feat: recalculate the branch head if the deleted branch version was t…

…he latest for the branch

lib/pact_broker/versions/branch_version_repository.rb

@@ -17,9 +17,20 @@ def add_branch(version, branch_name, auto_created: false)
       end
 
       # Deletes a branch version - that is, removes a version from a branch.
+      # Updates the branch head if the deleted branch version was the latest for the branch.
+      #
       # @param [PactBroker::Versions::BranchVersion] the branch version to delete
       def delete_branch_version(branch_version)
-        branch_version.delete
+        latest = branch_version.latest?
+        branch = branch_version.latest? ? branch_version.branch : nil
+        deleted = branch_version.delete
+        if latest
+          new_head_branch_version = BranchVersion.find_latest_for_branch(branch)
+          if new_head_branch_version
+            PactBroker::Versions::BranchHead.new(branch: branch, branch_version: new_head_branch_version).upsert
+          end
+        end
+        deleted
       end
 
       private

spec/lib/pact_broker/versions/branch_version_repository_spec.rb

@@ -76,6 +76,53 @@ module Versions
           end
         end
       end
+
+      describe "delete_branch_version" do
+        subject { BranchVersionRepository.new.delete_branch_version(branch_version) }
+
+        context "when the branch version was not the branch head" do
+          before do
+            td.create_consumer("foo")
+              .create_consumer_version("1", branch: "main")
+              .create_consumer_version("2", branch: "main")
+          end
+
+          let(:branch_version) { BranchVersion.first }
+
+          subject { BranchVersionRepository.new.delete_branch_version(BranchVersion.first) }
+
+          it "does not update the branch head" do
+            expect { subject }.to_not change { BranchHead.first.version_id }
+          end
+        end
+
+        context "when the branch version was the branch head" do
+          before do
+            td.create_consumer("foo")
+              .create_consumer_version("1", branch: "main")
+              .create_consumer_version("2", branch: "main")
+          end
+
+          let(:branch_version) { BranchVersion.last }
+
+          it "does updates the branch head" do
+            expect { subject }.to change { BranchHead.first.version_id }
+          end
+        end
+
+        context "when the branch version was the last for its branch" do
+          before do
+            td.create_consumer("foo")
+              .create_consumer_version("1", branch: "main")
+          end
+
+          let(:branch_version) { BranchVersion.first }
+
+          it "does not create a new branch head" do
+            expect { subject }.to change { BranchHead.count }.by(-1)
+          end
+        end
+      end
     end
   end
 end