directory_test(async (t, root) => {
  const handle = await createEmptyFile(t, 'empty_blob', root);
  const stream = await handle.createWritable();

  await stream.write(new Blob([]));
  await stream.close();

  assert_equals(await getFileContents(handle), '');
  assert_equals(await getFileSize(handle), 0);
}, 'write() with an empty blob to an empty file');

directory_test(async (t, root) => {
  const handle = await createEmptyFile(t, 'valid_blob', root);
  const stream = await handle.createWritable();

  await stream.write(new Blob(['1234567890']));
  await stream.close();

  assert_equals(await getFileContents(handle), '1234567890');
  assert_equals(await getFileSize(handle), 10);
}, 'write() a blob to an empty file');

directory_test(async (t, root) => {
  const handle = await createEmptyFile(t, 'write_param_empty', root);
  const stream = await handle.createWritable();

  await stream.write({type: 'write', data: '1234567890'});
  await stream.close();

  assert_equals(await getFileContents(handle), '1234567890');
  assert_equals(await getFileSize(handle), 10);
}, 'write() with WriteParams without position to an empty file');

directory_test(async (t, root) => {
  const handle = await createEmptyFile(t, 'string_zero_offset', root);
  const stream = await handle.createWritable();

  await stream.write({type: 'write', position: 0, data: '1234567890'});
  await stream.close();

  assert_equals(await getFileContents(handle), '1234567890');
  assert_equals(await getFileSize(handle), 10);
}, 'write() a string to an empty file with zero offset');

directory_test(async (t, root) => {
  const handle = await createEmptyFile(t, 'blob_zero_offset', root);
  const stream = await handle.createWritable();

  await stream.write({type: 'write', position: 0, data: new Blob(['1234567890'])});
  await stream.close();

  assert_equals(await getFileContents(handle), '1234567890');
  assert_equals(await getFileSize(handle), 10);
}, 'write() a blob to an empty file with zero offset');

directory_test(async (t, root) => {
  const handle = await createEmptyFile(t, 'write_appends', root);
  const stream = await handle.createWritable();

  await stream.write('12345');
  await stream.write('67890');
  await stream.close();

  assert_equals(await getFileContents(handle), '1234567890');
  assert_equals(await getFileSize(handle), 10);
}, 'write() called consecutively appends');

directory_test(async (t, root) => {
  const handle = await createEmptyFile(t, 'write_appends_object_string', root);
  const stream = await handle.createWritable();

  await stream.write('12345');
  await stream.write({type: 'write', data: '67890'});
  await stream.close();

  assert_equals(await getFileContents(handle), '1234567890');
  assert_equals(await getFileSize(handle), 10);
}, 'write() WriteParams without position and string appends');

directory_test(async (t, root) => {
  const handle = await createEmptyFile(t, 'write_appends_object_blob', root);
  const stream = await handle.createWritable();

  await stream.write('12345');
  await stream.write({type: 'write', data: new Blob(['67890'])});
  await stream.close();

  assert_equals(await getFileContents(handle), '1234567890');
  assert_equals(await getFileSize(handle), 10);
}, 'write() WriteParams without position and blob appends');

directory_test(async (t, root) => {
  const handle = await createEmptyFile(t, 'string_with_offset', root);
  const stream = await handle.createWritable();

  await stream.write('1234567890');
  await stream.write({type: 'write', position: 4, data: 'abc'});
  await stream.close();

  assert_equals(await getFileContents(handle), '1234abc890');
  assert_equals(await getFileSize(handle), 10);
}, 'write() called with a string and a valid offset');

directory_test(async (t, root) => {
const handle = await createEmptyFile(t, 'blob_with_offset', root);
const stream = await handle.createWritable();

await stream.write('1234567890');
await stream.write({type: 'write', position: 4, data: new Blob(['abc'])});
await stream.close();

assert_equals(await getFileContents(handle), '1234abc890');
assert_equals(await getFileSize(handle), 10);
}, 'write() called with a blob and a valid offset');

directory_test(async (t, root) => {
  const handle = await createEmptyFile(t, 'bad_offset', root);
  const stream = await handle.createWritable();

  await stream.write({type: 'write', position: 4, data: new Blob(['abc'])});
  await stream.close();

  assert_equals(await getFileContents(handle), '\0\0\0\0abc');
  assert_equals(await getFileSize(handle), 7);
}, 'write() called with an offset beyond the end of the file');

directory_test(async (t, root) => {
  const handle = await createEmptyFile(t, 'empty_string', root);
  const stream = await handle.createWritable();

  await stream.write('');
  await stream.close();
  assert_equals(await getFileContents(handle), '');
  assert_equals(await getFileSize(handle), 0);
}, 'write() with an empty string to an empty file');

directory_test(async (t, root) => {
  const handle = await createEmptyFile(t, 'valid_utf8_string', root);
  const stream = await handle.createWritable();

  await stream.write('foo🤘');
  await stream.close();
  assert_equals(await getFileContents(handle), 'foo🤘');
  assert_equals(await getFileSize(handle), 7);
}, 'write() with a valid utf-8 string');

directory_test(async (t, root) => {
  const handle = await createEmptyFile(t, 'string_with_unix_line_ending', root);
  const stream = await handle.createWritable();

  await stream.write('foo\n');
  await stream.close();
  assert_equals(await getFileContents(handle), 'foo\n');
  assert_equals(await getFileSize(handle), 4);
}, 'write() with a string with unix line ending preserved');

directory_test(async (t, root) => {
  const handle =
      await createEmptyFile(t, 'string_with_windows_line_ending', root);
  const stream = await handle.createWritable();

  await stream.write('foo\r\n');
  await stream.close();
  assert_equals(await getFileContents(handle), 'foo\r\n');
  assert_equals(await getFileSize(handle), 5);
}, 'write() with a string with windows line ending preserved');

directory_test(async (t, root) => {
  const handle = await createEmptyFile(t, 'empty_array_buffer', root);
  const stream = await handle.createWritable();

  const buf = new ArrayBuffer(0);
  await stream.write(buf);
  await stream.close();
  assert_equals(await getFileContents(handle), '');
  assert_equals(await getFileSize(handle), 0);
}, 'write() with an empty array buffer to an empty file');

directory_test(async (t, root) => {
  const handle =
      await createEmptyFile(t, 'valid_string_typed_byte_array', root);
  const stream = await handle.createWritable();

  const buf = new ArrayBuffer(3);
  const intView = new Uint8Array(buf);
  intView[0] = 0x66;
  intView[1] = 0x6f;
  intView[2] = 0x6f;
  await stream.write(buf);
  await stream.close();
  assert_equals(await getFileContents(handle), 'foo');
  assert_equals(await getFileSize(handle), 3);
}, 'write() with a valid typed array buffer');

directory_test(async (t, root) => {
  const dir = await createDirectory(t, 'parent_dir', root);
  const file_name = 'close_fails_when_dir_removed.txt';
  const handle = await createEmptyFile(t, file_name, dir);
  const stream = await handle.createWritable();
  await stream.write('foo');

  await root.removeEntry('parent_dir', {recursive: true});
  await promise_rejects_dom(t, 'NotFoundError', stream.close());
}, 'atomic writes: close() fails when parent directory is removed');

directory_test(async (t, root) => {
  const handle = await createEmptyFile(t, 'atomic_writes.txt', root);
  const stream = await handle.createWritable();
  await stream.write('foox');

  const stream2 = await handle.createWritable();
  await stream2.write('bar');

  assert_equals(await getFileSize(handle), 0);

  await stream2.close();
  assert_equals(await getFileContents(handle), 'bar');
  assert_equals(await getFileSize(handle), 3);

  await stream.close();
  assert_equals(await getFileContents(handle), 'foox');
  assert_equals(await getFileSize(handle), 4);
}, 'atomic writes: writable file streams make atomic changes on close');

directory_test(async (t, root) => {
  const handle = await createEmptyFile(t, 'atomic_write_after_close.txt', root);
  const stream = await handle.createWritable();
  await stream.write('foo');

  await stream.close();
  assert_equals(await getFileContents(handle), 'foo');
  assert_equals(await getFileSize(handle), 3);

  await promise_rejects_js(
      t, TypeError, stream.write('abc'));
}, 'atomic writes: write() after close() fails');

directory_test(async (t, root) => {
  const handle =
      await createEmptyFile(t, 'atomic_truncate_after_close.txt', root);
  const stream = await handle.createWritable();
  await stream.write('foo');

  await stream.close();
  assert_equals(await getFileContents(handle), 'foo');
  assert_equals(await getFileSize(handle), 3);

  await promise_rejects_js(t, TypeError, stream.truncate(0));
}, 'atomic writes: truncate() after close() fails');

directory_test(async (t, root) => {
  const handle = await createEmptyFile(t, 'atomic_close_after_close.txt', root);
  const stream = await handle.createWritable();
  await stream.write('foo');

  await stream.close();
  assert_equals(await getFileContents(handle), 'foo');
  assert_equals(await getFileSize(handle), 3);

  await promise_rejects_js(t, TypeError, stream.close());
}, 'atomic writes: close() after close() fails');

directory_test(async (t, root) => {
  const handle = await createEmptyFile(t, 'there_can_be_only_one.txt', root);
  const stream = await handle.createWritable();
  await stream.write('foo');

  // This test might be flaky if there is a race condition allowing
  // close() to be called multiple times.
  const success_promises =
      [...Array(100)].map(() => stream.close().then(() => 1).catch(() => 0));
  const close_attempts = await Promise.all(success_promises);
  const success_count = close_attempts.reduce((x, y) => x + y);
  assert_equals(success_count, 1);
}, 'atomic writes: only one close() operation may succeed');

directory_test(async (t, root) => {
  const dir = await createDirectory(t, 'parent_dir', root);
  const file_name = 'atomic_writable_file_stream_persists_removed.txt';
  const handle = await createFileWithContents(t, file_name, 'foo', dir);

  const stream = await handle.createWritable();
  await stream.write('bar');

  await dir.removeEntry(file_name);
  await promise_rejects_dom(t, 'NotFoundError', getFileContents(handle));

  await stream.close();
  assert_equals(await getFileContents(handle), 'bar');
  assert_equals(await getFileSize(handle), 3);
}, 'atomic writes: writable file stream persists file on close, even if file is removed');

directory_test(async (t, root) => {
  const handle = await createEmptyFile(t, 'writer_written', root);
  const stream = await handle.createWritable();
  assert_false(stream.locked);
  const writer = stream.getWriter();
  assert_true(stream.locked);

  await writer.write('foo');
  await writer.write(new Blob(['bar']));
  await writer.write({type: 'seek', position: 0});
  await writer.write({type: 'write', data: 'baz'});
  await writer.close();

  assert_equals(await getFileContents(handle), 'bazbar');
  assert_equals(await getFileSize(handle), 6);
}, 'getWriter() can be used');

directory_test(async (t, root) => {
  const handle = await createFileWithContents(
      t, 'content.txt', 'very long string', root);
  const stream = await handle.createWritable();

  await promise_rejects_dom(
      t, "SyntaxError", stream.write({type: 'truncate'}), 'truncate without size');

}, 'WriteParams: truncate missing size param');

directory_test(async (t, root) => {
  const handle = await createEmptyFile(t, 'content.txt', root);
  const stream = await handle.createWritable();

  await promise_rejects_dom(
      t, "SyntaxError", stream.write({type: 'write'}), 'write without data');

}, 'WriteParams: write missing data param');

directory_test(async (t, root) => {
  const handle = await createFileWithContents(
      t, 'content.txt', 'seekable', root);
  const stream = await handle.createWritable();

  await promise_rejects_dom(
      t, "SyntaxError", stream.write({type: 'seek'}), 'seek without position');

}, 'WriteParams: seek missing position param');

directory_test(async (t, root) => {
  const source_file =
      await createFileWithContents(t, 'source_file', 'source data', root);
  const source_blob = await source_file.getFile();
  await root.removeEntry(source_file.name);

  const handle = await createEmptyFile(t, 'invalid_blob_test', root);
  const stream = await handle.createWritable();
  await promise_rejects_dom(t, "NotFoundError", stream.write(source_blob));
  await promise_rejects_js(t, TypeError, stream.close());

  assert_equals(await getFileContents(handle), '');
  assert_equals(await getFileSize(handle), 0);
}, 'write() with an invalid blob to an empty file should reject');