# Copyright 2020 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

import json
import logging
import os
import requests
import subprocess
import urlparse

from autotest_lib.client.bin import utils
from autotest_lib.client.common_lib import autotemp
from autotest_lib.client.common_lib import error


# JSON attributes used in payload properties. Look at nebraska.py for more
# information.
KEY_PUBLIC_KEY='public_key'
KEY_METADATA_SIZE='metadata_size'
KEY_SHA256='sha256_hex'


class NebraskaWrapper(object):
    """
    A wrapper around nebraska.py

    This wrapper is used to start a nebraska.py service and allow the
    update_engine to interact with it.

    """

    def __init__(self, log_dir=None, payload_url=None, **props_to_override):
        """
        Initializes the NebraskaWrapper module.

        @param log_dir: The directory to write nebraska.log into.
        @param payload_url: The payload that will returned in responses.
        @param props_to_override: Dictionary of key/values to use in responses
                instead of the default values in payload_url's properties file.

        """
        self._nebraska_server = None
        self._port = None
        self._log_dir = log_dir
        self._update_metadata_dir = None
        self._update_payloads_address = None

        if payload_url:
            self._update_metadata_dir = autotemp.tempdir()
            self._update_payloads_address = ''.join(
                payload_url.rpartition('/')[0:2])
            self.get_payload_properties_file(
                payload_url, self._update_metadata_dir.name,
                **props_to_override)

    def __enter__(self):
        """So that NebraskaWrapper can be used as a Context Manager."""
        self.start()
        return self

    def __exit__(self, *exception_details):
        """
        So that NebraskaWrapper can be used as a Context Manager.

        @param exception_details: Details of exceptions happened in the
                ContextManager.

        """
        self.stop()

    def start(self):
        """
        Starts the Nebraska server.

        @raise error.TestError: If fails to start the Nebraska server.

        """
        # Any previously-existing files (port, pid and log files) will be
        # overriden by Nebraska during bring up.
        runtime_root = '/tmp/nebraska'
        cmd = ['nebraska.py', '--runtime-root', runtime_root]
        if self._log_dir:
            cmd += ['--log-file', os.path.join(self._log_dir, 'nebraska.log')]
        if self._update_metadata_dir:
            cmd += ['--update-metadata', self._update_metadata_dir.name]
        if self._update_payloads_address:
            cmd += ['--update-payloads-address', self._update_payloads_address]

        logging.info('Starting nebraska.py with command: %s', cmd)

        try:
            self._nebraska_server = subprocess.Popen(cmd,
                                                     stdout=subprocess.PIPE,
                                                     stderr=subprocess.STDOUT)

            # Wait for port file to appear.
            port_file = os.path.join(runtime_root, 'port')
            utils.poll_for_condition(lambda: os.path.exists(port_file),
                                     timeout=5)

            with open(port_file, 'r') as f:
                self._port = int(f.read())

            # Send a health_check request to it to make sure its working.
            requests.get('http://127.0.0.1:%d/health_check' % self._port)

        except Exception as e:
            raise error.TestError('Failed to start Nebraska %s' % e)

    def stop(self):
        """Stops the Nebraska server."""
        if not self._nebraska_server:
            return
        try:
            self._nebraska_server.terminate()
            stdout, _ = self._nebraska_server.communicate()
            logging.info('Stopping nebraska.py with stdout %s', stdout)
            self._nebraska_server.wait()
        except subprocess.TimeoutExpired:
            logging.error('Failed to stop Nebraska. Ignoring...')
        finally:
            self._nebraska_server = None

    def get_update_url(self, **kwargs):
        """
        Returns a URL for getting updates from this Nebraska instance.

        @param kwargs: A set of key/values to form a search query to instruct
                Nebraska to do a set of activities. See
                nebraska.py::ResponseProperties for examples key/values.
        """

        query = '&'.join('%s=%s' % (k, v) for k, v in kwargs.items())
        url = urlparse.SplitResult(scheme='http',
                                   netloc='127.0.0.1:%d' % self._port,
                                   path='/update',
                                   query=query,
                                   fragment='')
        return urlparse.urlunsplit(url)

    def get_payload_properties_file(self, payload_url, target_dir, **kwargs):
        """
        Downloads the payload properties file into a directory.

        @param payload_url: The URL to the update payload file.
        @param target_dir: The directory to download the file into.
        @param kwargs: A dictionary of key/values that needs to be overridden on
                the payload properties file.

        """
        payload_props_url = payload_url + '.json'
        _, _, file_name = payload_props_url.rpartition('/')
        try:
            response = json.loads(requests.get(payload_props_url).text)
            # Override existing keys if any.
            for k, v in kwargs.iteritems():
                # Don't set default None values. We don't want to override good
                # values to None.
                if v is not None:
                    response[k] = v
            with open(os.path.join(target_dir, file_name), 'w') as fp:
                json.dump(response, fp)

        except (requests.exceptions.RequestException,
                IOError,
                ValueError) as err:
            raise error.TestError(
                'Failed to get update payload properties: %s with error: %s' %
                (payload_props_url, err))