rest-api/handler/base.go

package handler

import (
	"encoding/json"
	"go-rest-api/database"
	"go-rest-api/queue"
	"io/ioutil"
	"net/http"

	"github.com/Kamva/mgm/v3"
	"github.com/go-playground/validator/v10"
	"github.com/labstack/echo/v4"
	"go.mongodb.org/mongo-driver/bson"
)

var (
	internalErr       = "Unable to operate on Object."
	objectNotFoundErr = "Object not found."
	validationErr     = "Validation Error."
)

// DeserializeFromRequest func
func DeserializeFromRequest(request *http.Request, output interface{}) {
	defer request.Body.Close() // FIXME bad place for defer...?

	body, _ := ioutil.ReadAll(request.Body)
	_ = json.Unmarshal(body, output)
}

// BaseHandler type
type BaseHandler struct {
	Queue     *queue.AMQP
	db        *database.MongoDb
	validator *validator.Validate
}

// NewHandler Create BaseHandler instance
func NewHandler() *BaseHandler {
	return &BaseHandler{
		Queue:     queue.New(),
		db:        database.New(),
		validator: validator.New(),
	}
}

// GetAllObjects Retrieve all objects
func (h *BaseHandler) GetAllObjects(model mgm.Model, coll interface{}, filter bson.D) interface{} {
	h.db.FindAll(model, coll, filter)

	return coll
}

// GetSingleObject Retrieve single object
func (h *BaseHandler) GetSingleObject(model mgm.Model, id string) (mgm.Model, *echo.HTTPError) {
	if err := h.db.FindByID(model, id); err != nil {
		return nil, echo.NewHTTPError(http.StatusNotFound, objectNotFoundErr)
	}

	return model, nil
}

// CreateObject Try to create a new object
func (h *BaseHandler) CreateObject(model mgm.Model) (mgm.Model, *echo.HTTPError) {
	if err := h.Validate(model); err != nil {
		return nil, echo.NewHTTPError(http.StatusBadRequest, validationErr+" "+err.Error())
	}

	if err := h.db.Create(model); err != nil {
		return nil, echo.NewHTTPError(http.StatusInternalServerError, internalErr)
	}

	return model, nil
}

// UpdateObject Try to update a new object
func (h *BaseHandler) UpdateObject(model mgm.Model) (mgm.Model, *echo.HTTPError) {
	if err := h.Validate(model); err != nil {
		return nil, echo.NewHTTPError(http.StatusBadRequest, validationErr+" "+err.Error())
	}

	if err := h.db.Update(model); err != nil {
		return nil, echo.NewHTTPError(http.StatusInternalServerError, internalErr)
	}

	return model, nil
}

//RemoveObject Try to remove object
func (h *BaseHandler) RemoveObject(model mgm.Model) *echo.HTTPError {
	if err := h.db.Remove(model); err != nil {
		return echo.NewHTTPError(http.StatusInternalServerError, internalErr)
	}

	return nil
}

// Validate Validate model object
func (h *BaseHandler) Validate(i interface{}) error {
	return h.validator.Struct(i)
}

// JsonEncode Encode *object* to string
func (h *BaseHandler) JSONEncode(data interface{}) (string, error) {
	body, err := json.Marshal(data)
	if err != nil {
		return "", err
	}

	return string(body), nil
}