feat(cli): add progress bar and compression ratio to import

ProgressListener callback in ImportOptions/CsvImporter fires per chunk.
ImportCommand renders bar on stderr and prints CSV→vortex size savings.

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

Author: dfa1

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

@@ -1,6 +1,7 @@
 package io.github.dfa1.vortex.cli;
 
 import io.github.dfa1.vortex.csv.CsvImporter;
+import io.github.dfa1.vortex.csv.ImportOptions;
 
 import java.io.IOException;
 import java.nio.file.Files;
@@ -22,16 +23,47 @@ static int run(String[] args) {
             return 2;
         }
         Path vortexPath = args.length == 3 ? Path.of(args[2]) : deriveOutputPath(csvPath);
+        ImportOptions options = ImportOptions.defaults()
+                .withProgressListener(ImportCommand::renderProgress);
         try {
-            CsvImporter.importCsv(csvPath, vortexPath);
-            System.out.println("written: " + vortexPath);
+            CsvImporter.importCsv(csvPath, vortexPath, options);
+            clearProgress();
+            long csvBytes = Files.size(csvPath);
+            long vortexBytes = Files.size(vortexPath);
+            double savings = 1.0 - (double) vortexBytes / csvBytes;
+            System.out.printf("written: %s  (%s → %s, %.1f%% smaller)%n",
+                    vortexPath, formatBytes(csvBytes), formatBytes(vortexBytes), savings * 100);
             return 0;
         } catch (IOException e) {
+            clearProgress();
             System.err.println("error: " + e.getMessage());
             return 3;
         }
     }
 
+    private static void renderProgress(long done, long total) {
+        int pct = total > 0 ? (int) (done * 100L / total) : 100;
+        int filled = pct * 30 / 100;
+        String bar = "=".repeat(filled) + (filled < 30 ? ">" : "") + " ".repeat(Math.max(0, 29 - filled));
+        System.err.printf("\r  [%s] %3d%%  %,d / %,d rows", bar, pct, done, total);
+        System.err.flush();
+    }
+
+    private static void clearProgress() {
+        System.err.printf("\r%60s\r", "");
+        System.err.flush();
+    }
+
+    private static String formatBytes(long bytes) {
+        if (bytes < 1024L) {
+            return bytes + " B";
+        }
+        if (bytes < 1024L * 1024) {
+            return String.format("%.1f KB", bytes / 1024.0);
+        }
+        return String.format("%.1f MB", bytes / (1024.0 * 1024));
+    }
+
     private static Path deriveOutputPath(Path csvPath) {
         String name = csvPath.getFileName().toString();
         if (name.endsWith(".csv")) {

csv/src/main/java/io/github/dfa1/vortex/csv/CsvImporter.java

@@ -61,9 +61,13 @@ public static void importCsv(Path csvPath, Path vortexPath, ImportOptions option
                 StandardOpenOption.TRUNCATE_EXISTING);
              VortexWriter writer = VortexWriter.create(channel, schema, WriteOptions.defaults())) {
             int chunkSize = options.chunkSize();
-            for (int start = 0; start < dataRows.size(); start += chunkSize) {
-                int end = Math.min(start + chunkSize, dataRows.size());
+            int total = dataRows.size();
+            for (int start = 0; start < total; start += chunkSize) {
+                int end = Math.min(start + chunkSize, total);
                 writer.writeChunk(buildChunk(schema, dataRows.subList(start, end)));
+                if (options.progressListener() != null) {
+                    options.progressListener().onProgress(end, total);
+                }
             }
         }
     }

csv/src/main/java/io/github/dfa1/vortex/csv/ImportOptions.java

@@ -7,15 +7,20 @@ public record ImportOptions(
         char delimiter,
         int chunkSize,
         boolean hasHeader,
-        DType.Struct schema
+        DType.Struct schema,
+        ProgressListener progressListener
 ) {
     public static ImportOptions defaults() {
-        return new ImportOptions(',', 65_536, true, null);
+        return new ImportOptions(',', 65_536, true, null, null);
     }
 
     /// Override the inferred schema. The struct's field names become column names;
     /// types control how each CSV column is parsed (positionally).
     public ImportOptions withSchema(DType.Struct overrideSchema) {
-        return new ImportOptions(delimiter, chunkSize, hasHeader, overrideSchema);
+        return new ImportOptions(delimiter, chunkSize, hasHeader, overrideSchema, progressListener);
+    }
+
+    public ImportOptions withProgressListener(ProgressListener listener) {
+        return new ImportOptions(delimiter, chunkSize, hasHeader, schema, listener);
     }
 }

csv/src/main/java/io/github/dfa1/vortex/csv/ProgressListener.java

@@ -0,0 +1,7 @@
+package io.github.dfa1.vortex.csv;
+
+/// Callback invoked after each chunk is written during CSV import.
+@FunctionalInterface
+public interface ProgressListener {
+    void onProgress(long rowsDone, long rowsTotal);
+}

csv/src/test/java/io/github/dfa1/vortex/csv/CsvImporterTest.java

@@ -61,7 +61,7 @@ void usesCustomDelimiter(@TempDir Path tmp) throws Exception {
         Path vortex = tmp.resolve("data.vortex");
 
         // When
-        CsvImporter.importCsv(csv, vortex, new ImportOptions(';', 65_536, true, null));
+        CsvImporter.importCsv(csv, vortex, new ImportOptions(';', 65_536, true, null, null));
 
         // Then
         try (VortexReader reader = VortexReader.open(vortex)) {
@@ -78,7 +78,7 @@ void generatesHeadersWhenMissing(@TempDir Path tmp) throws Exception {
         Path vortex = tmp.resolve("data.vortex");
 
         // When
-        CsvImporter.importCsv(csv, vortex, new ImportOptions(',', 65_536, false, null));
+        CsvImporter.importCsv(csv, vortex, new ImportOptions(',', 65_536, false, null, null));
 
         // Then
         try (VortexReader reader = VortexReader.open(vortex)) {