# frozen_string_literal: true

require_relative '../config/environment'
require_relative '../lib/generators/post_deployment_migration/post_deployment_migration_generator'
require_relative './helpers/postgres_ai'

module Keeps
  # This is an implementation of a ::Gitlab::Housekeeper::Keep. This keep will locate any old batched background
  # migrations that were added before CUTOFF_MILESTONE and then check if they are finished by querying Postgres.ai
  # database archive. Once it has determined it is safe to finalize the batched background migration it will generate a
  # new migration which calls `ensure_batched_background_migration_is_finished` for this migration. It also updates the
  # `db/docs/batched_background_migrations` file with `finalized_by` and generates the `schema_migrations` file.
  #
  # This keep requires the following additional environment variables to be set:
  #  - POSTGRES_AI_CONNECTION_STRING: A valid postgres connection string
  #  - POSTGRES_AI_PASSWORD: The password for the postgres database in connection string
  #
  # You can run it individually with:
  #
  # ```
  # bundle exec gitlab-housekeeper -d \
  #   -r keeps/overdue_finalize_background_migration.rb \
  #   -k Keeps::OverdueFinalizeBackgroundMigration
  # ```
  class OverdueFinalizeBackgroundMigration < ::Gitlab::Housekeeper::Keep
    CUTOFF_MILESTONE = '16.8' # Only finalize migrations added before this

    def initialize; end

    def each_change
      each_batched_background_migration do |migration_yaml_file, migration|
        next unless before_cuttoff_milestone?(migration['milestone'])

        job_name = migration['migration_job_name']

        next if migration_finalized?(job_name)

        migration_record = fetch_migration_status(job_name)

        next unless migration_record

        # Finalize the migration
        title = "Finalize migration #{job_name}"

        identifiers = [self.class.name.demodulize, job_name]

        last_migration_file = last_migration_for_job(job_name)
        next unless last_migration_file

        # rubocop:disable Gitlab/DocUrl -- Not running inside rails application
        description = <<~MARKDOWN
        This migration was finished at `#{migration_record.finished_at || migration_record.updated_at}`, you can confirm
        the status using our
        [batched background migration chatops commands](https://docs.gitlab.com/ee/development/database/batched_background_migrations.html#monitor-the-progress-and-status-of-a-batched-background-migration).
          To confirm it is finished you can run:

          ```
        /chatops run batched_background_migrations status #{migration_record.id}
        ```

        The last time this background migration was triggered was in [#{last_migration_file}](https://gitlab.com/gitlab-org/gitlab/-/blob/master/#{last_migration_file})

          You can read more about the process for finalizing batched background migrations in
        https://docs.gitlab.com/ee/development/database/batched_background_migrations.html .

          As part of our process we want to ensure all batched background migrations have had at least one
        [required stop](https://docs.gitlab.com/ee/development/database/required_stops.html)
        to process the migration. Therefore we can finalize any batched background migration that was added before the
        last required stop.
        MARKDOWN
        # rubocop:enable Gitlab/DocUrl

        queue_method_node = find_queue_method_node(last_migration_file)

        # TODO: Can runner figure out what changed during this block?
        migration_name = truncate_migration_name("Finalize#{migration['migration_job_name']}")
        PostDeploymentMigration::PostDeploymentMigrationGenerator
          .source_root('generator_templates/post_deployment_migration/post_deployment_migration/')
        generator = ::PostDeploymentMigration::PostDeploymentMigrationGenerator.new([migration_name], force: true)
        migration_file = generator.invoke_all.first
        changed_files = [migration_file]

        add_ensure_call_to_migration(migration_file, queue_method_node, job_name)
        ::Gitlab::Housekeeper::Shell.execute('rubocop', '-a', migration_file)

        digest = Digest::SHA256.hexdigest(generator.migration_number)
        digest_file = Pathname.new('db').join('schema_migrations', generator.migration_number.to_s).to_s
        File.open(digest_file, 'w') { |f| f.write(digest) }

        add_finalized_by_to_yaml(migration_yaml_file, generator.migration_number)

        changed_files << digest_file
        changed_files << migration_yaml_file

        to_create = ::Gitlab::Housekeeper::Change.new(identifiers, title, description, changed_files)
        yield(to_create)
      end
    end

    def truncate_migration_name(migration_name)
      # File names not allowed to exceed 100 chars due to Cop/FilenameLength so we truncate to 70 because there will be
      # underscores added.

      migration_name[0...70]
    end

    def add_finalized_by_to_yaml(yaml_file, migration_number)
      content = YAML.load_file(yaml_file)
      content['finalized_by'] = migration_number
      File.open(yaml_file, 'w') { |f| f.write(YAML.dump(content)) }
    end

    def last_migration_for_job(job_name)
      files = ::Gitlab::Housekeeper::Shell.execute('git', 'grep', '--name-only', "MIGRATION = .#{job_name}.")
        .each_line.map(&:chomp)

      result = files.select do |file|
        File.read(file).include?('queue_batched_background_migration')
      end.max

      raise "Could not find migration for #{job_name}" unless result.present?

      result
    rescue ::Gitlab::Housekeeper::Shell::Error
      # `git grep` returns an error status code if it finds no results
      nil
    end

    def add_ensure_call_to_migration(file, queue_method_node, job_name)
      source = RuboCop::ProcessedSource.new(File.read(file), 3.1)
      ast = source.ast
      source_buffer = source.buffer
      rewriter = Parser::Source::TreeRewriter.new(source_buffer)

      up_method = ast.children[2].each_child_node(:def).find do |child|
        child.method_name == :up
      end

      table_name = queue_method_node.children[3]
      column_name = queue_method_node.children[4]
      job_arguments = queue_method_node.children[5..].select { |s| s.type != :hash } # All remaining non-keyword args

      gitlab_schema = ::Gitlab::Database::GitlabSchema.table_schema(table_name.value.to_s)

      added_content = <<~RUBY.strip
      disable_ddl_transaction!

      restrict_gitlab_migration gitlab_schema: :#{gitlab_schema}

        def up
          ensure_batched_background_migration_is_finished(
            job_class_name: '#{job_name}',
            table_name: #{table_name.source},
            column_name: #{column_name.source},
            job_arguments: [#{job_arguments.map(&:source).join(', ')}],
            finalize: true
          )
        end
      RUBY

      rewriter.replace(up_method.loc.expression, added_content)

      content = strip_comments(rewriter.process)

      File.write(file, content)
    end

    def strip_comments(code)
      result = []
      code.each_line.with_index do |line, index|
        result << line unless index > 0 && line.lstrip.start_with?('#')
      end
      result.join
    end

    def fetch_migration_status(job_name)
      result = postgres_ai.fetch_background_migration_status(job_name)

      return unless result.count == 1

      migration_model = ::Gitlab::Database::BackgroundMigration::BatchedMigration.new(result.first)

      migration_model if migration_model.finished?
    end

    def postgres_ai
      @postgres_ai ||= Keeps::Helpers::PostgresAi.new
    end

    def migration_finalized?(job_name)
      result = `git grep --name-only "#{job_name}"`.chomp
      result.each_line.select do |file|
        File.read(file.chomp).include?('ensure_batched_background_migration_is_finished')
      end.any?
    end

    def find_queue_method_node(file)
      source = RuboCop::ProcessedSource.new(File.read(file), 3.1)
      ast = source.ast

      up_method = ast.children[2].children.find do |child|
        child.def_type? && child.method_name == :up
      end

      up_method.each_descendant.find do |child|
        child && child.send_type? && child.method_name == :queue_batched_background_migration
      end
    end

    def before_cuttoff_milestone?(milestone)
      Gem::Version.new(milestone) < Gem::Version.new(CUTOFF_MILESTONE)
    end

    def each_batched_background_migration
      all_batched_background_migration_files.map do |f|
        yield(f, YAML.load_file(f))
      end
    end

    def all_batched_background_migration_files
      Dir.glob("db/docs/batched_background_migrations/*.yml")
    end
  end
end