add orderBy param

http/server.go

@@ -6,6 +6,7 @@ package http
 
 import (
 	"encoding/json"
+	"errors"
 	"fmt"
 	"math"
 	"net/http"
@@ -160,3 +161,58 @@ func readSkipCount(r *http.Request, skipMax, countMax int) (skip int, count int,
 
 	return skip, count, exists, nil
 }
+
+type Direction string
+
+const (
+	Ascending  Direction = "ASC"
+	Descending Direction = "DESC"
+)
+
+type OrderBy struct {
+	Name      string
+	Direction Direction
+}
+
+// GetOrderBy returns the field names and direction to order the response by
+func GetOrderBy(r *http.Request) ([]OrderBy, error) {
+	orderByParam := r.URL.Query().Get("orderBy")
+	if orderByParam == "" {
+		return []OrderBy{}, nil
+	}
+
+	paramSplit := strings.Split(orderByParam, ",")
+	var orderBys []OrderBy
+	for _, split := range paramSplit {
+		orderBy := strings.Split(split, ":")
+		if len(orderBy) != 2 {
+			return nil, fmt.Errorf("invalid orderBy: %s", orderBy)
+		}
+
+		name := strings.TrimSpace(orderBy[0])
+		if name == "" {
+			return nil, errors.New("missing orderBy name")
+		}
+
+		directionStr := strings.TrimSpace(orderBy[1])
+		if directionStr == "" {
+			return nil, errors.New("missing orderBy direction")
+		}
+		directionStr = strings.ToLower(directionStr)
+
+		var direction Direction
+		if strings.HasPrefix(directionStr, "asc") {
+			direction = Ascending
+		} else if strings.HasPrefix(directionStr, "desc") {
+			direction = Descending
+		} else {
+			return nil, fmt.Errorf("invalid orderBy direction: %s", direction)
+		}
+
+		orderBys = append(orderBys, OrderBy{
+			Name:      name,
+			Direction: direction,
+		})
+	}
+	return orderBys, nil
+}

http/server_test.go

@@ -337,3 +337,138 @@ func TestLimitedSkipCount(t *testing.T) {
 	require.Equal(t, 250, skip)
 	require.Equal(t, 100, count)
 }
+
+func TestGetOrderBy(t *testing.T) {
+	tests := []struct {
+		name     string
+		path     string
+		expected []OrderBy
+		wantErr  bool
+	}{
+		{
+			name:     "valid - missing",
+			path:     "/list",
+			expected: []OrderBy{},
+			wantErr:  false,
+		},
+		{
+			name:     "valid - empty",
+			path:     "/list?orderBy=",
+			expected: []OrderBy{},
+			wantErr:  false,
+		},
+		{
+			name: "valid - single",
+			path: "/list?orderBy=createdOn:ascending",
+			expected: []OrderBy{
+				{
+					Name:      "createdOn",
+					Direction: Ascending,
+				},
+			},
+			wantErr: false,
+		},
+		{
+			name: "valid - multiple",
+			path: "/list?orderBy=createdOn:ascending,updatedOn:descending",
+			expected: []OrderBy{
+				{
+					Name:      "createdOn",
+					Direction: Ascending,
+				},
+				{
+					Name:      "updatedOn",
+					Direction: Descending,
+				},
+			},
+			wantErr: false,
+		},
+		{
+			name: "valid - short name asc",
+			path: "/list?orderBy=createdOn:asc",
+			expected: []OrderBy{
+				{
+					Name:      "createdOn",
+					Direction: Ascending,
+				},
+			},
+			wantErr: false,
+		},
+		{
+			name: "valid - short name desc",
+			path: "/list?orderBy=createdOn:desc",
+			expected: []OrderBy{
+				{
+					Name:      "createdOn",
+					Direction: Descending,
+				},
+			},
+			wantErr: false,
+		},
+		{
+			name: "valid - mixed cases ascending",
+			path: "/list?orderBy=createdOn:AsCeNdInG",
+			expected: []OrderBy{
+				{
+					Name:      "createdOn",
+					Direction: Ascending,
+				},
+			},
+		},
+		{
+			name: "valid - mixed cases descending",
+			path: "/list?orderBy=createdOn:DeScEnDiNg",
+			expected: []OrderBy{
+				{
+					Name:      "createdOn",
+					Direction: Descending,
+				},
+			},
+		},
+		{
+			name:     "invalid - missing colon",
+			path:     "/list?orderBy=createdOndescending",
+			expected: nil,
+			wantErr:  true,
+		},
+		{
+			name:     "invalid - missing name",
+			path:     "/list?orderBy=:ascending",
+			expected: nil,
+			wantErr:  true,
+		},
+		{
+			name:     "invalid - missing direction",
+			path:     "/list?orderBy=createdOn:",
+			expected: nil,
+			wantErr:  true,
+		},
+		{
+			name:     "invalid - empty name",
+			path:     "/list?orderBy=%20%20:ascending",
+			expected: nil,
+			wantErr:  true,
+		},
+		{
+			name:     "invalid - empty direction",
+			path:     "/list?orderBy=createdOn:%20%20",
+			expected: nil,
+			wantErr:  true,
+		},
+		{
+			name:     "invalid - invalid direction",
+			path:     "/list?orderBy=createdOn:invalid",
+			expected: nil,
+			wantErr:  true,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			r := httptest.NewRequest("GET", test.path, nil)
+			orderBy, err := GetOrderBy(r)
+			require.Equal(t, test.wantErr, err != nil)
+			require.Equal(t, test.expected, orderBy)
+		})
+	}
+}