fix: harden upstream feed fetching

internal/service/http_test.go

@@ -0,0 +1,67 @@
+package service
+
+import (
+	"io"
+	"net/http"
+	"strings"
+	"testing"
+)
+
+type roundTripperFunc func(*http.Request) (*http.Response, error)
+
+func (fn roundTripperFunc) RoundTrip(req *http.Request) (*http.Response, error) {
+	return fn(req)
+}
+
+func TestUserAgentTransportSetsConfiguredUserAgent(t *testing.T) {
+	transport := &userAgentTransport{
+		base: roundTripperFunc(func(req *http.Request) (*http.Response, error) {
+			if got := req.Header.Get("User-Agent"); got != "feedreader/0.1" {
+				t.Fatalf("unexpected user-agent: %q", got)
+			}
+			return &http.Response{
+				StatusCode: http.StatusOK,
+				Body:       io.NopCloser(strings.NewReader("ok")),
+				Header:     make(http.Header),
+			}, nil
+		}),
+		userAgent: "feedreader/0.1",
+	}
+
+	req, err := http.NewRequest(http.MethodGet, "https://example.com", nil)
+	if err != nil {
+		t.Fatalf("new request: %v", err)
+	}
+	resp, err := transport.RoundTrip(req)
+	if err != nil {
+		t.Fatalf("round trip: %v", err)
+	}
+	_ = resp.Body.Close()
+}
+
+func TestUserAgentTransportPreservesExplicitUserAgent(t *testing.T) {
+	transport := &userAgentTransport{
+		base: roundTripperFunc(func(req *http.Request) (*http.Response, error) {
+			if got := req.Header.Get("User-Agent"); got != "custom-agent/1.0" {
+				t.Fatalf("unexpected user-agent: %q", got)
+			}
+			return &http.Response{
+				StatusCode: http.StatusOK,
+				Body:       io.NopCloser(strings.NewReader("ok")),
+				Header:     make(http.Header),
+			}, nil
+		}),
+		userAgent: "feedreader/0.1",
+	}
+
+	req, err := http.NewRequest(http.MethodGet, "https://example.com", nil)
+	if err != nil {
+		t.Fatalf("new request: %v", err)
+	}
+	req.Header.Set("User-Agent", "custom-agent/1.0")
+	resp, err := transport.RoundTrip(req)
+	if err != nil {
+		t.Fatalf("round trip: %v", err)
+	}
+	_ = resp.Body.Close()
+}

internal/service/service.go

@@ -27,12 +27,39 @@ func New(cfg config.Config, repo *repository.SQLiteRepository) *FeedService {
 		cfg:     cfg,
 		repo:    repo,
 		sources: sources.Build(),
-		client: &http.Client{
-			Timeout: time.Duration(cfg.RequestTimeoutSec * float64(time.Second)),
+		client:  newHTTPClient(cfg),
+	}
+}
+
+func newHTTPClient(cfg config.Config) *http.Client {
+	return &http.Client{
+		Timeout: time.Duration(cfg.RequestTimeoutSec * float64(time.Second)),
+		Transport: &userAgentTransport{
+			base:      http.DefaultTransport,
+			userAgent: strings.TrimSpace(cfg.UserAgent),
 		},
 	}
 }
 
+type userAgentTransport struct {
+	base      http.RoundTripper
+	userAgent string
+}
+
+func (t *userAgentTransport) RoundTrip(req *http.Request) (*http.Response, error) {
+	transport := t.base
+	if transport == nil {
+		transport = http.DefaultTransport
+	}
+	if strings.TrimSpace(t.userAgent) == "" || req.Header.Get("User-Agent") != "" {
+		return transport.RoundTrip(req)
+	}
+	clone := req.Clone(req.Context())
+	clone.Header = req.Header.Clone()
+	clone.Header.Set("User-Agent", t.userAgent)
+	return transport.RoundTrip(clone)
+}
+
 func (s *FeedService) StartScheduler(ctx context.Context) {
 	go func() {
 		location := loadScheduleLocation()

internal/sources/alphaxiv.go

@@ -21,11 +21,7 @@ func (AlphaXivSource) Label() string       { return "alphaXiv" }
 func (AlphaXivSource) HomePageURL() string { return "https://www.alphaxiv.org/" }
 
 func (s AlphaXivSource) Fetch(ctx context.Context, client *http.Client) ([]domain.FeedItem, error) {
-	req, err := http.NewRequestWithContext(ctx, http.MethodGet, s.HomePageURL(), nil)
-	if err != nil {
-		return nil, err
-	}
-	resp, err := client.Do(req)
+	resp, err := getWithRetry(ctx, client, s.HomePageURL())
 	if err != nil {
 		return nil, err
 	}

internal/sources/github.go

@@ -19,11 +19,7 @@ func (GitHubTrendingSource) Label() string       { return "GitHub Trending" }
 func (GitHubTrendingSource) HomePageURL() string { return "https://github.com/trending" }
 
 func (s GitHubTrendingSource) Fetch(ctx context.Context, client *http.Client) ([]domain.FeedItem, error) {
-	req, err := http.NewRequestWithContext(ctx, http.MethodGet, s.HomePageURL(), nil)
-	if err != nil {
-		return nil, err
-	}
-	resp, err := client.Do(req)
+	resp, err := getWithRetry(ctx, client, s.HomePageURL())
 	if err != nil {
 		return nil, err
 	}

internal/sources/hackernews.go

@@ -2,7 +2,7 @@ package sources
 
 import (
 	"context"
-	"encoding/xml"
+	"encoding/json"
 	"html"
 	"io"
 	"net/http"
@@ -14,18 +14,16 @@ import (
 	"feedreader/internal/domain"
 )
 
+const hackerNewsFrontPageAPI = "https://hn.algolia.com/api/v1/search?tags=front_page"
+
 type HackerNewsSource struct{}
 
 func (HackerNewsSource) Key() string         { return "hackernews" }
 func (HackerNewsSource) Label() string       { return "Hacker News" }
 func (HackerNewsSource) HomePageURL() string { return "https://news.ycombinator.com/" }
 
 func (s HackerNewsSource) Fetch(ctx context.Context, client *http.Client) ([]domain.FeedItem, error) {
-	req, err := http.NewRequestWithContext(ctx, http.MethodGet, "https://hnrss.org/frontpage", nil)
-	if err != nil {
-		return nil, err
-	}
-	resp, err := client.Do(req)
+	resp, err := getWithRetry(ctx, client, hackerNewsFrontPageAPI)
 	if err != nil {
 		return nil, err
 	}
@@ -41,115 +39,76 @@ func (s HackerNewsSource) Fetch(ctx context.Context, client *http.Client) ([]dom
 	return parseHackerNews(body)
 }
 
-type hnRSS struct {
-	Channel struct {
-		Items []hnItem `xml:"item"`
-	} `xml:"channel"`
+type hnFrontPage struct {
+	Hits []hnStory `json:"hits"`
 }
 
-type hnItem struct {
-	Title       string `xml:"title"`
-	Description string `xml:"description"`
-	PubDate     string `xml:"pubDate"`
-	Link        string `xml:"link"`
-	Comments    string `xml:"comments"`
-	Guid        string `xml:"guid"`
-	Creator     string `xml:"creator"`
+type hnStory struct {
+	ObjectID    string `json:"objectID"`
+	StoryID     int    `json:"story_id"`
+	Title       string `json:"title"`
+	StoryTitle  string `json:"story_title"`
+	URL         string `json:"url"`
+	StoryURL    string `json:"story_url"`
+	StoryText   string `json:"story_text"`
+	CommentText string `json:"comment_text"`
+	Author      string `json:"author"`
+	Points      *int   `json:"points"`
+	NumComments *int   `json:"num_comments"`
+	CreatedAt   string `json:"created_at"`
 }
 
 func parseHackerNews(payload []byte) ([]domain.FeedItem, error) {
-	var rss hnRSS
-	if err := xml.Unmarshal(payload, &rss); err != nil {
+	var rss hnFrontPage
+	if err := json.Unmarshal(payload, &rss); err != nil {
 		return nil, err
 	}
-	items := make([]domain.FeedItem, 0, len(rss.Channel.Items))
-	for idx, node := range rss.Channel.Items {
-		var publishedAt *time.Time
-		if node.PubDate != "" {
-			if parsed, err := time.Parse(time.RFC1123Z, node.PubDate); err == nil {
-				t := parsed.UTC()
-				publishedAt = &t
-			}
+	items := make([]domain.FeedItem, 0, len(rss.Hits))
+	for idx, node := range rss.Hits {
+		externalID := strings.TrimSpace(node.ObjectID)
+		if externalID == "" && node.StoryID > 0 {
+			externalID = strconv.Itoa(node.StoryID)
 		}
-		score := extractInt(node.Description, `Points:\s*(\d+)`)
-		commentsCount := extractInt(node.Description, `# Comments:\s*(\d+)`)
+		if externalID == "" {
+			continue
+		}
+		commentsURL := "https://news.ycombinator.com/item?id=" + externalID
 		metadata := map[string]any{}
-		if commentsCount != nil {
-			metadata["comments_count"] = *commentsCount
+		if node.NumComments != nil {
+			metadata["comments_count"] = *node.NumComments
 		}
 		items = append(items, domain.FeedItem{
 			Source:      "hackernews",
-			ExternalID:  extractStoryID(firstNonEmpty(node.Comments, node.Guid, node.Link)),
-			Title:       strings.TrimSpace(node.Title),
-			URL:         strings.TrimSpace(node.Link),
-			Summary:     cleanString(extractHNSummary(node.Description)),
-			Author:      cleanString(strings.TrimSpace(node.Creator)),
-			Score:       score,
-			CommentsURL: cleanString(strings.TrimSpace(node.Comments)),
-			PublishedAt: publishedAt,
+			ExternalID:  externalID,
+			Title:       strings.TrimSpace(firstNonEmpty(node.Title, node.StoryTitle, externalID)),
+			URL:         strings.TrimSpace(firstNonEmpty(node.URL, node.StoryURL, commentsURL)),
+			Summary:     cleanString(extractHNSummary(firstNonEmpty(node.StoryText, node.CommentText))),
+			Author:      cleanString(strings.TrimSpace(node.Author)),
+			Score:       node.Points,
+			CommentsURL: cleanString(commentsURL),
+			PublishedAt: parseHackerNewsTime(node.CreatedAt),
 			SourceRank:  idx + 1,
 			Metadata:    metadata,
 		})
 	}
 	return items, nil
 }
 
-func extractStoryID(value string) string {
-	re := regexp.MustCompile(`id=(\d+)`)
-	if match := re.FindStringSubmatch(value); len(match) == 2 {
-		return match[1]
-	}
-	return strings.TrimSpace(value)
-}
-
-func extractHNSummary(description string) string {
-	head := strings.SplitN(description, "<hr>", 2)[0]
-	replacer := regexp.MustCompile(`<a [^>]+>|</a>|<[^>]+>`)
-	cleaned := replacer.ReplaceAllString(head, " ")
-	cleaned = html.UnescapeString(cleaned)
-	patterns := []*regexp.Regexp{
-		regexp.MustCompile(`Comments URL:\s*\S+`),
-		regexp.MustCompile(`Article URL:\s*\S+`),
-		regexp.MustCompile(`Points:\s*\d+`),
-		regexp.MustCompile(`# Comments:\s*\d+`),
-		regexp.MustCompile(`\s+`),
-	}
-	for _, pattern := range patterns {
-		cleaned = pattern.ReplaceAllString(cleaned, " ")
-	}
-	return strings.TrimSpace(cleaned)
-}
-
-func extractInt(value, pattern string) *int {
-	re := regexp.MustCompile(pattern)
-	match := re.FindStringSubmatch(value)
-	if len(match) != 2 {
-		return nil
-	}
-	parsed := strings.ReplaceAll(match[1], ",", "")
-	if parsed == "" {
+func parseHackerNewsTime(value string) *time.Time {
+	if strings.TrimSpace(value) == "" {
 		return nil
 	}
-	out, err := strconv.Atoi(parsed)
+	parsed, err := time.Parse(time.RFC3339, strings.TrimSpace(value))
 	if err != nil {
 		return nil
 	}
-	return &out
+	utc := parsed.UTC()
+	return &utc
 }
 
-func firstNonEmpty(values ...string) string {
-	for _, value := range values {
-		if strings.TrimSpace(value) != "" {
-			return value
-		}
-	}
-	return ""
-}
-
-func cleanString(value string) *string {
-	value = strings.TrimSpace(value)
-	if value == "" {
-		return nil
-	}
-	return &value
+func extractHNSummary(description string) string {
+	cleaned := regexp.MustCompile(`<a [^>]+>|</a>|<[^>]+>`).ReplaceAllString(description, " ")
+	cleaned = html.UnescapeString(cleaned)
+	cleaned = regexp.MustCompile(`\s+`).ReplaceAllString(cleaned, " ")
+	return strings.TrimSpace(cleaned)
 }