# frozen_string_literal: true

require 'set'
require 'datasync/exceptions'
require 'datasync/sync_operation'

module Datasync
  # Implicit mapper handles sync between a source and destination, linking on a common field
  class LinkTableMapper < Mapper
    attr_reader :link_table_proc, :mapping_name

    # Specialized SyncOperation which knows how to handle linking / unlinking
    class LinkTableSyncOp < SyncOperation
      def initialize(mapper)
        super
        @link_ds = mapper.link_table_proc.call
        @mapping_name = mapper.mapping_name
      end

      def link(source_id, target_id)
        @link_ds.insert(mapping: @mapping_name, source_id: source_id, target_id: target_id)
      end

      def unlink(source_id, target_id)
        @link_ds.where(mapping: @mapping_name, source_id: source_id, target_id: target_id).delete
      end

      def configure_classifier(classifier)
        classifier.assume_nothing!
      end

      def links
        @link_ds.where(mapping: @mapping_name).select(:source_id, :target_id).all
      end
    end

    def sync_class
      LinkTableSyncOp
    end

    def option(name, value)
      case name
      when :link_table then @link_table_proc = value
      when :mapping_name then @mapping_name = value
      else raise OptionError, "Unknown option #{name}"
      end
    end

    def validate!
      super
      raise ValidationError, 'Link table must be specified' unless @link_table_proc
      raise ValidationError, 'Mapping name must be specified' unless @mapping_name
    end
  end
end