Refactor reporter class out of the bin/churn file

This also adds support for a JSON format output.

lib/churn/reporter.rb

@@ -0,0 +1,57 @@
+require 'json'
+
+require_relative 'calculator'
+require_relative 'version'
+
+module Churn
+
+  # The reporter of churn results. Knows how to report churn
+  # in different formats:
+  #
+  # - Console (stdout)
+  # - YAML
+  # - JSON
+  class ChurnReporter
+    attr_accessor :calculator, :options, :params
+
+    def initialize(_params)
+      self.params = _params
+      self.options = {
+        minimum_churn_count: params['minimum_churn_count'].value,
+        ignore_files: params['ignore_files'].value,
+        start_date: params['start_date'].value,
+        data_directory: params['data_directory'].value,
+        history: params['past_history'].value,
+        report: params['report'].value,
+        name: params['name'].value,
+        file_extension: params['extension'].value,
+        file_prefix: params['prefix'].value,
+        json: params['json'].value,
+        yaml: params['yaml'].value,
+      }
+      self.calculator = Churn::ChurnCalculator.new(options)
+    end
+
+    # Knows how to return a churn result in different formats.
+    #
+    # @return [String]
+    def report_churn
+      print_output = !options[:json] && !options[:yaml]
+
+      if params['version'].value
+        puts Churn::VERSION
+        return
+      end
+
+      result = calculator.report(print_output)
+
+      if options[:json]
+        JSON::dump(result)
+      elsif options[:yaml]
+        YAML::dump(result)
+      else
+        result
+      end
+    end
+  end
+end

test/unit/reporter_test.rb

@@ -0,0 +1,73 @@
+require 'minitest/autorun'
+require_relative '../../lib/churn/reporter'
+
+class ChurnReporterTest < Minitest::Test
+  StructOption = Struct.new(:value)
+
+  def setup
+    @params = {
+      'minimum_churn_count' => StructOption.new(3),
+      'ignore_files' => StructOption.new('file.rb'),
+      'start_date' => StructOption.new('2022-01-01'),
+      'data_directory' => StructOption.new('/data'),
+      'past_history' => StructOption.new(true),
+      'report' => StructOption.new('summary'),
+      'name' => StructOption.new('churn_report'),
+      'extension' => StructOption.new('.rb'),
+      'prefix' => StructOption.new('churn_'),
+      'json' => StructOption.new(false),
+      'yaml' => StructOption.new(false),
+      'version' => StructOption.new(false)
+    }
+    churn_calculator = Churn::ChurnCalculator.new({:minimum_churn_count => 3})
+
+    churn_calculator.stubs(:parse_log_for_changes).returns([['file.rb', 4],['less.rb',1]])
+    churn_calculator.stubs(:parse_log_for_revision_changes).returns(['revision'])
+    churn_calculator.stubs(:analyze)
+    @churn_reporter = Churn::ChurnReporter.new(@params)
+    @churn_reporter.calculator = churn_calculator
+  end
+
+  test "initialize sets the params as an instance variable" do
+    assert_equal @params, @churn_reporter.params
+  end
+
+  test "report churn prints version when version param is true" do
+    @params['version'].value = true
+
+    expected_output = "#{Churn::VERSION}\n"
+
+    assert_output(expected_output) { @churn_reporter.report_churn }
+  end
+
+  test "report churn returns result as json when json param is true" do
+    @churn_reporter.options[:json] = true
+
+    result = "{\"churn\":{\"changes\":[[\"file.rb\",4]],\"class_churn\":{},\"method_churn\":{}}}"
+
+    assert_equal result, @churn_reporter.report_churn
+  end
+
+  test "report churn returns result as yaml when yaml param is true" do
+    @churn_reporter.options[:yaml] = true
+
+    result =<<~EOS
+    ---
+    :churn:
+      :changes:
+      - - file.rb
+        - 4
+      :class_churn: {}
+      :method_churn: {}
+    EOS
+
+    assert_equal result, @churn_reporter.report_churn
+  end
+
+  test "report churn returns result when neither json nor yaml param is true" do
+    output = @churn_reporter.report_churn
+
+    assert_match /Revision Changes/, output
+    assert_match /Project Churn/, output
+  end
+end