perf(services): stop reading pull requests once a filtered page is full

Signed-off-by: bircni <bircni@icloud.com>

internal/services/pulls.go

@@ -176,24 +176,42 @@ func (s Pulls) List(ctx context.Context, options PullListOptions) ([]Pull, bool,
 }
 
 // ListPage is List that also reports how many pull requests match, when the server counts them
-// or every pull request was read for a filter without a server equivalent.
+// or every pull request was read for a filter without a server equivalent. Such a filter reads
+// pages only until one pull request past the requested page matches.
 func (s Pulls) ListPage(ctx context.Context, options PullListOptions) (Page[Pull], error) {
 	if !options.filtered() {
 		return s.listPage(ctx, options)
 	}
+	if options.Limit <= 0 || options.Page <= 0 {
+		return Page[Pull]{}, errors.New("limit and page must be positive")
+	}
 	query := options
 	if query.State == "merged" {
 		query.State = "closed"
 	}
-	all, err := listAll(func(page int) ([]Pull, error) {
+	matching, wanted := []Pull{}, options.Page*options.Limit+1
+	for page := 1; ; page++ {
+		if page > maxListPages {
+			return Page[Pull]{}, fmt.Errorf("listing exceeded %d pages", maxListPages)
+		}
 		query.Limit, query.Page = 50, page
 		window, err := s.listPage(ctx, query)
-		return window.Items, err
-	})
-	if err != nil {
-		return Page[Pull]{}, err
+		if err != nil {
+			return Page[Pull]{}, err
+		}
+		for _, item := range window.Items {
+			if options.matches(item) {
+				matching = append(matching, item)
+			}
+		}
+		if len(matching) >= wanted {
+			items, err := pageOf(matching, options.Limit, options.Page)
+			return Page[Pull]{Items: items, More: true}, err
+		}
+		if len(window.Items) == 0 || (!window.More && len(window.Items) < query.Limit) {
+			break
+		}
 	}
-	matching := slices.DeleteFunc(all, func(item Pull) bool { return !options.matches(item) })
 	items, err := pageOf(matching, options.Limit, options.Page)
 	if err != nil {
 		return Page[Pull]{}, err

internal/services/pulls_test.go

@@ -326,3 +326,40 @@ func TestPullFromToleratesMissingBranches(t *testing.T) {
 	require.Equal(t, Pull{Number: 1, Assignees: []string{}, Labels: []Label{}, Reviewers: []string{}, ReviewerTeams: []string{}},
 		pullFrom(decode[gitea.PullRequest](t, `{"number":1,"head":null,"base":null}`)))
 }
+
+func TestPullClientFiltersStopReadingOncePageIsFull(t *testing.T) {
+	requests := 0
+	client := newTestClient(t, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		requests++
+		page, _ := strconv.Atoi(r.URL.Query().Get("page"))
+		items := make([]string, 0, 50)
+		for i := range 50 {
+			items = append(items, `{"number":`+strconv.Itoa((page-1)*50+i+1)+`,"draft":true}`)
+		}
+		w.Header().Set("X-Total-Count", "5000")
+		_, _ = w.Write([]byte("[" + strings.Join(items, ",") + "]"))
+	}))
+	page, err := (Pulls{Client: client, Repository: "alice/project"}).ListPage(context.Background(), PullListOptions{State: "open", Draft: true, Limit: 30, Page: 2})
+	require.NoError(t, err)
+	require.Equal(t, 2, requests)
+	require.Len(t, page.Items, 30)
+	require.EqualValues(t, 31, page.Items[0].Number)
+	require.True(t, page.More)
+	require.False(t, page.Counted)
+}
+
+func TestPullClientFiltersCountWhenEveryPullWasRead(t *testing.T) {
+	client := newTestClient(t, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.URL.Query().Get("page") != "1" {
+			_, _ = w.Write([]byte(`[]`))
+			return
+		}
+		_, _ = w.Write([]byte(`[{"number":1,"draft":true},{"number":2},{"number":3,"draft":true}]`))
+	}))
+	page, err := (Pulls{Client: client, Repository: "alice/project"}).ListPage(context.Background(), PullListOptions{State: "open", Draft: true, Limit: 2, Page: 1})
+	require.NoError(t, err)
+	require.Len(t, page.Items, 2)
+	require.False(t, page.More)
+	require.True(t, page.Counted)
+	require.Equal(t, 2, page.Total)
+}