspend fun sendEmails(mails: List<Mail>) = mails.map {
+		sendEmail(it.to, it.from, it.subject, it.content)
+	}.let { responses ->
+		BatchResponse(
+			200.takeIf { responses.all { it.isSuccessful } } ?: 500,
+			responses.map { it.body ?: "Unknown error"}
+		)
+	}
+}