Use receive_snapshot to send notifications to Slack.

Rakefile

@@ -3,7 +3,8 @@ require 'rake/testtask'
 
 Rake::TestTask.new do |t|
   t.libs.push "lib"
-  t.test_files = FileList['test/*_test.rb']
+  t.libs.push "test"
+  t.test_files = FileList['test/**/*_test.rb']
   t.verbose = true
 end
 

lib/cc/formatters/snapshot_formatter.rb

@@ -0,0 +1,101 @@
+module CC::Formatters
+  module SnapshotFormatter
+    # Simple Comparator for rating letters.
+    class Rating
+      include Comparable
+
+      def initialize(letter)
+        @letter = letter
+      end
+
+      def <=>(other)
+        other.to_s <=> to_s
+      end
+
+      def hash
+        @letter.hash
+      end
+
+      def eql?(other)
+        to_s == other.to_s
+      end
+
+      def inspect
+        "<Rating:#{to_s}>"
+      end
+
+      def to_s
+        @letter.to_s
+      end
+    end
+
+    C = Rating.new("C")
+    D = Rating.new("D")
+
+    # SnapshotFormatter::Base takes the quality information from the payload and divides it
+    # between alerts and improvements.
+    #
+    # The information in the payload must be a comparison in time between two quality reports, aka snapshot.
+    # This information is in the payload when the service receive a `receive_snapshot` and also
+    # when it receives a `receive_test`. In this latest case, the comparison is between today and seven days ago.
+    class Base
+      attr_reader :alert_constants_payload, :improved_constants_payload, :details_url, :compare_url
+
+      def initialize(payload)
+        new_constants = Array(payload["new_constants"])
+        changed_constants = Array(payload["changed_constants"])
+
+        alert_constants = new_constants.select(&new_constants_selector)
+        alert_constants += changed_constants.select(&decreased_constants_selector)
+
+        improved_constants = changed_constants.select(&improved_constants_selector)
+
+        data = {
+          "from" => { "commit_sha" => payload["previous_commit_sha"] },
+          "to"   => { "commit_sha" => payload["commit_sha"] }
+        }
+
+        @alert_constants_payload    = data.merge("constants" => alert_constants) if alert_constants.any?
+        @improved_constants_payload = data.merge("constants" => improved_constants) if improved_constants.any?
+      end
+
+    private
+
+      def new_constants_selector
+        Proc.new { |constant| to_rating(constant) < C }
+      end
+
+      def decreased_constants_selector
+        Proc.new { |constant| from_rating(constant) > D && to_rating(constant) < C }
+      end
+
+      def improved_constants_selector
+        Proc.new { |constant| from_rating(constant) < C && to_rating(constant) > from_rating(constant) }
+      end
+
+      def to_rating(constant)
+        Rating.new(constant["to"]["rating"])
+      end
+
+      def from_rating(constant)
+        Rating.new(constant["from"]["rating"])
+      end
+    end
+
+    # Override the base snapshot formatter for be more lax grouping information.
+    # This is useful to show more information for testing the service.
+    class Sample < Base
+      def new_constants_selector
+        Proc.new { |_| true }
+      end
+
+      def decreased_constants_selector
+        Proc.new { |constant| to_rating(constant) < from_rating(constant) }
+      end
+
+      def improved_constants_selector
+        Proc.new { |constant| to_rating(constant) > from_rating(constant) }
+      end
+    end
+  end
+end

lib/cc/helpers/quality_helper.rb

@@ -23,13 +23,22 @@ def previous_remediation_cost
     payload.fetch("previous_remediation_cost", 0)
   end
 
-  def with_article(letter)
+  def with_article(letter, bold = false)
     letter ||= '?'
 
-    if %w( A F ).include?(letter)
-      "an #{letter}"
+    text = bold ? "*#{letter}*" : letter
+    if %w( A F ).include?(letter.to_s)
+      "an #{text}"
     else
-      "a #{letter}"
+      "a #{text}"
+    end
+  end
+
+  def constant_basename(name)
+    if name.include?(".")
+      File.basename(name)
+    else
+      name
     end
   end
 end

lib/cc/service/helper.rb

@@ -1,4 +1,6 @@
 module CC::Service::Helper
+  GREEN_HEX = "#38ae6f"
+  RED_HEX   = "#ed2f00"
 
   def repo_name
     payload["repo_name"]
@@ -30,9 +32,9 @@ def color
 
   def hex_color
     if improved?
-      "#38ae6f"
+      GREEN_HEX
     else
-      "#ed2f00"
+      RED_HEX
     end
   end
 

lib/cc/services/slack.rb

@@ -1,4 +1,8 @@
+ # encoding: UTF-8
+
 class CC::Service::Slack < CC::Service
+  include CC::Service::QualityHelper
+
   class Config < CC::Service::Config
     attribute :webhook_url, String,
       label: "Webhook URL",
@@ -13,17 +17,20 @@ class Config < CC::Service::Config
   def receive_test
     speak(formatter.format_test)
 
+    # payloads for test receivers include the weekly quality report.
+    send_snapshot_to_slack(CC::Formatters::SnapshotFormatter::Sample.new(payload))
+
     { ok: true, message: "Test message sent" }
   rescue => ex
     { ok: false, message: ex.message }
   end
 
-  def receive_coverage
-    speak(formatter.format_coverage, hex_color)
+  def receive_snapshot
+    send_snapshot_to_slack(CC::Formatters::SnapshotFormatter::Base.new(payload))
   end
 
-  def receive_quality
-    speak(formatter.format_quality, hex_color)
+  def receive_coverage
+    speak(formatter.format_coverage, hex_color)
   end
 
   def receive_vulnerability
@@ -51,4 +58,61 @@ def speak(message, color = nil)
     http.headers['Content-Type']  = 'application/json'
     http_post(config.webhook_url, body.to_json)
   end
+
+  def send_snapshot_to_slack(snapshot)
+    if snapshot.alert_constants_payload
+      speak(alerts_message(snapshot.alert_constants_payload), RED_HEX)
+    end
+
+    if snapshot.improved_constants_payload
+      speak(improvements_message(snapshot.improved_constants_payload), GREEN_HEX)
+    end
+  end
+
+  def alerts_message(constants_payload)
+    constants = constants_payload["constants"]
+    message = ["Quality alert triggered for *#{repo_name}* (<#{compare_url}|Compare>)\n"]
+
+    constants[0..2].each do |constant|
+      object_identifier = constant_basename(constant["name"])
+
+      if constant["from"]
+        from_rating = constant["from"]["rating"]
+        to_rating   = constant["to"]["rating"]
+
+        message << "• _#{object_identifier}_ just declined from #{with_article(from_rating, :bold)} to #{with_article(to_rating, :bold)}"
+      else
+        rating = constant["to"]["rating"]
+
+        message << "• _#{object_identifier}_ was just created and is #{with_article(rating, :bold)}"
+      end
+    end
+
+    if constants.size > 3
+      remaining = constants.size - 3
+      message << "\nAnd <#{details_url}|#{remaining} other #{"change".pluralize(remaining)}>"
+    end
+
+    message.join("\n")
+  end
+
+  def improvements_message(constants_payload)
+    constants = constants_payload["constants"]
+    message = ["Quality improvements in *#{repo_name}* (<#{compare_url}|Compare>)\n"]
+
+    constants[0..2].each do |constant|
+      object_identifier = constant_basename(constant["name"])
+      from_rating = constant["from"]["rating"]
+      to_rating   = constant["to"]["rating"]
+
+      message << "• _#{object_identifier}_ just improved from #{with_article(from_rating, :bold)} to #{with_article(to_rating, :bold)}"
+    end
+
+    if constants.size > 3
+      remaining = constants.size - 3
+      message << "\nAnd <#{details_url}|#{remaining} other #{"improvement".pluralize(remaining)}>"
+    end
+
+    message.join("\n")
+  end
 end

test/formatters/snapshot_formatter_test.rb

@@ -0,0 +1,47 @@
+require "helper"
+
+class TestSnapshotFormatter < Test::Unit::TestCase
+  def described_class
+    CC::Formatters::SnapshotFormatter::Base
+  end
+
+  def test_quality_alert_with_new_constants
+    f = described_class.new({"new_constants" => [{"to" => {"rating" => "D"}}], "changed_constants" => []})
+    refute_nil f.alert_constants_payload
+  end
+
+  def test_quality_alert_with_decreased_constants
+    f = described_class.new({"new_constants" => [],
+                             "changed_constants" => [{"to" => {"rating" => "D"}, "from" => {"rating" => "A"}}]
+    })
+    refute_nil f.alert_constants_payload
+  end
+
+  def test_quality_improvements_with_better_ratings
+    f = described_class.new({"new_constants" => [],
+                             "changed_constants" => [{"to" => {"rating" => "A"}, "from" => {"rating" => "D"}}]
+    })
+    refute_nil f.improved_constants_payload
+  end
+
+  def test_nothing_set_without_changes
+    f = described_class.new({"new_constants" => [], "changed_constants" => []})
+    assert_nil f.alert_constants_payload
+    assert_nil f.improved_constants_payload
+  end
+
+  def test_snapshot_formatter_test_with_relaxed_constraints
+    f = CC::Formatters::SnapshotFormatter::Sample.new({
+       "new_constants" => [{"name" => "foo", "to" => {"rating" => "A"}}, {"name" => "bar", "to" => {"rating" => "A"}}],
+       "changed_constants" => [
+         {"from" => {"rating" => "B"}, "to" => {"rating" => "C"}},
+         {"from" => {"rating" => "D"}, "to" => {"rating" => "D"}},
+         {"from" => {"rating" => "D"}, "to" => {"rating" => "D"}},
+         {"from" => {"rating" => "A"}, "to" => {"rating" => "B"}},
+         {"from" => {"rating" => "C"}, "to" => {"rating" => "B"}}
+       ]})
+
+    refute_nil f.alert_constants_payload
+    refute_nil f.improved_constants_payload
+  end
+end