chore: Improve translation service with HTML and plain text support (#11305)

# Pull Request Template

## Description

This PR changes to translation to properly handle different content
types during translation.

### Changes

1. **Email translation with HTML support**
   - Properly detects and preserves HTML content from emails
   - Sets `mime_type` to 'text/html' when HTML content is present

2. **Email translation with plain text support**
   - Falls back to email text content when HTML is not available
- Sets `mime_type` to 'text/plain' when HTML is not available and
content type includes 'text/plain'

3. **Plain message with plain text support (Non email channels)**
   - Sets `mime_type` to 'text/plain' for non-email channels
- Fixes an issue where Markdown formatting was being lost due to
incorrect `mime_type`
   
**Note**: Translation for very long emails is not currently supported.

Fixes
https://linear.app/chatwoot/issue/CW-4244/translate-button-doesnt-work-in-email-channels

## Type of change

- [x] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)

## How Has This Been Tested?

**Loom video**

https://www.loom.com/share/8f8428ed2cfe415ea5cb6c547c070f00?sid=eab9fa11-05f8-4838-9181-334bee1023c4


## Checklist:

- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [x] I have commented on my code, particularly in hard-to-understand
areas
- [ ] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [x] I have added tests that prove my fix is effective or that my
feature works
- [x] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged and published in downstream
modules

app/javascript/dashboard/components-next/message/TranslationToggle.vue

@@ -0,0 +1,24 @@
+<script setup>
+import { defineProps, defineEmits } from 'vue';
+
+defineProps({
+  showingOriginal: Boolean,
+});
+
+defineEmits(['toggle']);
+</script>
+
+<template>
+  <span>
+    <span
+      class="text-xs text-n-slate-11 cursor-pointer hover:underline select-none"
+      @click="$emit('toggle')"
+    >
+      {{
+        showingOriginal
+          ? $t('CONVERSATION.VIEW_TRANSLATED')
+          : $t('CONVERSATION.VIEW_ORIGINAL')
+      }}
+    </span>
+  </span>
+</template>

app/javascript/dashboard/components-next/message/bubbles/Email/Index.vue

@@ -9,9 +9,11 @@ import BaseBubble from 'next/message/bubbles/Base.vue';
 import FormattedContent from 'next/message/bubbles/Text/FormattedContent.vue';
 import AttachmentChips from 'next/message/chips/AttachmentChips.vue';
 import EmailMeta from './EmailMeta.vue';
+import TranslationToggle from 'dashboard/components-next/message/TranslationToggle.vue';
 
 import { useMessageContext } from '../../provider.js';
 import { MESSAGE_TYPES } from 'next/message/constants.js';
+import { useTranslations } from 'dashboard/composables/useTranslations';
 
 const { content, contentAttributes, attachments, messageType } =
   useMessageContext();
@@ -19,35 +21,77 @@ const { content, contentAttributes, attachments, messageType } =
 const isExpandable = ref(false);
 const isExpanded = ref(false);
 const showQuotedMessage = ref(false);
+const renderOriginal = ref(false);
 const contentContainer = useTemplateRef('contentContainer');
 
 onMounted(() => {
   isExpandable.value = contentContainer.value?.scrollHeight > 400;
 });
 
-const isOutgoing = computed(() => {
-  return messageType.value === MESSAGE_TYPES.OUTGOING;
-});
+const isOutgoing = computed(() => messageType.value === MESSAGE_TYPES.OUTGOING);
 const isIncoming = computed(() => !isOutgoing.value);
 
-const textToShow = computed(() => {
+const { hasTranslations, translationContent } =
+  useTranslations(contentAttributes);
+
+const originalEmailText = computed(() => {
   const text =
     contentAttributes?.value?.email?.textContent?.full ?? content.value;
   return text?.replace(/\n/g, '<br>');
 });
 
-// Use TextContent as the default to fullHTML
+const originalEmailHtml = computed(
+  () =>
+    contentAttributes?.value?.email?.htmlContent?.full ??
+    originalEmailText.value
+);
+
+const messageContent = computed(() => {
+  // If translations exist and we're showing translations (not original)
+  if (hasTranslations.value && !renderOriginal.value) {
+    return translationContent.value;
+  }
+  // Otherwise show original content
+  return content.value;
+});
+
+const textToShow = computed(() => {
+  // If translations exist and we're showing translations (not original)
+  if (hasTranslations.value && !renderOriginal.value) {
+    return translationContent.value;
+  }
+  // Otherwise show original text
+  return originalEmailText.value;
+});
+
 const fullHTML = computed(() => {
-  return contentAttributes?.value?.email?.htmlContent?.full ?? textToShow.value;
+  // If translations exist and we're showing translations (not original)
+  if (hasTranslations.value && !renderOriginal.value) {
+    return translationContent.value;
+  }
+  // Otherwise show original HTML
+  return originalEmailHtml.value;
 });
 
-const unquotedHTML = computed(() => {
-  return EmailQuoteExtractor.extractQuotes(fullHTML.value);
+const unquotedHTML = computed(() =>
+  EmailQuoteExtractor.extractQuotes(fullHTML.value)
+);
+
+const hasQuotedMessage = computed(() =>
+  EmailQuoteExtractor.hasQuotes(fullHTML.value)
+);
+
+// Ensure unique keys for <Letter> when toggling between original and translated views.
+// This forces Vue to re-render the component and update content correctly.
+const translationKeySuffix = computed(() => {
+  if (renderOriginal.value) return 'original';
+  if (hasTranslations.value) return 'translated';
+  return 'original';
 });
 
-const hasQuotedMessage = computed(() => {
-  return EmailQuoteExtractor.hasQuotes(fullHTML.value);
-});
+const handleSeeOriginal = () => {
+  renderOriginal.value = !renderOriginal.value;
+};
 </script>
 
 <template>
@@ -88,11 +132,12 @@ const hasQuotedMessage = computed(() => {
         <FormattedContent
           v-if="isOutgoing && content"
           class="text-n-slate-12"
-          :content="content"
+          :content="messageContent"
         />
         <template v-else>
           <Letter
             v-if="showQuotedMessage"
+            :key="`letter-quoted-${translationKeySuffix}`"
             class-name="prose prose-bubble !max-w-none letter-render"
             :allowed-css-properties="[
               ...allowedCssProperties,
@@ -104,6 +149,7 @@ const hasQuotedMessage = computed(() => {
           />
           <Letter
             v-else
+            :key="`letter-unquoted-${translationKeySuffix}`"
             class-name="prose prose-bubble !max-w-none letter-render"
             :html="unquotedHTML"
             :allowed-css-properties="[
@@ -135,6 +181,12 @@ const hasQuotedMessage = computed(() => {
         </button>
       </div>
     </section>
+    <TranslationToggle
+      v-if="hasTranslations"
+      class="py-2 px-3"
+      :showing-original="renderOriginal"
+      @toggle="handleSeeOriginal"
+    />
     <section
       v-if="Array.isArray(attachments) && attachments.length"
       class="px-4 pb-4 space-y-2"

app/javascript/dashboard/components-next/message/bubbles/Text/Index.vue

@@ -3,16 +3,16 @@ import { computed, ref } from 'vue';
 import BaseBubble from 'next/message/bubbles/Base.vue';
 import FormattedContent from './FormattedContent.vue';
 import AttachmentChips from 'next/message/chips/AttachmentChips.vue';
+import TranslationToggle from 'dashboard/components-next/message/TranslationToggle.vue';
 import { MESSAGE_TYPES } from '../../constants';
 import { useMessageContext } from '../../provider.js';
+import { useTranslations } from 'dashboard/composables/useTranslations';
 
 const { content, attachments, contentAttributes, messageType } =
   useMessageContext();
 
-const hasTranslations = computed(() => {
-  const { translations = {} } = contentAttributes.value;
-  return Object.keys(translations || {}).length > 0;
-});
+const { hasTranslations, translationContent } =
+  useTranslations(contentAttributes);
 
 const renderOriginal = ref(false);
 
@@ -22,8 +22,7 @@ const renderContent = computed(() => {
   }
 
   if (hasTranslations.value) {
-    const translations = contentAttributes.value.translations;
-    return translations[Object.keys(translations)[0]];
+    return translationContent.value;
   }
 
   return content.value;
@@ -37,12 +36,6 @@ const isEmpty = computed(() => {
   return !content.value && !attachments.value?.length;
 });
 
-const viewToggleKey = computed(() => {
-  return renderOriginal.value
-    ? 'CONVERSATION.VIEW_TRANSLATED'
-    : 'CONVERSATION.VIEW_ORIGINAL';
-});
-
 const handleSeeOriginal = () => {
   renderOriginal.value = !renderOriginal.value;
 };
@@ -55,15 +48,12 @@ const handleSeeOriginal = () => {
         {{ $t('CONVERSATION.NO_CONTENT') }}
       </span>
       <FormattedContent v-if="renderContent" :content="renderContent" />
-      <span class="-mt-3">
-        <span
-          v-if="hasTranslations"
-          class="text-xs text-n-slate-11 cursor-pointer hover:underline"
-          @click="handleSeeOriginal"
-        >
-          {{ $t(viewToggleKey) }}
-        </span>
-      </span>
+      <TranslationToggle
+        v-if="hasTranslations"
+        class="-mt-3"
+        :showing-original="renderOriginal"
+        @toggle="handleSeeOriginal"
+      />
       <AttachmentChips :attachments="attachments" class="gap-2" />
       <template v-if="isTemplate">
         <div

app/javascript/dashboard/composables/spec/useTranslations.spec.js

@@ -0,0 +1,39 @@
+import { ref } from 'vue';
+import { useTranslations } from '../useTranslations';
+
+describe('useTranslations', () => {
+  it('returns false and null when contentAttributes is null', () => {
+    const contentAttributes = ref(null);
+    const { hasTranslations, translationContent } =
+      useTranslations(contentAttributes);
+    expect(hasTranslations.value).toBe(false);
+    expect(translationContent.value).toBeNull();
+  });
+
+  it('returns false and null when translations are missing', () => {
+    const contentAttributes = ref({});
+    const { hasTranslations, translationContent } =
+      useTranslations(contentAttributes);
+    expect(hasTranslations.value).toBe(false);
+    expect(translationContent.value).toBeNull();
+  });
+
+  it('returns false and null when translations is an empty object', () => {
+    const contentAttributes = ref({ translations: {} });
+    const { hasTranslations, translationContent } =
+      useTranslations(contentAttributes);
+    expect(hasTranslations.value).toBe(false);
+    expect(translationContent.value).toBeNull();
+  });
+
+  it('returns true and correct translation content when translations exist', () => {
+    const contentAttributes = ref({
+      translations: { en: 'Hello' },
+    });
+    const { hasTranslations, translationContent } =
+      useTranslations(contentAttributes);
+    expect(hasTranslations.value).toBe(true);
+    // Should return the first translation (en: 'Hello')
+    expect(translationContent.value).toBe('Hello');
+  });
+});

app/javascript/dashboard/composables/useTranslations.js

@@ -0,0 +1,22 @@
+import { computed } from 'vue';
+
+/**
+ * Composable to extract translation state/content from contentAttributes.
+ * @param {Ref|Reactive} contentAttributes - Ref or reactive object containing `translations` property
+ * @returns {Object} { hasTranslations, translationContent }
+ */
+export function useTranslations(contentAttributes) {
+  const hasTranslations = computed(() => {
+    if (!contentAttributes.value) return false;
+    const { translations = {} } = contentAttributes.value;
+    return Object.keys(translations || {}).length > 0;
+  });
+
+  const translationContent = computed(() => {
+    if (!hasTranslations.value) return null;
+    const translations = contentAttributes.value.translations;
+    return translations[Object.keys(translations)[0]];
+  });
+
+  return { hasTranslations, translationContent };
+}

lib/integrations/google_translate/processor_service.rb

@@ -1,15 +1,19 @@
 require 'google/cloud/translate/v3'
+
 class Integrations::GoogleTranslate::ProcessorService
   pattr_initialize [:message!, :target_language!]
 
   def perform
-    return if message.content.blank?
     return if hook.blank?
 
+    content = translation_content
+    return if content.blank?
+
     response = client.translate_text(
-      contents: [message.content],
+      contents: [content],
       target_language_code: target_language,
-      parent: "projects/#{hook.settings['project_id']}"
+      parent: "projects/#{hook.settings['project_id']}",
+      mime_type: mime_type
     )
 
     return if response.translations.first.blank?
@@ -19,6 +23,43 @@ class Integrations::GoogleTranslate::ProcessorService
 
   private
 
+  def email_channel?
+    message&.inbox&.email?
+  end
+
+  def email_content
+    @email_content ||= {
+      html: message.content_attributes.dig('email', 'html_content', 'full'),
+      text: message.content_attributes.dig('email', 'text_content', 'full'),
+      content_type: message.content_attributes.dig('email', 'content_type')
+    }
+  end
+
+  def html_content_available?
+    email_content[:html].present?
+  end
+
+  def plain_text_content_available?
+    email_content[:content_type]&.include?('text/plain') &&
+      email_content[:text].present?
+  end
+
+  def translation_content
+    return message.content unless email_channel?
+    return email_content[:html] if html_content_available?
+    return email_content[:text] if plain_text_content_available?
+
+    message.content
+  end
+
+  def mime_type
+    if email_channel? && html_content_available?
+      'text/html'
+    else
+      'text/plain'
+    end
+  end
+
   def hook
     @hook ||= message.account.hooks.find_by(app_id: 'google_translate')
   end