Introduce the --seed flag

This patch makes each map generated from a random seed, the length of
the seed is controllerd by config.seed_length.

Since each run is seeded, it is possible to use a custom seed to start
the server, using:
```
$ ./rose-server --seed <seed>
```

This makes every run reproducible for debugging and testing.

Co-authored-by: Masha Shtivelberg <mashashtiv@gmail.com>
Co-authored-by: Zoe Sasportas <zoesasportas@gmail.com>

rose/common/config.py

@@ -11,6 +11,7 @@
 game_duration = 60
 number_of_cars = 4
 is_track_random = True
+seed_length = 5
 
 # Matrix
 

rose/common/obstacles.py

@@ -1,7 +1,5 @@
 """ Game obstacles """
 
-import random
-
 NONE = ""  # NOQA
 CRACK = "crack"  # NOQA
 TRASH = "trash"  # NOQA
@@ -11,7 +9,3 @@
 BARRIER = "barrier"  # NOQA
 
 ALL = (NONE, CRACK, TRASH, PENGUIN, BIKE, WATER, BARRIER)
-
-
-def get_random_obstacle():
-    return random.choice(ALL)

rose/server/game.py

@@ -17,9 +17,10 @@ class Game(object):
     Implements the server for the car race
     """
 
-    def __init__(self):
+    def __init__(self, seed):
         self.hub = None
-        self.track = track.Track()
+        self.rng = random.Random(seed)
+        self.track = track.Track(seed=seed)
         self.looper = task.LoopingCall(self.loop)
         self.players = {}
         self.free_cars = set(range(config.number_of_cars))
@@ -68,9 +69,9 @@ def add_player(self, name):
             raise error.PlayerExists(name)
         if not self.free_cars:
             raise error.TooManyPlayers()
-        car = random.choice(tuple(self.free_cars))
+        car = self.rng.choice(tuple(self.free_cars))
         self.free_cars.remove(car)
-        lane = random.choice(tuple(self.free_lanes))
+        lane = self.rng.choice(tuple(self.free_lanes))
         self.free_lanes.remove(lane)
         log.info("add player: %r, lane: %r, car: %r", name, lane, car)
         self.players[name] = player.Player(name, car, lane)

rose/server/main.py

@@ -1,6 +1,8 @@
+import random
 import socket
 import logging
 import argparse
+import string
 
 from twisted.internet import reactor
 from twisted.web import server, static
@@ -25,6 +27,13 @@ def main():
         help="Definition of driver tracks: random or same."
         "If not specified, random will be used.",
     )
+    parser.add_argument(
+        "--seed",
+        "-s",
+        dest="seed",
+        default="",
+        help="Optional, use a custom seed for the map generation",
+    )
 
     args = parser.parse_args()
     """
@@ -37,8 +46,16 @@ def main():
     else:
         config.is_track_random = True
 
+    if args.seed:
+        seed = args.seed
+    else:
+        seed = generate_seed(config.seed_length)
+
+    log.info(f"Seed for map: {seed}")
+    g = game.Game(seed=seed)
+
     log.info("starting server")
-    g = game.Game()
+
     h = net.Hub(g)
     reactor.listenTCP(config.game_port, net.PlayerFactory(h))
     root = static.File(config.web_root)
@@ -51,3 +68,7 @@ def main():
     site = server.Site(root)
     reactor.listenTCP(config.web_port, site)
     reactor.run()
+
+
+def generate_seed(seed_length=5):
+    return ''.join(random.choice(string.ascii_lowercase) for _ in range(seed_length))

rose/server/track.py

@@ -3,8 +3,9 @@
 
 
 class Track(object):
-    def __init__(self):
+    def __init__(self, seed):
         self._matrix = None
+        self.rng = random.Random(seed)
         self.reset()
 
     # Game state interface
@@ -53,15 +54,18 @@ def _generate_row(self):
         Otherwise, the tracks will be identical.
         """
         row = [obstacles.NONE] * config.matrix_width
-        obstacle = obstacles.get_random_obstacle()
+        obstacle = self.get_random_obstacle()
         if config.is_track_random:
             for lane in range(config.max_players):
                 low = lane * config.cells_per_player
                 high = low + config.cells_per_player
-                cell = random.choice(range(low, high))
+                cell = self.rng.choice(range(low, high))
                 row[cell] = obstacle
         else:
-            cell = random.choice(range(0, config.cells_per_player))
+            cell = self.rng.choice(range(0, config.cells_per_player))
             for lane in range(config.max_players):
                 row[cell + lane * config.cells_per_player] = obstacle
         return row
+
+    def get_random_obstacle(self):
+        return self.rng.choice(obstacles.ALL)