feat: translation (#389)

src/services/libre-translate.service.ts

@@ -0,0 +1,35 @@
+class LibreTranslateService {
+  static instance: LibreTranslateService
+
+  constructor() {
+    if (!LibreTranslateService.instance) {
+      LibreTranslateService.instance = this
+    }
+    return LibreTranslateService.instance
+  }
+
+  async translate(
+    text: string,
+    target: string,
+    server?: string,
+    api_key?: string
+  ): Promise<string | undefined> {
+    if (!server) {
+      throw new Error('LibreTranslate server address is not configured')
+    }
+    const url = new URL('/translate', server).toString()
+    const response = await fetch(url, {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({ q: text, target, source: 'auto', api_key })
+    })
+    const data = await response.json()
+    if (!response.ok) {
+      throw new Error(data.error ?? 'Failed to translate')
+    }
+    return data.translatedText
+  }
+}
+
+const instance = new LibreTranslateService()
+export default instance