permissions check, more db helper functions

contest/checks.py

@@ -0,0 +1,15 @@
+from discord.ext import commands
+
+
+def check_permissions(ctx, perms, *, check=all):
+    resolved = ctx.channel.permissions_for(ctx.author)
+    return check(getattr(resolved, name, None) == value for name, value in perms.items())
+
+
+def privileged():
+    def predicate(ctx):
+        return (ctx.guild is not None and ctx.guild.owner_id == ctx.author.id) \
+               or check_permissions(ctx, {'manage_guild': True}) \
+               or check_permissions(ctx, {'administrator': True})
+
+    return commands.check(predicate)

contest/db.py

@@ -76,6 +76,19 @@ class ContestDatabase(object):
         finally:
             await cur.close()
 
+    async def get_submission(self, guild_id: int) -> int:
+        cur = await self.conn.cursor()
+        try:
+            await cur.execute('''SELECT submission FROM guild WHERE id = ?''', [guild_id])
+            return (await cur.fetchone())[0]
+        finally:
+            await cur.close()
+
+    async def set_submission(self, guild_id: int, new_submission: int) -> None:
+        """Updates the submission channel for a specific guild in the database"""
+        await self.conn.execute('''UPDATE guild SET submission = ? WHERE id = ?''', [new_submission, guild_id])
+        await self.conn.commit()
+
     async def teardown_guild(self, guild_id: int) -> None:
         """Removes a guild from the database while completing appropriate teardown actions."""
         await self.conn.execute('''DELETE FROM guild WHERE id = ?''', [guild_id])