1 files changed, 78 insertions, 0 deletions
diff --git a/lib/gitlab/ci/config/interpolation/inputs.rb b/lib/gitlab/ci/config/interpolation/inputs.rb
new file mode 100644
index 00000000000..0fd3238d503
--- /dev/null
+++ b/lib/gitlab/ci/config/interpolation/inputs.rb
@@ -0,0 +1,78 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Ci
+    class Config
+      module Interpolation
+        # Interpolation inputs provided by the user.
+        class Inputs
+          UnknownInputTypeError = Class.new(StandardError)
+
+          TYPES = [
+            BooleanInput,
+            NumberInput,
+            StringInput
+          ].freeze
+
+          def self.input_types
+            TYPES.map(&:type_name)
+          end
+
+          def initialize(specs, args)
+            @specs = specs.to_h
+            @args = args.to_h
+            @inputs = []
+            @errors = []
+
+            validate!
+            fabricate!
+          end
+
+          def errors
+            @errors + @inputs.flat_map(&:errors)
+          end
+
+          def valid?
+            errors.none?
+          end
+
+          def to_hash
+            @inputs.inject({}) do |hash, input|
+              hash.merge(input.to_hash)
+            end
+          end
+
+          private
+
+          def validate!
+            unknown_inputs = @args.keys - @specs.keys
+            return if unknown_inputs.empty?
+
+            @errors.push("unknown input arguments: #{unknown_inputs.join(', ')}")
+          end
+
+          def fabricate!
+            @specs.each do |input_name, spec|
+              input_type = TYPES.find { |klass| klass.matches?(spec) }
+
+              unless input_type
+                @errors.push(
+                  "unknown input specification for `#{input_name}` (valid types: #{valid_type_names.join(', ')})")
+                next
+              end
+
+              @inputs.push(input_type.new(
+                name: input_name,
+                spec: spec,
+                value: @args[input_name]))
+            end
+          end
+
+          def valid_type_names
+            TYPES.map(&:type_name)
+          end
+        end
+      end
+    end
+  end
+end