feat: Support user-defined download directory for media

app/src/main/java/com/cappielloantonio/tempo/util/ExternalAudioWriter.java

@@ -0,0 +1,176 @@
+package com.cappielloantonio.tempo.util;
+
+import android.app.NotificationManager;
+import android.app.PendingIntent;
+import android.content.Context;
+import android.content.Intent;
+import android.net.Uri;
+import android.os.Handler;
+import android.os.Looper;
+import android.provider.Settings;
+import android.webkit.MimeTypeMap;
+import android.widget.Toast;
+
+import androidx.core.app.NotificationCompat;
+import androidx.documentfile.provider.DocumentFile;
+import androidx.media3.common.MediaItem;
+
+import com.cappielloantonio.tempo.util.Preferences;
+
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.net.HttpURLConnection;
+import java.net.URL;
+import java.text.Normalizer;
+import java.util.Locale;
+
+public class ExternalAudioWriter {
+
+    private static String sanitizeFileName(String name) {
+        String sanitized = name.replaceAll("[\\/:*?\\\"<>|]", "_");
+        sanitized = sanitized.replaceAll("\\s+", " ").trim();
+        return sanitized;
+    }
+
+    private static String normalizeForComparison(String name) {
+        String s = sanitizeFileName(name);
+        s = Normalizer.normalize(s, Normalizer.Form.NFKD);
+        s = s.replaceAll("\\p{InCombiningDiacriticalMarks}+", "");
+        return s.toLowerCase(Locale.ROOT);
+    }
+
+    private static DocumentFile findFile(DocumentFile dir, String fileName) {
+        String normalized = normalizeForComparison(fileName);
+        for (DocumentFile file : dir.listFiles()) {
+            String existing = file.getName();
+            if (existing != null && normalizeForComparison(existing).equals(normalized)) {
+                return file;
+            }
+        }
+        return null;
+    }
+
+    public static void downloadToUserDirectory(Context context, MediaItem mediaItem, String fallbackName) {
+        new Thread(() -> {
+            String uriString = Preferences.getDownloadDirectoryUri();
+
+            if (uriString == null) {
+                notifyUnavailable(context);
+                return;
+            }
+
+            Uri treeUri = Uri.parse(uriString);
+            DocumentFile directory = DocumentFile.fromTreeUri(context, treeUri);
+            if (directory == null || !directory.canWrite()) {
+                notifyFailure(context, "Cannot write to folder.");
+                return;
+            }
+
+            try {
+                Uri mediaUri = mediaItem.requestMetadata.mediaUri;
+                if (mediaUri == null) {
+                    notifyFailure(context, "Invalid media URI.");
+                    return;
+                }
+
+                HttpURLConnection connection = (HttpURLConnection) new URL(mediaUri.toString()).openConnection();
+                connection.connect();
+
+                String mimeType = connection.getContentType();
+                if (mimeType == null) mimeType = "application/octet-stream";
+
+                String extension = MimeTypeMap.getSingleton().getExtensionFromMimeType(mimeType);
+                if (extension == null) extension = "bin";
+
+                String artist = mediaItem.mediaMetadata.artist != null ? mediaItem.mediaMetadata.artist.toString() : "";
+                String title = mediaItem.mediaMetadata.title != null ? mediaItem.mediaMetadata.title.toString() : fallbackName;
+                String album = mediaItem.mediaMetadata.albumTitle != null ? mediaItem.mediaMetadata.albumTitle.toString() : "";
+                String name = artist.isEmpty() ? title : artist + " - " + title;
+                if (!album.isEmpty()) name += " (" + album + ")";
+
+                String sanitized = sanitizeFileName(name);
+                String fullName = sanitized + "." + extension;
+
+                DocumentFile existingFile = findFile(directory, fullName);
+                long remoteLength = connection.getContentLengthLong();
+                if (existingFile != null && existingFile.exists()) {
+                    long localLength = existingFile.length();
+                    if (remoteLength > 0 && localLength == remoteLength) {
+                        notifyExists(context, fullName);
+                        return;
+                    } else {
+                        existingFile.delete();
+                    }
+                }
+
+                DocumentFile targetFile = directory.createFile(mimeType, fullName);
+                if (targetFile == null) {
+                    notifyFailure(context, "Failed to create file.");
+                    return;
+                }
+
+                try (InputStream in = connection.getInputStream();
+                OutputStream out = context.getContentResolver().openOutputStream(targetFile.getUri())) {
+                    if (out == null) {
+                        notifyFailure(context, "Cannot open output stream.");
+                        return;
+                    }
+
+                    byte[] buffer = new byte[8192];
+                    int len;
+                    long total = 0;
+                    while ((len = in.read(buffer)) != -1) {
+                        out.write(buffer, 0, len);
+                        total += len;
+                    }
+
+                    if (remoteLength > 0 && total != remoteLength) {
+                        targetFile.delete();
+                        notifyFailure(context, "Incomplete download.");
+                    } else {
+                        notifySuccess(context, fullName);
+                    }
+                }
+            } catch (Exception e) {
+                notifyFailure(context, e.getMessage());
+            }
+        }).start();
+    }
+
+    private static void notifyUnavailable(Context context) {
+        NotificationManager manager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
+        Intent settingsIntent = new Intent(Settings.ACTION_APPLICATION_DETAILS_SETTINGS,
+            Uri.fromParts("package", context.getPackageName(), null));
+        PendingIntent openSettings = PendingIntent.getActivity(context, 0, settingsIntent,
+            PendingIntent.FLAG_UPDATE_CURRENT | PendingIntent.FLAG_IMMUTABLE);
+
+        NotificationCompat.Builder builder = new NotificationCompat.Builder(context, DownloadUtil.DOWNLOAD_NOTIFICATION_CHANNEL_ID)
+            .setContentTitle("No download folder set")
+            .setContentText("Tap to set one in settings")
+            .setSmallIcon(android.R.drawable.stat_notify_error)
+            .setPriority(NotificationCompat.PRIORITY_LOW)
+            .setSilent(true)
+            .setContentIntent(openSettings)
+            .setAutoCancel(true);
+
+        manager.notify(1011, builder.build());
+    }
+
+    private static void notifyFailure(Context context, String message) {
+        new Handler(Looper.getMainLooper()).post(() ->
+            Toast.makeText(context, "External download failed: " + message, Toast.LENGTH_LONG).show()
+        );
+    }
+
+    private static void notifySuccess(Context context, String name) {
+        new Handler(Looper.getMainLooper()).post(() ->
+            Toast.makeText(context, "Download success: " + name, Toast.LENGTH_SHORT).show()
+        );
+    }
+
+    private static void notifyExists(Context context, String name) {
+        new Handler(Looper.getMainLooper()).post(() ->
+            Toast.makeText(context, "Already exists: " + name, Toast.LENGTH_SHORT).show()
+        );
+    }
+}