feat(converters): add parquet to csv conversion with compressor support

tests/converters/parquet.test.ts

@@ -0,0 +1,81 @@
+import { expect, test, describe, mock } from "bun:test";
+import { Writable } from "node:stream";
+
+const mockParquetMetadataAsync = mock(async () => {
+  return {
+    row_groups: [{ num_rows: 1 }],
+  };
+});
+
+const mockParquetRead = mock(
+  async (options: {
+    file: unknown;
+    rowStart: number;
+    rowEnd: number;
+    rowFormat: string;
+    onComplete: (rows: { col1: string }[]) => void;
+  }) => {
+    if (options.onComplete) {
+      options.onComplete([{ col1: "value" }]);
+    }
+    return [];
+  },
+);
+
+const mockCreateWriteStream = mock(() => {
+  return new Writable({
+    write(_chunk, _encoding, callback) {
+      callback();
+    },
+  });
+});
+
+const mockFileHandle = {
+  stat: mock(async () => ({ size: 100 })),
+  read: mock(async (buf: Buffer) => {
+    return { bytesRead: buf.length, buffer: buf };
+  }),
+  close: mock(async () => {}),
+};
+
+mock.module("node:fs/promises", () => ({
+  open: mock(async () => mockFileHandle),
+}));
+
+mock.module("hyparquet", () => {
+  return {
+    parquetMetadataAsync: mockParquetMetadataAsync,
+    parquetRead: mockParquetRead,
+  };
+});
+
+mock.module("node:fs", () => {
+  return {
+    createWriteStream: mockCreateWriteStream,
+  };
+});
+
+import { convert } from "../../src/converters/parquet";
+
+describe("parquet converter", () => {
+  test("convert resolves when process succeeds", async () => {
+    const result = await convert("input.parquet", "parquet", "csv", "output.csv");
+    expect(result).toBe("Done");
+  });
+
+  test("convert rejects when parquetRead fails", async () => {
+    mockParquetRead.mockRejectedValueOnce(new Error("Read error"));
+
+    await expect(convert("invalid.parquet", "parquet", "csv", "output.csv")).rejects.toThrow(
+      "Read error",
+    );
+  });
+
+  test("convert rejects when metadata fails", async () => {
+    mockParquetMetadataAsync.mockRejectedValueOnce(new Error("Metadata error"));
+
+    await expect(convert("invalid.parquet", "parquet", "csv", "output.csv")).rejects.toThrow(
+      "Metadata error",
+    );
+  });
+});