allow connection to offline mode servers without a password

mosfet/bot.py

@@ -3,14 +3,15 @@ if __name__ == '__main__':
     exit(1)
 
 import os
+import sys
 import time
 import importlib
 from math import floor, ceil
 from copy import copy
 
-USERNAME = os.environ['USERNAME']
-PASSWORD = os.environ['PASSWORD']
-SERVER = os.environ['SERVER']
+USERNAME = os.getenv('USERNAME')
+PASSWORD = os.getenv('PASSWORD')
+SERVER = os.getenv('SERVER')
 PORT = int(os.environ.get('PORT', 25565))
 
 from . import monkey_patch # must be before any possible pyCraft imports
@@ -249,15 +250,22 @@ def bot(global_state):
     if not g.mcdata:
         g.mcdata = DataManager('./minecraft_data')
 
-    if not g.connection:
-        auth_token = authentication.AuthenticationToken()
-        try:
-            auth_token.authenticate(USERNAME, PASSWORD)
-        except YggdrasilError as e:
-            print(e)
-            sys.exit()
-        print("Logged in as %s..." % auth_token.username)
-        g.connection = Connection(SERVER, PORT, auth_token=auth_token)
+    if not SERVER:
+        print('You must specify a server to connect to.')
+        sys.exit()
+    elif not g.connection:
+        if USERNAME and PASSWORD:
+            auth_token = authentication.AuthenticationToken()
+            try:
+                auth_token.authenticate(USERNAME, PASSWORD)
+            except YggdrasilError as e:
+                print(e)
+                sys.exit()
+            print("Logged in as %s..." % auth_token.username)
+            g.connection = Connection(SERVER, PORT, auth_token=auth_token)
+        elif USERNAME:
+            print('No password provided, attempting to connect in offline mode...')
+            g.connection = Connection(SERVER, PORT, username=USERNAME)
 
         g.chunks = ChunksManager(g.mcdata)