Pagination bug (#250)

* Check next_offset before making next page request

* test pagination small page

* small refactor for clarity

lib/vbms/service/paged_documents.rb

@@ -19,12 +19,11 @@ def call(file_number:)
         pages = 1
 
         # if we need to fetch more docs, iterate till we exhaust the pages
-        while total_docs > documents.length
+        while total_docs > documents.length && next_offset > 0
           next_page = client.send_request(next_request(file_number, next_offset))
           (documents << next_page.map { |section| section[:documents] }).flatten!
           next_offset = next_page.first[:paging][:@next_start_index].to_i
           pages += 1
-          break if next_offset <= 0 # reality check
         end
 
         { paging: pagination, pages: pages, documents: documents }

spec/service/paged_documents_spec.rb

@@ -8,6 +8,7 @@
   let(:page_size) { 20 }
   let(:total_docs) { 101 }
   let(:version_sets) { 2 } # MUST divide page_size evenly.
+  let(:small_return_set) { false }
 
   subject { described_class.new(client: client) }
 
@@ -28,6 +29,11 @@ def next_response
     end
     documents = build_documents(num_docs)
 
+    if small_return_set
+      @offset = -1
+      documents.pop # make returned set smaller than total_docs
+    end
+
     (1..num_sets).map do
       {
         paging: { :@next_start_index => @offset, :@total_result_count => total_docs },
@@ -62,5 +68,18 @@ def next_response
         expect(r[:paging][:@total_result_count]).to eq total_docs
       end
     end
+
+    context "when the first page reports more pages than it contains" do
+      let(:small_return_set) { true }
+      let(:total_docs) { page_size - 1 }
+
+      it "believes the next_offset over the returned document count" do
+        r = subject.call(file_number: file_number)
+
+        expect(r[:pages]).to eq(1)
+        expect(r[:documents].length).to eq(total_docs - 1)
+        expect(r[:paging][:@total_result_count]).to eq total_docs
+      end
+    end
   end
 end