gzip http requests (#336)

* gzip http requests

* remove unused alias

* add version checks before gzipping

* swallow errors when checking backend version

* I do not know why my editor keeps adding this

internal/api/api.go

@@ -10,13 +10,16 @@ import (
 	"io/ioutil"
 	"net/http"
 	"os"
+	"regexp"
 	"strings"
 
+	"github.com/Masterminds/semver"
 	"github.com/hashicorp/go-multierror"
 	"github.com/jig/teereadcloser"
 	"github.com/kballard/go-shellquote"
 	"github.com/mattn/go-isatty"
 	"github.com/pkg/errors"
+	"github.com/sourcegraph/codeintelutils"
 )
 
 // Client instances provide methods to create API requests.
@@ -53,7 +56,8 @@ type Request interface {
 
 // client is the internal concrete type implementing Client.
 type client struct {
-	opts ClientOpts
+	opts         ClientOpts
+	supportsGzip *bool
 }
 
 // request is the internal concrete type implementing Request.
@@ -113,6 +117,39 @@ func (c *client) NewRequest(query string, vars map[string]interface{}) Request {
 }
 
 func (c *client) NewHTTPRequest(ctx context.Context, method, p string, body io.Reader) (*http.Request, error) {
+	if c.supportsGzip == nil {
+		// set to false, unless we have a new enough version
+		supportsGzip := false
+		c.supportsGzip = &supportsGzip
+
+		version, err := c.getSourcegraphVersion(ctx)
+
+		// ignore errors; we only care if the version is sufficently new
+		if err == nil {
+			supportsGzip, err = sourcegraphVersionCheck(version, ">= 3.21.0", "2020-10-12")
+			if err == nil {
+				c.supportsGzip = &supportsGzip
+			}
+		}
+	}
+
+	if *c.supportsGzip && body != nil {
+		body = codeintelutils.Gzip(body)
+	}
+
+	req, err := c.createHTTPRequest(ctx, method, p, body)
+	if err != nil {
+		return nil, err
+	}
+
+	if *c.supportsGzip {
+		req.Header.Set("Content-Encoding", "gzip")
+	}
+
+	return req, nil
+}
+
+func (c *client) createHTTPRequest(ctx context.Context, method, p string, body io.Reader) (*http.Request, error) {
 	req, err := http.NewRequestWithContext(ctx, method, strings.TrimRight(c.opts.Endpoint, "/")+"/"+p, body)
 	if err != nil {
 		return nil, err
@@ -126,6 +163,7 @@ func (c *client) NewHTTPRequest(ctx context.Context, method, p string, body io.R
 	for k, v := range c.opts.AdditionalHeaders {
 		req.Header.Set(k, v)
 	}
+
 	return req, nil
 }
 
@@ -265,3 +303,80 @@ func (r *request) curlCmd() (string, error) {
 	s += fmt.Sprintf("   %s", shellquote.Join(r.client.opts.Endpoint+"/.api/graphql"))
 	return s, nil
 }
+
+const sourcegraphVersionQuery = `query SourcegraphVersion {
+	site {
+	  productVersion
+	}
+  }
+  `
+
+func (c *client) getSourcegraphVersion(ctx context.Context) (string, error) {
+	var sourcegraphVersion struct {
+		Data struct {
+			Site struct {
+				ProductVersion string
+			}
+		}
+	}
+
+	// Create the JSON object.
+	reqBody, err := json.Marshal(map[string]interface{}{
+		"query": sourcegraphVersionQuery,
+	})
+	if err != nil {
+		return "", err
+	}
+
+	// Create the HTTP request.
+	req, err := c.createHTTPRequest(ctx, "POST", ".api/graphql", bytes.NewBuffer(reqBody))
+	if err != nil {
+		return "", err
+	}
+
+	// Perform the request.
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return "", err
+	}
+	defer resp.Body.Close()
+
+	respBytes, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return "", err
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		return "", fmt.Errorf("checking sourcegraph backend version; got status code %d", resp.StatusCode)
+	}
+
+	err = json.Unmarshal(respBytes, &sourcegraphVersion)
+	if err != nil {
+		return "", err
+	}
+
+	return sourcegraphVersion.Data.Site.ProductVersion, err
+}
+
+func sourcegraphVersionCheck(version, constraint, minDate string) (bool, error) {
+	if version == "dev" || version == "0.0.0+dev" {
+		return true, nil
+	}
+
+	buildDate := regexp.MustCompile(`^\d+_(\d{4}-\d{2}-\d{2})_[a-z0-9]{7}$`)
+	matches := buildDate.FindStringSubmatch(version)
+	if len(matches) > 1 {
+		return matches[1] >= minDate, nil
+	}
+
+	c, err := semver.NewConstraint(constraint)
+	if err != nil {
+		return false, nil
+	}
+
+	v, err := semver.NewVersion(version)
+	if err != nil {
+		return false, err
+	}
+	return c.Check(v), nil
+}