rework dataset function and class structure

server/dataset/DatasetExporter.py

@@ -1,15 +1,15 @@
 from pathlib import Path
 import argparse, json
 
+from server.dataset.DatasetIO import DatasetIO
+
 class DatasetExporter:
   def __init__(self, input_dir:str, output_file:str):
     self.input_dir = Path(input_dir)
     self.output_file = Path(output_file)
 
   def _iter_game_files(self):
-    if not self.input_dir.exists():
-      return []
-    return sorted(self.input_dir.rglob("*.json"))
+    return DatasetIO.list_directory_files(self.input_dir, directory_pattern="*.json")
 
   def _extract_samples(self, payload:dict, source_file:Path):
     dataset = payload.get("dataset", {})
@@ -37,7 +37,7 @@ class DatasetExporter:
     self.output_file.parent.mkdir(parents=True, exist_ok=True)
 
     sample_count = 0
-    with self.output_file.open("w", encoding="utf-8") as output:
+    with DatasetIO.open_text(self.output_file, "w") as output:
       for game_file in game_files:
         with game_file.open("r", encoding="utf-8") as source:
           payload = json.load(source)