import argparse
import os
import sys

import process_known_hosts
import write_file

def main():
	# TODO: Provide a way to add comments
	parser = argparse.ArgumentParser(
		description = """Export .ssh/known_hosts as a sshwot file.
		By default the output is written to stdout.""",
		# We want to provide help on --help, but the default thing
		# also adds -h, which we don't want
		add_help = False
	)

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

	# -i and --include-ips can be used to not ignore the IPs in the file
	parser.add_argument('-i', '--include-ips',
		# We store a constant into a property depending on whether
		# this argument is used or not
		action = 'store_const',
		# The property is ignore_ips (to match the argument of
		# process_known_hosts.process_file()). Store False if this
		# switch is used and True otherwise
		dest = 'ignore_ips', const = False, default = True,
		help = 'includes IPs in addition to domain names'
	)

	# -o can be used to write the .sshwot thing 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'
	)

	try:
		homedir = os.environ['HOME']
	except KeyError as err:
		raise KeyError('$HOME is not set') from err

	# The input file
	# Default to ~/.ssh/known_hosts
	parser.add_argument('infile',
		nargs = '?',
		default = os.path.join(homedir, '.ssh/known_hosts'),
		help = 'a file in .ssh/known_hosts format'
	)

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

	with open(args.infile, 'r') as f:
		known_host_entries = process_known_hosts.process_file(f, args.ignore_ips)

	# Convert to the entry format for .sshwot files
	entries = []
	for known_hosts_entry in known_host_entries:
		entries.append(process_known_hosts.known_hosts_to_entry(known_hosts_entry))

	write_file.write(args.outfile, entries)

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