feat(cli): add export and schema subcommands

export writes CSV to stdout; schema prints machine-readable dtype.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: dfa1

cli/src/main/java/io/github/dfa1/vortex/cli/ExportCommand.java

@@ -0,0 +1,38 @@
+package io.github.dfa1.vortex.cli;
+
+import io.github.dfa1.vortex.csv.CsvExporter;
+import io.github.dfa1.vortex.csv.ExportOptions;
+
+import java.io.IOException;
+import java.io.OutputStreamWriter;
+import java.io.Writer;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+final class ExportCommand {
+
+    private ExportCommand() {
+    }
+
+    static int run(String[] args) {
+        if (args.length != 2) {
+            System.err.println("usage: export <file.vortex>");
+            return 1;
+        }
+        Path path = Path.of(args[1]);
+        if (!Files.exists(path)) {
+            System.err.println("file not found: " + path);
+            return 2;
+        }
+        try {
+            Writer stdout = new OutputStreamWriter(System.out, StandardCharsets.UTF_8);
+            CsvExporter.exportCsv(path, stdout, ExportOptions.defaults());
+            stdout.flush();
+            return 0;
+        } catch (IOException e) {
+            System.err.println("error: " + e.getMessage());
+            return 3;
+        }
+    }
+}

cli/src/main/java/io/github/dfa1/vortex/cli/SchemaCommand.java

@@ -0,0 +1,60 @@
+package io.github.dfa1.vortex.cli;
+
+import io.github.dfa1.vortex.core.DType;
+import io.github.dfa1.vortex.io.VortexReader;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+final class SchemaCommand {
+
+    private SchemaCommand() {
+    }
+
+    static int run(String[] args) {
+        if (args.length != 2) {
+            System.err.println("usage: schema <file.vortex>");
+            return 1;
+        }
+        Path path = Path.of(args[1]);
+        if (!Files.exists(path)) {
+            System.err.println("file not found: " + path);
+            return 2;
+        }
+        try (VortexReader reader = VortexReader.open(path)) {
+            System.out.println(formatDType(reader.dtype()));
+            return 0;
+        } catch (IOException e) {
+            System.err.println("error: " + e.getMessage());
+            return 3;
+        }
+    }
+
+    private static String formatDType(DType dtype) {
+        return switch (dtype) {
+            case DType.Struct s -> {
+                var sb = new StringBuilder("struct<");
+                for (int i = 0; i < s.fieldNames().size(); i++) {
+                    if (i > 0) {
+                        sb.append(", ");
+                    }
+                    sb.append(s.fieldNames().get(i)).append(": ").append(formatDType(s.fieldTypes().get(i)));
+                }
+                sb.append('>');
+                yield sb.toString();
+            }
+            case DType.Primitive(var pt, var nullable) -> pt.name() + (nullable ? "?" : "");
+            case DType.Utf8(var nullable) -> "utf8" + (nullable ? "?" : "");
+            case DType.Binary(var nullable) -> "binary" + (nullable ? "?" : "");
+            case DType.Bool(var nullable) -> "bool" + (nullable ? "?" : "");
+            case DType.Null ignored -> "null";
+            case DType.Decimal(var p, var s, var nullable) -> "decimal(" + p + "," + s + ")" + (nullable ? "?" : "");
+            case DType.List(var elem, var nullable) -> "list<" + formatDType(elem) + ">" + (nullable ? "?" : "");
+            case DType.FixedSizeList(var elem, var size, var nullable) ->
+                    "list<" + formatDType(elem) + ">[" + size + "]" + (nullable ? "?" : "");
+            case DType.Extension(var id, var storage, var meta, var nullable) ->
+                    "ext<" + id + ">" + (nullable ? "?" : "");
+        };
+    }
+}

cli/src/main/java/io/github/dfa1/vortex/cli/VortexCli.java

@@ -17,7 +17,9 @@ public static void main(String[] args) {
         }
         int exit = switch (args[0]) {
             case "inspect" -> InspectCommand.run(args);
+            case "export"  -> ExportCommand.run(args);
             case "import"  -> ImportCommand.run(args);
+            case "schema"  -> SchemaCommand.run(args);
             default -> {
                 System.err.println("unknown subcommand: " + args[0]);
                 printUsage(System.err);
@@ -30,6 +32,8 @@ public static void main(String[] args) {
     static void printUsage(PrintStream out) {
         out.println("Usage: java -jar vortex.jar <subcommand> [args]");
         out.println("  inspect <file.vortex>            print file structure");
+        out.println("  export  <file.vortex>            write CSV to stdout");
         out.println("  import  <file.csv> [out.vortex]  convert CSV to Vortex");
+        out.println("  schema  <file.vortex>            print dtype (machine-readable)");
     }
 }