1 files changed, 140 insertions, 0 deletions
diff --git a/internal/vfs/zip/http_reader.go b/internal/vfs/zip/http_reader.go
new file mode 100644
index 00000000..99c94b11
--- /dev/null
+++ b/internal/vfs/zip/http_reader.go
@@ -0,0 +1,140 @@
+package zip
+
+import (
+	"archive/zip"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/http"
+	"strings"
+	"time"
+
+	"gitlab.com/gitlab-org/gitlab-pages/internal/httptransport"
+	"gitlab.com/gitlab-org/gitlab-pages/metrics"
+)
+
+type httpReader struct {
+	URL string
+	Off int64
+	N   int64
+	res *http.Response
+}
+
+var httpClient = &http.Client{
+	// TODO: we need connect timeout
+	// The longest time the request can be executed
+	Timeout:   30 * time.Minute,
+	Transport: httptransport.NewTransportWithMetrics(metrics.ZIPHttpReaderReqDuration, metrics.ZIPHttpReaderReqTotal),
+}
+
+func (h *httpReader) ensureRequest() error {
+	if h.res != nil {
+		return nil
+	}
+
+	req, err := http.NewRequest("GET", h.URL, nil)
+	if err != nil {
+		return err
+	}
+
+	req.Header.Set("Range", fmt.Sprintf("%d-%d", h.Off, h.Off+h.N-1))
+	res, err := httpClient.Do(req)
+	if err != nil {
+		return err
+	}
+	if res.StatusCode != http.StatusOK {
+		res.Body.Close()
+		// TODO: sanitize URL
+		return fmt.Errorf("the %q failed with %d: %q", h.URL, res.StatusCode, res.Status)
+	}
+
+	return nil
+}
+
+func (h *httpReader) Read(p []byte) (n int, err error) {
+	if len(p) == 0 {
+		return 0, nil
+	}
+
+	if err := h.ensureRequest(); err != nil {
+		return 0, err
+	}
+
+	return h.res.Body.Read(p)
+}
+
+func (h *httpReader) Close() error {
+	if h.res != nil {
+		// TODO: should we read till end?
+		return h.res.Body.Close()
+	}
+	return nil
+}
+
+type httpReadAt struct {
+	URL string
+}
+
+func (h *httpReadAt) ReadAt(p []byte, off int64) (n int, err error) {
+	r := httpReader{URL: h.URL, Off: off, N: int64(len(p))}
+	defer r.Close()
+
+	// TODO:
+	// Even if ReadAt returns n < len(p), it may use all of p as scratch space during the call.
+	// If some data is available but not len(p) bytes, ReadAt blocks until either all the data
+	// is available or an error occurs. In this respect ReadAt is different from Read.
+	return r.Read(p)
+}
+
+func isHTTPArchive(path string) bool {
+	return strings.HasPrefix(path, "https://")
+}
+
+func httpSize(path string) (int64, error) {
+	// the `h.URL` is likely presigned only for GET
+	req, err := http.NewRequest("GET", path, nil)
+	if err != nil {
+		return 0, err
+	}
+
+	req.Header.Set("Range", fmt.Sprintf("%d-%d", 0, 0))
+	res, err := httpClient.Do(req)
+	if err != nil {
+		return 0, err
+	}
+	defer io.Copy(ioutil.Discard, res.Body)
+	defer res.Body.Close()
+
+	if res.StatusCode != http.StatusOK {
+		// TODO: sanitize URL
+		return 0, fmt.Errorf("the %q failed with %d: %q", path, res.StatusCode, res.Status)
+	}
+
+	return res.ContentLength, nil
+}
+
+func openZIPHTTPArchive(url string) (*zip.Reader, io.Closer, error) {
+	size, err := httpSize(url)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	r, err := zip.NewReader(&httpReadAt{URL: url}, size)
+	return r, nil, err
+}
+
+func openZIPDiskArchive(path string) (*zip.Reader, io.Closer, error) {
+	r, err := zip.OpenReader(path)
+	if err != nil {
+		return nil, nil, err
+	}
+	return &r.Reader, r, nil
+}
+
+func openZIPArchive(path string) (*zip.Reader, io.Closer, error) {
+	if isHTTPArchive(path) {
+		return openZIPHTTPArchive(path)
+	}
+
+	return openZIPDiskArchive(path)
+}