Prepare suggestion implementation for multi-line

Adds the groundwork needed in order to persist multi-line suggestions,
while providing the parsing strategy which will be reused for the
**Preview** as well.

2 files changed, 161 insertions, 0 deletions

diff --git a/spec/lib/gitlab/diff/suggestion_spec.rb b/spec/lib/gitlab/diff/suggestion_spec.rb
new file mode 100644
index 00000000000..71fd25df698
--- /dev/null
+++ b/spec/lib/gitlab/diff/suggestion_spec.rb
@@ -0,0 +1,88 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Gitlab::Diff::Suggestion do
+  shared_examples 'correct suggestion raw content' do
+    it 'returns correct raw data' do
+      expect(suggestion.to_hash).to include(from_content: expected_lines.join,
+                                            to_content: "#{text}\n",
+                                            lines_above: above,
+                                            lines_below: below)
+    end
+  end
+
+  let(:merge_request) { create(:merge_request) }
+  let(:project) { merge_request.project }
+  let(:position) do
+    Gitlab::Diff::Position.new(old_path: "files/ruby/popen.rb",
+                               new_path: "files/ruby/popen.rb",
+                               old_line: nil,
+                               new_line: 9,
+                               diff_refs: merge_request.diff_refs)
+  end
+  let(:diff_file) do
+    position.diff_file(project.repository)
+  end
+  let(:text) { "# parsed suggestion content\n# with comments" }
+
+  def blob_lines_data(from_line, to_line)
+    diff_file.new_blob_lines_between(from_line, to_line)
+  end
+
+  def blob_data
+    blob = diff_file.new_blob
+    blob.load_all_data!
+    blob.data
+  end
+
+  let(:suggestion) do
+    described_class.new(text, line: line, above: above, below: below, diff_file: diff_file)
+  end
+
+  describe '#to_hash' do
+    context 'when changing content surpasses the top limit' do
+      let(:line) { 4 }
+      let(:above) { 5 }
+      let(:below) { 2 }
+      let(:expected_above) { line - 1 }
+      let(:expected_below) { below }
+      let(:expected_lines) { blob_lines_data(line - expected_above, line + expected_below) }
+
+      it_behaves_like 'correct suggestion raw content'
+    end
+
+    context 'when changing content surpasses the amount of lines in the blob (bottom)' do
+      let(:line) { 5 }
+      let(:above) { 1 }
+      let(:below) { blob_data.lines.size + 10 }
+      let(:expected_below) { below }
+      let(:expected_above) { above }
+      let(:expected_lines) { blob_lines_data(line - expected_above, line + expected_below) }
+
+      it_behaves_like 'correct suggestion raw content'
+    end
+
+    context 'when lines are within blob lines boundary' do
+      let(:line) { 5 }
+      let(:above) { 2 }
+      let(:below) { 3 }
+      let(:expected_below) { below }
+      let(:expected_above) { above }
+      let(:expected_lines) { blob_lines_data(line - expected_above, line + expected_below) }
+
+      it_behaves_like 'correct suggestion raw content'
+    end
+
+    context 'when no extra lines (single-line suggestion)' do
+      let(:line) { 5 }
+      let(:above) { 0 }
+      let(:below) { 0 }
+      let(:expected_below) { below }
+      let(:expected_above) { above }
+      let(:expected_lines) { blob_lines_data(line - expected_above, line + expected_below) }
+
+      it_behaves_like 'correct suggestion raw content'
+    end
+  end
+end
diff --git a/spec/lib/gitlab/diff/suggestions_parser_spec.rb b/spec/lib/gitlab/diff/suggestions_parser_spec.rb
new file mode 100644
index 00000000000..1119ea04995
--- /dev/null
+++ b/spec/lib/gitlab/diff/suggestions_parser_spec.rb
@@ -0,0 +1,73 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Gitlab::Diff::SuggestionsParser do
+  describe '.parse' do
+    let(:merge_request) { create(:merge_request) }
+    let(:project) { merge_request.project }
+    let(:position) do
+      Gitlab::Diff::Position.new(old_path: "files/ruby/popen.rb",
+                                 new_path: "files/ruby/popen.rb",
+                                 old_line: nil,
+                                 new_line: 9,
+                                 diff_refs: merge_request.diff_refs)
+    end
+
+    let(:diff_file) do
+      position.diff_file(project.repository)
+    end
+
+    subject do
+      described_class.parse(markdown, project: merge_request.project,
+                                      position: position)
+    end
+
+    def blob_lines_data(from_line, to_line)
+      diff_file.new_blob_lines_between(from_line, to_line).join
+    end
+
+    context 'single-line suggestions' do
+      let(:markdown) do
+        <<-MARKDOWN.strip_heredoc
+          ```suggestion
+            foo
+            bar
+          ```
+
+          ```
+            nothing
+          ```
+
+          ```suggestion
+            xpto
+            baz
+          ```
+
+          ```thing
+            this is not a suggestion, it's a thing
+          ```
+        MARKDOWN
+      end
+
+      it 'returns a list of Gitlab::Diff::Suggestion' do
+        expect(subject).to all(be_a(Gitlab::Diff::Suggestion))
+        expect(subject.size).to eq(2)
+      end
+
+      it 'parsed suggestion has correct data' do
+        from_line, to_line = position.new_line, position.new_line
+
+        expect(subject.first.to_hash).to include(from_content: blob_lines_data(from_line, to_line),
+                                                 to_content: "  foo\n  bar\n",
+                                                 lines_above: 0,
+                                                 lines_below: 0)
+
+        expect(subject.second.to_hash).to include(from_content: blob_lines_data(from_line, to_line),
+                                                  to_content: "  xpto\n  baz\n",
+                                                  lines_above: 0,
+                                                  lines_below: 0)
+      end
+    end
+  end
+end