Add gitlab provider

backend/app/gitprovider/factory.go

@@ -19,6 +19,12 @@ func NewProvider(serverType, protocol, baseUrl, authToken string) (GitProvider,
 			baseUrl:   baseUrl,
 			authToken: authToken,
 		}, nil
+	case "gitlab":
+		return &GitLabProvider{
+			protocol:  protocol,
+			baseUrl:   baseUrl,
+			authToken: authToken,
+		}, nil
 	default:
 		return nil, fmt.Errorf("unsupported git provider: %s", serverType)
 	}

backend/app/gitprovider/gitlab.go

@@ -0,0 +1,143 @@
+package gitprovider
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+type GitLabProvider struct {
+	protocol  string
+	baseUrl   string
+	authToken string
+}
+
+var _ GitProvider = (*GitLabProvider)(nil)
+
+func (p *GitLabProvider) FetchAndDeployBranch(owner, repo, branch, destPath string) (*DeployResult, error) {
+	apiUrl := fmt.Sprintf("%s://%s/api/v4/", p.protocol, strings.TrimSuffix(p.baseUrl, "/"))
+
+	result, err := fetchGitLabBranchHead(apiUrl, owner, repo, branch, p.authToken)
+	if err != nil {
+		return nil, fmt.Errorf("fetching branch head: %w", err)
+	}
+
+	if err = downloadAndExtractGitLab(apiUrl, owner, repo, branch, p.authToken, destPath); err != nil {
+		return nil, err
+	}
+
+	return result, nil
+}
+
+func fetchGitLabBranchHead(apiUrl, owner, repo, branch, token string) (*DeployResult, error) {
+	// GitLab identifies projects by URL-encoded "namespace/repo" path.
+	projectID := url.PathEscape(owner + "/" + repo)
+	encodedBranch := url.PathEscape(branch)
+	reqUrl := fmt.Sprintf("%sprojects/%s/repository/branches/%s", apiUrl, projectID, encodedBranch)
+
+	req, err := http.NewRequest(http.MethodGet, reqUrl, nil)
+	if err != nil {
+		return nil, fmt.Errorf("creating request: %w", err)
+	}
+	req.Header.Set("PRIVATE-TOKEN", token)
+
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("fetching branch: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("GitLab returned %s for %s", resp.Status, reqUrl)
+	}
+
+	var payload struct {
+		Commit struct {
+			ID    string `json:"id"`
+			Title string `json:"title"` // first line of the commit message
+		} `json:"commit"`
+	}
+	if err = json.NewDecoder(resp.Body).Decode(&payload); err != nil {
+		return nil, fmt.Errorf("decoding branch response: %w", err)
+	}
+
+	return &DeployResult{
+		CommitHash:    payload.Commit.ID,
+		CommitMessage: payload.Commit.Title,
+	}, nil
+}
+
+func downloadAndExtractGitLab(apiUrl, owner, repo, branch, token, destDir string) error {
+	// GET /projects/:id/repository/archive.zip?sha=<branch>
+	projectID := url.PathEscape(owner + "/" + repo)
+	archiveURL := fmt.Sprintf("%sprojects/%s/repository/archive.zip?sha=%s", apiUrl, projectID, url.QueryEscape(branch))
+
+	req, err := http.NewRequest(http.MethodGet, archiveURL, nil)
+	if err != nil {
+		return fmt.Errorf("creating request: %w", err)
+	}
+	req.Header.Set("PRIVATE-TOKEN", token)
+
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return fmt.Errorf("fetching archive: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return fmt.Errorf("GitLab returned %s for %s", resp.Status, archiveURL)
+	}
+
+	storageRoot := filepath.Dir(destDir)
+
+	tmpZip, err := os.CreateTemp(storageRoot, "gitlabbranch-*.zip")
+	if err != nil {
+		return fmt.Errorf("creating temp zip: %w", err)
+	}
+	defer os.Remove(tmpZip.Name())
+
+	if _, err = io.Copy(tmpZip, resp.Body); err != nil {
+		tmpZip.Close()
+		return fmt.Errorf("writing zip: %w", err)
+	}
+	tmpZip.Close()
+
+	tmpDir, err := os.MkdirTemp(storageRoot, "gitlabbranch-unpack-*")
+	if err != nil {
+		return fmt.Errorf("creating temp dir: %w", err)
+	}
+	defer os.RemoveAll(tmpDir)
+
+	if err = unzip(tmpZip.Name(), tmpDir); err != nil {
+		return fmt.Errorf("unzipping: %w", err)
+	}
+
+	// GitLab names the root folder {repo}-{branch}-{sha}/.
+	entries, err := os.ReadDir(tmpDir)
+	if err != nil {
+		return fmt.Errorf("reading temp dir: %w", err)
+	}
+	if len(entries) != 1 || !entries[0].IsDir() {
+		return fmt.Errorf("unexpected archive layout: expected a single root directory")
+	}
+	extractedRoot := filepath.Join(tmpDir, entries[0].Name())
+
+	if err = os.MkdirAll(filepath.Dir(destDir), 0o755); err != nil {
+		return fmt.Errorf("creating destination parent dirs: %w", err)
+	}
+	os.RemoveAll(destDir)
+
+	if err = os.Rename(extractedRoot, destDir); err == nil {
+		return nil
+	}
+
+	if err = copyDir(extractedRoot, destDir); err != nil {
+		return fmt.Errorf("cross-device copy to destination: %w", err)
+	}
+	return nil
+}