1 files changed, 97 insertions, 0 deletions
diff --git a/lib/knapsack_solver/output_printer.rb b/lib/knapsack_solver/output_printer.rb
new file mode 100644
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+++ b/lib/knapsack_solver/output_printer.rb
@@ -0,0 +1,97 @@
+module KnapsackSolver
+  # This class provides support for printing results and statistics of a
+  # dataset solving either to stdout or to a text file.
+  class OutputPrinter
+    # Initializes printer for output log (results, statistics).
+    #
+    # @param dataset_filenames [Array<String>] dataset filenames
+    # @param suffix [String] suffix of the created files
+    # @param results [Hash] results of solving or statistics to print
+    def initialize(dataset_filenames, suffix, results)
+      @dataset_basenames = file_basenames(dataset_filenames)
+      @suffix = suffix
+      @results = results
+    end
+
+    # Prints results or statistics to stdout or to files in output directory.
+    #
+    # @param out_dir [String] path to output directory
+    def print(out_dir = nil)
+      @results.each_value.with_index do |results, index|
+        results.each do |method, res|
+          print_solving_method_results(method, res, out_dir, @dataset_basenames[index])
+        end
+      end
+    end
+
+    protected
+
+    # Prints results of solving or statistics.
+    #
+    # @param method [Symbol] symbol for solving method
+    # @param res [Hash] results of the solving method
+    # @param out_dir [String] path to output directory
+    # @param basename [String] basename of dataset input file corresponding to the results
+    def print_solving_method_results(method, res, out_dir, basename)
+      of = output_filename(out_dir, basename, method.to_s)
+      os = output_stream(out_dir, of)
+      print_header(os, of, res)
+      res.each do |r|
+        os.puts r.values.each_with_object([]) { |v, a| a << v.to_s }.join(' ')
+      end
+      os.puts if out_dir.nil?
+    end
+
+    # Opens output file and turns on synchronized writes (this is neede for
+    # testing with Rspec).
+    #
+    # @param fname [String] path to the output file
+    # @return [#puts] output stream
+    def open_output_file(fname)
+      f = File.new(fname, 'w')
+      f.sync = true
+      f
+    end
+
+    # Sets output stream to stdout or to a file if path to it was provided.
+    #
+    # @param out_dir [String] directory for output files
+    # @param out_file [String] output file
+    def output_stream(out_dir, out_file)
+      return $stdout if out_dir.nil?
+      open_output_file(out_file)
+    end
+
+    # Prints header of output log file.
+    #
+    # @param out_stream [#puts] stream to which output will be printed
+    # @param out_file [String] name of output file
+    # @param results [Hash] results of solving or statistics
+    def print_header(out_stream, out_file, results)
+      out_stream.puts "# #{out_file}"
+      out_stream.puts "# #{results.first.keys.join('    ')}"
+    end
+
+    # Gets basenames of supplied file paths.
+    #
+    # @param paths [Array<String>] path to files
+    # @return [Array<String>] basenames of the paths
+    def file_basenames(paths)
+      paths.each_with_object([]) do |path, basenames|
+        basenames << File.basename(path, File.extname(path))
+      end
+    end
+
+    # Construct filename for output log.
+    #
+    # @param output_dir [String] output directory
+    # @param basename [String] basename of the output file
+    # @param solving_method [String] name of solving method
+    # @return [String] filename for output log
+    def output_filename(output_dir, basename, solving_method)
+      filename = basename + '_' + solving_method + @suffix
+      return filename if output_dir.nil?
+      File.join(output_dir, filename)
+    end
+  end
+end