require_relative 'operator'

module ConceptQL
  module Operators
    # A SourceVocabularyOperator is a superclass for a operator that represents a criterion whose column stores information associated with a source vocabulary.
    #
    # If that seems confusing, then think of ICD-9 or NDC criteria.  That type of criterion takes a set of values that are mapped via the source_to_concept_map table into a standard vocabulary.
    #
    # This kind of criterion can have some interesting issues when we are searching for rows that match.  Let's take ICD-9 286.53 for example. That code maps to concept_id 0, so if we try to pull all conditions that match just the concept_id of 0 we'll pull all condtions that have no match in the SNOMED standard vocabulary.  That's not what we want!  So we need to search the condition_source_value field for matches on this code instead.
    #
    # But there's another, more complicated problem.  Say we're looking for ICD-9 289.81.  OMOP maps this to concept_id 432585.  OMOP also maps 20 other conditions, 6 of which are other ICD-9 codes, to this same concept_id.  So if we look for ICD-9s that have a non-zero condition_condept_id, we might pull up conditions that match on concept_id, but aren't the same exact code as the one we're looking for.
    #
    # My coworker came up with a nice, gneralized query that checks for matching concept_ids and matching source_code values.  This class encapsulates that query.
    #
    # Subclasses must provide the following methods:
    # * table
    #   * The CDM table name where the criterion will fetch its rows
    #   * e.g. for ICD-9, this would be condition_occurrence
    # * concept_column
    #   * Name of the column in the table that stores a concept_id related to the criterion
    #   * e.g. for ICD-9, this would be condition_concept_id
    # * source_column
    #   * Name of the column in the table that stores the "raw" value related to the criterion
    #   * e.g. for ICD-9, this would be condition_source_value
    # * vocabulary_id
    #   * The vocabulary ID of the source vocabulary for the criterion
    #   * e.g. for ICD-9, a value of 2 (for ICD-9-CM)
    class SourceVocabularyOperator < Operator
      category 'Source Vocabulary'
      category 'Code Lists'

      def query(db)
        db.from(table_name)
          .join(:vocabulary__source_to_concept_map___scm, scm__target_concept_id: table_concept_column)
          .where(Sequel.expr(scm__source_code: values, scm__source_vocabulary_id: vocabulary_id).&(Sequel.expr(scm__source_code: table_source_column)))
      end

      def type
        table
      end

      private

      def table_name
        @table_name ||= make_table_name(table)
      end

      def table_concept_column
        "tab__#{concept_column}".to_sym
      end

      def table_source_column
        "tab__#{source_column}".to_sym
      end
    end
  end
end