#!/usr/bin/python

import argparse
import sys
import subprocess
import os

""" This script prints to stdout /etc/network/interfaces entries for
    requested interfaces.

    Currently it supports generation of interfaces(5) section for all
    swp interfaces on the system. And also an interface section 
    for a bridge with all swp ports.

    Example use of this script:

    generate the swp_defaults file:
    (bkup existing /etc/network/interfaces.d/swp_defaults file if one exists)

    #generate_interfaces.py -s > /etc/network/interfaces.d/swp_defaults

    User -m option if you want the new swp_defaults to be auto merged
    with the contents from the old file, use -m option

    #generate_interfaces.py -s -m /etc/network/interfaces.d/swp_defaults > /etc/network/interfaces.d/swp_defaults.new

    Include the swp_defaults file in /etc/network/interfaces file
    (if not already there) using the source command as shown below:

    source /etc/network/interfaces.d/swp_defaults

"""

def get_pci_interfaces():
    ports = []
    FNULL = open(os.devnull, 'w')
    try:
        cmd = '(ip -o link show | grep -v "@" | cut -d" " -f2 | sed \'s/:$//\')'
        output = subprocess.check_output(cmd, shell=True).split()
        for interface in output:
            cmd = 'udevadm info -a -p /sys/class/net/%s | grep \'SUBSYSTEMS=="pci"\'' % interface
            try:
                subprocess.check_call(cmd, shell=True, stdout=FNULL)
                ports.append(interface)
            except Exception:
                pass
    except Exception:
        pass
    finally:
        FNULL.close()
    return ports

def get_swp_interfaces():
    porttab_path = '/var/lib/cumulus/porttab'
    ports = []
    try:
        with open(porttab_path, 'r') as f:
            for line in f.readlines():
                line = line.strip()
                if '#' in line:
                    continue
                try:
                    ports.append(line.split()[0])
                except ValueError:
                    continue
    except Exception:
        try:
            ports = get_pci_interfaces()
        except Exception as e:
            print('Error: Unsupported script: %s' % str(e))
            exit(1)
    if not ports:
        print('Error: No ports found in %s' % porttab_path)
        exit(1)
    return ports

def print_swp_defaults_header():
    print('''
# ** This file is autogenerated by /usr/share/doc/ifupdown2/generate_interfaces.py **
#
# This is /etc/network/interfaces section for all available swp
# ports on the system.
#
# To include this file in the main /etc/network/interfaces file,
# copy this file under /etc/network/interfaces.d/ and use the
# source line in the /etc/network/interfaces file.
#
# example entry in /etc/network/interfaces:
#   source /etc/network/interfaces.d/<filename>
#
# See manpage interfaces(5) for details.
''')

def print_bridge_untagged_defaults_header():
    print('''
# ** This file is autogenerated by /usr/share/doc/ifupdown2/generate_interfaces.py **
#
# This is /etc/network/interfaces section for a bridge device with all swp
# ports in the system.
#
# To include this file in the main /etc/network/interfaces file,
# copy this file under /etc/network/interfaces.d/ and use the
# source line in the /etc/network/interfaces file as shown below.
# details.
#
# example entry in /etc/network/interfaces:
#   source /etc/network/interfaces.d/filename
#
# See manpage interfaces(5) for details
''')

def interfaces_print_swp_default(swp_intf):
    outbuf = None
    if args.mergefile:
        try:
            cmd = ['/sbin/ifquery', '%s' %swp_intf, '-i', '%s' %args.mergefile]
            outbuf = subprocess.check_output(cmd, stderr=subprocess.STDOUT)
        except Exception as e:
            # no interface found gen latest
            pass
    if not outbuf:
        outbuf = 'auto %s\niface %s\n\n' %(swp_intf, swp_intf)
    return outbuf

def interfaces_print_swp_defaults(swp_intfs):
    print_swp_defaults_header()
    outbuf = ''
    for i in swp_intfs:
        outbuf += interfaces_print_swp_default(i)
    print(outbuf)

def interfaces_print_bridge_default(swp_intfs):
    print_bridge_untagged_defaults_header()
    outbuf = 'auto bridge-untagged\n' 
    outbuf += 'iface bridge-untagged\n'
    outbuf += '  bridge-ports \\\n'
    linen = 5
    ports = ''
    for i in range(0, len(swp_intfs), linen):
        if ports:
            ports += ' \\\n'
        ports += '      %s' %(' '.join(swp_intfs[i:i+linen]))
    outbuf += ports
    print(outbuf)

def populate_argparser(argparser):
    group = argparser.add_mutually_exclusive_group(required=False)
    group.add_argument('-s', '--swp-defaults', action='store_true',
                       dest='swpdefaults', help='generate swp defaults file')
    group.add_argument('-b', '--bridge-default', action='store_true',
                       dest='bridgedefault',
                       help='generate default untagged bridge')
    argparser.add_argument('-m', '--merge', dest='mergefile', help='merge ' +
                           'new generated iface content with the old one')

argparser =  argparse.ArgumentParser(description='ifupdown interfaces file gen helper')
populate_argparser(argparser)
args = argparser.parse_args(sys.argv[1:])

if not args.swpdefaults and not args.bridgedefault:
    argparser.print_help()
    exit(1)

if args.bridgedefault and args.mergefile:
    print('error: mergefile option currently only supported with -s')
    argparser.print_help()
    exit(1)

swp_intfs = get_swp_interfaces()

if args.swpdefaults:
    interfaces_print_swp_defaults(swp_intfs)
elif args.bridgedefault:
    interfaces_print_bridge_default(swp_intfs)
else:
    argparser.print_help()