#!/usr/bin/env python

# Copyright (c) 2011 Citrix Systems, Inc.
# Copyright 2011 OpenStack Foundation
# Copyright 2011 United States Government as represented by the
# Administrator of the National Aeronautics and Space Administration.
# All Rights Reserved.
#
#    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

# TODO(sfinucan): Remove the symlinks in this folder once Ocata is released

#
# XenAPI plugin for reading/writing information to xenstore
#

import base64
try:
    from subprocess import getoutput
except ImportError:
    from commands import getoutput  # noqa
try:
    import json
except ImportError:
    import simplejson as json
import time

import XenAPIPlugin

import dom0_pluginlib
dom0_pluginlib.configure_logging("agent")
import xenstore


DEFAULT_TIMEOUT = 30
PluginError = dom0_pluginlib.PluginError


class TimeoutError(Exception):
    pass


class RebootDetectedError(Exception):
    pass


def version(self, arg_dict):
    """Get version of agent."""
    timeout = int(arg_dict.pop('timeout', DEFAULT_TIMEOUT))
    arg_dict["value"] = json.dumps({"name": "version", "value": "agent"})
    request_id = arg_dict["id"]
    arg_dict["path"] = "data/host/%s" % request_id
    xenstore.write_record(self, arg_dict)
    try:
        resp = _wait_for_agent(self, request_id, arg_dict, timeout)
    except TimeoutError as e:  # noqa
        raise PluginError(e)
    return resp


def key_init(self, arg_dict):
    """Handles the Diffie-Hellman key exchange with the agent to

    establish the shared secret key used to encrypt/decrypt sensitive
    info to be passed, such as passwords. Returns the shared
    secret key value.
    """
    timeout = int(arg_dict.pop('timeout', DEFAULT_TIMEOUT))
    # WARNING: Some older Windows agents will crash if the public key isn't
    # a string
    pub = arg_dict["pub"]
    arg_dict["value"] = json.dumps({"name": "keyinit", "value": pub})
    request_id = arg_dict["id"]
    arg_dict["path"] = "data/host/%s" % request_id
    xenstore.write_record(self, arg_dict)
    try:
        resp = _wait_for_agent(self, request_id, arg_dict, timeout)
    except TimeoutError as e:  # noqa
        raise PluginError(e)
    return resp


def password(self, arg_dict):
    """Writes a request to xenstore that tells the agent to set

    the root password for the given VM. The password should be
    encrypted using the shared secret key that was returned by a
    previous call to key_init. The encrypted password value should
    be passed as the value for the 'enc_pass' key in arg_dict.
    """
    timeout = int(arg_dict.pop('timeout', DEFAULT_TIMEOUT))
    enc_pass = arg_dict["enc_pass"]
    arg_dict["value"] = json.dumps({"name": "password", "value": enc_pass})
    request_id = arg_dict["id"]
    arg_dict["path"] = "data/host/%s" % request_id
    xenstore.write_record(self, arg_dict)
    try:
        resp = _wait_for_agent(self, request_id, arg_dict, timeout)
    except TimeoutError as e:  # noqa
        raise PluginError(e)
    return resp


def resetnetwork(self, arg_dict):
    """Writes a request to xenstore that tells the agent to reset networking.

    """
    timeout = int(arg_dict.pop('timeout', DEFAULT_TIMEOUT))
    arg_dict['value'] = json.dumps({'name': 'resetnetwork', 'value': ''})
    request_id = arg_dict['id']
    arg_dict['path'] = "data/host/%s" % request_id
    xenstore.write_record(self, arg_dict)
    try:
        resp = _wait_for_agent(self, request_id, arg_dict, timeout)
    except TimeoutError as e:  # noqa
        raise PluginError(e)
    return resp


def inject_file(self, arg_dict):
    """Expects a file path and the contents of the file to be written.

    Should be base64-encoded in order to eliminate errors as they are passed
    through the stack. Writes that information to xenstore for the agent,
    which will decode the file and intended path, and create it on the
    instance. The original agent munged both of these into a single entry;
    the new agent keeps them separate. We will need to test for the new agent,
    and write the xenstore records to match the agent version. We will also
    need to test to determine if the file injection method on the agent has
    been disabled, and raise a NotImplemented error if that is the case.
    """
    timeout = int(arg_dict.pop('timeout', DEFAULT_TIMEOUT))
    b64_path = arg_dict["b64_path"]
    b64_file = arg_dict["b64_contents"]
    request_id = arg_dict["id"]
    agent_features = _get_agent_features(self, arg_dict)
    if "file_inject" in agent_features:
        # New version of the agent.  Agent should receive a 'value'
        # key whose value is a dictionary containing 'b64_path' and
        # 'b64_file'.  See old version below.
        arg_dict["value"] = json.dumps({"name": "file_inject",
                                        "value": {"b64_path": b64_path,
                                                  "b64_file": b64_file}})
    elif "injectfile" in agent_features:
        # Old agent requires file path and file contents to be
        # combined into one base64 value.
        raw_path = base64.b64decode(b64_path)
        raw_file = base64.b64decode(b64_file)
        new_b64 = base64.b64encode("%s,%s" % (raw_path, raw_file))
        arg_dict["value"] = json.dumps({"name": "injectfile",
                                        "value": new_b64})
    else:
        # Either the methods don't exist in the agent, or they
        # have been disabled.
        raise NotImplementedError("NOT IMPLEMENTED: Agent does not"
                                  " support file injection.")
    arg_dict["path"] = "data/host/%s" % request_id
    xenstore.write_record(self, arg_dict)
    try:
        resp = _wait_for_agent(self, request_id, arg_dict, timeout)
    except TimeoutError as e:  # noqa
        raise PluginError(e)
    return resp


def agent_update(self, arg_dict):
    """Expects an URL and md5sum of the contents

     Then directs the agent to update itself.
    """
    timeout = int(arg_dict.pop('timeout', DEFAULT_TIMEOUT))
    request_id = arg_dict["id"]
    url = arg_dict["url"]
    md5sum = arg_dict["md5sum"]
    arg_dict["value"] = json.dumps({"name": "agentupdate",
                                    "value": "%s,%s" % (url, md5sum)})
    arg_dict["path"] = "data/host/%s" % request_id
    xenstore.write_record(self, arg_dict)
    try:
        resp = _wait_for_agent(self, request_id, arg_dict, timeout)
    except TimeoutError as e:  # noqa
        raise PluginError(e)
    return resp


def _get_agent_features(self, arg_dict):
    """Return an array of features that an agent supports."""
    timeout = int(arg_dict.pop('timeout', DEFAULT_TIMEOUT))
    tmp_id = getoutput("uuidgen")
    dct = {}
    dct.update(arg_dict)
    dct["value"] = json.dumps({"name": "features", "value": ""})
    dct["path"] = "data/host/%s" % tmp_id
    xenstore.write_record(self, dct)
    try:
        resp = _wait_for_agent(self, tmp_id, dct, timeout)
    except TimeoutError as e:  # noqa
        raise PluginError(e)
    response = json.loads(resp)
    if response['returncode'] != 0:
        return response["message"].split(",")
    else:
        return {}


def _wait_for_agent(self, request_id, arg_dict, timeout):
    """Periodically checks xenstore for a response from the agent.

    The request is always written to 'data/host/{id}', and
    the agent's response for that request will be in 'data/guest/{id}'.
    If no value appears from the agent within the timeout specified,
    the original request is deleted and a TimeoutError is raised.
    """
    arg_dict["path"] = "data/guest/%s" % request_id
    arg_dict["ignore_missing_path"] = True
    start = time.time()
    reboot_detected = False
    while time.time() - start < timeout:
        ret = xenstore.read_record(self, arg_dict)
        # Note: the response for None with be a string that includes
        # double quotes.
        if ret != '"None"':
            # The agent responded
            return ret

        time.sleep(.5)

        # NOTE(johngarbutt) If we can't find this domid, then
        # the VM has rebooted, so we must trigger domid refresh.
        # Check after the sleep to give xenstore time to update
        # after the VM reboot.
        exists_args = {
            "dom_id": arg_dict["dom_id"],
            "path": "name",
        }
        dom_id_is_present = xenstore.record_exists(exists_args)
        if not dom_id_is_present:
            reboot_detected = True
            break

    # No response within the timeout period; bail out
    # First, delete the request record
    arg_dict["path"] = "data/host/%s" % request_id
    xenstore.delete_record(self, arg_dict)

    if reboot_detected:
        raise RebootDetectedError("REBOOT: dom_id %s no longer "
                                  "present" % arg_dict["dom_id"])
    else:
        raise TimeoutError("TIMEOUT: No response from agent within"
                           " %s seconds." % timeout)


if __name__ == "__main__":
    XenAPIPlugin.dispatch(
        {"version": version,
         "key_init": key_init,
         "password": password,
         "resetnetwork": resetnetwork,
         "inject_file": inject_file,
         "agentupdate": agent_update})