internal(fs): add js support

fs_sync/fs_sync_js.mbt

@@ -0,0 +1,82 @@
+// Copyright 2025 International Digital Economy Academy
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+///|
+extern "js" fn read_file_ffi(path : String) -> Int =
+  #| function(path) {
+  #|   fs = require('fs');
+  #|   try {
+  #|     const content = fs.readFileSync(path);
+  #|     globalThis.fileContent = content;
+  #|     return 0;
+  #|   } catch (error) {
+  #|     globalThis.errorMessage = error.message;
+  #|     return -1;
+  #|   }
+  #| }
+
+///|
+extern "js" fn write_file_ffi(path : String, content : Bytes) -> Int =
+  #| function(path, content) {
+  #|   fs = require('fs');
+  #|   try {
+  #|     fs.writeFileSync(path, Buffer.from(content));
+  #|     return 0;
+  #|   } catch (error) {
+  #|     globalThis.errorMessage = error.message;
+  #|     return -1;
+  #|   }
+  #| }
+
+///|
+extern "js" fn get_file_content_ffi() -> FixedArray[Byte] =
+  #| function() {
+  #|   return globalThis.fileContent;
+  #| }
+
+///|
+extern "js" fn get_error_message_ffi() -> String =
+  #| function() {
+  #|   return globalThis.errorMessage || '';
+  #| }
+
+///|
+fn read_file_to_bytes_internal(path : String) -> Bytes! {
+  let res = read_file_ffi(path)
+  if res == -1 {
+    raise IOError(get_error_message_ffi())
+  }
+  let content = get_file_content_ffi()
+  Bytes::from_iter(content.iter())
+}
+
+fn read_file_to_string_internal(path : String, encoding~ : String = "utf8") -> String! {
+  guard encoding == "utf8" else { raise IOError("Unsupported encoding: \{encoding}, only utf8 is supported for now") }
+  let bytes = read_file_to_bytes_internal!(path)
+  utf8_bytes_to_mbt_string(bytes)
+}
+
+///|
+fn write_bytes_to_file_internal(path : String, content : Bytes) -> Unit! {
+  let res = write_file_ffi(path, content)
+  if res == -1 {
+    raise IOError(get_error_message_ffi())
+  }
+}
+
+fn write_string_to_file_internal(path : String, content : String, encoding~ : String = "utf8") -> Unit! {
+  guard encoding == "utf8" else { raise IOError("Unsupported encoding: \{encoding}, only utf8 is supported for now") }
+  let bytes = mbt_string_to_utf8_bytes(content, false)
+  write_bytes_to_file_internal!(path, bytes)
+}