feat(gitlab-sim): 🚀 ajout graph

internal/fetcher/gitlab.go

@@ -0,0 +1,152 @@
+// Package fetcher retrieves remote GitLab CI YAML files via the GitLab REST API.
+package fetcher
+
+import (
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"os"
+	"strings"
+)
+
+// TokenSource describes where a token was found, which determines the correct
+// authentication header to use with the GitLab API.
+type TokenSource int
+
+const (
+	TokenNone     TokenSource = iota
+	TokenPrivate              // GITLAB_TOKEN or GITLAB_PRIVATE_TOKEN → PRIVATE-TOKEN header
+	TokenJobToken             // CI_JOB_TOKEN → JOB-TOKEN header
+)
+
+// GitLabConfig holds everything needed to reach a GitLab instance.
+type GitLabConfig struct {
+	BaseURL string
+	Token   string
+	Source  TokenSource
+}
+
+// AutoConfig builds a GitLabConfig from environment variables.
+//
+// Base URL resolution order: CI_SERVER_URL → GITLAB_URL → https://gitlab.com
+// Token resolution order:    GITLAB_TOKEN → CI_JOB_TOKEN → GITLAB_PRIVATE_TOKEN
+func AutoConfig() GitLabConfig {
+	baseURL := firstNonEmpty(
+		os.Getenv("CI_SERVER_URL"),
+		os.Getenv("GITLAB_URL"),
+		"https://gitlab.com",
+	)
+
+	cfg := GitLabConfig{BaseURL: strings.TrimRight(baseURL, "/")}
+
+	if t := os.Getenv("GITLAB_TOKEN"); t != "" {
+		cfg.Token = t
+		cfg.Source = TokenPrivate
+	} else if t := os.Getenv("CI_JOB_TOKEN"); t != "" {
+		cfg.Token = t
+		cfg.Source = TokenJobToken
+	} else if t := os.Getenv("GITLAB_PRIVATE_TOKEN"); t != "" {
+		cfg.Token = t
+		cfg.Source = TokenPrivate
+	}
+
+	return cfg
+}
+
+// WithOverrides returns a copy of cfg with non-empty overrides applied.
+func (cfg GitLabConfig) WithOverrides(baseURL, token string) GitLabConfig {
+	if baseURL != "" {
+		cfg.BaseURL = strings.TrimRight(baseURL, "/")
+	}
+	if token != "" {
+		cfg.Token = token
+		cfg.Source = TokenPrivate
+	}
+	return cfg
+}
+
+// ForHost returns a copy of cfg with BaseURL set to https://<host>.
+// Used when a CI/CD component reference specifies a different GitLab host.
+func (cfg GitLabConfig) ForHost(host string) GitLabConfig {
+	cfg.BaseURL = "https://" + host
+	return cfg
+}
+
+// HasToken reports whether the config carries a usable token.
+func (cfg GitLabConfig) HasToken() bool { return cfg.Token != "" }
+
+// FetchFile downloads a single file from a GitLab project repository.
+// If no token is configured the request is sent unauthenticated (works for
+// public projects and GitLab CI/CD catalog components).
+//
+//   - project  — namespace/project path, e.g. "my-group/my-project"
+//   - filePath — repository file path, e.g. "/templates/ci.yml"
+//   - ref      — branch, tag, or commit SHA; empty string defaults to HEAD
+func (cfg GitLabConfig) FetchFile(project, filePath, ref string) ([]byte, error) {
+	encodedProject := url.PathEscape(project)
+	encodedFile := url.PathEscape(strings.TrimPrefix(filePath, "/"))
+
+	apiURL := fmt.Sprintf("%s/api/v4/projects/%s/repository/files/%s/raw",
+		cfg.BaseURL, encodedProject, encodedFile)
+
+	if ref == "" {
+		ref = "HEAD"
+	}
+
+	req, err := http.NewRequest(http.MethodGet, apiURL, nil)
+	if err != nil {
+		return nil, fmt.Errorf("building request: %w", err)
+	}
+
+	q := req.URL.Query()
+	q.Set("ref", ref)
+	req.URL.RawQuery = q.Encode()
+
+	// Add auth header only when a token is available.
+	if cfg.Token != "" {
+		switch cfg.Source {
+		case TokenJobToken:
+			req.Header.Set("JOB-TOKEN", cfg.Token)
+		default:
+			req.Header.Set("PRIVATE-TOKEN", cfg.Token)
+		}
+	}
+
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("GET %s: %w", apiURL, err)
+	}
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, fmt.Errorf("reading response body: %w", err)
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		msg := strings.TrimSpace(string(body))
+		switch resp.StatusCode {
+		case http.StatusUnauthorized:
+			if cfg.Token == "" {
+				return nil, fmt.Errorf("authentication required (401) — set GITLAB_TOKEN or CI_JOB_TOKEN")
+			}
+			return nil, fmt.Errorf("authentication failed (401) — check your token")
+		case http.StatusNotFound:
+			return nil, fmt.Errorf("not found (404): %s@%s in project %s — check the project path, file path, and token permissions", filePath, ref, project)
+		default:
+			return nil, fmt.Errorf("unexpected status %d: %s", resp.StatusCode, msg)
+		}
+	}
+
+	return body, nil
+}
+
+func firstNonEmpty(values ...string) string {
+	for _, v := range values {
+		if v != "" {
+			return v
+		}
+	}
+	return ""
+}