module Exports
  class CaseLogExportService
    QUARTERS = {
      0 => "jan_mar",
      1 => "apr_jun",
      2 => "jul_sep",
      3 => "oct_dec",
    }.freeze

    LOG_ID_OFFSET = 300_000_000_000
    MAX_XML_RECORDS = 10_000

    def initialize(storage_service, logger = Rails.logger)
      @storage_service = storage_service
      @logger = logger
    end

    def export_case_logs(full_update: false)
      start_time = Time.zone.now
      case_logs = retrieve_case_logs(start_time, full_update)
      export = build_export_run(start_time, full_update)
      daily_run = get_daily_run_number
      archive_datetimes = write_export_archive(export, case_logs)
      export.empty_export = archive_datetimes.empty?
      write_master_manifest(daily_run, archive_datetimes)
      export.save!
    end

    def is_omitted_field?(field_name)
      omitted_attrs = %w[ethnic_group]
      pattern_age = /age\d_known/
      field_name.starts_with?("details_known_") || pattern_age.match(field_name) || omitted_attrs.include?(field_name) ? true : false
    end

  private

    def get_daily_run_number
      today = Time.zone.today
      LogsExport.where(created_at: today.beginning_of_day..today.end_of_day).count + 1
    end

    def build_export_run(current_time, full_update)
      previous_exports_with_data = LogsExport.where(empty_export: false)

      if previous_exports_with_data.empty?
        return LogsExport.new(started_at: current_time)
      end

      base_number = previous_exports_with_data.maximum(:base_number)
      increment_number = previous_exports_with_data.where(base_number:).maximum(:increment_number)

      if full_update
        base_number += 1
        increment_number = 1
      else
        increment_number += 1
      end

      LogsExport.new(started_at: current_time, base_number:, increment_number:)
    end

    def write_master_manifest(daily_run, archive_datetimes)
      today = Time.zone.today
      increment_number = daily_run.to_s.rjust(4, "0")
      month = today.month.to_s.rjust(2, "0")
      day = today.day.to_s.rjust(2, "0")
      file_path = "Manifest_#{today.year}_#{month}_#{day}_#{increment_number}.csv"
      string_io = build_manifest_csv_io(archive_datetimes)
      @storage_service.write_file(file_path, string_io)
    end

    def get_archive_name(case_log, base_number, increment)
      return unless case_log.startdate

      collection_start = case_log.collection_start_year
      month = case_log.startdate.month
      quarter = QUARTERS[(month - 1) / 3]
      base_number_str = "f#{base_number.to_s.rjust(4, '0')}"
      increment_str = "inc#{increment.to_s.rjust(4, '0')}"
      "core_#{collection_start}_#{collection_start + 1}_#{quarter}_#{base_number_str}_#{increment_str}"
    end

    def write_export_archive(export, case_logs)
      # Order case logs per archive
      case_logs_per_archive = {}
      case_logs.each do |case_log|
        archive = get_archive_name(case_log, export.base_number, export.increment_number)
        next unless archive

        if case_logs_per_archive.key?(archive)
          case_logs_per_archive[archive] << case_log
        else
          case_logs_per_archive[archive] = [case_log]
        end
      end

      # Write all archives
      archive_datetimes = {}
      case_logs_per_archive.each do |archive, case_logs_to_export|
        manifest_xml = build_manifest_xml(case_logs_to_export.count)
        zip_file = Zip::File.open_buffer(StringIO.new)
        zip_file.add("manifest.xml", manifest_xml)

        part_number = 1
        case_logs_to_export.each_slice(MAX_XML_RECORDS) do |case_logs_slice|
          data_xml = build_export_xml(case_logs_slice)
          part_number_str = "pt#{part_number.to_s.rjust(3, '0')}"
          zip_file.add("#{archive}_#{part_number_str}.xml", data_xml)
          part_number += 1
        end

        # Required by S3 to avoid Aws::S3::Errors::BadDigest
        zip_io = zip_file.write_buffer
        zip_io.rewind
        @storage_service.write_file("#{archive}.zip", zip_io)
        archive_datetimes[archive] = Time.zone.now
      end

      archive_datetimes
    end

    def retrieve_case_logs(start_time, full_update)
      recent_export = LogsExport.order("started_at").last
      if !full_update && recent_export
        params = { from: recent_export.started_at, to: start_time }
        CaseLog.where("updated_at >= :from and updated_at <= :to", params)
      else
        params = { to: start_time }
        CaseLog.where("updated_at <= :to", params)
      end
    end

    def build_manifest_csv_io(archive_datetimes)
      headers = ["zip-name", "date-time zipped folder generated", "zip-file-uri"]
      csv_string = CSV.generate do |csv|
        csv << headers
        archive_datetimes.each do |archive, datetime|
          csv << [archive, datetime, "#{archive}.zip"]
        end
      end
      StringIO.new(csv_string)
    end

    def xml_doc_to_temp_file(xml_doc)
      file = Tempfile.new
      xml_doc.write_xml_to(file, encoding: "UTF-8")
      file.rewind
      file
    end

    def build_manifest_xml(record_number)
      doc = Nokogiri::XML("<report/>")
      doc.at("report") << doc.create_element("form-data-summary")
      doc.at("form-data-summary") << doc.create_element("records")
      doc.at("records") << doc.create_element("count-of-records", record_number)

      xml_doc_to_temp_file(doc)
    end

    def build_export_xml(case_logs)
      doc = Nokogiri::XML("<forms/>")

      case_logs.each do |case_log|
        form = doc.create_element("form")
        doc.at("forms") << form
        case_log.attributes.each do |key, _|
          if is_omitted_field?(key)
            next
          else
            value = case_log.read_attribute_before_type_cast(key)
            value += LOG_ID_OFFSET if key == "id"
            form << doc.create_element(key, value)
          end
        end
        form << doc.create_element("providertype", case_log.owning_organisation.read_attribute_before_type_cast(:provider_type))
      end

      xml_doc_to_temp_file(doc)
    end
  end
end