#
# Rake tasks for receiving article updates by email.
#
# Mail setup is heavily inspired by Foodsoft's reply-by-mail feature for messages
# @see https://github.com/foodcoops/foodsoft/blob/master/lib/foodsoft_mail_receiver.rb
#
require "mail"
require "midi-smtp-server"

class ReplyEmailSmtpServer < MidiSmtpServer::Smtpd

  def start
    super
    @from = nil
    @supplier = nil
  end

  private

  def on_mail_from_event(ctx, from)
    @from = from
  end

  def on_rcpt_to_event(ctx, rcpt_to)
    recipient = rcpt_to.gsub(/\A\s*<\s*(.*)\s*>\s*\z/, '\1')
    @supplier = find_supplier(recipient)
    rcpt_to
  rescue => error
    logger.info("Can not accept mail for '#{rcpt_to}': #{error}")
    raise MidiSmtpServer::Smtpd550Exception
  end

  def on_message_data_event(ctx)
    handle_mail(ctx[:message][:data])
  end

  def find_supplier(recipient)
    m = /\A#{Regexp.escape(ENV['MAILER_PREFIX'])}(?<supplier_id>\d+)\.(?<hash>\w+)(@(?<hostname>.*))?/.match(recipient)
    raise "recipient is missing or has an invalid format" if m.nil?

    supplier = Supplier.mail_sync.find_by_id(m[:supplier_id])
    raise "supplier id #{m[:supplier_id]} could not be found" if supplier.nil?

    hash = supplier.articles_mail_hash
    hash.casecmp(m[:hash]) == 0 or raise "hash '#{m[:hash]}' does not match expectations for supplier '#{supplier.name}'"

    supplier
  end

  def handle_mail(data)
    message = Mail.read_from_string(data)

    # message checks
    if @supplier.mail_from.present?
      m, s = message.from, @supplier.mail_from
      m.any? {|n| n.include?(s) } or raise "Expected to find '#{s}' in from address '#{m.join(', ')}' for supplier #{@supplier.name}"
    end
    if @supplier.mail_subject.present?
      m, s = message.subject, @supplier.mail_subject
      m.downcase.include?(s.downcase) or raise "Expected to find '#{s}' in subject '#{m}' for supplier #{@supplier.name}"
    end

    # get attachment
    filename = nil
    message.attachments.each do |part|
      # @todo perhaps get heuristic from article import filters?
      if part.filename.match(/\.(xls|xlsx|ods|sxc|csv|tsv|xml)$/i)
        FileUtils.mkdir_p(@supplier.mail_path)
        filename = "#{message.date.strftime '%Y%m%d'}_#{part.filename.gsub(/[^-a-z0-9_\.]+/i, '_')}"
        filename = @supplier.mail_path.join(filename)
        File.open(filename, 'w+b') { |f| f.write part.body.decoded }
      end
    end

    raise "No spreadsheet attachment found" unless filename.present?

    # import!
    outlisted_counter, new_counter, updated_counter, invalid_articles =
        @supplier.update_articles_from_file(File.new(filename), type: @supplier.mail_type)

    msg = "Handled articles update email for #{@supplier.name}: "
    msg += "#{new_counter} new, #{updated_counter} updated, #{outlisted_counter} outlisted, #{invalid_articles.size} invalid"
    invalid_articles.map do |article|
      msg += "\n* invalid article '#{article.name}'"
      article.errors.each do |attr, errmsg|
        errmsg.split("\n").each do |l|
          msg += "\n  - #{': ' unless attr.blank?}" + l
        end
      end
    end

    logger.info(msg)
  end
end

namespace :mail do
  desc "Parse incoming email on stdin (options: RECIPIENT=1.a1b2c3d3e5)"
  task parse_reply_email: :environment do
    hande_mail(ENV['RECIPIENT'], STDIN.read)
  end

  desc "Start STMP server for incoming email (options: SMTP_SERVER_PORT=2525, SMTP_SERVER_HOST=127.0.0.1)"
  task :smtp_server => :environment do
    port = ENV['SMTP_SERVER_PORT'] || '2525'
    host = ENV['SMTP_SERVER_HOST'] || '127.0.0.1'
    rake_say "Started SMTP server for incoming email on #{host}:#{port}."
    server = ReplyEmailSmtpServer.new(ports: port, hosts: host)
    server.start
    server.join
  end
end

# Helper
def rake_say(message)
  puts message unless Rake.application.options.silent
end