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

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)
+			}
+		})
+	}
+}