VOL-3190 support nested ordering;
throw errors when fields don't exist

Change-Id: Ia607db45aec03413ffaf0696ee4043e42679803a
diff --git a/pkg/order/order.go b/pkg/order/order.go
index 0f324cd..bcf097b 100644
--- a/pkg/order/order.go
+++ b/pkg/order/order.go
@@ -83,12 +83,44 @@
 	return s, nil
 }
 
+func (s Sorter) GetField(val reflect.Value, name string) (reflect.Value, error) {
+	// If the user gave us an explicitly named dotted field, then split it
+	if strings.Contains(name, ".") {
+		parts := strings.SplitN(name, ".", 2)
+
+		if val.Kind() != reflect.Struct {
+			return val, fmt.Errorf("Dotted field name specified in filter did not resolve to a valid field")
+		}
+
+		field := val.FieldByName(parts[0])
+		if !field.IsValid() {
+			return field, fmt.Errorf("Failed to find dotted field %s while sorting", parts[0])
+		}
+		if field.Kind() == reflect.Ptr {
+			field = reflect.Indirect(field)
+		}
+		return s.GetField(field, parts[1])
+	}
+
+	if val.Kind() != reflect.Struct {
+		return val, fmt.Errorf("Dotted field name specified in filter did not resolve to a valid field")
+	}
+
+	field := val.FieldByName(name)
+	if !field.IsValid() {
+		return field, fmt.Errorf("Failed to find field %s while sorting", name)
+	}
+	return field, nil
+}
+
 func (s Sorter) Process(data interface{}) (interface{}, error) {
 	slice := reflect.ValueOf(data)
 	if slice.Kind() != reflect.Slice {
 		return data, nil
 	}
 
+	var sortError error = nil
+
 	sort.SliceStable(data, func(i, j int) bool {
 		left := reflect.ValueOf(slice.Index(i).Interface())
 		right := reflect.ValueOf(slice.Index(j).Interface())
@@ -102,8 +134,18 @@
 		}
 
 		for _, term := range s {
-			fleft := left.FieldByName(term.Name)
-			fright := right.FieldByName(term.Name)
+			fleft, err := s.GetField(left, term.Name)
+			if err != nil {
+				sortError = err
+				return false
+			}
+
+			fright, err := s.GetField(right, term.Name)
+			if err != nil {
+				sortError = err
+				return false
+			}
+
 			switch fleft.Kind() {
 			case reflect.Uint:
 				fallthrough
@@ -156,8 +198,8 @@
 					}
 				}
 			default:
-				sleft := fmt.Sprintf("%v", left.FieldByName(term.Name))
-				sright := fmt.Sprintf("%v", right.FieldByName(term.Name))
+				sleft := fmt.Sprintf("%v", fleft)
+				sright := fmt.Sprintf("%v", fright)
 				diff := strings.Compare(sleft, sright)
 				if term.Op != DSC {
 					if diff == -1 {
@@ -177,5 +219,9 @@
 		return false
 	})
 
+	if sortError != nil {
+		return nil, sortError
+	}
+
 	return data, nil
 }
diff --git a/pkg/order/order_test.go b/pkg/order/order_test.go
index eba6fe2..28132d9 100644
--- a/pkg/order/order_test.go
+++ b/pkg/order/order_test.go
@@ -17,15 +17,21 @@
 package order
 
 import (
+	"github.com/stretchr/testify/assert"
 	"testing"
 )
 
+type SortIncludedStruct struct {
+	Seven string
+}
+
 type SortTestStruct struct {
 	Id    int
 	One   string
 	Two   string
 	Three uint
 	Four  int
+	Six   SortIncludedStruct
 }
 
 var testSetOne = []SortTestStruct{
@@ -35,6 +41,7 @@
 		Two:   "x",
 		Three: 10,
 		Four:  1,
+		Six:   SortIncludedStruct{Seven: "o"},
 	},
 	{
 		Id:    1,
@@ -42,6 +49,7 @@
 		Two:   "c",
 		Three: 1,
 		Four:  10,
+		Six:   SortIncludedStruct{Seven: "p"},
 	},
 	{
 		Id:    2,
@@ -49,6 +57,7 @@
 		Two:   "b",
 		Three: 2,
 		Four:  1000,
+		Six:   SortIncludedStruct{Seven: "q"},
 	},
 	{
 		Id:    3,
@@ -56,6 +65,7 @@
 		Two:   "a",
 		Three: 3,
 		Four:  100,
+		Six:   SortIncludedStruct{Seven: "r"},
 	},
 	{
 		Id:    4,
@@ -63,6 +73,7 @@
 		Two:   "a",
 		Three: 3,
 		Four:  0,
+		Six:   SortIncludedStruct{Seven: "s"},
 	},
 }
 
@@ -245,3 +256,54 @@
 		t.Errorf("results don't match input")
 	}
 }
+
+func TestSortDotted(t *testing.T) {
+	s, err := Parse("+Six.Seven")
+	if err != nil {
+		t.Errorf("Unable to parse sort specification")
+	}
+	o, err := s.Process(testSetOne)
+	if err != nil {
+		t.Errorf("Sort failed: %s", err.Error())
+	}
+
+	if !Verify(o.([]SortTestStruct), []int{0, 1, 2, 3, 4}) {
+		t.Errorf("incorrect sort")
+	}
+}
+
+func TestInvaliodDotted(t *testing.T) {
+	s, err := Parse("+Six.Nonexistent")
+	if err != nil {
+		t.Errorf("Unable to parse sort specification")
+	}
+	o, err := s.Process(testSetOne)
+	assert.EqualError(t, err, "Failed to find field Nonexistent while sorting")
+	if o != nil {
+		t.Errorf("expected no results, got some")
+	}
+}
+
+func TestDotOnString(t *testing.T) {
+	s, err := Parse("+One.IsNotAStruct")
+	if err != nil {
+		t.Errorf("Unable to parse sort specification")
+	}
+	o, err := s.Process(testSetOne)
+	assert.EqualError(t, err, "Dotted field name specified in filter did not resolve to a valid field")
+	if o != nil {
+		t.Errorf("expected no results, got some")
+	}
+}
+
+func TestTrailingDot(t *testing.T) {
+	s, err := Parse("+Six.Seven.")
+	if err != nil {
+		t.Errorf("Unable to parse sort specification")
+	}
+	o, err := s.Process(testSetOne)
+	assert.EqualError(t, err, "Dotted field name specified in filter did not resolve to a valid field")
+	if o != nil {
+		t.Errorf("expected no results, got some")
+	}
+}