python: Implement main module

This commit implements the python main cli module. Currently it supports
a preliminary set of command line options but should be able to
successfully generate passwords.

python/passgeny/__main__.py

@@ -0,0 +1,37 @@
+import argparse
+import getpass
+import os
+import sys
+
+from passgeny import passgeny
+
+pargs = argparse.ArgumentParser("Passgeny - Password Generator")
+pargs.add_argument("domain", help="Domain or unique site identifier")
+pargs.add_argument("user", help="Username or unique user identifier")
+pargs.add_argument("tokens", nargs='*', help="Additional tokens")
+pargs.add_argument("--verbose", "-v", action='store_true', help="Verbose")
+pargs.add_argument("--pattern", "-p", help="Set pattern")
+
+pargs_pass = pargs.add_mutually_exclusive_group()
+pargs_pass.add_argument("--stdin", "-s", action='store_true', help="Read password from stdin")
+pargs_pass.add_argument("--env", "-e", help="Read password from environment")
+
+popt = pargs.parse_args()
+
+# Read master password
+if popt.env:
+    mpw = os.getenv(popt.env)
+    if mpw is None:
+        raise Exception("Environment {} not defined.".format(popt.env))
+elif popt.stdin:
+    mpw = sys.stdin.readline().rstrip('\n\r')
+else:
+    mpw = getpass.getpass("Master password: ")
+
+pg = passgeny.Passgeny(mpw)
+del mpw
+
+if popt.pattern:
+    pg.set_pattern(popt.pattern)
+
+print(pg.generate(popt.domain, popt.user, *popt.tokens))