Detect user based on key, username or id

This allows gitlab-shell to be called with an argument of the format
`key-123` or `username-name`.

When called in this way, `gitlab-shell` will call the GitLab internal
API. If the API responds with user information, it will print a
welcome message including the username.

If the API responds with a successful but empty response, gitlab-shell
will print a welcome message for an anonymous user.

If the API response includes an error message in JSON, this message
will be printed to stderr.

If the API call fails, an error message including the status code will
be printed to stderr.

1 files changed, 77 insertions, 0 deletions

diff --git a/go/internal/gitlabnet/client.go b/go/internal/gitlabnet/client.go
new file mode 100644
index 0000000..abc218f
--- /dev/null
+++ b/go/internal/gitlabnet/client.go
@@ -0,0 +1,77 @@
+package gitlabnet
+
+import (
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"strings"
+
+	"gitlab.com/gitlab-org/gitlab-shell/go/internal/config"
+)
+
+const (
+	internalApiPath  = "/api/v4/internal"
+	secretHeaderName = "Gitlab-Shared-Secret"
+)
+
+type GitlabClient interface {
+	Get(path string) (*http.Response, error)
+	// TODO: implement posts
+	// Post(path string) (http.Response, error)
+}
+
+type ErrorResponse struct {
+	Message string `json:"message"`
+}
+
+func GetClient(config *config.Config) (GitlabClient, error) {
+	url := config.GitlabUrl
+	if strings.HasPrefix(url, UnixSocketProtocol) {
+		return buildSocketClient(config), nil
+	}
+
+	return nil, fmt.Errorf("Unsupported protocol")
+}
+
+func normalizePath(path string) string {
+	if !strings.HasPrefix(path, "/") {
+		path = "/" + path
+	}
+
+	if !strings.HasPrefix(path, internalApiPath) {
+		path = internalApiPath + path
+	}
+	return path
+}
+
+func parseError(resp *http.Response) error {
+	if resp.StatusCode >= 200 && resp.StatusCode <= 299 {
+		return nil
+	}
+	defer resp.Body.Close()
+	parsedResponse := &ErrorResponse{}
+
+	if err := json.NewDecoder(resp.Body).Decode(parsedResponse); err != nil {
+		return fmt.Errorf("Internal API error (%v)", resp.StatusCode)
+	} else {
+		return fmt.Errorf(parsedResponse.Message)
+	}
+
+}
+
+func doRequest(client *http.Client, config *config.Config, request *http.Request) (*http.Response, error) {
+	encodedSecret := base64.StdEncoding.EncodeToString([]byte(config.Secret))
+	request.Header.Set(secretHeaderName, encodedSecret)
+
+	response, err := client.Do(request)
+	if err != nil {
+		return nil, fmt.Errorf("Internal API unreachable")
+	}
+
+	if err := parseError(response); err != nil {
+		return nil, err
+	}
+
+	return response, nil
+}