Implement the rdf transcode command

README.md

@@ -41,6 +41,14 @@ $ ./jelly-cli rdf from-jelly input.jelly --out-format=ttl > output.ttl
 You can specify most well-known formats supported by Apache Jena, but also a custom Jelly-Text format. 
 Jelly-Text is a human-readable translation of Jelly binary. It's not meant for machine consumption. It is useful for debugging and inspecting Jelly files.
 
+### Transcode Jelly files
+
+The `rdf transcode` command turns one or more input Jelly streams into a single output stream. It's extremely fast, using a dedicated transcoding algorithm, but the output stream's options must the same or greater than the inputs.
+
+```shell
+$ ./jelly-cli rdf transcode input.jelly > output.jelly
+```
+
 ### Inspect Jelly files
 
 To inspect a Jelly file and get basic information describing its contents, such as stream options or number of triples in the file, run
@@ -74,6 +82,7 @@ Use the `--help` option to learn more about all the available settings:
 ```shell
 $ ./jelly-cli rdf to-jelly --help
 $ ./jelly-cli rdf from-jelly --help
+$ ./jelly-cli rdf transcode --help
 $ ./jelly-cli rdf inspect --help
 $ ./jelly-cli rdf validate --help
 ```

src/main/scala/eu/neverblink/jelly/cli/App.scala

@@ -22,6 +22,7 @@ object App extends CommandsEntryPoint:
     Version,
     RdfFromJelly,
     RdfToJelly,
+    RdfTranscode,
     RdfInspect,
     RdfValidate,
   )

src/main/scala/eu/neverblink/jelly/cli/command/rdf/RdfFromJelly.scala

@@ -38,7 +38,7 @@ case class RdfFromJellyOptions(
     @ExtraName("out-format") outputFormat: Option[String] = None,
 ) extends HasJellyCommandOptions
 
-object RdfFromJelly extends RdfTranscodeCommand[RdfFromJellyOptions, RdfFormat.Writeable]:
+object RdfFromJelly extends RdfSerDesCommand[RdfFromJellyOptions, RdfFormat.Writeable]:
 
   override def names: List[List[String]] = List(
     List("rdf", "from-jelly"),

src/main/scala/eu/neverblink/jelly/cli/command/rdf/RdfTranscodeCommand.scala → src/main/scala/eu/neverblink/jelly/cli/command/rdf/RdfSerDesCommand.scala

@@ -13,8 +13,8 @@ import java.io.{InputStream, OutputStream}
 
 /** This abstract class is responsible for the common logic in both RDF parsing commands
   */
-abstract class RdfTranscodeCommand[T <: HasJellyCommandOptions: {Parser, Help}, F <: RdfFormat](
-    using tt: TypeTest[RdfFormat, F],
+abstract class RdfSerDesCommand[T <: HasJellyCommandOptions: {Parser, Help}, F <: RdfFormat](using
+    tt: TypeTest[RdfFormat, F],
 ) extends JellyCommand[T]:
 
   override final def group = "rdf"

src/main/scala/eu/neverblink/jelly/cli/command/rdf/RdfToJelly.scala

@@ -55,7 +55,7 @@ case class RdfToJellyOptions(
     delimited: Boolean = true,
 ) extends HasJellyCommandOptions
 
-object RdfToJelly extends RdfTranscodeCommand[RdfToJellyOptions, RdfFormat.Readable]:
+object RdfToJelly extends RdfSerDesCommand[RdfToJellyOptions, RdfFormat.Readable]:
 
   override def names: List[List[String]] = List(
     List("rdf", "to-jelly"),

src/main/scala/eu/neverblink/jelly/cli/command/rdf/RdfTranscode.scala

@@ -0,0 +1,79 @@
+package eu.neverblink.jelly.cli.command.rdf
+
+import caseapp.*
+import eu.neverblink.jelly.cli.*
+import eu.neverblink.jelly.cli.command.rdf.util.*
+import eu.ostrzyciel.jelly.core.proto.v1.RdfStreamOptions
+import eu.ostrzyciel.jelly.core.{JellyOptions, ProtoTranscoder}
+
+import java.io.{InputStream, OutputStream}
+
+@HelpMessage(
+  "Quickly transcodes the input Jelly file into another Jelly file.\n" +
+    "If no input file is specified, the input is read from stdin.\n" +
+    "The input may be a concatenation of multiple Jelly streams.\n" +
+    "Currently only frame-by-frame transcoding is supported.\n" +
+    "The output's options must be greater than or equal to the input options.\n" +
+    "Note: this command works in a streaming manner and scales well to large files.",
+)
+@ArgsName("<file-to-transcode>")
+case class RdfTranscodeOptions(
+    @Recurse
+    common: JellyCommandOptions = JellyCommandOptions(),
+    @HelpMessage(
+      "Output file to write the Jelly data to. If not specified, the output is written to stdout.",
+    )
+    @ExtraName("to") outputFile: Option[String] = None,
+    @Recurse
+    jellySerializationOptions: RdfJellySerializationOptions = RdfJellySerializationOptions(),
+    // TODO: supported input options
+    // TODO: make it possible to not only frame-by-frame transcode, but also regroup the rows
+    // TODO: make it possible to do full transcoding (with Jena parsing)
+) extends HasJellyCommandOptions
+
+object RdfTranscode extends JellyCommand[RdfTranscodeOptions]:
+  override def names: List[List[String]] = List(
+    List("rdf", "transcode"),
+  )
+
+  override final def group = "rdf"
+
+  override def doRun(options: RdfTranscodeOptions, remainingArgs: RemainingArgs): Unit =
+    val outOpt = options.jellySerializationOptions.asRdfStreamOptions
+    val (inputStream, outputStream) =
+      getIoStreamsFromOptions(remainingArgs.remaining.headOption, options.outputFile)
+    jellyToJelly(inputStream, outputStream, outOpt)
+
+  /** Transcodes the input Jelly stream into another Jelly stream.
+    * @param inputStream
+    *   input
+    * @param outputStream
+    *   output
+    * @param outOpt
+    *   user-defined options for the output
+    */
+  private def jellyToJelly(
+      inputStream: InputStream,
+      outputStream: OutputStream,
+      outOpt: RdfStreamOptions,
+  ): Unit =
+    val in = JellyUtil.iterateRdfStream(inputStream).buffered
+    val head = in.head
+    if head.rows.isEmpty then throw CriticalException("Empty input stream")
+    if !head.rows.head.row.isOptions then
+      throw CriticalException("First input row is not an options row")
+    val inOpt = head.rows.head.row.options
+
+    val transcoder = ProtoTranscoder.fastMergingTranscoder(
+      supportedInputOptions = JellyOptions.defaultSupportedOptions,
+      outputOptions = outOpt.copy(
+        // There is no way to specify the physical type with options currently.
+        // Just use the one from the input.
+        physicalType = inOpt.physicalType,
+        logicalType =
+          if outOpt.logicalType.isUnspecified then inOpt.logicalType else outOpt.logicalType,
+      ),
+    )
+
+    in.map(transcoder.ingestFrame)
+      .foreach(_.writeDelimitedTo(outputStream))

src/test/scala/eu/neverblink/jelly/cli/command/rdf/RdfTranscodeSpec.scala

@@ -0,0 +1,81 @@
+package eu.neverblink.jelly.cli.command.rdf
+
+import eu.neverblink.jelly.cli.command.helpers.TestFixtureHelper
+import eu.neverblink.jelly.cli.command.rdf.util.{JellyUtil, RdfJellySerializationOptions}
+import eu.ostrzyciel.jelly.core.proto.v1.*
+import org.scalatest.matchers.should.Matchers
+import org.scalatest.wordspec.AnyWordSpec
+
+import java.io.{ByteArrayInputStream, FileInputStream}
+
+class RdfTranscodeSpec extends AnyWordSpec, Matchers, TestFixtureHelper:
+  protected val testCardinality: Int = 36
+
+  private val defaultOpt = RdfJellySerializationOptions().asRdfStreamOptions
+
+  private def checkOutputWithDefaultOptions(b: Array[Byte]): Unit =
+    val outF = RdfStreamFrame.parseDelimitedFrom(ByteArrayInputStream(b))
+    outF.get.rows.size should be > 36
+    val opt = outF.get.rows.head.row.options
+    opt.physicalType should be(PhysicalStreamType.TRIPLES)
+    opt.logicalType should be(LogicalStreamType.FLAT_TRIPLES)
+    opt.maxNameTableSize should be(defaultOpt.maxNameTableSize)
+    opt.maxPrefixTableSize should be(defaultOpt.maxPrefixTableSize)
+    opt.maxDatatypeTableSize should be(defaultOpt.maxDatatypeTableSize)
+    opt.rdfStar should be(defaultOpt.rdfStar)
+    opt.generalizedStatements should be(defaultOpt.generalizedStatements)
+
+  "transcode input file with no additional options" in withFullJellyFile { j =>
+    RdfTranscode.runTestCommand(List("rdf", "transcode", j))
+    val outB = RdfTranscode.getOutBytes
+    checkOutputWithDefaultOptions(outB)
+  }
+
+  "transcode stdin with no additional options" in withFullJellyFile { j =>
+    val inBytes = FileInputStream(j).readAllBytes()
+    RdfTranscode.setStdIn(ByteArrayInputStream(inBytes))
+    RdfTranscode.runTestCommand(List("rdf", "transcode"))
+    val outB = RdfTranscode.getOutBytes
+    checkOutputWithDefaultOptions(outB)
+  }
+
+  "transcode input file to output file with no additional options" in withEmptyJellyFile { jOut =>
+    withFullJellyFile { jIn =>
+      RdfTranscode.runTestCommand(List("rdf", "transcode", "--to", jOut, jIn))
+      val outB = FileInputStream(jOut).readAllBytes()
+      checkOutputWithDefaultOptions(outB)
+    }
+  }
+
+  "merge 100 input streams" in withFullJellyFile { j =>
+    val inBytes1 = FileInputStream(j).readAllBytes()
+    val inBytes = (0 until 100).map(_ => inBytes1).reduce(_ ++ _)
+    RdfTranscode.setStdIn(ByteArrayInputStream(inBytes))
+    RdfTranscode.runTestCommand(List("rdf", "transcode"))
+    val outB = RdfTranscode.getOutBytes
+    checkOutputWithDefaultOptions(outB)
+    val outFrames = JellyUtil.iterateRdfStream(ByteArrayInputStream(outB)).toSeq
+    outFrames.size should be(100)
+    outFrames.foreach { f =>
+      f.rows.size should be >= testCardinality
+    }
+  }
+
+  "transcode input file with changed output options" in withFullJellyFile { j =>
+    RdfTranscode.runTestCommand(
+      List(
+        "rdf",
+        "transcode",
+        "--opt.max-prefix-table-size=600",
+        "--opt.logical-type=GRAPHS",
+        j,
+      ),
+    )
+    val outB = RdfTranscode.getOutBytes
+    val f = RdfStreamFrame.parseDelimitedFrom(ByteArrayInputStream(outB)).get
+    f.rows.size should be > testCardinality
+    val opt = f.rows.head.row.options
+    opt.maxPrefixTableSize should be(600)
+    opt.physicalType should be(PhysicalStreamType.TRIPLES)
+    opt.logicalType should be(LogicalStreamType.GRAPHS)
+  }