Add CommitRange class

app/models/commit_range.rb

+# CommitRange makes it easier to work with commit ranges
+#
+# Examples:
+#
+#   range = CommitRange.new('f3f85602...e86e1013')
+#   range.inclusive?      # => false
+#   range.to_s            # => "f3f85602...e86e1013"
+#   range.reference_title # => "Commits f3f85602 through e86e1013"
+#
+#   range = CommitRange.new('f3f856029bc5f966c5a7ee24cf7efefdd20e6019..e86e1013709735be5bb767e2b228930c543f25ae')
+#   range.inclusive? # => true
+#   range.to_s       # => "f3f85602..e86e1013"
+#   range.to_param   # => {from: "f3f856029bc5f966c5a7ee24cf7efefdd20e6019^", to: "e86e1013709735be5bb767e2b228930c543f25ae"}
+#
+#   # Assuming `project` is a Project with a repository containing both commits:
+#   range.project = project
+#   range.valid_commits? # => true
+#   range.to_a           # => [#<Commit ...>, #<Commit ...>]
+#
+class CommitRange
+  include ActiveModel::Conversion
+
+  attr_reader :sha_from, :notation, :sha_to
+
+  # Optional Project model
+  attr_accessor :project
+
+  # See `inclusive?`
+  attr_reader :inclusive
+
+  # The beginning and ending SHA sums can be between 6 and 40 hex characters,
+  # and the range selection can be double- or triple-dot.
+  PATTERN = /\h{6,40}\.{2,3}\h{6,40}/
+
+  # Initialize a CommitRange
+  #
+  # range_string - The String commit range.
+  # project      - An optional Project model.
+  #
+  # Raises ArgumentError if `range_string` does not match `PATTERN`.
+  def initialize(range_string, project = nil)
+    range_string.strip!
+
+    unless range_string.match(/\A#{PATTERN}\z/)
+      raise ArgumentError, "invalid CommitRange string format: #{range_string}"
+    end
+
+    @inclusive = range_string !~ /\.{3}/
+    @sha_from, @notation, @sha_to = range_string.split(/(\.{2,3})/, 2)
+
+    @project = project
+
+    @_commit_map = {}
+  end
+
+  def inspect
+    %(#<#{self.class}:#{object_id} #{to_s}>)
+  end
+
+  # Returns an Array of Commit objects, where the first value is the starting
+  # commit, and the second value is the ending commit
+  #
+  # Returns `[nil, nil]` if `valid_commits?` is falsey
+  def to_a
+    if valid_commits?
+      [commit(sha_from), commit(sha_to)]
+    else
+      [nil, nil]
+    end
+  end
+
+  def to_s(short: true)
+    if short
+      "#{sha_from[0..7]}#{notation}#{sha_to[0..7]}"
+    else
+      "#{sha_from}#{notation}#{sha_to}"
+    end
+  end
+
+  # Returns a String for use in a link's title attribute
+  def reference_title
+    "Commits #{sha_from} through #{sha_to}"
+  end
+
+  # Return a Hash of parameters for passing to a URL helper
+  #
+  # See `namespace_project_compare_url`
+  def to_param
+    { from: sha_from_as_param, to: sha_to }
+  end
+
+  # Check if the range is inclusive
+  #
+  # We consider a CommitRange "inclusive" when it uses the two-dot syntax.
+  def inclusive?
+    inclusive
+  end
+
+  # Check if both the starting and ending commit IDs exist in a project's
+  # repository
+  #
+  # project - An optional Project to check (default: `project`)
+  def valid_commits?(project = project)
+    return nil   unless project.present?
+    return false unless project.valid_repo?
+
+    commit(sha_from).present? && commit(sha_to).present?
+  end
+
+  def persisted?
+    true
+  end
+
+  private
+
+  def sha_from_as_param
+    sha_from + (inclusive? ? '^' : '')
+  end
+
+  def commit(sha)
+    unless @_commit_map[sha]
+      # FIXME (rspeicher): Law of Demeter
+      @_commit_map[sha] = project.repository.commit(sha)
+    end
+
+    @_commit_map[sha]
+  end
+end

spec/models/commit_range_spec.rb

+require 'spec_helper'
+
+describe CommitRange do
+  let(:sha_from) { 'f3f85602' }
+  let(:sha_to)   { 'e86e1013' }
+
+  let(:range)  { described_class.new("#{sha_from}...#{sha_to}") }
+  let(:range2) { described_class.new("#{sha_from}..#{sha_to}") }
+
+  it 'raises ArgumentError when given an invalid range string' do
+    expect { described_class.new("Foo") }.to raise_error
+  end
+
+  describe '#to_a' do
+    context 'when valid' do
+      let(:commit1) { double('commit1') }
+      let(:commit2) { double('commit2') }
+
+      before do
+        expect(range).to receive(:valid_commits?).and_return(true)
+        allow(range).to receive(:commit).with(sha_from).and_return(commit1)
+        allow(range).to receive(:commit).with(sha_to).and_return(commit2)
+      end
+
+      it 'returns an Array of Commits' do
+        expect(range.to_a).to eq [commit1, commit2]
+      end
+    end
+
+    context 'when invalid' do
+      before do
+        expect(range).to receive(:valid_commits?).and_return(false)
+      end
+
+      it 'returns [nil, nil]' do
+        expect(range.to_a).to eq [nil, nil]
+      end
+    end
+  end
+
+  describe '#to_s' do
+    context 'with short IDs' do
+      it 'is correct for three-dot syntax' do
+        expect(range.to_s).to eq "#{sha_from[0..7]}...#{sha_to[0..7]}"
+      end
+
+      it 'is correct for two-dot syntax' do
+        expect(range2.to_s).to eq "#{sha_from[0..7]}..#{sha_to[0..7]}"
+      end
+    end
+
+    context 'with full IDs' do
+      it 'is correct for three-dot syntax' do
+        expect(range.to_s(short: false)).to eq "#{sha_from}...#{sha_to}"
+      end
+
+      it 'is correct for two-dot syntax' do
+        expect(range2.to_s(short: false)).to eq "#{sha_from}..#{sha_to}"
+      end
+    end
+  end
+
+  describe '#reference_title' do
+    it 'returns the correct String' do
+      expect(range.reference_title).to eq "Commits #{sha_from} through #{sha_to}"
+    end
+  end
+
+  describe '#to_param' do
+    it 'includes the correct keys' do
+      expect(range.to_param.keys).to eq %i(from to)
+    end
+
+    it 'includes the correct values for a three-dot range' do
+      expect(range.to_param).to eq({from: sha_from, to: sha_to})
+    end
+
+    it 'includes the correct values for a two-dot range' do
+      expect(range2.to_param).to eq({from: sha_from + '^', to: sha_to})
+    end
+  end
+
+  describe '#inclusive?' do
+    it 'is false for three-dot ranges' do
+      expect(range).not_to be_inclusive
+    end
+
+    it 'is true for two-dot ranges' do
+      expect(range2).to be_inclusive
+    end
+  end
+
+  describe '#valid_commits?' do
+    context 'without a project' do
+      it 'returns nil' do
+        expect(range.valid_commits?).to be_nil
+      end
+    end
+
+    it 'accepts an optional project argument' do
+      project1 = double('project1').as_null_object
+      project2 = double('project2').as_null_object
+
+      # project1 gets assigned through the accessor, but ignored when not given
+      # as an argument to `valid_commits?`
+      expect(project1).not_to receive(:present?)
+      range.project = project1
+
+      # project2 gets passed to `valid_commits?`
+      expect(project2).to receive(:present?).and_return(false)
+
+      range.valid_commits?(project2)
+    end
+
+    context 'with a project' do
+      let(:project) { double('project', repository: double('repository')) }
+
+      context 'with a valid repo' do
+        before do
+          expect(project).to receive(:valid_repo?).and_return(true)
+          range.project = project
+        end
+
+        it 'is false when `sha_from` is invalid' do
+          expect(project.repository).to receive(:commit).with(sha_from).and_return(false)
+          expect(project.repository).not_to receive(:commit).with(sha_to)
+          expect(range).not_to be_valid_commits
+        end
+
+        it 'is false when `sha_to` is invalid' do
+          expect(project.repository).to receive(:commit).with(sha_from).and_return(true)
+          expect(project.repository).to receive(:commit).with(sha_to).and_return(false)
+          expect(range).not_to be_valid_commits
+        end
+
+        it 'is true when both `sha_from` and `sha_to` are valid' do
+          expect(project.repository).to receive(:commit).with(sha_from).and_return(true)
+          expect(project.repository).to receive(:commit).with(sha_to).and_return(true)
+          expect(range).to be_valid_commits
+        end
+      end
+
+      context 'without a valid repo' do
+        before do
+          expect(project).to receive(:valid_repo?).and_return(false)
+          range.project = project
+        end
+
+        it 'returns false' do
+          expect(range).not_to be_valid_commits
+        end
+      end
+    end
+  end
+end