#!/usr/bin/env python
#
# Copyright (c) 2014, Arista Networks, Inc.
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#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are
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# this list of conditions and the following disclaimer.
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# this software without specific prior written permission.
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# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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#pylint: disable=W0703,E1103

EXTENSIONS_DIR = '/mnt/flash/.extensions'
BOOT_EXTENSIONS = '/mnt/flash/boot-extensions'

import ast
import os

def main(attributes):
    '''Installs EOS extension.

    Installs extension based on the value of the
    'url' attribute. If 'force' is
    set, then the dependency checks are overridden.

    This action is NOT dual-supervisor compatible.

    Args:
       attributes: list of attributes; use attributes.get(<ATTRIBUTE_NAME>)
                   to read attribute values

       Special attributes:
           node: attributes.get('NODE')
                 API: see documentation
    '''

    node = attributes.get('NODE')
    url = attributes.get('url')

    if not url:
        return 'Missing attribute(\'url\')'

    force = ast.literal_eval(
        str(attributes.get('force')))

    try:
        os.makedirs(EXTENSIONS_DIR)
    except OSError:
        # file exists
        pass

    name = url.split('/')[ -1 ]
    try:
        node.retrieve_url(url, '%s/%s' % (EXTENSIONS_DIR, name))
    except Exception as exc:
        return 'Unable to retrieve extension from URL (%s)' % exc

    line = name
    if force:
        line = line + ' force'

    open(BOOT_EXTENSIONS, 'a').write('\r\n%s' % line)
