refactor: serialize metadata to json and add file-ending to attachments (planning#1796)

java/cli/src/main/java/dev/fitko/fitconnect/cli/CommandExecutor.java

 package dev.fitko.fitconnect.cli;
 
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.ObjectWriter;
 import dev.fitko.fitconnect.api.domain.crypto.JWKPair;
 import dev.fitko.fitconnect.api.domain.model.attachment.Attachment;
+import dev.fitko.fitconnect.api.domain.model.metadata.Metadata;
 import dev.fitko.fitconnect.api.domain.model.submission.SentSubmission;
 import dev.fitko.fitconnect.api.domain.model.submission.SubmissionForPickup;
 import dev.fitko.fitconnect.api.domain.sender.SendableSubmission;
@@ -23,6 +26,7 @@ import dev.fitko.fitconnect.client.SenderClient;
 import dev.fitko.fitconnect.client.SubscriberClient;
 import dev.fitko.fitconnect.core.utils.StopWatch;
 import org.apache.tika.Tika;
+import org.apache.tika.mime.MimeType;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -50,12 +54,16 @@ class CommandExecutor {
     private final TestKeyBuilder testKeyBuilder;
     private final Supplier<SenderClient> senderSupplier;
     private final Supplier<SubscriberClient> subscriberSupplier;
+    private final Tika mimeTypeDetector;
+    private final ObjectWriter jsonWriter;
 
     CommandExecutor(final Supplier<SenderClient> senderSupplier, final Supplier<SubscriberClient> subscriberSupplier, final BatchImporter batchImporter, final TestKeyBuilder testKeyBuilder) {
         this.batchImporter = batchImporter;
         this.testKeyBuilder = testKeyBuilder;
         this.senderSupplier = senderSupplier;
         this.subscriberSupplier = subscriberSupplier;
+        this.mimeTypeDetector = new Tika();
+        this.jsonWriter = new ObjectMapper().writerWithDefaultPrettyPrinter();
     }
 
     void getOneSubmission(final GetOneSubmissionCommand getOneSubmissionCommand) throws IOException {
@@ -93,7 +101,6 @@ class CommandExecutor {
 
     SentSubmission sendSubmission(final SendSubmissionCommand sendSubmissionCommand) throws IOException {
         LOGGER.info("Sending new submission to destination {}", sendSubmissionCommand.destinationId);
-        final Tika mimeTypeDetector = new Tika();
         final var startTime = StopWatch.start();
         final List<Attachment> attachments = sendSubmissionCommand.attachments.stream().map(toAttachment(mimeTypeDetector)).collect(Collectors.toList());
         final SentSubmission submission;
@@ -189,15 +196,29 @@ class CommandExecutor {
         LOGGER.info("Writing data.{}", fileEnding);
         Files.write(filePath, receivedSubmission.getDataAsString().getBytes(StandardCharsets.UTF_8));
 
+        LOGGER.info("Writing metadata");
+        final Metadata metadata = receivedSubmission.getMetadata();
+        Files.write(Path.of(dataDirPath, "metadata.json"), jsonWriter.writeValueAsString(metadata).getBytes());
+
         final List<Attachment> attachments = receivedSubmission.getAttachments();
         for (int i = 0; i < attachments.size(); i++) {
             final Attachment attachment = attachments.get(i);
-            final String filename = attachment.getFileName() != null ? attachment.getFileName() : "attachment_" + i;
+            final String filename = getAttachmentFilename(attachment, i);
             LOGGER.info("Writing attachment {}", filename);
             Files.write(Path.of(dataDirPath, filename), attachment.getDataAsBytes());
         }
     }
 
+    private String getAttachmentFilename(Attachment attachment, int i) {
+        if (attachment.getFileName() == null) {
+            if (MimeType.isValid(attachment.getMimeType())) {
+                return "attachment_" + i + "." + attachment.getMimeType().split("/")[1];
+            }
+            return attachment + "_" + i;
+        }
+        return attachment.getFileName();
+    }
+
     private SendSubmissionCommand mapToSubmissionToSend(final ImportRecord importRecord) {
         final var submission = new SendSubmissionCommand();
         submission.setDestinationId(importRecord.getDestinationId());