core/internal/port/handler_http_api_error.go

package port

import (
	"errors"
	"net/http"

	"gitea.dwysokinski.me/twhelp/corev3/internal/domain"
	"gitea.dwysokinski.me/twhelp/corev3/internal/port/internal/apimodel"
	"github.com/ettle/strcase"
	"github.com/oapi-codegen/runtime"
)

type apiError struct {
	status  int
	code    string
	path    []string
	params  map[string]any
	message string
}

func (e apiError) Error() string {
	return e.message
}

func (e apiError) toResponse() apimodel.ErrorResponse {
	return apimodel.ErrorResponse{
		Errors: []apimodel.Error{
			{
				Message: e.message,
				Params:  e.params,
				Path:    e.path,
				Code:    e.code,
			},
		},
	}
}

type apiErrors []apiError

func (es apiErrors) status() int {
	if len(es) == 0 {
		return http.StatusOK
	}

	status := es[0].status

	for _, e := range es {
		if e.status > status {
			status = e.status
		}
	}

	return status
}

func (es apiErrors) toResponse() apimodel.ErrorResponse {
	resp := apimodel.ErrorResponse{
		Errors: make([]apimodel.Error, 0, len(es)),
	}

	for _, e := range es {
		resp.Errors = append(resp.Errors, e.toResponse().Errors...)
	}

	return resp
}

type errorPathSegment struct {
	model string
	field string
	index int // index may be <0 and this means that it is unset
}

type apiErrorRenderer struct {
	errors []error
	// formatErrorPath allows to override the default path formatter
	// for domain.ValidationError and domain.SliceElementValidationError.
	// If formatErrorPath returns an empty slice, an internal server error is rendered.
	formatErrorPath func(segments []errorPathSegment) []string
}

var errAPIInternalServerError = apiError{
	status:  http.StatusInternalServerError,
	code:    "internal-server-error",
	message: "internal server error",
}

func (re apiErrorRenderer) render(w http.ResponseWriter, r *http.Request) {
	errs := make(apiErrors, 0, len(re.errors))

	for _, err := range re.errors {
		var apiErr apiError
		var domainErr domain.Error
		var paramFormatErr *apimodel.InvalidParamFormatError

		switch {
		case errors.As(err, &apiErr):
		case errors.As(err, &paramFormatErr):
			apiErr = re.invalidParamFormatErrorToAPIError(paramFormatErr)
		case errors.As(err, &domainErr):
			apiErr = re.domainErrorToAPIError(domainErr)
		default:
			apiErr = errAPIInternalServerError
		}

		errs = append(errs, apiErr)
	}

	renderJSON(w, r, errs.status(), errs.toResponse())
}

func (re apiErrorRenderer) invalidParamFormatErrorToAPIError(
	paramFormatErr *apimodel.InvalidParamFormatError,
) apiError {
	var location string

	switch paramFormatErr.Location {
	case runtime.ParamLocationPath:
		location = "$path"
	case runtime.ParamLocationHeader:
		location = "$header"
	case runtime.ParamLocationQuery:
		location = "$query"
	case runtime.ParamLocationCookie:
		location = "$cookie"
	case runtime.ParamLocationUndefined:
		fallthrough
	default:
		location = "$unknown"
	}

	return apiError{
		status:  http.StatusBadRequest,
		code:    "invalid-param-format",
		path:    []string{location, paramFormatErr.ParamName},
		message: paramFormatErr.Err.Error(),
	}
}

func (re apiErrorRenderer) domainErrorToAPIError(domainErr domain.Error) apiError {
	message := domainErr.Error()
	var pathSegments []errorPathSegment

	var err error = domainErr
	for err != nil {
		var validationErr domain.ValidationError
		var sliceElementValidationErr domain.SliceElementValidationError

		switch {
		case errors.As(err, &validationErr):
			pathSegments = append(pathSegments, errorPathSegment{
				model: validationErr.Model,
				field: validationErr.Field,
				index: -1,
			})
			err = validationErr.Unwrap()
			message = err.Error()
		case errors.As(err, &sliceElementValidationErr):
			pathSegments = append(pathSegments, errorPathSegment{
				model: sliceElementValidationErr.Model,
				field: sliceElementValidationErr.Field,
				index: sliceElementValidationErr.Index,
			})
			err = sliceElementValidationErr.Unwrap()
			message = err.Error()
		default:
			err = nil
		}
	}

	var path []string

	if len(pathSegments) > 0 {
		if re.formatErrorPath == nil {
			return errAPIInternalServerError
		}

		path = re.formatErrorPath(pathSegments)

		if len(path) == 0 {
			return errAPIInternalServerError
		}
	}

	var params map[string]any
	if withParams, ok := domainErr.(domain.ErrorWithParams); ok {
		params = withParams.Params()
	}

	cloned := make(map[string]any, len(params))
	for k, v := range params {
		cloned[strcase.ToCamel(k)] = v
	}

	return apiError{
		status:  errorTypeToStatusCode(domainErr.Type()),
		code:    domainErr.Code(),
		path:    path,
		params:  cloned,
		message: message,
	}
}

func errorTypeToStatusCode(code domain.ErrorType) int {
	switch code {
	case domain.ErrorTypeIncorrectInput:
		return http.StatusBadRequest
	case domain.ErrorTypeNotFound:
		return http.StatusNotFound
	case domain.ErrorTypeUnknown:
		fallthrough
	default:
		return http.StatusInternalServerError
	}
}