1 files changed, 63 insertions, 0 deletions
diff --git a/lib/rubygems/resolver/molinillo/lib/molinillo/modules/ui.rb b/lib/rubygems/resolver/molinillo/lib/molinillo/modules/ui.rb
new file mode 100644
index 0000000000..18f5363950
--- /dev/null
+++ b/lib/rubygems/resolver/molinillo/lib/molinillo/modules/ui.rb
@@ -0,0 +1,63 @@
+module Gem::Resolver::Molinillo
+  # Conveys information about the resolution process to a user.
+  module UI
+    # The {IO} object that should be used to print output. `STDOUT`, by default.
+    #
+    # @return [IO]
+    def output
+      STDOUT
+    end
+
+    # Called roughly every {#progress_rate}, this method should convey progress
+    # to the user.
+    #
+    # @return [void]
+    def indicate_progress
+      output.print '.' unless debug?
+    end
+
+    # How often progress should be conveyed to the user via
+    # {#indicate_progress}, in seconds. A third of a second, by default.
+    #
+    # @return [Float]
+    def progress_rate
+      0.33
+    end
+
+    # Called before resolution begins.
+    #
+    # @return [void]
+    def before_resolution
+      output.print 'Resolving dependencies...'
+    end
+
+    # Called after resolution ends (either successfully or with an error).
+    # By default, prints a newline.
+    #
+    # @return [void]
+    def after_resolution
+      output.puts
+    end
+
+    # Conveys debug information to the user.
+    #
+    # @param [Integer] depth the current depth of the resolution process.
+    # @return [void]
+    def debug(depth = 0)
+      if debug?
+        debug_info = yield
+        debug_info = debug_info.inspect unless debug_info.is_a?(String)
+        output.puts debug_info.split("\n").map { |s| '  ' * depth + s }
+      end
+    end
+
+    # Whether or not debug messages should be printed.
+    # By default, whether or not the `MOLINILLO_DEBUG` environment variable is
+    # set.
+    #
+    # @return [Boolean]
+    def debug?
+      @debug_mode ||= ENV['MOLINILLO_DEBUG']
+    end
+  end
+end