feat(templates): allow managing git based templates [EE-2600] (#7855)

Co-authored-by: itsconquest <william.conquest@portainer.io>
Co-authored-by: oscarzhou <oscar.zhou@portainer.io>
Co-authored-by: Chaim Lev-Ari <chiptus@users.noreply.github.com>

api/http/handler/customtemplates/customtemplate_git_fetch.go

@@ -0,0 +1,124 @@
+package customtemplates
+
+import (
+	"fmt"
+	"net/http"
+	"os"
+	"sync"
+
+	httperror "github.com/portainer/libhttp/error"
+	"github.com/portainer/libhttp/request"
+	"github.com/portainer/libhttp/response"
+	portainer "github.com/portainer/portainer/api"
+	"github.com/portainer/portainer/api/stacks/stackutils"
+	"github.com/rs/zerolog/log"
+)
+
+// @id CustomTemplateGitFetch
+// @summary Fetch the latest config file content based on custom template's git repository configuration
+// @description Retrieve details about a template created from git repository method.
+// @description **Access policy**: authenticated
+// @tags custom_templates
+// @security ApiKeyAuth
+// @security jwt
+// @produce json
+// @param id path int true "Template identifier"
+// @success 200 {object} fileResponse "Success"
+// @failure 400 "Invalid request"
+// @failure 404 "Custom template not found"
+// @failure 500 "Server error"
+// @router /custom_templates/{id}/git_fetch [put]
+func (handler *Handler) customTemplateGitFetch(w http.ResponseWriter, r *http.Request) *httperror.HandlerError {
+	customTemplateID, err := request.RetrieveNumericRouteVariableValue(r, "id")
+	if err != nil {
+		return httperror.BadRequest("Invalid Custom template identifier route variable", err)
+	}
+
+	customTemplate, err := handler.DataStore.CustomTemplate().CustomTemplate(portainer.CustomTemplateID(customTemplateID))
+	if handler.DataStore.IsErrObjectNotFound(err) {
+		return httperror.NotFound("Unable to find a custom template with the specified identifier inside the database", err)
+	} else if err != nil {
+		return httperror.InternalServerError("Unable to find a custom template with the specified identifier inside the database", err)
+	}
+
+	if customTemplate.GitConfig == nil {
+		return httperror.BadRequest("Git configuration does not exist in this custom template", err)
+	}
+
+	// If multiple users are trying to fetch the same custom template simultaneously, a lock needs to be added
+	mu, ok := handler.gitFetchMutexs[portainer.TemplateID(customTemplateID)]
+	if !ok {
+		mu = &sync.Mutex{}
+		handler.gitFetchMutexs[portainer.TemplateID(customTemplateID)] = mu
+	}
+	mu.Lock()
+	defer mu.Unlock()
+
+	// back up the current custom template folder
+	backupPath, err := backupCustomTemplate(customTemplate.ProjectPath)
+	if err != nil {
+		return httperror.InternalServerError("Failed to backup the custom template folder", err)
+	}
+
+	// remove backup custom template folder
+	defer cleanUpBackupCustomTemplate(backupPath)
+
+	commitHash, err := stackutils.DownloadGitRepository(*customTemplate.GitConfig, handler.GitService, func() string {
+		return customTemplate.ProjectPath
+	})
+	if err != nil {
+		log.Warn().Err(err).Msg("failed to download git repository")
+		rbErr := rollbackCustomTemplate(backupPath, customTemplate.ProjectPath)
+		if err != nil {
+			return httperror.InternalServerError("Failed to rollback the custom template folder", rbErr)
+		}
+		return httperror.InternalServerError("Failed to download git repository", err)
+	}
+
+	if customTemplate.GitConfig.ConfigHash != commitHash {
+		customTemplate.GitConfig.ConfigHash = commitHash
+
+		err = handler.DataStore.CustomTemplate().UpdateCustomTemplate(customTemplate.ID, customTemplate)
+		if err != nil {
+			return httperror.InternalServerError("Unable to persist custom template changes inside the database", err)
+		}
+	}
+
+	fileContent, err := handler.FileService.GetFileContent(customTemplate.ProjectPath, customTemplate.GitConfig.ConfigFilePath)
+	if err != nil {
+		return httperror.InternalServerError("Unable to retrieve custom template file from disk", err)
+	}
+
+	return response.JSON(w, &fileResponse{FileContent: string(fileContent)})
+}
+
+func backupCustomTemplate(projectPath string) (string, error) {
+	stat, err := os.Stat(projectPath)
+	if err != nil {
+		return "", err
+	}
+
+	backupPath := fmt.Sprintf("%s-backup", projectPath)
+	err = os.Rename(projectPath, backupPath)
+	if err != nil {
+		return "", err
+	}
+
+	err = os.Mkdir(projectPath, stat.Mode())
+	if err != nil {
+		return backupPath, err
+	}
+	return backupPath, nil
+}
+
+func rollbackCustomTemplate(backupPath, projectPath string) error {
+	err := os.RemoveAll(projectPath)
+	if err != nil {
+		return err
+	}
+	return os.Rename(backupPath, projectPath)
+}
+
+func cleanUpBackupCustomTemplate(backupPath string) error {
+	return os.RemoveAll(backupPath)
+}