# GOV.UK Mini Environment Admin
# Copyright © 2018  Christopher Baines <mail@cbaines.net>
#
# This file is part of the GOV.UK Mini Environment Admin.
#
# The GOV.UK Mini Environment Admin is free software: you can
# redistribute it and/or modify it under the terms of the GNU Affero
# General Public License as published by the Free Software Foundation,
# either version 3 of the License, or (at your option) any later
# version.
#
# The GOV.UK Mini Environment Admin is distributed in the hope that it
# will be useful, but WITHOUT ANY WARRANTY; without even the implied
# warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
# See the GNU Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public
# License along with the GOV.UK Mini Environment Admin.  If not, see
# <http://www.gnu.org/licenses/>.

module GovukGuix::BuildMiniEnvironment
  extend ::ShellUtils

  DEFAULT_ARGUMENTS = {
    'rails-environment' => 'production',
    'use-high-ports' => 'false',
    'fallback' => true
  }.freeze

  def self.build(mini_environment_id, options)
    logger.info(self.class) do
      "Building mini environment #{mini_environment_id}"
    end

    mini_environment = MiniEnvironment.find(mini_environment_id)

    remote_host = options[:run_remotely_on_host]

    if remote_host && Guix.available_locally?
      # TODO: This doesn't use the private key specified by the
      # backend, so it'll only work when the default SSH key has
      # access to the remote host.

      # Copy the revision to the remote host, to ensure it's available
      # there
      run_command(
        'guix',
        'copy',
        "--to=#{remote_host.user_at_address}",
        mini_environment.govuk_guix_revision.store_path
      )
    end

    data_snapshot_arguments = {}

    if mini_environment.data_snapshot
      data_snapshot_arguments[:data_snapshot] =
        mini_environment.data_snapshot.store_path
    end

    output = run_command(
      "#{mini_environment.govuk_guix_revision.store_path}/bin/govuk",
      'system',
      'build',
      *hash_to_arguments(
        DEFAULT_ARGUMENTS
          .merge(options[:arguments])
          .merge(data_snapshot_arguments)
      ),
      *signon_user_arguments(mini_environment.signon_users),
      *options[:services],
      run_remotely_on_host: remote_host
    )

    build_output = output.last.strip

    raise 'InvalidOutput' unless build_output.starts_with? '/gnu/store'

    logger.debug(self.class) { "build_output: #{build_output}" }

    mini_environment.update(
      backend_data: {
        build_output: build_output
      }
    )

    build_output
  end

  def self.signon_user_to_sexp(signon_user)
    keys = %w(name email role passphrase)

    sexp_contents = keys.zip(
      signon_user.values_at(*keys)
    ).map do |(key, value)|
      "#:#{key} \"#{value}\""
    end

    "(#{sexp_contents.join(' ')})"
  end

  def self.signon_user_arguments(signon_users)
    signon_users.map do |signon_user|
      "--signon-user=#{signon_user_to_sexp(signon_user)}"
    end
  end
end