feat: take Retry-After header into consideration for rate limited feeds

internal/reader/fetcher/response_handler.go

@@ -13,7 +13,9 @@ import (
 	"net/http"
 	"net/url"
 	"os"
+	"strconv"
 	"strings"
+	"time"
 
 	"miniflux.app/v2/internal/locale"
 )
@@ -51,6 +53,26 @@ func (r *ResponseHandler) ETag() string {
 	return r.httpResponse.Header.Get("ETag")
 }
 
+func (r *ResponseHandler) ParseRetryDelay() int {
+	retryAfterHeaderValue := r.httpResponse.Header.Get("Retry-After")
+	if retryAfterHeaderValue != "" {
+		// First, try to parse as an integer (number of seconds)
+		if seconds, err := strconv.Atoi(retryAfterHeaderValue); err == nil {
+			return seconds
+		}
+
+		// If not an integer, try to parse as an HTTP-date
+		if t, err := time.Parse(time.RFC1123, retryAfterHeaderValue); err == nil {
+			return int(time.Until(t).Seconds())
+		}
+	}
+	return 0
+}
+
+func (r *ResponseHandler) IsRateLimited() bool {
+	return r.httpResponse.StatusCode == http.StatusTooManyRequests
+}
+
 func (r *ResponseHandler) IsModified(lastEtagValue, lastModifiedValue string) bool {
 	if r.httpResponse.StatusCode == http.StatusNotModified {
 		return false

internal/reader/fetcher/response_handler_test.go

@@ -6,6 +6,7 @@ package fetcher // import "miniflux.app/v2/internal/reader/fetcher"
 import (
 	"net/http"
 	"testing"
+	"time"
 )
 
 func TestIsModified(t *testing.T) {
@@ -67,3 +68,37 @@ func TestIsModified(t *testing.T) {
 		})
 	}
 }
+
+func TestRetryDelay(t *testing.T) {
+	var testCases = map[string]struct {
+		RetryAfterHeader string
+		ExpectedDelay    int
+	}{
+		"Empty header": {
+			RetryAfterHeader: "",
+			ExpectedDelay:    0,
+		},
+		"Integer value": {
+			RetryAfterHeader: "42",
+			ExpectedDelay:    42,
+		},
+		"HTTP-date": {
+			RetryAfterHeader: time.Now().Add(42 * time.Second).Format(time.RFC1123),
+			ExpectedDelay:    41,
+		},
+	}
+	for name, tc := range testCases {
+		t.Run(name, func(tt *testing.T) {
+			header := http.Header{}
+			header.Add("Retry-After", tc.RetryAfterHeader)
+			rh := ResponseHandler{
+				httpResponse: &http.Response{
+					Header: header,
+				},
+			}
+			if tc.ExpectedDelay != rh.ParseRetryDelay() {
+				tt.Errorf("Expected %d, got %d for scenario %q", tc.ExpectedDelay, rh.ParseRetryDelay(), name)
+			}
+		})
+	}
+}