Add command to get an attachment (#1080)

* Add command to get an attachment

* Refactor retrieving of attachments to use StreamDetails

* Refactor AttachmentCommand to GetAttachmentCommand

* Minor improvements to GetAttachmentCommand

* Use JSON serializer to serialize binary data

Serializing the stream is better for memory handling than
loading the whole thing into the file.

* Clean up unneeded class

* Added command to doc

Co-authored-by: cedb <cedb@keylimebox.org>

src/main/java/org/asamk/signal/commands/Commands.java

@@ -11,6 +11,7 @@ public class Commands {
 
     static {
         addCommand(new AddDeviceCommand());
+        addCommand(new GetAttachmentCommand());
         addCommand(new BlockCommand());
         addCommand(new DaemonCommand());
         addCommand(new DeleteLocalAccountDataCommand());

src/main/java/org/asamk/signal/commands/GetAttachmentCommand.java

@@ -0,0 +1,63 @@
+package org.asamk.signal.commands;
+
+import net.sourceforge.argparse4j.inf.Namespace;
+import net.sourceforge.argparse4j.inf.Subparser;
+
+import org.asamk.signal.commands.exceptions.CommandException;
+import org.asamk.signal.commands.exceptions.UnexpectedErrorException;
+import org.asamk.signal.commands.exceptions.UserErrorException;
+import org.asamk.signal.json.JsonAttachmentData;
+import org.asamk.signal.manager.Manager;
+import org.asamk.signal.output.JsonWriter;
+import org.asamk.signal.output.OutputWriter;
+import org.asamk.signal.output.PlainTextWriter;
+
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.Base64;
+
+public class GetAttachmentCommand implements JsonRpcLocalCommand {
+
+    @Override
+    public String getName() {
+        return "getAttachment";
+    }
+
+    @Override
+    public void attachToSubparser(final Subparser subparser) {
+        subparser.addArgument("--id")
+                .required(true)
+                .help("The ID of the attachment file.");
+        var mut = subparser.addMutuallyExclusiveGroup()
+                .required(true);
+        mut.addArgument("--recipient")
+                .help("Sender of the attachment");
+        mut.addArgument("-g", "--group-id")
+                .help("Group in which the attachment was received");
+    }
+
+    @Override
+    public void handleCommand(
+            final Namespace ns,
+            final Manager m,
+            final OutputWriter outputWriter
+    ) throws CommandException {
+
+        final var id = ns.getString("id");
+
+        try(InputStream attachment = m.retrieveAttachment(id)) {
+            if (outputWriter instanceof PlainTextWriter writer) {
+                final var bytes = attachment.readAllBytes();
+                final var base64 = Base64.getEncoder().encodeToString(bytes);
+                writer.println(base64);
+            } else if (outputWriter instanceof JsonWriter writer) {
+                writer.write(new JsonAttachmentData(attachment));
+            }
+        } catch (FileNotFoundException ex) {
+            throw new UserErrorException("Could not find attachment with ID: " + id, ex);
+        } catch (IOException ex) {
+            throw new UnexpectedErrorException("An error occurred reading attachment: " + id, ex);
+        }
+    }
+}

src/main/java/org/asamk/signal/dbus/DbusManagerImpl.java

@@ -46,6 +46,7 @@ import org.freedesktop.dbus.types.Variant;
 
 import java.io.File;
 import java.io.IOException;
+import java.io.InputStream;
 import java.net.URI;
 import java.net.URISyntaxException;
 import java.time.Duration;
@@ -916,6 +917,11 @@ public class DbusManagerImpl implements Manager {
         }).toList();
     }
 
+    @Override
+    public InputStream retrieveAttachment(final String id) throws IOException {
+        throw new UnsupportedOperationException();
+    }
+
     @SuppressWarnings("unchecked")
     private <T> T getValue(
             final Map<String, Variant<?>> stringVariantMap, final String field

src/main/java/org/asamk/signal/json/JsonAttachmentData.java

@@ -0,0 +1,9 @@
+package org.asamk.signal.json;
+
+import com.fasterxml.jackson.databind.annotation.JsonSerialize;
+
+import java.io.InputStream;
+
+public record JsonAttachmentData(
+        @JsonSerialize(using=JsonStreamSerializer.class) InputStream data
+) {}

src/main/java/org/asamk/signal/json/JsonStreamSerializer.java

@@ -0,0 +1,20 @@
+package org.asamk.signal.json;
+
+import com.fasterxml.jackson.core.JsonGenerator;
+import com.fasterxml.jackson.databind.JsonSerializer;
+import com.fasterxml.jackson.databind.SerializerProvider;
+
+import java.io.IOException;
+import java.io.InputStream;
+
+public class JsonStreamSerializer extends JsonSerializer<InputStream> {
+
+    @Override
+    public void serialize(
+            final InputStream value,
+            final JsonGenerator jsonGenerator,
+            final SerializerProvider serializers
+    ) throws IOException {
+        jsonGenerator.writeBinary(value, -1);
+    }
+}