require 'time'
require 'dmao_api'
require 'dmao/ingesters/errors/generic_ingester'
require 'dmao/ingesters/errors/empty_attributes'
require 'dmao/ingesters/errors/ingest_entity_error'

module DMAO
  module Ingesters
    module Generic

      class Ingester

        ENTITY = nil
        ENTITY_ERROR = nil
        INVALID_ENTITY_ERROR = nil
        ENTITY_ERROR_MESSAGE = nil

        def initialize(api_url=nil, api_token=nil, institution_id=nil)
          DMAO::API.configure do |config|
            config.base_url = api_url
            config.api_token = api_token
            config.institution_id = institution_id
          end
        end

        def ingest
          raise DMAO::Ingesters::Errors::GenericIngester.new("Calling ingest on generic ingester is not allowed.")
        end

        def ingest_entity attributes = {}

          raise DMAO::Ingesters::Errors::EmptyAttributes.new("Cannot ingest #{entity_name} without attributes.") if attributes.nil? || attributes.empty?

          begin

            entity = self.class::ENTITY.find_by_system_uuid attributes[:system_uuid]

            current_modified_at = Time.parse(entity.system_modified_at)
            new_modified_at = Time.parse(attributes[:system_modified_at])

            return false if current_modified_at >= new_modified_at

            update_entity entity.id, attributes

          rescue DMAO::API::Errors::EntityNotFound
            add_entity attributes
          rescue DMAO::API::Errors::InvalidResponseLength
            raise self.class::ENTITY_ERROR.new("More than one #{entity_name} returned for system uuid #{attributes[:system_uuid]}.")
          end

        end

        def parse_unprocessable_errors errors

          error_messages = ""

          errors.each_with_index do |(k, v), index|
            v.each_with_index do |msg, msg_index|
              error_messages += "#{k} - #{msg}"
              error_messages += ", " unless msg_index == v.size - 1
            end
            error_messages += ", " unless index == errors.size - 1
          end

          raise self.class::ENTITY_ERROR.new("#{self.class::ENTITY_ERROR_MESSAGE}, #{error_messages}")

        end

        def add_entity attributes={}

          begin
            self.class::ENTITY.create attributes
          rescue DMAO::API::Errors::InstitutionNotFound
            raise self.class::ENTITY_ERROR.new("Institution not found, cannot ingest #{entity_name} to non-existent institution")
          rescue self.class::INVALID_ENTITY_ERROR => e
            parse_unprocessable_errors(e.errors)
          end

        end

        def update_entity entity_id, attributes={}

          begin
            self.class::ENTITY.update entity_id, attributes
          rescue DMAO::API::Errors::EntityNotFound
            raise self.class::ENTITY_ERROR.new("#{entity_name.capitalize} not found, cannot update #{entity_name} that does not exist")
          rescue self.class::INVALID_ENTITY_ERROR => e
            parse_unprocessable_errors(e.errors)
          end

        end

        def entity_name
          self.class::ENTITY.to_s.split('::')[-1].gsub(/[A-Z]/, " \\0").strip.downcase
        end

      end

    end
  end
end