i18n: remember chosen language across launches, timeouts, error on bad HTTP

app/src/main/java/io/github/abrarul/modularai/i18n/LocaleManager.kt

@@ -8,6 +8,7 @@ import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.withContext
 import org.json.JSONObject
 import java.io.File
+import java.net.HttpURLConnection
 import java.net.URL
 
 /**
@@ -16,24 +17,41 @@ import java.net.URL
  */
 class LocaleManager(ctx: Context, private val baseUrl: String) {
     private val dir = File(ctx.filesDir, "locales").apply { mkdirs() }
+    private val prefs = ctx.getSharedPreferences("locale", Context.MODE_PRIVATE)
     private var strings by mutableStateOf<Map<String, String>>(emptyMap())
     var current by mutableStateOf("en")
         private set
 
-    /** English fallback keys live in code; missing keys return the key's default. */
+    /** English defaults live in code; a missing key returns [default]. */
     fun t(key: String, default: String): String = strings[key] ?: default
 
     suspend fun apply(code: String, persist: Boolean = true) = withContext(Dispatchers.IO) {
+        require(code.matches(Regex("[A-Za-z]{2,3}(-[A-Za-z0-9]{2,8})?"))) { "Invalid language code: $code" }
         val cached = File(dir, "$code.json")
-        val text = if (cached.exists()) cached.readText() else URL("$baseUrl/$code.json").readText()
+        val text = if (cached.exists()) cached.readText() else {
+            val c = URL("$baseUrl/$code.json").openConnection() as HttpURLConnection
+            c.connectTimeout = 15_000
+            c.readTimeout = 15_000
+            if (c.responseCode !in 200..299) error("Language '$code' not available (HTTP ${c.responseCode})")
+            c.inputStream.bufferedReader().use { it.readText() }
+        }
         val json = JSONObject(text)
         val map = json.keys().asSequence().associateWith { json.getString(it) }
-        if (persist) cached.writeText(text)
+        if (persist) {
+            cached.writeText(text)
+            prefs.edit().putString("code", code).apply()
+        }
         strings = map
         current = code
     }
 
-    fun reset() { strings = emptyMap(); current = "en" }
-    fun purge(code: String) { File(dir, "$code.json").delete() }
-    fun purgeAll() { dir.listFiles()?.forEach { it.delete() } }
+    /** Re-applies the saved language from cache at app start; no network needed. */
+    suspend fun restore() {
+        val code = prefs.getString("code", null) ?: return
+        if (File(dir, "$code.json").exists()) apply(code, persist = false)
+    }
+
+    fun reset() { strings = emptyMap(); current = "en"; prefs.edit().remove("code").apply() }
+    fun purge(code: String) { File(dir, "$code.json").delete(); if (current == code) reset() }
+    fun purgeAll() { dir.listFiles()?.forEach { it.delete() }; reset() }
 }