feat: finalize working impl of react emails renderer

Author: cyyynthia

DEVELOPMENT.md

@@ -67,6 +67,10 @@ To learn more about externalized configuration in Spring boot, read [the docs](h
 
 Since we set the active profile to `dev`, Spring uses the `application-dev.yaml` configuration file.
 
+## Writing emails
+
+Please refer to [email/HACKING.md](email/HACKING.md).
+
 ## Updating the database changelog
 
 Tolgee uses Liquibase to handle the database migration. The migrations are run on every app startup. To update the changelog, run:

backend/data/src/main/kotlin/io/tolgee/email/EmailMessageSource.kt

@@ -0,0 +1,129 @@
+package io.tolgee.email
+
+import com.transferwise.icu.ICUMessageSource
+import org.springframework.context.MessageSource
+import org.springframework.context.MessageSourceResolvable
+import org.springframework.context.NoSuchMessageException
+import java.util.Locale
+import java.util.regex.Pattern
+
+/**
+ * Transforms a classic ICUMessageSource into an XML-aware message source.
+ * The transformation performed is specific to emails template structure, and isn't suitable for general-purpose use.
+ *
+ * Cannot be written as a subclass of ICUReloadableResourceBundleMessageSource as its `getMessage` methods are final.
+ */
+class EmailMessageSource(
+	private val provider: ICUMessageSource
+) : ICUMessageSource {
+	private var counter = 0L
+
+	override fun getMessage(
+		code: String,
+		args: Array<out Any?>?,
+		defaultMessage: String?,
+		locale: Locale
+	): String? {
+		return provider.getMessage(code, args, defaultMessage, locale)?.postProcessMessage(code)
+	}
+
+	override fun getMessage(
+		code: String,
+		args: Array<out Any?>?,
+		locale: Locale
+	): String {
+		return provider.getMessage(code, args, locale).postProcessMessage(code)
+	}
+
+	override fun getMessage(
+		code: String,
+		args: Map<String, Any?>?,
+		defaultMessage: String?,
+		locale: Locale
+	): String? {
+		return provider.getMessage(code, args, defaultMessage, locale)?.postProcessMessage(code)
+	}
+
+	override fun getMessage(
+		code: String,
+		args: Map<String, Any?>?,
+		locale: Locale
+	): String? {
+		return provider.getMessage(code, args, locale).postProcessMessage(code)
+	}
+
+	override fun getMessage(
+		resolvable: MessageSourceResolvable,
+		locale: Locale
+	): String {
+		resolvable.codes?.forEach { code ->
+			getMessage(code, resolvable.arguments, null, locale)?.let {
+				return it
+			}
+		}
+
+		throw NoSuchMessageException(resolvable.codes?.lastOrNull() ?: "", locale)
+	}
+
+	override fun getParentMessageSource(): MessageSource? {
+		return provider.parentMessageSource
+	}
+
+	override fun setParentMessageSource(parent: MessageSource?) {
+		provider.parentMessageSource = parent
+	}
+
+	@Synchronized
+	private fun count(): Long {
+		val ret = counter
+		if (counter == Long.MAX_VALUE) {
+			counter = 0L
+		} else {
+			counter += 1L
+		}
+		return ret
+	}
+
+	private fun makeRef(): String = "intl-ref-${count()}"
+
+	private fun String.postProcessMessage(code: String): String {
+		var str = this.replace("\n", "<br/>")
+			// Prevent Thymeleaf injection (for the second pass)
+			.replace("{", "&#123;")
+			.replace("[", "&#91;")
+			.replace("$", "&#36;")
+			.replace("*", "&#42;")
+			.replace("#", "&#35;")
+			.replace("~", "&#126;")
+
+		// Dumb heuristic to skip XML parsing for trivial cases, to improve performance.
+		if (contains('<') && contains('>')) {
+			var delta = 0
+			val stack = mutableListOf(code)
+			val m = XML_PATTERN.matcher(str)
+
+			while (m.find()) {
+				if (m.group(1) == null) {
+					stack.add(m.group(2))
+
+					val ref = makeRef()
+					val replacement = "<div th:ref=\"$ref\" th:replace=\"~{::intl-${stack.joinToString("--")}(~{:: $ref/content})}\"><content th:remove=\"tag\">"
+					str = str.replaceRange(delta + m.start(), delta + m.end(), replacement)
+					delta += replacement.length - (m.end() - m.start())
+				} else {
+					stack.removeLast()
+
+					val replacement = "</content></div>"
+					str = str.replaceRange(delta + m.start(), delta + m.end(), replacement)
+					delta += replacement.length - (m.end() - m.start())
+				}
+			}
+		}
+
+		return str
+	}
+
+	companion object {
+		private val XML_PATTERN = Pattern.compile("<(/)?([a-zA-Z-]+)>")
+	}
+}

backend/data/src/main/kotlin/io/tolgee/email/EmailService.kt

@@ -50,9 +50,17 @@ class EmailService(
     attachments: List<EmailAttachment> = listOf(),
   ) {
     val context = Context(locale, properties)
-    val html = templateEngine.process(template, context)
-    val subject = extractEmailTitle(html)
 
+		// Do two passes, so Thymeleaf expressions rendered by messages can get processed
+		context.setVariable("isSecondPass", false)
+    val firstPass = templateEngine.process(template, context)
+
+		println(firstPass)
+
+		context.setVariable("isSecondPass", true)
+		val html = templateEngine.process(firstPass, context)
+
+    val subject = extractEmailTitle(html)
     sendEmail(recipient, subject, html, attachments)
   }
 

backend/data/src/main/kotlin/io/tolgee/email/EmailTemplateConfig.kt

@@ -26,6 +26,7 @@ import org.thymeleaf.TemplateEngine
 import org.thymeleaf.spring6.SpringTemplateEngine
 import org.thymeleaf.templateresolver.ClassLoaderTemplateResolver
 import org.thymeleaf.templateresolver.ITemplateResolver
+import org.thymeleaf.templateresolver.StringTemplateResolver
 import java.util.*
 
 @Configuration
@@ -45,17 +46,20 @@ class EmailTemplateConfig {
     messageSource.setBasenames("email-i18n/messages", "email-i18n-test/messages")
     messageSource.setDefaultEncoding("UTF-8")
     messageSource.setDefaultLocale(Locale.ENGLISH)
-    return messageSource
+    return EmailMessageSource(messageSource)
   }
 
   @Bean("emailTemplateEngine")
   fun templateEngine(
     @Qualifier("emailTemplateResolver") templateResolver: ITemplateResolver,
     @Qualifier("emailMessageSource") messageSource: MessageSource,
   ): TemplateEngine {
+		val stringTemplateResolver = StringTemplateResolver()
+		stringTemplateResolver.resolvablePatternSpec.addPattern("<!DOCTYPE*")
+
     val templateEngine = SpringTemplateEngine()
     templateEngine.enableSpringELCompiler = true
-    templateEngine.templateResolvers = setOf(templateResolver)
+    templateEngine.templateResolvers = setOf(stringTemplateResolver, templateResolver)
     templateEngine.setTemplateEngineMessageSource(messageSource)
     return templateEngine
   }