#!/usr/bin/env python

# Copyright 2018 The Kubernetes Authors.
#
# 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.
import json
import os
import subprocess
import sys

from .config_exception import ConfigException


class ExecProvider(object):
  """
    Implementation of the proposal for out-of-tree client
    authentication providers as described here --
    https://github.com/kubernetes/community/blob/master/contributors/design-proposals/auth/kubectl-exec-plugins.md

    Missing from implementation:

    * TLS cert support
    * caching
    """

  def __init__(self, exec_config):
    """
        exec_config must be of type ConfigNode because we depend on
        safe_get(self, key) to correctly handle optional exec provider
        config parameters.
        """
    for key in ['command', 'apiVersion']:
      if key not in exec_config:
        raise ConfigException('exec: malformed request. missing key \'%s\'' %
                              key)
    self.api_version = exec_config['apiVersion']
    self.args = [exec_config['command']]
    if exec_config.safe_get('args'):
      self.args.extend(exec_config['args'])
    self.env = os.environ.copy()
    if exec_config.safe_get('env'):
      additional_vars = {}
      for item in exec_config['env']:
        name = item['name']
        value = item['value']
        additional_vars[name] = value
      self.env.update(additional_vars)

  def run(self, previous_response=None):
    kubernetes_exec_info = {
        'apiVersion': self.api_version,
        'kind': 'ExecCredential',
        'spec': {
            'interactive': sys.stdout.isatty()
        }
    }
    if previous_response:
      kubernetes_exec_info['spec']['response'] = previous_response
    self.env['KUBERNETES_EXEC_INFO'] = json.dumps(kubernetes_exec_info)
    process = subprocess.Popen(
        self.args,
        stdout=subprocess.PIPE,
        stderr=subprocess.PIPE,
        env=self.env,
        universal_newlines=True)
    (stdout, stderr) = process.communicate()
    exit_code = process.wait()
    if exit_code != 0:
      msg = 'exec: process returned %d' % exit_code
      stderr = stderr.strip()
      if stderr:
        msg += '. %s' % stderr
      raise ConfigException(msg)
    try:
      data = json.loads(stdout)
    except ValueError as de:
      raise ConfigException('exec: failed to decode process output: %s' % de)
    for key in ('apiVersion', 'kind', 'status'):
      if key not in data:
        raise ConfigException('exec: malformed response. missing key \'%s\'' %
                              key)
    if data['apiVersion'] != self.api_version:
      raise ConfigException('exec: plugin api version %s does not match %s' %
                            (data['apiVersion'], self.api_version))
    return data['status']