fix: fail if repo has too many star

Signed-off-by: Carlos Alexandro Becker <caarlos0@gmail.com>

controller/repositories.go

@@ -1,6 +1,7 @@
 package controller
 
 import (
+	"errors"
 	"fmt"
 	"html/template"
 	"io/fs"
@@ -45,7 +46,7 @@ func IntValueFormatter(v interface{}) string {
 //
 // nolint: funlen
 // TODO: refactor.
-func GetRepoChart(github *github.GitHub, cache *cache.Redis) http.HandlerFunc {
+func GetRepoChart(gh *github.GitHub, cache *cache.Redis) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		name := fmt.Sprintf(
 			"%s/%s",
@@ -54,13 +55,24 @@ func GetRepoChart(github *github.GitHub, cache *cache.Redis) http.HandlerFunc {
 		)
 		log := log.WithField("repo", name)
 		defer log.Trace("collect_stars").Stop(nil)
-		repo, err := github.RepoDetails(r.Context(), name)
+		repo, err := gh.RepoDetails(r.Context(), name)
 		if err != nil {
 			http.Error(w, err.Error(), http.StatusBadRequest)
 			return
 		}
-		stargazers, err := github.Stargazers(r.Context(), repo)
+
+		w.Header().Add("content-type", "image/svg+xml;charset=utf-8")
+		w.Header().Add("cache-control", "public, max-age=86400")
+		w.Header().Add("date", time.Now().Format(time.RFC1123))
+		w.Header().Add("expires", time.Now().Format(time.RFC1123))
+
+		stargazers, err := gh.Stargazers(r.Context(), repo)
+		if errors.Is(err, github.ErrTooManyStars) {
+			w.Write([]byte(errSvg(err)))
+			return
+		}
 		if err != nil {
+			log.WithError(err).Error("failed to get stars")
 			http.Error(w, err.Error(), http.StatusServiceUnavailable)
 			return
 		}
@@ -119,12 +131,14 @@ func GetRepoChart(github *github.GitHub, cache *cache.Redis) http.HandlerFunc {
 			Series: []chart.Series{series},
 		}
 		defer log.Trace("chart").Stop(&err)
-		w.Header().Add("content-type", "image/svg+xml;charset=utf-8")
-		w.Header().Add("cache-control", "public, max-age=86400")
-		w.Header().Add("date", time.Now().Format(time.RFC1123))
-		w.Header().Add("expires", time.Now().Format(time.RFC1123))
 		if err := graph.Render(chart.SVG, w); err != nil {
 			log.WithError(err).Error("failed to render graph")
 		}
 	}
 }
+
+func errSvg(err error) string {
+	return fmt.Sprintf(`<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="1024" height="50">
+	<text xmlns="http://www.w3.org/2000/svg" y="20" x="100" fill="red">%s</text>
+ </svg>`, err.Error())
+}

internal/github/stars.go

@@ -16,6 +16,7 @@ import (
 )
 
 var errNoMorePages = errors.New("no more pages to get")
+var ErrTooManyStars = errors.New("repo has too many stargazers, github won't allow us to list all stars")
 
 // Stargazer is a star at a given time.
 type Stargazer struct {
@@ -25,6 +26,11 @@ type Stargazer struct {
 // Stargazers returns all the stargazers of a given repo.
 func (gh *GitHub) Stargazers(ctx context.Context, repo Repository) (stars []Stargazer, err error) {
 	sem := make(chan bool, 4)
+
+	if gh.totalPages(repo) > 400 {
+		return stars, ErrTooManyStars
+	}
+
 	var g errgroup.Group
 	var lock sync.Mutex
 	for page := 1; page <= gh.lastPage(repo); page++ {
@@ -130,8 +136,13 @@ func (gh *GitHub) getStargazersPage(ctx context.Context, repo Repository, page i
 	}
 }
 
+func (gh *GitHub) totalPages(repo Repository) int {
+	return repo.StargazersCount / gh.pageSize
+}
+
+
 func (gh *GitHub) lastPage(repo Repository) int {
-	return (repo.StargazersCount / gh.pageSize) + 1
+	return gh.totalPages(repo) + 1
 }
 
 func (gh *GitHub) makeStarPageRequest(ctx context.Context, repo Repository, page int, etag string) (*http.Response, error) {