WIP towards Alma SRU model

app/models/alma_sru.rb

@@ -0,0 +1,70 @@
+# frozen_string_literal: true
+
+# Queries the Alma SRU endpoint for holdings data
+#
+# @reference https://developers.exlibrisgroup.com/alma/integrations/SRU/
+class AlmaSru
+  class LookupFailure < StandardError; end
+
+  class InvalidAlmaId < StandardError; end
+
+  # lookup will receive an Alma ID, validate it, look it up in the Alma SRU, and return a formatted result.
+  #
+  # It accepts an "alma_client" argument for use when testing, but this is not used in normal operations.
+  def self.lookup(raw_identifier, alma_client: nil)
+    return nil unless alma_base_url
+
+    # Validate the raw identifier received. This will raise an InvalidAlmaId if validation fails.
+    identifier = validate_alma_id(raw_identifier)
+
+    # Build URL
+    url = alma_sru_url(identifier)
+
+    # Retrieve that URL
+    alma_http = setup(url, alma_client)
+
+    parse_response(alma_http.timeout(6).get(url))
+  rescue InvalidAlmaId
+    Rails.logger.error("Invalid Alma ID: #{raw_identifier}")
+  rescue LookupFailure => e
+    Rails.logger.error("Alma lookup failure: #{e}")
+  end
+
+  def self.parse_response(raw_response)
+    raise LookupFailure, raw_response.status unless raw_response.status == 200
+
+    raw_response
+  end
+
+  # validate_alma_id ensures we are only submitting valid Alma IDs to the SRU endpoint.
+  #
+  # It needs to do two thigns:
+  # 1. Remove the "alma" prefix if one is present. Otherwise, no manipulation of the submitted value should occur.
+  # 2. Enforce the formatting requirements for a valid alma identifier (start with "99", and end with "6761").
+  def self.validate_alma_id(raw)
+    parsed = if raw.start_with?('alma')
+               raw.delete_prefix('alma')
+             else
+               raw
+             end
+
+    raise InvalidAlmaId unless parsed.to_s.start_with?('99')
+    raise InvalidAlmaId unless parsed.to_s.end_with?('6761')
+
+    parsed
+  end
+
+  def self.alma_base_url
+    ENV.fetch('MIT_ALMA_URL', nil)
+  end
+
+  def self.alma_sru_url(identifier)
+    # example identifier: 990000959610106761
+    "#{alma_base_url}/view/sru/#{ENV.fetch('EXL_INST_ID')}?version=1.2&operation=searchRetrieve&recordSchema=marcxml" \
+      "&query=alma.all_for_ui=#{identifier}"
+  end
+
+  def self.setup(url, alma_client)
+    alma_client || HTTP.persistent(url)
+  end
+end

test/models/alma_sru_test.rb

@@ -0,0 +1,23 @@
+require 'test_helper'
+
+class AlmaSruTest < ActiveSupport::TestCase
+  test 'validate_alma_id succeeds with valid numeric input' do
+    needle = '990002935920106761'
+    assert_nothing_raised do
+      AlmaSru.validate_alma_id(needle)
+    end
+  end
+
+  test 'validate_alma_id succeeds despite and "alma" prefix' do
+    needle = 'alma990002935920106761'
+    assert_nothing_raised do
+      AlmaSru.validate_alma_id(needle)
+    end
+  end
+
+  test 'validate_alma_id raises InvalidAlmaId with invalid input' do
+    assert_raises(AlmaSru::InvalidAlmaId) do
+      AlmaSru.validate_alma_id('foo')
+    end
+  end
+end