import argparse
import sys

def usage(file):
	print('usage: %s add-comment [-o outfile] [-p port] [-f fingerprint] host comment [infile]' % sys.argv[0])

def add_comment():
	parser = argparse.ArgumentParser(
		description = """Add a comment to entry / entries matching the
		given criteria""",
		# We want to provide help on --help, but the default thing
		# also adds -h, which we don't want
		add_help = False,
		# Display our name with the add-comment
		prog = '% add-comment' % sys.argv[0]
	)

	# --help to get help
	parser.add_argument('--help',
		action = 'help',
		help = 'show this help message and exit'
	)

	# -o can be used to write the results to a file instead of stdout
	parser.add_argument('-o',
		# Given one argument, we open a file of that name and store it
		# to outfile, which will be sys.stdout.buffer otherwise.
		# We use .buffer since we're going to write binary data
		action = 'store',
		dest = 'outfile',
		type = argparse.FileType('wb'),
		default = sys.stdout.buffer,
		# This is what will be displayed in the help after -o
		metavar = 'outfile',
		help = 'write the sshwot file to a given file instead of the stdout'
	)

	# -p/--port for port (default port is 22)
	parser.add_argument('-p', '--port',
		action = 'store',
		dest = 'port',
		# Automatically convert to integer
		type = int,
		help = 'the port associated with the given host'
	)

	# -f/--fingerprint for fingerprint
	parser.add_argument('-f', '--fingerprint',
		action = 'store',
		dest = 'fingerprint',
		help = 'the fingerprint to filter for'
	)

	# Host and comment are required
	parser.add_argument('host',
		help = 'the domain to filter for'
	)
	parser.add_argument('comment',
		help = 'the comment to add to the entries'
	)

	# Input file
	parser.add_argument('infile',
		nargs = '?',
		type = argparse.FileType('rb'),
		# Default to stdin. .buffer is because we do binary I/O
		default = sys.stdin.buffer,
		# The text shown for these in the usage
		help = 'a sshwot file to alter'
	)

	# This automatically parses the command line args for us. If it
	# returns, we have correct arguments
	args = parser.parse_args(sys.argv[2:])

	print(args) #debg

def main():
	if len(sys.argv) < 2:
		usage(sys.stderr)
		sys.exit(1)

	if sys.argv[1] == 'add-comment':
		add_comment()
	else:
		usage(sys.stderr)
		sys.exit(1)

if __name__ == '__main__':
	try:
		main()
	except Exception as err:
		print('Error: %s' % err, file=sys.stderr)
		sys.exit(1)