#!/usr/bin/python

#    Licensed under the Apache License, Version 2.0 (the "License"); you may
#    not use this file except in compliance with the License. You may obtain
#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#    License for the specific language governing permissions and limitations
#    under the License.

# NOTE: XenServer still only supports Python 2.4 in it's dom0 userspace
# which means the Nova xenapi plugins must use only Python 2.4 features

# TODO(sfinucan): Resolve all 'noqa' items once the above is no longer true

"""
To configure this plugin, you must set the following xenstore key:
/local/logconsole/@ = "/var/log/xen/guest/console.%d"

This can be done by running:
xenstore-write /local/logconsole/@ "/var/log/xen/guest/console.%d"

WARNING:
You should ensure appropriate log rotation to ensure
guests are not able to consume too much Dom0 disk space,
and equally should not be able to stop other guests from logging.
Adding and removing the following xenstore key will reopen the log,
as will be required after a log rotate:
/local/logconsole/<dom_id>
"""

import base64
import logging
import zlib

import XenAPIPlugin

import dom0_pluginlib
dom0_pluginlib.configure_logging("console")

CONSOLE_LOG_DIR = '/var/log/xen/guest'
CONSOLE_LOG_FILE_PATTERN = CONSOLE_LOG_DIR + '/console.%d'

MAX_CONSOLE_BYTES = 102400
SEEK_SET = 0
SEEK_END = 2


def _last_bytes(file_like_object):
    try:
        file_like_object.seek(-MAX_CONSOLE_BYTES, SEEK_END)
    except IOError as e:  # noqa
        if e.errno == 22:
            file_like_object.seek(0, SEEK_SET)
        else:
            raise
    return file_like_object.read()


def get_console_log(session, arg_dict):
    try:
        raw_dom_id = arg_dict['dom_id']
    except KeyError:
        raise dom0_pluginlib.PluginError("Missing dom_id")
    try:
        dom_id = int(raw_dom_id)
    except ValueError:
        raise dom0_pluginlib.PluginError("Invalid dom_id")

    logfile = open(CONSOLE_LOG_FILE_PATTERN % dom_id, 'rb')
    try:
        try:
            log_content = _last_bytes(logfile)
        except IOError as e:  # noqa
            msg = "Error reading console: %s" % e
            logging.debug(msg)
            raise dom0_pluginlib.PluginError(msg)
    finally:
        logfile.close()

    return base64.b64encode(zlib.compress(log_content))


if __name__ == "__main__":
    XenAPIPlugin.dispatch({"get_console_log": get_console_log})
