Use bounded independent Android cache files for each attachment

tools/chatgui-android/app/src/main/java/com/utun/chat/viewmodel/ChatViewModel.kt

@@ -1130,16 +1130,29 @@ class ChatViewModel : ViewModel() {
     }
 
     fun copyUriToCache(context: Context, uri: Uri, fileName: String): String? {
+        var cacheFile: File? = null
         try {
-            val cacheDir = File(context.cacheDir, "attachments")
-            cacheDir.mkdirs()
-            val cacheFile = File(cacheDir, fileName)
+            val name = fileName.substringAfterLast('/').substringAfterLast('\\')
+            require(name.isNotBlank() && name != "." && name != "..") { "Неверное имя файла" }
+            val cacheDir = File(context.cacheDir, "attachments/${java.util.UUID.randomUUID()}")
+            check(cacheDir.mkdirs()) { "Не удалось создать каталог вложения" }
+            val outputFile = File(cacheDir, name)
+            cacheFile = outputFile
             context.contentResolver.openInputStream(uri)?.use { input ->
-                FileOutputStream(cacheFile).use { output -> input.copyTo(output) }
-            } ?: return null
-            LogManager.addLog("INFO", "VM", "copied attachment to cache: ${cacheFile.absolutePath}")
-            return cacheFile.absolutePath
+                FileOutputStream(outputFile).use { output ->
+                    val buffer = ByteArray(65536); var size = 0L
+                    while (true) {
+                        val n = input.read(buffer)
+                        if (n < 0) break
+                        size += n; check(size <= 1024L * 1024 * 1024) { "Файл больше 1 ГиБ" }
+                        output.write(buffer, 0, n)
+                    }
+                }
+            } ?: throw IllegalStateException("Не удалось открыть вложение")
+            LogManager.addLog("INFO", "VM", "copied attachment to cache: ${outputFile.absolutePath}")
+            return outputFile.absolutePath
         } catch (e: Exception) {
+            cacheFile?.delete(); cacheFile?.parentFile?.delete()
             LogManager.addLog("ERROR", "VM", "copyUriToCache failed: ${e.message}")
             return null
         }