#
# Author:: Joshua Timberman (<joshua@chef.io>)
# Author:: Lamont Granquist (<lamont@chef.io>)
# Copyright:: Copyright 2009-2016, 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 "chef/log"
require "chef/mixin/shell_out"
require "chef/provider"

class Chef
  class Provider
    class Mount < Chef::Provider
      include Chef::Mixin::ShellOut

      attr_accessor :unmount_retries

      def whyrun_supported?
        true
      end

      def load_current_resource
        true
      end

      def initialize(new_resource, run_context)
        super
        self.unmount_retries = 20
      end

      def action_mount
        if current_resource.mounted
          if mount_options_unchanged?
            Chef::Log.debug("#{new_resource} is already mounted")
          else
            action_remount
          end
        else
          converge_by("mount #{current_resource.device} to #{current_resource.mount_point}") do
            mount_fs
            Chef::Log.info("#{new_resource} mounted")
          end
        end
      end

      def action_umount
        if current_resource.mounted
          converge_by("unmount #{current_resource.device}") do
            umount_fs
            Chef::Log.info("#{new_resource} unmounted")
          end
        else
          Chef::Log.debug("#{new_resource} is already unmounted")
        end
      end

      def action_remount
        if current_resource.mounted
          if new_resource.supports[:remount]
            converge_by("remount #{current_resource.device}") do
              remount_fs
              Chef::Log.info("#{new_resource} remounted")
            end
          else
            converge_by("unmount #{current_resource.device}") do
              umount_fs
              Chef::Log.info("#{new_resource} unmounted")
            end
            wait_until_unmounted(unmount_retries)
            converge_by("mount #{current_resource.device}") do
              mount_fs
              Chef::Log.info("#{new_resource} mounted")
            end
          end
        else
          Chef::Log.debug("#{new_resource} not mounted, nothing to remount")
        end
      end

      def action_enable
        unless current_resource.enabled && mount_options_unchanged?
          converge_by("enable #{current_resource.device}") do
            enable_fs
            Chef::Log.info("#{new_resource} enabled")
          end
        else
          Chef::Log.debug("#{new_resource} already enabled")
        end
      end

      def action_disable
        if current_resource.enabled
          converge_by("disable #{current_resource.device}") do
            disable_fs
            Chef::Log.info("#{new_resource} disabled")
          end
        else
          Chef::Log.debug("#{new_resource} already disabled")
        end
      end

      #
      # Abstract Methods to be implemented by subclasses
      #

      # should actually check if the filesystem is mounted (not just return current_resource) and return true/false
      def mounted?
        raise Chef::Exceptions::UnsupportedAction, "#{self} does not implement #mounted?"
      end

      # should check new_resource against current_resource to see if mount options need updating, returns true/false
      def mount_options_unchanged?
        raise Chef::Exceptions::UnsupportedAction, "#{self} does not implement #mount_options_unchanged?"
      end

      #
      # NOTE: for the following methods, this superclass will already have checked if the filesystem is
      # enabled and/or mounted and they will be called in converge_by blocks, so most defensive checking
      # does not need to be done in the subclass implementation -- just do the thing.
      #

      # should implement mounting of the filesystem, raises if action does not succeed
      def mount_fs
        raise Chef::Exceptions::UnsupportedAction, "#{self} does not support :mount"
      end

      # should implement unmounting of the filesystem, raises if action does not succeed
      def umount_fs
        raise Chef::Exceptions::UnsupportedAction, "#{self} does not support :umount"
      end

      # should implement remounting of the filesystem (via a -o remount or some other atomic-ish action that isn't
      # simply a umount/mount style remount), raises if action does not succeed
      def remount_fs
        raise Chef::Exceptions::UnsupportedAction, "#{self} does not support :remount"
      end

      # should implement enabling of the filesystem (e.g. in /etc/fstab), raises if action does not succeed
      def enable_fs
        raise Chef::Exceptions::UnsupportedAction, "#{self} does not support :enable"
      end

      # should implement disabling of the filesystem (e.g. in /etc/fstab), raises if action does not succeed
      def disable_fs
        raise Chef::Exceptions::UnsupportedAction, "#{self} does not support :disable"
      end

      private

      def wait_until_unmounted(tries)
        while mounted?
          if (tries -= 1) < 0
            raise Chef::Exceptions::Mount, "Retries exceeded waiting for filesystem to unmount"
          end
          sleep 0.1
        end
      end
    end
  end
end