Code refactoring

- Code refactoring
- Fix a bug that the other player will not become the host of the room at once, when the player disconnect in link play.

> Maybe add many unknown bugs. XD
> The song database `arcsong.db` will not used in the future. You can use a tool in `tool` folder to import old data.

latest version/core/song.py

@@ -1,7 +1,42 @@
+from .error import NoData
+
+
 class Chart:
     # defnum: chart const * 10
 
-    def __init__(self, song_id: str = None, difficulty: int = None, defnum: int = None) -> None:
+    def __init__(self, c=None, song_id: str = None, difficulty: int = None) -> None:
+        self.c = c
+        self.set_chart(song_id, difficulty)
+        self.defnum: int = None
+
+    @property
+    def chart_const(self) -> float:
+        return self.defnum / 10 if self.defnum else -1
+
+    @property
+    def song_id_difficulty(self) -> str:
+        return '%s%d' % (self.song_id, self.difficulty)
+
+    def set_chart(self, song_id: str = None, difficulty: int = None) -> None:
         self.song_id = song_id
-        self.difficulty = difficulty
-        self.defnum = defnum
+        self.difficulty = int(difficulty) if difficulty is not None else None
+
+    def select(self) -> None:
+        self.c.execute(
+            '''select rating_pst, rating_prs, rating_ftr, rating_byn from chart where song_id=:a''', {'a': self.song_id})
+        x = self.c.fetchone()
+        if x is None:
+            raise NoData('The song `%s` does not exist.' % self.song_id)
+        self.defnum = x[self.difficulty]
+
+
+class Song:
+    def __init__(self, c=None, song_id=None) -> None:
+        self.c = c
+        self.song_id: str = song_id
+        self.name: str = None
+        self.charts: dict = None
+
+    def insert(self) -> None:
+        self.c.execute(
+            '''insert into chart values (?,?,?,?,?,?)''', (self.song_id, self.name, self.charts[0].defnum, self.charts[1].defnum, self.charts[2].defnum, self.charts[3].defnum))