golang-api-skeleton/lib/apperrors/apperrors.go

package apperrors

import (
	"net/http"
	"strings"
)

type APPError interface {
	GetType() ErrorKey
	GetHTTPStatus() int
	GetDetail() string
	SetDetail(string)
	Error() string
}

// Error response structure
type Error struct {
	Code       int      `json:"code"`
	Type       ErrorKey `json:"-"`
	Message    string   `json:"message"`
	Detail     string   `json:"detail"`
	HTTPStatus int      `json:"-"`
	ObjectID   uint64   `json:"-"`
	ObjectName string   `json:"-"`
}

func (err Error) GetType() ErrorKey {
	return err.Type
}

func (err Error) GetDetail() string {
	return err.Detail
}

func (err Error) SetDetail(detail string) {
	err.Detail = detail
}

func (err Error) GetHTTPStatus() int {
	return customErrors[err.Type].HTTPStatus
}

func (err Error) Error() string {
	return err.Detail
}

func NewError(errType ErrorKey, detail string) (err APPError) {
	switch errType {
	case DBError, InvalidDBQuery:
		detail = humanReadableDatabaseError(detail)
	case ValidationFailed:
		detail = humanReadableMarshalError(detail)
	}
	return Error{
		Type:       errType,
		Code:       customErrors[errType].Code,
		Message:    customErrors[errType].Message,
		Detail:     detail,
		HTTPStatus: customErrors[errType].HTTPStatus,
	}
}

// customErrors object contains self defined error codes and messages
var customErrors = map[ErrorKey]Error{
	ItemNotFound: {
		Code:       1000,
		Message:    MessageItemNotFound,
		HTTPStatus: http.StatusNotFound,
	},
	InvalidID: {
		Code:       1001,
		Message:    MessageInvalidID,
		HTTPStatus: http.StatusBadRequest,
	},
	ValidationFailed: {
		Code:       1002,
		Message:    MessageValidationFailed,
		HTTPStatus: http.StatusBadRequest,
	},
	PathNotFound: {
		Code:       4000,
		Message:    MessagePathNotFound,
		HTTPStatus: http.StatusNotFound,
	},
	MalformedQueryParameter: {
		Code:       4001,
		Message:    MessageMalformedQueryParameter,
		HTTPStatus: http.StatusBadRequest,
	},
	MalformedFilterString: {
		Code:       4002,
		Message:    MessageMalformedFilterString,
		HTTPStatus: http.StatusBadRequest,
	},
	InvalidPagination: {
		Code:       4003,
		Message:    MessageInvalidPagination,
		HTTPStatus: http.StatusBadRequest,
	},
	UnknownError: {
		Code:       5000,
		Message:    MessageUnknownError,
		HTTPStatus: http.StatusInternalServerError,
	},
	DBError: {
		Code:       5002,
		Message:    MessageDBError,
		HTTPStatus: http.StatusInternalServerError,
	},
	InvalidDBQuery: {
		Code:       5003,
		Message:    MessageInvalidDBQuery,
		HTTPStatus: http.StatusInternalServerError,
	},
	EmptyDBResponse: {
		Code:       5004,
		Message:    MessageEmptyDBResponse,
		HTTPStatus: http.StatusNotFound,
	},
	Unauthorized: {
		Code:       6000,
		Message:    MessageUnauthorized,
		HTTPStatus: http.StatusUnauthorized,
	},
	Forbidden: {
		Code:       6001,
		Message:    MessageForbidden,
		HTTPStatus: http.StatusForbidden,
	},
	ReportBug: {
		Code:       9999,
		Message:    MessageReportBug,
		HTTPStatus: http.StatusInternalServerError,
	},
}

// humanReadableMarshalError translates some cryptic error messages
func humanReadableMarshalError(detail string) string {
	switch {
	case strings.Contains(detail, "decode slice: expect [ or n, but found {"):
		return "payload must be a list"
	case strings.Contains(detail, "json: cannot unmarshal object into Go value of type ["):
		return "payload must be a list"
	case strings.Contains(detail, "strconv.ParseUint: parsing "):
		return "id must be numeric"
	case strings.Contains(detail, "json: cannot unmarshal array into Go value of type"),
		strings.HasPrefix(detail, "readObjectStart: expect { or n, but found ["):
		return "payload must be an object"
	default:
		return detail
	}
}

// humanReadableDatabaseError translates some cryptic error messages
func humanReadableDatabaseError(detail string) string {
	switch {
	case strings.Contains(detail, "Cannot insert duplicate key row in object 'dbo.users' with unique index 'username'."):
		return "username already in use, no duplicate usernames allowed"
	case strings.Contains(detail, "Cannot insert duplicate key row in object 'dbo.roles' with unique index 'rolename'."):
		return "rolename already in use, no duplicate rolenames allowed"
	case (strings.Contains(detail, "Duplicate entry") && strings.HasSuffix(detail, "for key 'idx_property_name_tenant_sid'")):
		return "propertyname already in use, no duplicate propertynames allowed: " + detail
	case strings.Contains(detail, "Cannot insert duplicate key in object 'dbo.tenants'."):
		return "Tenant name or id in use, no duplicates allowed"
	default:
		return detail
	}
}