sul-dlss/argo

# frozen_string_literal: true

# This exports the cocina description to a rectangularized data structure
class DescriptionExport
  def self.export(source_id:, description:)
    new(source_id:, description:).export
  end

  def initialize(source_id:, description:)
    @description = description
    @source_id = source_id.presence || '' # identification.sourceId is not a required property.
  end

  def export
    flatten(squish(description.to_h).merge('source_id' => @source_id))
  end

  # Transform the COCINA datastructure into a hash structure by converting
  # arrays to hashes with index (starting at 1) as the key
  def squish(source)
    return source unless source.is_a? Hash

    source.each_with_object({}) do |(k, value), sink|
      new_value = if value.is_a? Array
                    # Transform to hash
                    value.each_with_object({}).with_index(1) { |(el, acc), index| acc[index] = squish(el) }
                  else
                    squish(value)
                  end
      sink[k.to_s] = new_value.presence
    end.compact
  end

  # Change the nested hash structure into a single level hash
  def flatten(source)
    source.each_with_object({}) do |(key, value), sink|
      if value.is_a? String
        sink[key] = value
      else
        flatten(value).each do |k, v|
          new_key = k.start_with?(/\d/) ? "#{key}#{k}" : "#{key}.#{k}"
          sink[new_key] = v
        end
      end
    end
  end

  attr_reader :description
end