# frozen_string_literal: true

# Copyright 2019 Google LLC
#
# 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 "shellwords"

require "appengine/util/gcloud"
require "appengine/exec"

module AppEngine
  ##
  # # App Engine Rake Tasks.
  #
  # To make these tasks available, add the line `require "appengine/tasks"`
  # to your Rakefile. If your app uses Ruby on Rails, then the appengine gem
  # provides a railtie that adds its tasks automatically, so you don't have
  # to do anything beyond adding the gem to your Gemfile.
  #
  # The following tasks are defined:
  #
  # ## Rake appengine:exec
  #
  # Executes a given command in the context of an App Engine application, using
  # App Engine remote execution. See {AppEngine::Exec} for more information on
  # this capability.
  #
  # The command to be run may either be provided as a rake argument, or as
  # command line arguments, delimited by two dashes `--`. (The dashes are
  # needed to separate your command from rake arguments and flags.)
  # For example, to run a production database migration, you can run either of
  # the following equivalent commands:
  #
  #     bundle exec rake "appengine:exec[bundle exec bin/rails db:migrate]"
  #     bundle exec rake appengine:exec -- bundle exec bin/rails db:migrate
  #
  # To display usage instructions, provide two dashes but no command:
  #
  #     bundle exec rake appengine:exec --
  #
  # ### Parameters
  #
  # You may customize the behavior of App Engine execution through a few
  # enviroment variable parameters. These are set via the normal mechanism at
  # the end of a rake command line. For example, to set GAE_CONFIG:
  #
  #     bundle exec rake appengine:exec GAE_CONFIG=myservice.yaml -- bundle exec bin/rails db:migrate
  #
  # Be sure to set these parameters before the double dash. Any arguments
  # following the double dash are interpreted as part of the command itself.
  #
  # The following environment variable parameters are supported:
  #
  # #### GAE_TIMEOUT
  #
  # Amount of time to wait before appengine:exec terminates the command.
  # Expressed as a string formatted like: "2h15m10s". Default is "10m".
  #
  # #### GAE_PROJECT
  #
  # The ID of your Google Cloud project. If not specified, uses the current
  # project from gcloud.
  #
  # #### GAE_CONFIG
  #
  # Path to the App Engine config file, used when your app has multiple
  # services, or the config file is otherwise not called `./app.yaml`. The
  # config file is used to determine the name of the App Engine service.
  #
  # #### GAE_SERVICE
  #
  # Name of the service to be used. Overrides any service name specified in
  # your config file.
  #
  # #### GAE_EXEC_STRATEGY
  #
  # The execution strategy to use. Valid values are "deployment" (which is the
  # default for App Engine Standard apps) and "cloud_build" (which is the
  # default for App Engine Flexible apps).
  #
  # Normally you should leave the strategy set to the default. The main reason
  # to change it is if your app runs on the Flexible Environment and talks to
  # a database over a VPC (using a private IP address). The "cloud_build"
  # strategy used by default for Flexible apps cannot connect to a VPC, so you
  # should use "deployment" in this case. (But note that, otherwise, the
  # "deployment" strategy is significantly slower for apps on the Flexible
  # environment.)
  #
  # #### GAE_VERSION
  #
  # The version of the service, used to identify which application image to
  # use to run your command. If not specified, uses the most recently created
  # version, regardless of whether that version is actually serving traffic.
  # Applies only to the "cloud_build" strategy. (The "deployment" strategy
  # deploys its own temporary version of your app.)
  #
  # #### GAE_EXEC_WRAPPER_IMAGE
  #
  # The fully-qualified name of the wrapper image to use. (This is a Docker
  # image that emulates the App Engine environment in Google Cloud Build for
  # the "cloud_build" strategy, and applies only to that strategy.) Normally,
  # you should not override this unless you are testing a new wrapper.
  #
  module Tasks
    ## @private
    PROJECT_ENV = "GAE_PROJECT"
    ## @private
    STRATEGY_ENV = "GAE_EXEC_STRATEGY"
    ## @private
    CONFIG_ENV = "GAE_CONFIG"
    ## @private
    SERVICE_ENV = "GAE_SERVICE"
    ## @private
    VERSION_ENV = "GAE_VERSION"
    ## @private
    TIMEOUT_ENV = "GAE_TIMEOUT"
    ## @private
    WRAPPER_IMAGE_ENV = "GAE_EXEC_WRAPPER_IMAGE"

    @defined = false

    class << self
      ##
      # @private
      # Define rake tasks.
      #
      def define
        if @defined
          puts "AppEngine rake tasks already defined."
          return
        end
        @defined = true

        setup_exec_task
      end

      private

      def setup_exec_task
        ::Rake.application.last_description =
          "Execute the given command in Google App Engine."
        ::Rake::Task.define_task "appengine:exec", [:cmd] do |_t, args|
          verify_gcloud_and_report_errors
          command = extract_command args[:cmd], ::ARGV
          app_exec = Exec.new command,
                              project:       ::ENV[PROJECT_ENV],
                              service:       ::ENV[SERVICE_ENV],
                              config_path:   ::ENV[CONFIG_ENV],
                              version:       ::ENV[VERSION_ENV],
                              timeout:       ::ENV[TIMEOUT_ENV],
                              wrapper_image: ::ENV[WRAPPER_IMAGE_ENV],
                              strategy:      ::ENV[STRATEGY_ENV]
          start_and_report_errors app_exec
          exit
        end
      end

      def extract_command cmd, argv
        if cmd
          ::Shellwords.split cmd
        else
          i = (argv.index { |a| a.to_s == "--" } || -1) + 1
          if i.zero?
            report_error <<~MESSAGE
              No command provided for appengine:exec.
              Did you remember to delimit it with two dashes? e.g.
              bundle exec rake appengine:exec -- bundle exec ruby myscript.rb
              For detailed usage instructions, provide two dashes but no command:
              bundle exec rake appengine:exec --
            MESSAGE
          end
          command = ::ARGV[i..-1]
          if command.empty?
            show_usage
            exit
          end
          command
        end
      end

      def show_usage
        puts <<~USAGE
          rake appengine:exec

          This Rake task executes a given command in the context of an App Engine
          application, using App Engine remote execution. For more information,
          on this capability, see the AppEngine::Exec documentation at
          http://www.rubydoc.info/gems/appengine/AppEngine/Exec

          The command to be run may either be provided as a rake argument, or as
          command line arguments delimited by two dashes `--`. (The dashes are
          needed to separate your command from rake arguments and flags.)
          For example, to run a production database migration, you can run either
          of the following equivalent commands:

              bundle exec rake "appengine:exec[bundle exec bin/rails db:migrate]"
              bundle exec rake appengine:exec -- bundle exec bin/rails db:migrate

          To display these usage instructions, provide two dashes but no command:

              bundle exec rake appengine:exec --

          You may customize the behavior of App Engine execution through a few
          enviroment variable parameters. These are set via the normal mechanism at
          the end of a rake command line but before the double dash. For example, to
          set GAE_CONFIG:

              bundle exec rake appengine:exec GAE_CONFIG=myservice.yaml -- bundle exec bin/rails db:migrate

          Be sure to set these parameters before the double dash. Any arguments
          following the double dash are interpreted as part of the command itself.

          The following environment variable parameters are supported:

          GAE_TIMEOUT

            Amount of time to wait before appengine:exec terminates the command.
            Expressed as a string formatted like: "2h15m10s". Default is "10m".

          GAE_PROJECT

            The ID of your Google Cloud project. If not specified, uses the current
            project from gcloud.

          GAE_CONFIG

            Path to the App Engine config file, used when your app has multiple
            services, or the config file is otherwise not called `./app.yaml`. The
            config file is used to determine the name of the App Engine service.

          GAE_SERVICE

            Name of the service to be used. Overrides any service name specified in
            your config file.

          GAE_EXEC_STRATEGY

            The execution strategy to use. Valid values are "deployment" (which is the
            default for App Engine Standard apps) and "cloud_build" (which is the
            default for App Engine Flexible apps).

            Normally you should leave the strategy set to the default. The main reason
            to change it is if your app runs on the Flexible Environment and talks to
            a database over a VPC (using a private IP address). The "cloud_build"
            strategy used by default for Flexible apps cannot connect to a VPC, so you
            should use "deployment" in this case. (But note that, otherwise, the
            "deployment" strategy is significantly slower for apps on the Flexible
            environment.)

          GAE_VERSION

            The version of the service, used to identify which application image to
            use to run your command. If not specified, uses the most recently created
            version, regardless of whether that version is actually serving traffic.
            Applies only to the "cloud_build" strategy. (The "deployment" strategy
            deploys its own temporary version of your app.)

          GAE_EXEC_WRAPPER_IMAGE

            The fully-qualified name of the wrapper image to use. (This is a Docker
            image that emulates the App Engine environment in Google Cloud Build for
            the "cloud_build" strategy, and applies only to that strategy.) Normally,
            you should not override this unless you are testing a new wrapper.

          This rake task is provided by the "appengine" gem. To make these tasks
          available, add the following line to your Rakefile:

              require "appengine/tasks"

          If your app uses Ruby on Rails, the gem provides a railtie that adds its
          tasks automatically, so you don't have to do anything beyond adding the
          gem to your Gemfile.

          For more information or to report issues, visit the Github page:
          https://github.com/GoogleCloudPlatform/appengine-ruby
        USAGE
      end

      def verify_gcloud_and_report_errors
        Util::Gcloud.verify!
      rescue Util::Gcloud::BinaryNotFound
        report_error <<~MESSAGE
          Could not find the `gcloud` binary in your system path.
          This tool requires the Google Cloud SDK. To download and install it,
          visit https://cloud.google.com/sdk/downloads
        MESSAGE
      rescue Util::Gcloud::GcloudNotAuthenticated
        report_error <<~MESSAGE
          The gcloud authorization has not been completed. If you have not yet
          initialized the Google Cloud SDK, we recommend running the `gcloud init`
          command as described at https://cloud.google.com/sdk/docs/initializing
          Alternately, you may log in directly by running `gcloud auth login`.
        MESSAGE
      rescue Util::Gcloud::ProjectNotSet
        report_error <<~MESSAGE
          The gcloud project configuration has not been set. If you have not yet
          initialized the Google Cloud SDK, we recommend running the `gcloud init`
          command as described at https://cloud.google.com/sdk/docs/initializing
          Alternately, you may set the default project configuration directly by
          running `gcloud config set project <project-name>`.
        MESSAGE
      end

      def start_and_report_errors app_exec
        app_exec.start
      rescue Exec::ConfigFileNotFound => e
        report_error <<~MESSAGE
          Could not determine which service should run this command because the App
          Engine config file "#{e.config_path}" was not found.
          Specify the config file using the GAE_CONFIG argument. e.g.
            bundle exec rake appengine:exec GAE_CONFIG=myapp.yaml -- myscript.sh
          Alternately, you may specify a service name directly with GAE_SERVICE. e.g.
            bundle exec rake appengine:exec GAE_SERVICE=myservice -- myscript.sh
        MESSAGE
      rescue Exec::BadConfigFileFormat => e
        report_error <<~MESSAGE
          Could not determine which service should run this command because the App
          Engine config file "#{e.config_path}" was malformed.
          It must be a valid YAML file.
          Specify the config file using the GAE_CONFIG argument. e.g.
            bundle exec rake appengine:exec GAE_CONFIG=myapp.yaml -- myscript.sh
          Alternately, you may specify a service name directly with GAE_SERVICE. e.g.
            bundle exec rake appengine:exec GAE_SERVICE=myservice -- myscript.sh
        MESSAGE
      rescue Exec::NoSuchVersion => e
        if e.version
          report_error <<~MESSAGE
            Could not find version "#{e.version}" of service "#{e.service}".
            Please double-check the version exists. To use the most recent version by
            default, omit the GAE_VERSION argument.
          MESSAGE
        else
          report_error <<~MESSAGE
            Could not find any versions of service "#{e.service}".
            Please double-check that you have deployed this service. If you want to run
            a command against a different service, you may provide a GAE_CONFIG argument
            pointing to your App Engine config file, or a GAE_SERVICE argument to specify
            a service directly.
          MESSAGE
        end
      rescue Exec::NoDefaultProject
        report_error <<~MESSAGE
          Could not get the default project from gcloud.
          Please either set the current project using
            gcloud config set project my-project-id
          or specify the project by setting the GAE_PROJECT argument. e.g.
            bundle exec rake appengine:exec GAE_PROJECT=my-project-id -- myscript.sh
        MESSAGE
      rescue Exec::UsageError => e
        report_error e.message
      end

      def report_error str
        ::STDERR.puts str
        exit 1
      end
    end
  end
end

::AppEngine::Tasks.define