Implement pagination token and page size

Author: KyleJu

lib/gcpspanner/missing_one_implementation_feature_list.go

@@ -40,6 +40,24 @@ type MissingOneImplFeatureListPage struct {
 	FeatureList   []MissingOneImplFeature
 }
 
+// missingOneImplCursor: Represents a point for resuming queries based on the
+// numerical offset from the start of the result set. Useful for pagination.
+type missingOneImplFeatureListCursor struct {
+	Offset int `json:"offset"`
+}
+
+// decodemissingOneImplFeatureListCursor provides a wrapper around the generic decodeCursor.
+func decodemissingOneImplFeatureListCursor(cursor string) (*missingOneImplFeatureListCursor, error) {
+	return decodeCursor[missingOneImplFeatureListCursor](cursor)
+}
+
+// encodemissingOneImplFeatureListCursor provides a wrapper around the generic encodeCursor.
+func encodemissingOneImplFeatureListCursor(offset int) string {
+	return encodeCursor(missingOneImplFeatureListCursor{
+		Offset: offset,
+	})
+}
+
 // MissingOneImplFeature contains information regarding the list of features implemented in all other browsers but not
 // in the target browser.
 type MissingOneImplFeature struct {
@@ -69,16 +87,23 @@ AND
 {{ end }}
 1=1
 ORDER BY KEY ASC
+LIMIT @limit
+{{ if .Offset }}
+OFFSET {{ .Offset }}
+{{ end }}
 `
 
 type missingOneImplFeatureListTemplateData struct {
 	OtherBrowsersParamNames []string
+	Offset                  int
 }
 
 func buildMissingOneImplFeatureListTemplate(
 	targetBrowser string,
 	otherBrowsers []string,
 	targetDate time.Time,
+	cursor *missingOneImplFeatureListCursor,
+	pageSize int,
 ) spanner.Statement {
 	params := map[string]interface{}{}
 	allBrowsers := make([]string, len(otherBrowsers)+1)
@@ -93,9 +118,11 @@ func buildMissingOneImplFeatureListTemplate(
 	}
 
 	params["targetDate"] = targetDate
+	params["limit"] = pageSize
 
 	tmplData := missingOneImplFeatureListTemplateData{
 		OtherBrowsersParamNames: otherBrowsersParamNames,
+		Offset:                  cursor.Offset,
 	}
 
 	sql := missingOneImplFeatureListTemplate.Execute(tmplData)
@@ -110,14 +137,27 @@ func (c *Client) MissingOneImplFeatureList(
 	targetBrowser string,
 	otherBrowsers []string,
 	targetDate time.Time,
+	pageSize int,
+	pageToken *string,
 ) (*MissingOneImplFeatureListPage, error) {
+	var cursor *missingOneImplFeatureListCursor
+	var err error
+	if pageToken != nil {
+		cursor, err = decodemissingOneImplFeatureListCursor(*pageToken)
+		if err != nil {
+			return nil, errors.Join(ErrInternalQueryFailure, err)
+		}
+	}
+
 	txn := c.ReadOnlyTransaction()
 	defer txn.Close()
 
 	stmt := buildMissingOneImplFeatureListTemplate(
 		targetBrowser,
 		otherBrowsers,
 		targetDate,
+		cursor,
+		pageSize,
 	)
 
 	it := txn.Query(ctx, stmt)
@@ -144,5 +184,14 @@ func (c *Client) MissingOneImplFeatureList(
 		NextPageToken: nil,
 	}
 
+	if len(results) == pageSize {
+		previousOffset := 0
+		if cursor != nil {
+			previousOffset = cursor.Offset
+		}
+		token := encodemissingOneImplFeatureListCursor(previousOffset + pageSize)
+		page.NextPageToken = &token
+	}
+
 	return &page, nil
 }

lib/gcpspanner/missing_one_implementation_feature_list_test.go

@@ -128,12 +128,14 @@ func loadDataForListMissingOneImplFeatureList(ctx context.Context, t *testing.T,
 }
 
 func assertMissingOneImplFeatureList(ctx context.Context, t *testing.T, targetDate time.Time,
-	targetBrowser string, otherBrowsers []string, expectedPage *MissingOneImplFeatureListPage) {
+	targetBrowser string, otherBrowsers []string, expectedPage *MissingOneImplFeatureListPage, token *string, pageSize int) {
 	result, err := spannerClient.MissingOneImplFeatureList(
 		ctx,
 		targetBrowser,
 		otherBrowsers,
 		targetDate,
+		pageSize,
+		token,
 	)
 	if err != nil {
 		t.Errorf("Unexpected error: %v", err)
@@ -157,6 +159,8 @@ func testMissingOneImplFeatureListSuite(
 			"barBrowser",
 		}
 		targetDate := time.Date(2024, 4, 15, 0, 0, 0, 0, time.UTC)
+		pageSize := 25
+		token := encodemissingOneImplFeatureListCursor(0)
 
 		t.Run("simple successful query", func(t *testing.T) {
 			expectedResult := &MissingOneImplFeatureListPage{
@@ -183,6 +187,8 @@ func testMissingOneImplFeatureListSuite(
 				targetBrowser,
 				otherBrowsers,
 				expectedResult,
+				&token,
+				pageSize,
 			)
 		})
 
@@ -199,6 +205,8 @@ func testMissingOneImplFeatureListSuite(
 				targetBrowser,
 				otherBrowsers,
 				expectedResult,
+				&token,
+				pageSize,
 			)
 		})
 
@@ -231,8 +239,68 @@ func testMissingOneImplFeatureListSuite(
 				targetBrowser,
 				subsetBrowsers,
 				expectedResult,
+				&token,
+				pageSize,
 			)
 		})
+
+		t.Run("simple successful query with pagination", func(t *testing.T) {
+			pageToken := encodemissingOneImplFeatureListCursor(1)
+			expectedResult := &MissingOneImplFeatureListPage{
+				NextPageToken: nil,
+				FeatureList: []MissingOneImplFeature{
+					// fooBrowser 113 release
+					// Currently supported features:
+					// fooBrowser: FeatureX, FeatureZ, FeatureY, FeatureW
+					// barBrowser: FeatureX, FeatureZ, FeatureY, FeatureW
+					// bazBrowser: FeatureX, FeatureY
+					// Missing in on for bazBrowser: FeatureW, FeatureZ
+					{
+						WebFeatureID: "FeatureZ",
+					},
+				},
+			}
+			assertMissingOneImplFeatureList(
+				ctx,
+				t,
+				targetDate,
+				targetBrowser,
+				otherBrowsers,
+				expectedResult,
+				&pageToken,
+				pageSize,
+			)
+		})
+
+		t.Run("Return a page token with page size 1", func(t *testing.T) {
+			onePerPage := 1
+			nextToken := encodemissingOneImplFeatureListCursor(1)
+			expectedResult := &MissingOneImplFeatureListPage{
+				NextPageToken: &nextToken,
+				FeatureList: []MissingOneImplFeature{
+					// fooBrowser 113 release
+					// Currently supported features:
+					// fooBrowser: FeatureX, FeatureZ, FeatureY, FeatureW
+					// barBrowser: FeatureX, FeatureZ, FeatureY, FeatureW
+					// bazBrowser: FeatureX, FeatureY
+					// Missing in on for bazBrowser: FeatureW, FeatureZ
+					{
+						WebFeatureID: "FeatureW",
+					},
+				},
+			}
+			assertMissingOneImplFeatureList(
+				ctx,
+				t,
+				targetDate,
+				targetBrowser,
+				otherBrowsers,
+				expectedResult,
+				&token,
+				onePerPage,
+			)
+		})
+
 	})
 }