feat: handle template build error

internal/apierror/api_error.go

@@ -0,0 +1,17 @@
+package apierror
+
+import "fmt"
+
+type APIError struct {
+	StatusCode int    `json:"-"`
+	Code       string `json:"code"`
+	Message    string `json:"error"`
+}
+
+func New(status int, code, message string) *APIError {
+	return &APIError{status, code, message}
+}
+
+func (err *APIError) Error() string {
+	return fmt.Sprintf("%s: %s", err.Code, err.Message)
+}

internal/template/errors.go

@@ -0,0 +1,9 @@
+package template
+
+type errBadTemplate struct {
+	message string
+}
+
+func (err *errBadTemplate) Error() string {
+	return err.message
+}

internal/template/http_handlers.go

@@ -7,6 +7,7 @@ import (
 	"github.com/labstack/echo/v4"
 	"io"
 	"net/http"
+	"tesseract/internal/apierror"
 	"tesseract/internal/service"
 )
 
@@ -136,6 +137,10 @@ func buildTemplate(c echo.Context, body postTemplateRequestBody) error {
 		buildArgs: body.BuildArgs,
 	})
 	if err != nil {
+		var errBadTemplate *errBadTemplate
+		if errors.As(err, &errBadTemplate) {
+			return apierror.New(http.StatusBadRequest, "BAD_TEMPLATE", errBadTemplate.message)
+		}
 		return err
 	}
 

internal/template/template_manager.go

@@ -11,8 +11,10 @@ import (
 	"fmt"
 	"github.com/docker/docker/api/types"
 	"github.com/docker/docker/client"
+	"github.com/docker/docker/errdefs"
 	"github.com/google/uuid"
 	"github.com/uptrace/bun"
+	"strings"
 	"time"
 )
 
@@ -252,6 +254,14 @@ func (mgr *templateManager) buildTemplate(ctx context.Context, template *templat
 		BuildArgs: opts.buildArgs,
 	})
 	if err != nil {
+		if errdefs.IsInvalidParameter(err) {
+			return nil, &errBadTemplate{
+				// the docker sdk returns an error message that looks like:
+				// "Error response from daemon: dockerfile parse error on line 1: unknown instruction: FR (did you mean FROM?)"
+				// we don't want the "error response..." part because it is meaningless
+				message: strings.Replace(err.Error(), "Error response from daemon: ", "", 1),
+			}
+		}
 		return nil, err
 	}