# vi: ts=4 expandtab
#
#    Copyright (C) 2013 Yahoo! Inc.
#
#    Author: Joshua Harlow <harlowja@yahoo-inc.com>
#
#    This program is free software: you can redistribute it and/or modify
#    it under the terms of the GNU General Public License version 3, as
#    published by the Free Software Foundation.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU General Public License for more details.
#
#    You should have received a copy of the GNU General Public License
#    along with this program.  If not, see <http://www.gnu.org/licenses/>.

import base64
from StringIO import StringIO

import jsonschema
from jsonschema import exceptions as js_exc

from cloudinit import exceptions as exc
from cloudinit.settings import PER_INSTANCE
from cloudinit import util

frequency = PER_INSTANCE
schema = {
    'type': 'object',
    'properties': {
        "random_seed": {
            "type": "object",
            "oneOf": [
                {"$ref": "#/definitions/random_seed"},
            ],
        },
    },
    "required": ["random_seed"],
    "additionalProperties": True,
    "definitions": {
        'random_seed': {
            'type': 'object',
            "properties" : {
                'data': {
                    'type': "string",
                },
                'file': {
                    'type': 'string',
                },
                'encoding': {
                    "enum": ["base64", 'gzip', 'b64', 'gz', ''],
                },
            },
            "additionalProperties": True,
        },
    },
}


def validate(cfg):
    """Method that can be used to ask if the given configuration will be
    accepted as valid by this module, without having to actually activate this
    module."""
    if not cfg or "random_seed" not in cfg:
        return
    try:
        jsonschema.validate(cfg, schema)
    except js_exc.ValidationError as e:
        raise exc.FormatValidationError("Invalid configuration: %s" % str(e))


def _decode(data, encoding=None):
    if not encoding:
        return data
    if not data:
        return ''
    if encoding.lower() in ['base64', 'b64']:
        return base64.b64decode(data)
    elif encoding.lower() in ['gzip', 'gz']:
        return util.decomp_gzip(data, quiet=False)
    else:
        raise IOError("Unknown random_seed encoding: %s" % (encoding))


def handle(name, cfg, cloud, log, _args):
    if not cfg or "random_seed" not in cfg:
        log.debug(("Skipping module named %s, "
                   "no 'random_seed' configuration found"), name)
        return

    validate(cfg)
    my_cfg = cfg['random_seed']
    seed_path = my_cfg.get('file', '/dev/urandom')
    seed_buf = StringIO()
    seed_buf.write(_decode(my_cfg.get('data', ''),
                           encoding=my_cfg.get('encoding')))

    metadata = cloud.datasource.metadata
    if metadata and 'random_seed' in metadata:
        seed_buf.write(metadata['random_seed'])

    seed_data = seed_buf.getvalue()
    if len(seed_data):
        log.debug("%s: adding %s bytes of random seed entrophy to %s", name,
                  len(seed_data), seed_path)
        util.append_file(seed_path, seed_data)