Allow custom lookup functions

.rubocop_todo.yml

@@ -292,7 +292,6 @@ Rails/FilePath:
 # Include: **/test/**/*
 Rails/RefuteMethods:
   Exclude:
-    - 'test/models/hiera_data/hierarchy_test.rb'
     - 'test/models/hiera_data/yaml_file_test.rb'
     - 'test/models/hierarchy_test.rb'
     - 'test/models/user_test.rb'
@@ -336,7 +335,6 @@ Style/ClassAndModuleChildren:
     - 'test/models/hiera_data/config_test.rb'
     - 'test/models/hiera_data/data_file_test.rb'
     - 'test/models/hiera_data/git_repo_test.rb'
-    - 'test/models/hiera_data/hierarchy_test.rb'
     - 'test/models/hiera_data/interpolation_test.rb'
     - 'test/models/hiera_data/yaml_file_test.rb'
     - 'test/test_helper.rb'
@@ -375,7 +373,6 @@ Style/GuardClause:
     - 'app/controllers/page_controller.rb'
     - 'app/controllers/sessions_controller.rb'
     - 'app/models/hiera_data/data_file.rb'
-    - 'app/models/hiera_data/hierarchy.rb'
 
 # Offense count: 1
 # Configuration parameters: MinBranchesCount.
@@ -399,7 +396,6 @@ Style/IfUnlessModifier:
     - 'app/controllers/sessions_controller.rb'
     - 'app/controllers/users_controller.rb'
     - 'app/models/hiera_data/config.rb'
-    - 'app/models/hiera_data/hierarchy.rb'
 
 # Offense count: 1
 # This cop supports safe auto-correction (--auto-correct).
@@ -416,7 +412,6 @@ Style/MutableConstant:
 Style/NumericLiteralPrefix:
   Exclude:
     - 'app/models/hiera_data/yaml_file.rb'
-    - 'test/models/hiera_data/hierarchy_test.rb'
     - 'test/models/hiera_data/yaml_file_test.rb'
 
 # Offense count: 1
@@ -431,10 +426,8 @@ Style/NumericLiterals:
 # Configuration parameters: PreferredDelimiters.
 Style/PercentLiteralDelimiters:
   Exclude:
-    - 'app/models/hiera_data/hierarchy.rb'
     - 'config/initializers/friendly_id.rb'
     - 'test/models/environment_test.rb'
-    - 'test/models/hiera_data/hierarchy_test.rb'
     - 'test/models/key_test.rb'
 
 # Offense count: 5
@@ -444,7 +437,6 @@ Style/PercentLiteralDelimiters:
 Style/PreferredHashMethods:
   Exclude:
     - 'app/models/hiera_data/data_file.rb'
-    - 'app/models/hiera_data/hierarchy.rb'
     - 'app/models/hiera_data/yaml_file.rb'
 
 # Offense count: 3

app/models/hiera_data/data_file.rb

@@ -61,7 +61,7 @@ def create_file(type)
       when :yaml
         YamlFile.new(path: @path)
       else
-        raise HDM::Error, "unsupported data file type #{type}"
+        raise Hdm::Error, "unsupported data file type #{type}"
       end
     end
   end

app/models/hiera_data/hierarchy.rb

@@ -1,6 +1,16 @@
 class HieraData
   class Hierarchy
-    LOOKUP_FUNCTIONS = %w(lookup_key data_hash data_dig hiera3_backend).freeze
+    LOOKUP_FUNCTIONS = %w[lookup_key data_hash data_dig hiera3_backend].freeze
+    BACKENDS = {
+      "data_hash" => {
+        "json_data" => :json,
+        "yaml_data" => :yaml
+      },
+      "lookup_key" => {
+        "eyaml_lookup_key" => :eyaml
+      }
+    }.freeze
+
     attr_reader :raw_hash
 
     def initialize(raw_hash:, base_path:)
@@ -17,17 +27,7 @@ def lookup_function
     end
 
     def backend
-      @backend ||=
-        case [lookup_function, raw_hash[lookup_function]]
-        when ["data_hash", "yaml_data"]
-          :yaml
-        when ["data_hash", "json_data"]
-          :json
-        when ["lookup_key", "eyaml_lookup_key"]
-          :eyaml
-        else
-          raise HDM::Error, "unknown backend #{raw_hash[lookup_function]}"
-        end
+      @backend ||= determine_backend
     end
 
     def datadir(facts: nil)
@@ -44,15 +44,15 @@ def datadir(facts: nil)
     end
 
     def private_key
-      if backend == :eyaml
-        @base_path.join(raw_hash.dig("options", "pkcs7_private_key"))
-      end
+      return unless backend == :eyaml
+
+      @base_path.join(raw_hash.dig("options", "pkcs7_private_key"))
     end
 
     def public_key
-      if backend == :eyaml
-        @base_path.join(raw_hash.dig("options", "pkcs7_public_key"))
-      end
+      return unless backend == :eyaml
+
+      @base_path.join(raw_hash.dig("options", "pkcs7_public_key"))
     end
 
     def encryptable?
@@ -62,7 +62,7 @@ def encryptable?
     end
 
     def uses_globs?
-      raw_hash.has_key?("glob") || raw_hash.has_key?("globs")
+      raw_hash.key?("glob") || raw_hash.key?("globs")
     end
 
     def paths
@@ -93,5 +93,16 @@ def setup_paths
       base_key = uses_globs? ? "glob" : "path"
       Array(raw_hash[base_key] || raw_hash.fetch("#{base_key}s", []))
     end
+
+    def determine_backend
+      key = lookup_function
+      value = raw_hash[lookup_function]
+      backends = BACKENDS
+      custom_mappings = Rails.configuration.hdm[:custom_lookup_function_mapping]
+      backends = backends.deep_merge({ "lookup_key" => custom_mappings }) if custom_mappings.present?
+      backends.fetch(key).fetch(value).to_sym
+    rescue KeyError
+      raise Hdm::Error, "unknown backend #{value}"
+    end
   end
 end

config/hdm.yml.template

@@ -79,3 +79,12 @@ production:
 #     idp_cert_fingerprint: "aaa"
 #     idp_cert: "cert" # use either fingerprint _or_ cert but not both
 
+# Example for a custom lookup function, called `my_custom_function`,
+# mapped to an existing backend, `eyaml`
+# production:
+#   read_only: false
+#   allow_encryption: true
+#   puppet_db:
+#     server: "https://localhost:8081"
+#   custom_lookup_function_mapping:
+#     my_custom_function: eyaml