CLI arguments for number of relays for concurrent scan and goal (#1)

This commit adds command-line arguments for the tunables.

By @gp2112:

* add argparse and .gitignore
* remove TIMEOUT constant
* remove TIMEOUT and add the right descriptions

.gitignore

@@ -0,0 +1,2 @@
+*.pyz
+torparse/*

src/tor_relay_scanner/scanner.py

@@ -4,14 +4,13 @@ import asyncio
 import random
 import sys
 import urllib.parse
-
+import argparse
 import requests
 
-TIMEOUT = 10.0
-
+DESCRIPTION = "Downloads all Tor Relay IP addresses from onionoo.torproject.org and checks whether random Relays are available."
 
 class TCPSocketConnectChecker:
-    def __init__(self, host, port, timeout=TIMEOUT):
+    def __init__(self, host, port, timeout=10.0):
         self.host = host
         self.port = port
         self.timeout = timeout
@@ -26,7 +25,7 @@ class TCPSocketConnectChecker:
         try:
             # Open connection
             reader, writer = await asyncio.wait_for(
-                asyncio.open_connection(self.host, self.port), TIMEOUT)
+                asyncio.open_connection(self.host, self.port), self.timeout)
             # And close it
             writer.close()
             await writer.wait_closed()
@@ -36,10 +35,12 @@ class TCPSocketConnectChecker:
             self.connection_status = False
             return (False, e)
 
-
 class TorRelayGrabber:
+    def __init__(self, timeout=10.0):
+        self.timeout = timeout
+
     def _grab(self, url):
-        with requests.get(url, timeout=int(TIMEOUT)) as r:
+        with requests.get(url, timeout=int(self.timeout)) as r:
             return r.json()
 
     def grab(self):
@@ -105,14 +106,15 @@ class TorRelay:
         return bool(self.reachable)
 
 
-async def main_async():
-    NUM_RELAYS = 30
-    WORKING_RELAY_NUM_GOAL = 5
+async def main_async(args):
+    NUM_RELAYS = args.num_relays
+    WORKING_RELAY_NUM_GOAL = args.working_relay_num_goal
+    TIMEOUT = args.timeout
 
     print(f"Tor Relay Scanner. Will scan up to {WORKING_RELAY_NUM_GOAL}" +
           " working relays (or till the end)", file=sys.stderr)
     print("Downloading Tor Relay information from onionoo.torproject.org…", file=sys.stderr)
-    relays = TorRelayGrabber().grab_parse()
+    relays = TorRelayGrabber(timeout=TIMEOUT).grab_parse()
     print("Done!", file=sys.stderr)
 
     random.shuffle(relays)
@@ -164,4 +166,9 @@ async def main_async():
 
 
 def main():
-    asyncio.run(main_async())
+    parser = argparse.ArgumentParser(description=DESCRIPTION)
+    parser.add_argument('-n', type=int, dest='num_relays', nargs='?', default=30, help='The number of concurrent relays tested.')
+    parser.add_argument('-g', '--goal', type=int, dest='working_relay_num_goal', nargs='?', default=5, help='Test until at least this number of working relays are found')
+    parser.add_argument('--timeout', type=float, nargs='?', default=10.0, help='socket connection timeout')
+    args = parser.parse_args()
+    asyncio.run(main_async(args))