module PatientMatcher

# File app/lib/patient_matcher.rb, line 74
def self.from_enumerable(
  candidates,
  nhs_number:,
  given_name:,
  family_name:,
  date_of_birth:,
  address_postcode:,
  include_3_out_of_4_matches: true
)
  nhs_number = normalise_nhs_number(nhs_number)
  address_postcode = normalise_postcode(address_postcode)

  if nhs_number.present?
    matched =
      candidates.find { normalise_nhs_number(it.nhs_number) == nhs_number }

    return [matched] if matched.present?
  end

  given_name_downcase = given_name.downcase
  family_name_downcase = family_name.downcase

  results =
    candidates.select do
      patient_nhs_number = normalise_nhs_number(it.nhs_number)
      next false if nhs_number.present? && patient_nhs_number.present?

      given_name_matches = it.given_name.to_s.downcase == given_name_downcase
      family_name_matches =
        it.family_name.to_s.downcase == family_name_downcase
      date_of_birth_matches = it.date_of_birth == date_of_birth

      if address_postcode.present?
        postcode_matches =
          normalise_postcode(it.address_postcode) == address_postcode

        if include_3_out_of_4_matches
          (
            given_name_matches && family_name_matches && date_of_birth_matches
          ) ||
            (given_name_matches && family_name_matches && postcode_matches) ||
            (
              given_name_matches && date_of_birth_matches && postcode_matches
            ) ||
            (family_name_matches && date_of_birth_matches && postcode_matches)
        else
          given_name_matches && family_name_matches &&
            date_of_birth_matches && postcode_matches
        end
      else
        given_name_matches && family_name_matches && date_of_birth_matches
      end
    end

  narrow_to_single_exact_match_if_possible(
    results,
    given_name:,
    family_name:,
    date_of_birth:,
    address_postcode:
  )
end

# File app/lib/patient_matcher.rb, line 4
def self.from_relation(
  relation,
  nhs_number:,
  given_name:,
  family_name:,
  date_of_birth:,
  address_postcode:,
  include_3_out_of_4_matches: true
)
  nhs_number = normalise_nhs_number(nhs_number)
  address_postcode = normalise_postcode(address_postcode)

  if nhs_number.present? && (patient = relation.find_by(nhs_number:)).present?
    return [patient]
  end

  scope =
    relation.where(
      "lower(given_name) = lower(?) AND lower(family_name) = lower(?)",
      given_name,
      family_name
    ).where(date_of_birth:)

  if address_postcode.present?
    scope =
      if include_3_out_of_4_matches
        scope
          .or(
            relation.where(
              "lower(given_name) = lower(?) AND lower(family_name) = lower(?)",
              given_name,
              family_name
            ).where(address_postcode:)
          )
          .or(
            relation.where("lower(given_name) = lower(?)", given_name).where(
              date_of_birth:,
              address_postcode:
            )
          )
          .or(
            relation.where(
              "lower(family_name) = lower(?)",
              family_name
            ).where(date_of_birth:, address_postcode:)
          )
      else
        scope.where(address_postcode:)
      end
  end

  results =
    if nhs_number.blank?
      scope.to_a
    else
      # This prevents us from finding a patient that happens to have at least
      # three of the other fields the same, but with a different NHS number,
      # and therefore cannot be a match.
      relation.where(nhs_number: nil).merge(scope).to_a
    end

  narrow_to_single_exact_match_if_possible(
    results,
    given_name:,
    family_name:,
    date_of_birth:,
    address_postcode:
  )
end