Allow operator characters on the RHS of filter

Fixes an issue where filters with operator characters on the RHS would
return 400s. This is because it parses the operator as the first one
found anywhere in the filter. By taking a more LALR-ish approach, we
can avoid this problem by parsing it as the first operator found in
the string.

Fixes https://bugzilla.redhat.com/show_bug.cgi?id=1365013

lib/api/filter.rb

@@ -48,12 +48,21 @@ def parse
 
     def parse_filter(filter)
       logical_or = filter.gsub!(/^or /i, '').present?
-      operator, methods = OPERATORS.find { |op, _methods| filter.partition(op).second == op }
+
+      operator = nil
+      operators_from_longest_to_shortest = OPERATORS.keys.sort_by(&:size).reverse
+      filter.size.times do |i|
+        operator = operators_from_longest_to_shortest.detect do |o|
+          o == filter[(i..(i + o.size - 1))]
+        end
+        break if operator
+      end
 
       if operator.blank?
         raise BadRequestError, "Unknown operator specified in filter #{filter}"
       end
 
+      methods = OPERATORS[operator]
       filter_attr, _, filter_value = filter.partition(operator)
       filter_attr.strip!
       filter_value.strip!

spec/lib/api/filter_spec.rb

@@ -346,5 +346,14 @@
       expected = {"=" => {"field" => "Vm-ems_id", "value" => 1_000_000_000_123}}
       expect(actual.exp).to eq(expected)
     end
+
+    it "can handle operator characters on the right hand side" do
+      filters = ["name=Vms with free space > 50 percent"]
+
+      actual = described_class.parse(filters, MiqReport)
+
+      expected = {"=" => {"field" => "MiqReport-name", "value" => "Vms with free space > 50 percent"}}
+      expect(actual.exp).to eq(expected)
+    end
   end
 end