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backend/internal/httpfetch/httpfetch.go

@@ -0,0 +1,62 @@
+package httpfetch
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"net/http"
+	"strings"
+
+	log "github.com/sirupsen/logrus"
+)
+
+// Doer abstracts the HTTP client used to execute requests.
+type Doer interface {
+	Do(*http.Request) (*http.Response, error)
+}
+
+// GetBytes performs a GET request with the supplied headers, requires a
+// success status, and returns the response body. When maxSize is positive
+// the body is rejected once it exceeds maxSize bytes.
+func GetBytes(ctx context.Context, client Doer, requestURL string, headers map[string]string, maxSize int64) ([]byte, error) {
+	if client == nil {
+		client = http.DefaultClient
+	}
+	req, errRequest := http.NewRequestWithContext(ctx, http.MethodGet, requestURL, nil)
+	if errRequest != nil {
+		return nil, fmt.Errorf("create request: %w", errRequest)
+	}
+	for key, value := range headers {
+		if value != "" {
+			req.Header.Set(key, value)
+		}
+	}
+
+	resp, errDo := client.Do(req)
+	if errDo != nil {
+		return nil, fmt.Errorf("request failed: %w", errDo)
+	}
+	defer func() {
+		if errClose := resp.Body.Close(); errClose != nil {
+			log.WithError(errClose).Debug("failed to close response body")
+		}
+	}()
+
+	if resp.StatusCode < http.StatusOK || resp.StatusCode >= http.StatusMultipleChoices {
+		body, _ := io.ReadAll(io.LimitReader(resp.Body, 4096))
+		return nil, fmt.Errorf("unexpected status %d: %s", resp.StatusCode, strings.TrimSpace(string(body)))
+	}
+
+	reader := io.Reader(resp.Body)
+	if maxSize > 0 {
+		reader = io.LimitReader(resp.Body, maxSize+1)
+	}
+	data, errRead := io.ReadAll(reader)
+	if errRead != nil {
+		return nil, fmt.Errorf("read response: %w", errRead)
+	}
+	if maxSize > 0 && int64(len(data)) > maxSize {
+		return nil, fmt.Errorf("response exceeds maximum allowed size of %d bytes", maxSize)
+	}
+	return data, nil
+}

backend/internal/httpfetch/httpfetch_test.go

@@ -0,0 +1,67 @@
+package httpfetch
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+)
+
+func TestGetBytesReturnsBodyAndSendsHeaders(t *testing.T) {
+	t.Parallel()
+
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Header.Get("User-Agent") != "agent" || r.Header.Get("Accept") != "application/json" {
+			http.Error(w, "missing headers", http.StatusBadRequest)
+			return
+		}
+		_, _ = w.Write([]byte("payload"))
+	}))
+	t.Cleanup(server.Close)
+
+	data, errGet := GetBytes(context.Background(), server.Client(), server.URL, map[string]string{
+		"User-Agent": "agent",
+		"Accept":     "application/json",
+	}, 0)
+	if errGet != nil {
+		t.Fatalf("GetBytes() error = %v", errGet)
+	}
+	if string(data) != "payload" {
+		t.Fatalf("GetBytes() = %q, want payload", data)
+	}
+}
+
+func TestGetBytesRejectsErrorStatus(t *testing.T) {
+	t.Parallel()
+
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		http.Error(w, "missing", http.StatusNotFound)
+	}))
+	t.Cleanup(server.Close)
+
+	_, errGet := GetBytes(context.Background(), server.Client(), server.URL, nil, 0)
+	if errGet == nil {
+		t.Fatal("GetBytes() error = nil")
+	}
+	if !strings.Contains(errGet.Error(), "unexpected status 404") {
+		t.Fatalf("GetBytes() error = %v, want status 404", errGet)
+	}
+}
+
+func TestGetBytesEnforcesMaxSize(t *testing.T) {
+	t.Parallel()
+
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		_, _ = w.Write([]byte("0123456789"))
+	}))
+	t.Cleanup(server.Close)
+
+	_, errGet := GetBytes(context.Background(), server.Client(), server.URL, nil, 4)
+	if errGet == nil {
+		t.Fatal("GetBytes() error = nil")
+	}
+	if !strings.Contains(errGet.Error(), "maximum allowed size") {
+		t.Fatalf("GetBytes() error = %v, want size limit error", errGet)
+	}
+}