# 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/>.

require 'open3'
require 'shellwords'
require 'tempfile'

module ShellUtils
  def run_command(
        *command,
        run_remotely_on_host: nil,
        environment_variables: {}
      )
    if run_remotely_on_host
      command = command.map do |arg|
        Shellwords.escape(arg)
      end

      identity_file = Tempfile.new(
        'private-identity-file',
        Rails.root.join('tmp')
      )
      identity_file.write(run_remotely_on_host.private_key)
      identity_file.close

      command = [
        'ssh',
        # Use a automatically trust on first use model
        '-o', 'StrictHostKeyChecking=no',
        '-o', 'ServerAliveInterval=20',
        '-i', identity_file.path,
        run_remotely_on_host.user_at_address,
        *environment_variables_to_shell_arguments(environment_variables),
        *command
      ]

      local_environment_variables = {}
    else
      local_environment_variables = environment_variables
    end

    logger.info("#{self.class}: Running command #{command.join(' ')}")

    Open3.popen2e(
      local_environment_variables,
      *command
    ) do |_stdin, stdout_and_stderr, wait_thr|
      logger.info("#{self.class}: commmand running, pid #{wait_thr.pid}")

      output = []
      stdout_and_stderr.each_line do |line|
        logger.info(self.class) { line.chomp }
        output << line
      end

      exit_status = wait_thr.value
      unless exit_status == 0
        logger.error(self.class) { "failed, exit status #{exit_status}" }

        identity_file.unlink if identity_file
        raise "Running #{command.join(' ')} failed:\n\n#{output.join}\n"
      end

      identity_file.unlink if identity_file

      output
    end
  end

  def read_json_file(filename, from_remote_host: nil)
    if from_remote_host
      identity_file = Tempfile.new(
        'private-identity-file',
        Rails.root.join('tmp')
      )
      identity_file.write(from_remote_host.private_key)
      identity_file.close

      command = [
        'ssh',
        from_remote_host.user_at_address,
        # Use a automatically trust on first use model
        '-o', 'StrictHostKeyChecking=no',
        '-i', identity_file.path,
        'cat',
        filename
      ]

      stdout_str, status = Open3.capture2(*command)

      identity_file.unlink if identity_file

      unless status.exitstatus == 0
        logger.error(self.class) { "failed, exit status #{exit_status}" }

        raise "Running #{command.join(' ')} failed:\n\n#{output.join}\n"
      end

      JSON.parse(stdout_str)
    else
      JSON.parse(File.read(filename))
    end
  end

  def hash_to_arguments(hash)
    hash.flat_map do |(key, value)|
      transformed_key = key.to_s.tr('_', '-')

      if value == true
        ["--#{transformed_key}"]
      elsif value.kind_of?(Array)
        value.map { |x| "--#{transformed_key}=#{x}" }
      else
        ["--#{transformed_key}=#{value}"]
      end
    end
  end

  def environment_variables_to_shell_arguments(environment_variables)
    environment_variables.map do |key, value|
      "#{key}=\"#{value}\""
    end
  end
end