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.

tools/update_song.py

@@ -0,0 +1,60 @@
+import sqlite3
+
+class Connect():
+    # 数据库连接类，上下文管理
+
+    def __init__(self, file_path='./arcaea_database.db'):
+        """
+            数据库连接，默认连接arcaea_database.db\ 
+            接受：文件路径\ 
+            返回：sqlite3连接操作对象
+        """
+        self.file_path = file_path
+
+    def __enter__(self):
+        self.conn = sqlite3.connect(self.file_path)
+        self.c = self.conn.cursor()
+        return self.c
+
+    def __exit__(self, exc_type, exc_val, exc_tb) -> bool:
+        if exc_type is not None:
+            if self.conn:
+                self.conn.rollback()
+
+        if self.conn:
+            self.conn.commit()
+            self.conn.close()
+
+        return True
+
+
+def insert(cursor, song_id, name, a, b, c, d):
+    '''Insert a new song into database.'''
+    cursor.execute(
+        '''select exists(select * from chart where song_id=?)''', (song_id, ))
+    if cursor.fetchone()[0]:
+        return None
+    cursor.execute(
+        '''insert into chart values (?,?,?,?,?,?)''', (song_id, name, a, b, c, d))
+
+
+def old_to_new():
+    '''Update old database to new database.'''
+    with Connect('./arcsong.db') as c:
+        c.execute(
+            '''select sid, name_en, rating_pst, rating_prs, rating_ftr, rating_byn from songs''')
+        data = c.fetchall()
+    with Connect() as c:
+        for x in data:
+            insert(c, x[0], x[1], x[2], x[3], x[4], x[5])
+
+
+def main():
+    old_to_new()
+
+
+if __name__ == '__main__':
+    main()
+    print('Done.')
+    input()
+    exit()