require "csv"
require "email/mboxrd/message"

module Imap::Backup
  module Serializer; end

  class Serializer::Mbox < Serializer::Base
    def initialize(path, folder)
      super
      create_containing_directory
      assert_files
    end

    # TODO: cleanup locks, close file handles

    def uids
      return @uids if @uids

      @uids = []
      return @uids if !exist?

      CSV.foreach(imap_pathname) do |row|
        @uids << row[0]
      end
      @uids = @uids.map(&:to_i).sort
      @uids
    end

    def save(uid, message)
      uid = uid.to_s
      if uids.include?(uid)
        Imap::Backup.logger.debug(
          "[#{folder}] message #{uid} already downloaded - skipping"
        )
        return
      end

      # invalidate cache
      @uids = nil

      body = message["RFC822"]
      mboxrd_message = Email::Mboxrd::Message.new(body)
      mbox = imap = nil
      begin
        mbox = File.open(mbox_pathname, "ab")
        imap = File.open(imap_pathname, "ab")
        mbox.write mboxrd_message.to_serialized
        imap.write uid + "\n"
      rescue => e
        message = <<-ERROR.gsub(/^\s*/m, "")
          [#{folder}] failed to save message #{uid}:
          #{body}. #{e}:
          #{e.backtrace.join("\n")}"
        ERROR
        Imap::Backup.logger.warn message
      ensure
        mbox.close if mbox
        imap.close if imap
      end
    end

    private

    def assert_files
      mbox = mbox_exist?
      imap = imap_exist?
      raise ".imap file missing" if mbox && (!imap)
      raise ".mbox file missing" if imap && (!mbox)
    end

    def create_containing_directory
      mbox_relative_path = File.dirname(mbox_relative_pathname)
      return if mbox_relative_path == "."
      Utils.make_folder(
        path, mbox_relative_path, Serializer::DIRECTORY_PERMISSIONS
      )
    end

    def exist?
      mbox_exist? && imap_exist?
    end

    def mbox_exist?
      File.exist?(mbox_pathname)
    end

    def imap_exist?
      File.exist?(imap_pathname)
    end

    def mbox_relative_pathname
      folder + ".mbox"
    end

    def mbox_pathname
      File.join(path, mbox_relative_pathname)
    end

    def imap_pathname
      filename = folder + ".imap"
      File.join(path, filename)
    end

    def lock
      # lock mbox and imap files
      # create both empty if missing
    end

    def unlock
    end
  end
end