#
# Author:: Stephen Haynes (<sh@nomitor.com>)
# Author:: Davide Cavalca (<dcavalca@fb.com>)
# Copyright:: Copyright (c) Chef Software Inc.
# License:: Apache License, Version 2.0
#
# 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.
#

require_relative "../../resource/service"
require_relative "simple"
require_relative "../../mixin/which"
require "shellwords" unless defined?(Shellwords)

class Chef::Provider::Service::Systemd < Chef::Provider::Service::Simple

  include Chef::Mixin::Which

  provides :service, os: "linux", target_mode: true do |node|
    systemd?
  end

  attr_accessor :status_check_success

  def self.supports?(resource, action)
    service_script_exist?(:systemd, resource.service_name)
  end

  def load_current_resource
    @current_resource = Chef::Resource::Service.new(new_resource.name)
    current_resource.service_name(new_resource.service_name)
    @status_check_success = true

    if new_resource.status_command
      logger.trace("#{new_resource} you have specified a status command, running..")

      unless shell_out(new_resource.status_command).error?
        current_resource.running(true)
      else
        @status_check_success = false
        current_resource.running(false)
        current_resource.enabled(false)
        current_resource.masked(false)
        current_resource.static(false)
        current_resource.indirect(false)
      end
    else
      current_resource.running(is_active?)
    end

    current_resource.enabled(is_enabled?)
    current_resource.masked(is_masked?)
    current_resource.static(is_static?)
    current_resource.indirect(is_indirect?)
    current_resource
  end

  # systemd supports user services just fine
  def user_services_requirements; end

  def define_resource_requirements
    shared_resource_requirements
    requirements.assert(:all_actions) do |a|
      a.assertion { status_check_success }
      # We won't stop in any case, but in whyrun warn and tell what we're doing.
      a.whyrun ["Failed to determine status of #{new_resource}, using command #{new_resource.status_command}.",
        "Assuming service would have been installed and is disabled"]
    end
  end

  def systemd_service_status
    @systemd_service_status ||= begin
      # Collect all the status information for a service and returns it at once
      options, args = get_systemctl_options_args
      s = shell_out!(systemctl_path, args, "show", "-p", "UnitFileState", "-p", "ActiveState", new_resource.service_name, **options)
      # e.g. /bin/systemctl --system show  -p UnitFileState -p ActiveState sshd.service
      # Returns something like:
      # ActiveState=active
      # UnitFileState=enabled
      status = {}
      s.stdout.each_line do |line|
        k, v = line.strip.split("=")
        status[k] = v
      end

      # Assert requisite keys exist
      unless status.key?("UnitFileState") && status.key?("ActiveState")
        raise Chef::Exceptions::Service, "'#{systemctl_path} show' not reporting status for #{new_resource.service_name}!"
      end

      status
    end
  end

  def get_systemctl_options_args
    if new_resource.user
      raise NotImplementedError, "#{new_resource} does not support the user property on a target_mode host (yet)" if Chef::Config.target_mode?

      uid = Etc.getpwnam(new_resource.user).uid
      options = {
        environment: {
          "DBUS_SESSION_BUS_ADDRESS" => "unix:path=/run/user/#{uid}/bus",
        },
        user: new_resource.user,
      }
      args = "--user"
    else
      options = {}
      args = "--system"
    end

    [options, args]
  end

  def start_service
    if current_resource.running
      logger.debug("#{new_resource} already running, not starting")
    else
      if new_resource.start_command
        super
      else
        options, args = get_systemctl_options_args
        shell_out!(systemctl_path, args, "start", new_resource.service_name, default_env: false, **options)
      end
    end
  end

  def stop_service
    unless current_resource.running
      logger.debug("#{new_resource} not running, not stopping")
    else
      if new_resource.stop_command
        super
      else
        options, args = get_systemctl_options_args
        shell_out!(systemctl_path, args, "stop", new_resource.service_name, default_env: false, **options)
      end
    end
  end

  def restart_service
    if new_resource.restart_command
      super
    else
      options, args = get_systemctl_options_args
      shell_out!(systemctl_path, args, "restart", new_resource.service_name, default_env: false, **options)
    end
  end

  def reload_service
    if new_resource.reload_command
      super
    else
      if current_resource.running
        options, args = get_systemctl_options_args
        shell_out!(systemctl_path, args, "reload", new_resource.service_name, default_env: false, **options)
      else
        start_service
      end
    end
  end

  def enableable?(action)
    if current_resource.masked
      logger.debug("#{new_resource} cannot be #{action}d: it is masked")
      return false
    end
    if current_resource.static
      logger.debug("#{new_resource} cannot be #{action}d: it is static")
      return false
    end
    if current_resource.indirect
      logger.debug("#{new_resource} cannot be #{action}d: it is indirect")
      return false
    end
    true
  end

  def enable_service
    # This function can safely assume that enableable? is true
    options, args = get_systemctl_options_args
    shell_out!(systemctl_path, args, "enable", new_resource.service_name, **options)
  end

  def disable_service
    options, args = get_systemctl_options_args
    shell_out!(systemctl_path, args, "disable", new_resource.service_name, **options)
  end

  def mask_service
    options, args = get_systemctl_options_args
    shell_out!(systemctl_path, args, "mask", new_resource.service_name, **options)
  end

  def unmask_service
    options, args = get_systemctl_options_args
    shell_out!(systemctl_path, args, "unmask", new_resource.service_name, **options)
  end

  def is_active?
    # Note: "activating" is not active (as with type=notify or a oneshot)
    systemd_service_status["ActiveState"] == "active"
  end

  def is_enabled?
    # if the service is in sysv compat mode, shellout to determine if enabled
    if systemd_service_status["UnitFileState"] == "bad"
      options, args = get_systemctl_options_args
      return shell_out(systemctl_path, args, "is-enabled", new_resource.service_name, "--quiet", **options).exitstatus == 0
    end
    # See https://github.com/systemd/systemd/blob/master/src/systemctl/systemctl-is-enabled.c
    # Note: enabled-runtime is excluded because this is volatile, and the state of enabled-runtime
    # specifically means that the service is not enabled
    %w{enabled static generated alias indirect}.include?(systemd_service_status["UnitFileState"])
  end

  def is_indirect?
    systemd_service_status["UnitFileState"] == "indirect"
  end

  def is_static?
    systemd_service_status["UnitFileState"] == "static"
  end

  def is_masked?
    # Note: masked-runtime is excluded, because runtime is volatile, and
    # because masked-runtime is not masked.
    systemd_service_status["UnitFileState"] == "masked"
  end

  private

  def systemctl_path
    if @systemctl_path.nil?
      @systemctl_path = which("systemctl")
    end
    @systemctl_path
  end

end