Correct v2 (#55)

* refactor library and upgrade version * remove useless environment variable * remove unsupported versions from go.mod * fixes for error handling & data types * different improvements for errors * fixes for types and tests * better coverage, fix error with the unmarshalers
2024-11-24 05:46:05 +03:00 · 2021-10-27 15:49:06 +03:00 · 2021-10-27 15:49:06 +03:00 · 97b1abf470
commit 97b1abf470
parent 269764175e
24 changed files with 2173 additions and 1193 deletions
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@ -9,7 +9,6 @@ on:
  pull_request:

 env:
-  DEVELOPER_NODE: 1
  RETAILCRM_URL: https://test.retailcrm.pro
  RETAILCRM_KEY: key

@ -41,7 +40,7 @@ jobs:
    runs-on: ubuntu-latest
    strategy:
      matrix:
-        go-version: ['1.11', '1.12', '1.13', '1.14', '1.15', '1.16', '1.17']
+        go-version: ['1.13', '1.14', '1.15', '1.16', '1.17']
        include:
          - go-version: '1.17'
            coverage: 1
--- a/.gitignore
+++ b/.gitignore
@ -5,6 +5,7 @@

 # Folders
 _obj
+vendor

 # Architecture specific extensions/prefixes
 *.[568vq]
--- a/.golangci.yml
+++ b/.golangci.yml
@ -146,9 +146,9 @@ linters-settings:
  gocyclo:
    min-complexity: 25
  goimports:
-    local-prefixes: github.com/retailcrm/api-client-go
+    local-prefixes: github.com/retailcrm/api-client-go/v2
  lll:
-    line-length: 120
+    line-length: 160
  maligned:
    suggest-new: true
  misspell:
@ -180,6 +180,9 @@ issues:
        - gocognit
        - gocyclo
        - godot
+        - gocritic
+        - gosec
+        - staticcheck
  exclude-use-default: true
  exclude-case-sensitive: false
  max-issues-per-linter: 0
--- a/README.md
+++ b/README.md
@ -10,51 +10,51 @@

 This is golang RetailCRM API client.

-## Install
+## Installation

 ```bash
-go get -x github.com/retailcrm/api-client-go
+go get -u github.com/retailcrm/api-client-go/v2
 ```

 ## Usage

-```golang
+Example:
+
+```go
 package main

 import (
-	"fmt"
-	"net/http"
+	"log"

-	"github.com/retailcrm/api-client-go/v5"
+	"github.com/retailcrm/api-client-go/v2"
 )

 func main() {
-	var client = v5.New("https://demo.retailcrm.pro", "09jIJ09j0JKhgyfvyuUIKhiugF")
+	var client = retailcrm.New("https://demo.retailcrm.pro", "09jIJ09j0JKhgyfvyuUIKhiugF")

-	data, status, err := client.Orders(v5.OrdersRequest{
-		Filter: v5.OrdersFilter{},
+	data, status, err := client.Orders(retailcrm.OrdersRequest{
+		Filter: retailcrm.OrdersFilter{},
 		Limit: 20,
 		Page: 1,
-	},)
+	})
 	if err != nil {
-		fmt.Printf("%v", err.Error())
+		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+			log.Fatalf("http status: %d, %s", status, apiErr.String())
        }

-	if status >= http.StatusBadRequest {
-		fmt.Printf("%v", err.ApiError())
+		log.Fatalf("http status: %d, error: %s", status, err)
 	}

 	for _, value := range data.Orders {
-		fmt.Printf("%v\n", value.Email)
+		log.Printf("%v\n", value.Email)
 	}

-	fmt.Println(data.Orders[1].FirstName)
+	log.Println(data.Orders[1].FirstName)

-	idata, status, err := c.InventoriesUpload(
-		[]InventoryUpload{
+	inventories, status, err := client.InventoriesUpload([]retailcrm.InventoryUpload{
 			{
 				XMLID: "pTKIKAeghYzX21HTdzFCe1",
-				Stores: []InventoryUploadStore{
+				Stores: []retailcrm.InventoryUploadStore{
 					{
 						Code: "test-store-v5",
 						Available: 10,
@ -74,7 +74,7 @@ func main() {
 			},
 			{
 				XMLID: "JQIvcrCtiSpOV3AAfMiQB3",
-				Stores: []InventoryUploadStore{
+				Stores: []retailcrm.InventoryUploadStore{
 					{
 						Code: "test-store-v5",
 						Available: 45,
@ -95,13 +95,70 @@ func main() {
 		},
 	)
 	if err != nil {
-		fmt.Printf("%v", err.Error())
+		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+			log.Fatalf("http status: %d, %s", status, apiErr.String())
 		}

-	if status >= http.StatusBadRequest {
-		fmt.Printf("%v", err.ApiError())
+		log.Fatalf("http status: %d, error: %s", status, err)
 	}

-	fmt.Println(idata.processedOffersCount)
+	log.Println(inventories.ProcessedOffersCount)
 }
 ```
+
+You can use different error types and `retailcrm.AsAPIError` to process client errors. Example:
+
+```go
+package retailcrm
+
+import (
+	"errors"
+	"log"
+	"os"
+	"strings"
+
+	"github.com/retailcrm/api-client-go/v2"
+)
+
+func main() {
+	var client = retailcrm.New("https://demo.retailcrm.pro", "09jIJ09j0JKhgyfvyuUIKhiugF")
+
+	resp, status, err := client.APICredentials()
+	if err != nil {
+		apiErr, ok := retailcrm.AsAPIError(err)
+		if !ok {
+			log.Fatalf("http status: %d, error: %s", status, err)
+		}
+
+		switch {
+		case errors.Is(apiErr, retailcrm.ErrMissingCredentials):
+			log.Fatalln("No API key provided.")
+		case errors.Is(apiErr, retailcrm.ErrInvalidCredentials):
+			log.Fatalln("Invalid API key.")
+		case errors.Is(apiErr, retailcrm.ErrAccessDenied):
+			log.Fatalln("Access denied. Please check that the provided key has access to the credentials info.")
+		case errors.Is(apiErr, retailcrm.ErrAccountDoesNotExist):
+			log.Fatalln("There is no RetailCRM at the provided URL.")
+		case errors.Is(apiErr, retailcrm.ErrMissingParameter):
+			// retailcrm.APIError in this case will always contain "Name" key in the errors list with the parameter name.
+			log.Fatalln("This parameter should be present:", apiErr.Errors()["Name"])
+		case errors.Is(apiErr, retailcrm.ErrValidation):
+			log.Println("Validation errors from the API:")
+
+			for name, value := range apiErr.Errors() {
+				log.Printf(" - %s: %s\n", name, value)
+			}
+
+			os.Exit(1)
+		case errors.Is(apiErr, retailcrm.ErrGeneric):
+			log.Fatalf("failure from the API. %s", apiErr.String())
+		}
+	}
+
+	log.Println("Available scopes:", strings.Join(resp.Scopes, ", "))
+}
+```
+
+## Upgrading
+
+Please check the [UPGRADING.md](UPGRADING.md) to learn how to upgrade to the new version.
--- a/UPGRADING.md
+++ b/UPGRADING.md
@ -0,0 +1,70 @@
+# Upgrading to the v2
+
+### Install the new version
+
+```bash
+go get -u github.com/retailcrm/api-client-go/v2
+```
+
+### Update all imports
+
+Before:
+```go
+package main
+
+import v5 "github.com/retailcrm/api-client-go/v5"
+```
+
+After:  
+```go
+package main
+
+import "github.com/retailcrm/api-client-go/v2"
+```
+
+You can use package alias `v5` to skip the second step.
+
+### Replace package name for all imported symbols
+
+Before:
+
+```go
+package main
+
+import v5 "github.com/retailcrm/api-client-go/v5"
+
+func main() {
+    client := v5.New("https://test.retailcrm.pro", "key")
+	data, status, err := client.Orders(v5.OrdersRequest{
+		Filter: v5.OrdersFilter{
+			City: "Moscow",
+		},
+		Page: 1,
+	})
+	...
+}
+```
+
+After:
+
+```go
+package main
+
+import "github.com/retailcrm/api-client-go/v2"
+
+func main() {
+    client := retailcrm.New("https://test.retailcrm.pro", "key")
+	data, status, err := client.Orders(retailcrm.OrdersRequest{
+		Filter: retailcrm.OrdersFilter{
+			City: "Moscow",
+		},
+		Page: 1,
+	})
+	...
+}
+```
+
+### Upgrade client usages
+
+This major release contains some breaking changes regarding field names and fully redesigned error handling. Use the second example from 
+the readme to learn how to process errors correctly.
--- a/v5/client.go
+++ b/v5/client.go
--- a/v5/client_test.go
+++ b/v5/client_test.go
@ -1,4 +1,4 @@
-package v5
+package retailcrm

 import (
 	"encoding/json"
@ -20,14 +20,12 @@ import (
 )

 func TestMain(m *testing.M) {
-	if os.Getenv("DEVELOPER_NODE") == "1" {
-		err := godotenv.Load("../.env")
+	err := godotenv.Load(".env")
 	if err != nil {
 		log.Fatal("Error loading .env file")
 	}

 	os.Exit(m.Run())
-	}
 }

 func init() {
@ -494,7 +492,7 @@ func TestClient_CustomersUpload_Fail(t *testing.T) {
 		MatchType("url").
 		BodyString(p.Encode()).
 		Reply(460).
-		BodyString(`{"success": false, "errorMsg": "Customers are loaded with errors"}`)
+		BodyString(`{"success": false, "errorMsg": "Customers are loaded with ErrorsList"}`)

 	data, _, err := c.CustomersUpload(customers)
 	if err == nil {
@ -631,7 +629,7 @@ func TestClient_CustomersFixExternalIds_Fail(t *testing.T) {
 		MatchType("url").
 		BodyString(p.Encode()).
 		Reply(400).
-		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "errors": {"id": "ID must be an integer"}}`)
+		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "ErrorsList": {"id": "ID must be an integer"}}`)

 	data, _, err := c.CustomersFixExternalIds(customers)
 	if err == nil {
@ -690,7 +688,7 @@ func TestClient_CustomersHistory_Fail(t *testing.T) {
 		Get("/customers/history").
 		MatchParam("filter[startDate]", "2020-13-12").
 		Reply(400).
-		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "errors": {"children[startDate]": "Значение недопустимо."}}`)
+		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "ErrorsList": {"children[startDate]": "Значение недопустимо."}}`)

 	data, _, err := c.CustomersHistory(f)
 	if err == nil {
@ -885,7 +883,7 @@ func TestClient_CorporateCustomersFixExternalIds_Fail(t *testing.T) {
 		MatchType("url").
 		BodyString(p.Encode()).
 		Reply(400).
-		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "errors": {"id": "ID must be an integer"}}`)
+		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "ErrorsList": {"id": "ID must be an integer"}}`)

 	data, _, err := c.CorporateCustomersFixExternalIds(customers)
 	if err == nil {
@ -944,7 +942,7 @@ func TestClient_CorporateCustomersHistory_Fail(t *testing.T) {
 		Get("/customers-corporate/history").
 		MatchParam("filter[startDate]", "2020-13-12").
 		Reply(400).
-		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "errors": {"children[startDate]": "Значение недопустимо."}}`)
+		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "ErrorsList": {"children[startDate]": "Значение недопустимо."}}`)

 	data, _, err := c.CorporateCustomersHistory(f)
 	if err == nil {
@ -1130,7 +1128,7 @@ func TestClient_CorporateCustomersUpload_Fail(t *testing.T) {
 		MatchType("url").
 		BodyString(p.Encode()).
 		Reply(460).
-		BodyString(`{"success": false, "errorMsg": "Customers are loaded with errors"}`)
+		BodyString(`{"success": false, "errorMsg": "Customers are loaded with ErrorsList"}`)

 	data, _, err := c.CorporateCustomersUpload(customers)
 	if err == nil {
@ -1703,7 +1701,7 @@ func TestClient_NotesNotes_Fail(t *testing.T) {
 		Get("/customers/notes").
 		MatchParam("filter[createdAtFrom]", "2020-13-12").
 		Reply(400).
-		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "errors": {"children[createdAtFrom]": "This value is not valid."}}`)
+		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "ErrorsList": {"children[createdAtFrom]": "This value is not valid."}}`)

 	data, _, err := c.CustomerNotes(NotesRequest{
 		Filter: NotesFilter{CreatedAtFrom: "2020-13-12"},
@ -1803,7 +1801,7 @@ func TestClient_NotesCreateDelete_Fail(t *testing.T) {
 		MatchType("url").
 		BodyString(p.Encode()).
 		Reply(400).
-		BodyString(`{"success": false, "errorMsg": "Errors in the entity format", "errors": {"customer": "Set one of the following fields: id, externalId"}}`)
+		BodyString(`{"success": false, "errorMsg": "Errors in the entity format", "ErrorsList": {"customer": "Set one of the following fields: id, externalId"}}`)

 	data, _, err := c.CustomerNoteCreate(note)
 	if err == nil {
@ -1875,7 +1873,7 @@ func TestClient_OrdersOrders_Fail(t *testing.T) {
 		Get("/orders").
 		MatchParam("filter[attachments]", "7").
 		Reply(400).
-		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "errors": {"children[attachments]": "SThis value is not valid."}}`)
+		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "ErrorsList": {"children[attachments]": "SThis value is not valid."}}`)

 	data, _, err := c.Orders(OrdersRequest{Filter: OrdersFilter{Attachments: 7}})
 	if err == nil {
@ -2166,7 +2164,7 @@ func TestClient_OrdersUpload_Fail(t *testing.T) {
 		MatchType("url").
 		BodyString(p.Encode()).
 		Reply(460).
-		BodyString(`{"success": false, "errorMsg": "Orders are loaded with errors"}`)
+		BodyString(`{"success": false, "errorMsg": "Orders are loaded with ErrorsList"}`)

 	data, _, err := c.OrdersUpload(orders)
 	if err == nil {
@ -2395,7 +2393,7 @@ func TestClient_OrdersHistory_Fail(t *testing.T) {
 		Get("/orders/history").
 		MatchParam("filter[startDate]", "2020-13-12").
 		Reply(400).
-		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "errors": {"children[startDate]": "Значение недопустимо."}}`)
+		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "ErrorsList": {"children[startDate]": "Значение недопустимо."}}`)

 	data, _, err := c.OrdersHistory(OrdersHistoryRequest{Filter: OrdersHistoryFilter{StartDate: "2020-13-12"}})
 	if err == nil {
@ -2521,7 +2519,7 @@ func TestClient_PaymentCreateEditDelete_Fail(t *testing.T) {
 		MatchType("url").
 		BodyString(p.Encode()).
 		Reply(400).
-		BodyString(`{"success": false, "errorMsg": "Errors in the entity format", "errors": {"order": "Set one of the following fields: id, externalId, number"}}`)
+		BodyString(`{"success": false, "errorMsg": "Errors in the entity format", "ErrorsList": {"order": "Set one of the following fields: id, externalId, number"}}`)

 	data, _, err := c.OrderPaymentCreate(f)
 	if err == nil {
@ -2743,7 +2741,7 @@ func TestClient_TaskChange_Fail(t *testing.T) {
 		MatchType("url").
 		BodyString(p.Encode()).
 		Reply(400).
-		BodyString(`{"success": false, "errorMsg": "Task is not loaded", "errors": {"performerId": "This value should not be blank."}}`)
+		BodyString(`{"success": false, "errorMsg": "Task is not loaded", "ErrorsList": {"performerId": "This value should not be blank."}}`)

 	data, _, err := c.TaskEdit(f)
 	if err == nil {
@ -2792,7 +2790,7 @@ func TestClient_UsersUsers_Fail(t *testing.T) {
 		MatchParam("filter[active]", "3").
 		MatchParam("page", "1").
 		Reply(400).
-		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "errors": {"active": "he value you selected is not a valid choice."}}`)
+		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "ErrorsList": {"active": "he value you selected is not a valid choice."}}`)

 	data, _, err := c.Users(UsersRequest{Filter: UsersFilter{Active: 3}, Page: 1})
 	if err == nil {
@ -3550,8 +3548,8 @@ func TestClient_Courier(t *testing.T) {
 	cur := Courier{
 		Active:    true,
 		Email:     fmt.Sprintf("%s@example.com", RandomString(5)),
-		FirstName: fmt.Sprintf("%s", RandomString(5)),
-		LastName:  fmt.Sprintf("%s", RandomString(5)),
+		FirstName: RandomString(5),
+		LastName:  RandomString(5),
 	}

 	defer gock.Off()
@ -3583,7 +3581,7 @@ func TestClient_Courier(t *testing.T) {
 	}

 	cur.ID = data.ID
-	cur.Patronymic = fmt.Sprintf("%s", RandomString(5))
+	cur.Patronymic = RandomString(5)

 	jr, _ = json.Marshal(&cur)

@ -3629,7 +3627,7 @@ func TestClient_Courier_Fail(t *testing.T) {
 		MatchType("url").
 		BodyString(p.Encode()).
 		Reply(400).
-		BodyString(`{"success": false, "errorMsg": "Errors in the entity format", "errors": {"firstName": "Specify the first name"}}`)
+		BodyString(`{"success": false, "errorMsg": "Errors in the entity format", "ErrorsList": {"firstName": "Specify the first name"}}`)

 	data, st, err := c.CourierCreate(Courier{})
 	if err == nil {
@ -3644,7 +3642,7 @@ func TestClient_Courier_Fail(t *testing.T) {
 		t.Error(successFail)
 	}

-	cur := Courier{Patronymic: fmt.Sprintf("%s", RandomString(5))}
+	cur := Courier{Patronymic: RandomString(5)}
 	jr, _ = json.Marshal(&cur)

 	p = url.Values{
@ -5793,7 +5791,7 @@ func TestClient_CostsUpload_Fail(t *testing.T) {
 		MatchType("url").
 		BodyString(p.Encode()).
 		Reply(460).
-		BodyString(`{"success": false, "errorMsg": "Costs are loaded with errors"}`)
+		BodyString(`{"success": false, "errorMsg": "Costs are loaded with ErrorsList"}`)

 	data, _, err := c.CostsUpload(costsUpload)
 	if err == nil {
--- a/error.go
+++ b/error.go
@ -0,0 +1,192 @@
+package retailcrm
+
+import (
+	"encoding/json"
+	"fmt"
+	"regexp"
+	"strings"
+)
+
+var missingParameterMatcher = regexp.MustCompile(`^Parameter \'([\w\]\[\_\-]+)\' is missing$`)
+var (
+	// ErrMissingCredentials will be returned if no API key was provided to the API.
+	ErrMissingCredentials = NewAPIError(`apiKey is missing`)
+	// ErrInvalidCredentials will be returned if provided API key is invalid.
+	ErrInvalidCredentials = NewAPIError(`wrong "apiKey" value`)
+	// ErrAccessDenied will be returned in case of "Access denied" error.
+	ErrAccessDenied = NewAPIError("access denied")
+	// ErrAccountDoesNotExist will be returned if target system does not exist.
+	ErrAccountDoesNotExist = NewAPIError("account does not exist")
+	// ErrValidation will be returned in case of validation errors.
+	ErrValidation = NewAPIError("validation error")
+	// ErrMissingParameter will be returned if parameter is missing.
+	// Underlying error messages list will contain parameter name in the "Name" key.
+	ErrMissingParameter = NewAPIError("missing parameter")
+	// ErrGeneric will be returned if error cannot be classified as one of the errors above.
+	ErrGeneric = NewAPIError("API error")
+)
+
+// APIErrorsList struct.
+type APIErrorsList map[string]string
+
+// APIError returns when an API error was occurred.
+type APIError interface {
+	error
+	fmt.Stringer
+	withWrapped(error) APIError
+	withErrors(APIErrorsList) APIError
+	Unwrap() error
+	Errors() APIErrorsList
+}
+
+type apiError struct {
+	ErrorMsg   string        `json:"errorMsg,omitempty"`
+	ErrorsList APIErrorsList `json:"errors,omitempty"`
+	wrapped    error
+}
+
+// CreateAPIError from the provided response data. Different error types will be returned depending on the response,
+// all of them can be matched using errors.Is. APi errors will always implement APIError interface.
+func CreateAPIError(dataResponse []byte) error {
+	a := &apiError{}
+
+	if len(dataResponse) > 0 && dataResponse[0] == '<' {
+		return ErrAccountDoesNotExist
+	}
+
+	if err := json.Unmarshal(dataResponse, &a); err != nil {
+		return err
+	}
+
+	var found APIError
+	switch a.ErrorMsg {
+	case `"apiKey" is missing.`:
+		found = ErrMissingCredentials
+	case `Wrong "apiKey" value.`:
+		found = ErrInvalidCredentials
+	case "Access denied.":
+		found = ErrAccessDenied
+	case "Account does not exist.":
+		found = ErrAccountDoesNotExist
+	case "Errors in the entity format":
+		fallthrough
+	case "Validation error":
+		found = ErrValidation
+	default:
+		if param, ok := asMissingParameterErr(a.ErrorMsg); ok {
+			return a.withWrapped(ErrMissingParameter).withErrors(APIErrorsList{"Name": param})
+		}
+		found = ErrGeneric
+	}
+
+	result := NewAPIError(a.ErrorMsg).withWrapped(found)
+	if len(a.ErrorsList) > 0 {
+		return result.withErrors(a.ErrorsList)
+	}
+
+	return result
+}
+
+// CreateGenericAPIError for the situations when API response cannot be processed, but response was actually received.
+func CreateGenericAPIError(message string) APIError {
+	return NewAPIError(message).withWrapped(ErrGeneric)
+}
+
+// NewAPIError returns API error with the provided message.
+func NewAPIError(message string) APIError {
+	return &apiError{ErrorMsg: message}
+}
+
+// AsAPIError returns APIError and true if provided error is an APIError or contains wrapped APIError.
+// Returns (nil, false) otherwise.
+func AsAPIError(err error) (APIError, bool) {
+	apiErr := unwrapAPIError(err)
+	return apiErr, apiErr != nil
+}
+
+func unwrapAPIError(err error) APIError {
+	if err == nil {
+		return nil
+	}
+
+	if apiErr, ok := err.(APIError); ok { // nolint:errorlint
+		return apiErr
+	}
+
+	wrapper, ok := err.(interface { // nolint:errorlint
+		Unwrap() error
+	})
+	if ok {
+		return unwrapAPIError(wrapper.Unwrap())
+	}
+
+	return nil
+}
+
+// asMissingParameterErr returns true if "Parameter 'name' is missing" error message is provided.
+func asMissingParameterErr(message string) (string, bool) {
+	matches := missingParameterMatcher.FindAllStringSubmatch(message, -1)
+	if len(matches) == 1 && len(matches[0]) == 2 {
+		return matches[0][1], true
+	}
+	return "", false
+}
+
+// Error returns errorMsg field from the response.
+func (e *apiError) Error() string {
+	return e.ErrorMsg
+}
+
+// Unwrap returns wrapped error. It is usually one of the predefined types like ErrGeneric or ErrValidation.
+// It can be used directly, but it's main purpose is to make errors matchable via errors.Is call.
+func (e *apiError) Unwrap() error {
+	return e.wrapped
+}
+
+// Errors returns errors field from the response.
+func (e *apiError) Errors() APIErrorsList {
+	return e.ErrorsList
+}
+
+// String returns string representation of an APIError.
+func (e *apiError) String() string {
+	var sb strings.Builder
+	sb.Grow(256) // nolint:gomnd
+	sb.WriteString(fmt.Sprintf(`errorMsg: "%s"`, e.Error()))
+
+	if len(e.Errors()) > 0 {
+		i := 0
+		useIndex := true
+		errorList := make([]string, len(e.Errors()))
+
+		for index, errText := range e.Errors() {
+			if i == 0 && index == "0" {
+				useIndex = false
+			}
+
+			if useIndex {
+				errorList[i] = fmt.Sprintf(`%s: "%s"`, index, errText)
+			} else {
+				errorList[i] = errText
+			}
+
+			i++
+		}
+
+		sb.WriteString(", errors: [" + strings.Join(errorList, ", ") + "]")
+	}
+
+	return sb.String()
+}
+
+// withWrapped is a wrapped setter.
+func (e *apiError) withWrapped(err error) APIError {
+	e.wrapped = err
+	return e
+}
+
+// withErrors is an ErrorsList setter.
+func (e *apiError) withErrors(m APIErrorsList) APIError {
+	e.ErrorsList = m
+	return e
+}
--- a/error_test.go
+++ b/error_test.go
@ -0,0 +1,171 @@
+package retailcrm
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/suite"
+)
+
+type ErrorTest struct {
+	suite.Suite
+}
+
+func TestError(t *testing.T) {
+	suite.Run(t, new(ErrorTest))
+}
+
+func (t *ErrorTest) TestFailure_ApiErrorsSlice() {
+	b := []byte(`{"success": false,
+				"errorMsg": "Failed to activate module",
+				"errors": [
+					"Your account has insufficient funds to activate integration module",
+					"Test error"
+				]}`)
+	expected := APIErrorsList{
+		"0": "Your account has insufficient funds to activate integration module",
+		"1": "Test error",
+	}
+
+	e := CreateAPIError(b)
+	apiErr, ok := AsAPIError(e)
+
+	t.Require().ErrorIs(e, ErrGeneric)
+	t.Require().NotNil(apiErr)
+	t.Require().True(ok)
+	t.Assert().Equal(expected, apiErr.Errors())
+}
+
+func (t *ErrorTest) TestFailure_ApiErrorsMap() {
+	b := []byte(`{"success": false,
+				"errorMsg": "Failed to activate module",
+				"errors": {"id": "ID must be an integer", "test": "Test error"}}`,
+	)
+	expected := APIErrorsList{
+		"id":   "ID must be an integer",
+		"test": "Test error",
+	}
+
+	e := CreateAPIError(b)
+	apiErr, ok := AsAPIError(e)
+
+	t.Require().ErrorIs(e, ErrGeneric)
+	t.Require().NotNil(apiErr)
+	t.Require().True(ok)
+	t.Assert().Equal(expected, apiErr.Errors())
+}
+
+func (t *ErrorTest) TestFailure_APIKeyMissing() {
+	b := []byte(`{"success": false,
+				"errorMsg": "\"apiKey\" is missing."}`,
+	)
+
+	e := CreateAPIError(b)
+	apiErr, ok := AsAPIError(e)
+
+	t.Require().NotNil(apiErr)
+	t.Require().True(ok)
+	t.Require().ErrorIs(e, ErrMissingCredentials)
+}
+
+func (t *ErrorTest) TestFailure_APIKeyWrong() {
+	b := []byte(`{"success": false,
+				"errorMsg": "Wrong \"apiKey\" value."}`,
+	)
+
+	e := CreateAPIError(b)
+	apiErr, ok := AsAPIError(e)
+
+	t.Require().NotNil(apiErr)
+	t.Require().True(ok)
+	t.Require().ErrorIs(e, ErrInvalidCredentials)
+}
+
+func (t *ErrorTest) TestFailure_AccessDenied() {
+	b := []byte(`{"success": false,
+				"errorMsg": "Access denied."}`,
+	)
+
+	e := CreateAPIError(b)
+	apiErr, ok := AsAPIError(e)
+
+	t.Require().NotNil(apiErr)
+	t.Require().True(ok)
+	t.Require().ErrorIs(e, ErrAccessDenied)
+}
+
+func (t *ErrorTest) TestFailure_AccountDoesNotExist() {
+	b := []byte(`{"success": false,
+				"errorMsg": "Account does not exist."}`,
+	)
+
+	e := CreateAPIError(b)
+	apiErr, ok := AsAPIError(e)
+
+	t.Require().NotNil(apiErr)
+	t.Require().True(ok)
+	t.Require().ErrorIs(e, ErrAccountDoesNotExist)
+}
+
+func (t *ErrorTest) TestFailure_Validation() {
+	b := []byte(`{"success": false,
+				"errorMsg": "Errors in the entity format",
+				"errors": {"name": "name must be provided"}}`,
+	)
+
+	e := CreateAPIError(b)
+	apiErr, ok := AsAPIError(e)
+
+	t.Require().NotNil(apiErr)
+	t.Require().True(ok)
+	t.Require().ErrorIs(e, ErrValidation)
+	t.Assert().Equal("name must be provided", apiErr.Errors()["name"])
+}
+
+func (t *ErrorTest) TestFailure_Validation2() {
+	b := []byte(`{"success": false,
+				"errorMsg": "Validation error",
+				"errors": {"name": "name must be provided"}}`,
+	)
+
+	e := CreateAPIError(b)
+	apiErr, ok := AsAPIError(e)
+
+	t.Require().NotNil(apiErr)
+	t.Require().True(ok)
+	t.Require().ErrorIs(e, ErrValidation)
+	t.Assert().Equal("name must be provided", apiErr.Errors()["name"])
+	t.Assert().Equal("errorMsg: \"Validation error\", errors: [name: \"name must be provided\"]", apiErr.String())
+}
+
+func (t *ErrorTest) TestFailure_MissingParameter() {
+	b := []byte(`{"success": false,
+				"errorMsg": "Parameter 'item' is missing"}`,
+	)
+
+	e := CreateAPIError(b)
+	apiErr, ok := AsAPIError(e)
+
+	t.Require().NotNil(apiErr)
+	t.Require().True(ok)
+	t.Require().ErrorIs(e, ErrMissingParameter)
+	t.Assert().Equal("item", apiErr.Errors()["Name"])
+}
+
+func (t *ErrorTest) Test_CreateGenericAPIError() {
+	e := CreateGenericAPIError("generic error message")
+	apiErr, ok := AsAPIError(e)
+
+	t.Require().NotNil(apiErr)
+	t.Require().True(ok)
+	t.Assert().ErrorIs(apiErr, ErrGeneric)
+	t.Assert().Equal("generic error message", e.Error())
+}
+
+func (t *ErrorTest) TestFailure_HTML() {
+	e := CreateAPIError([]byte{'<'})
+	apiErr, ok := AsAPIError(e)
+
+	t.Require().NotNil(apiErr)
+	t.Require().True(ok)
+	t.Assert().ErrorIs(apiErr, ErrAccountDoesNotExist)
+}
--- a/v5/filters.go
+++ b/v5/filters.go
@ -1,4 +1,4 @@
-package v5
+package retailcrm

 // CustomersFilter type.
 type CustomersFilter struct {
--- a/go.mod
+++ b/go.mod
@ -1,12 +1,10 @@
-module github.com/retailcrm/api-client-go
+module github.com/retailcrm/api-client-go/v2

 go 1.13

 require (
 	github.com/google/go-querystring v1.1.0
 	github.com/joho/godotenv v1.3.0
-	golang.org/x/net v0.0.0-20191021144547-ec77196f6094 // indirect
-	golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543
-	gopkg.in/h2non/gentleman.v1 v1.0.4 // indirect
+	github.com/stretchr/testify v1.7.0
 	gopkg.in/h2non/gock.v1 v1.1.2
 )
--- a/go.sum
+++ b/go.sum
@ -1,3 +1,5 @@
+github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/google/go-cmp v0.5.2 h1:X2ev0eStA3AbceY54o37/0PQ/UWqKEiiO2dKL5OPaFM=
 github.com/google/go-cmp v0.5.2/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/google/go-querystring v1.1.0 h1:AnCroh3fv4ZBgVIf1Iwtovgjaw/GiKJo8M8yD/fhyJ8=
@ -8,14 +10,16 @@ github.com/joho/godotenv v1.3.0 h1:Zjp+RcGpHhGlrMbJzXTrZZPrWj+1vfm90La1wgB6Bhc=
 github.com/joho/godotenv v1.3.0/go.mod h1:7hK45KPybAkOC6peb+G5yklZfMxEjkZhHbwpqxOKXbg=
 github.com/nbio/st v0.0.0-20140626010706-e9e8d9816f32 h1:W6apQkHrMkS0Muv8G/TipAy/FJl/rCYT0+EuS8+Z0z4=
 github.com/nbio/st v0.0.0-20140626010706-e9e8d9816f32/go.mod h1:9wM+0iRr9ahx58uYLpLIr5fm8diHn0JbqRycJi6w0Ms=
-golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
-golang.org/x/net v0.0.0-20191021144547-ec77196f6094/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
-golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
-golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.7.0 h1:nwc3DEeHmmLAfoZucVR881uASk0Mfjw8xYJ99tb5CcY=
+github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543 h1:E7g+9GITq07hpfrRu66IVDexMakfv52eLZ2CXBWiKr4=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
-gopkg.in/h2non/gentleman.v1 v1.0.4/go.mod h1:JYuHVdFzS4MKOXe0o+chKJ4hCe6tqKKw9XH9YP6WFrg=
-gopkg.in/h2non/gock.v1 v1.0.16 h1:F11k+OafeuFENsjei5t2vMTSTs9L62AdyTe4E1cgdG8=
-gopkg.in/h2non/gock.v1 v1.0.16/go.mod h1:XVuDAssexPLwgxCLMvDTWNU5eqklsydR6I5phZ9oPB8=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/h2non/gock.v1 v1.1.2 h1:jBbHXgGBK/AoPVfJh5x4r/WxIrElvbLel8TCZkkZJoY=
 gopkg.in/h2non/gock.v1 v1.1.2/go.mod h1:n7UGz/ckNChHiK05rDoiC4MYSunEC/lyaUm2WWaDva0=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
--- a/log.go
+++ b/log.go
@ -0,0 +1,25 @@
+package retailcrm
+
+// BasicLogger provides basic functionality for logging.
+type BasicLogger interface {
+	Printf(string, ...interface{})
+}
+
+// DebugLogger can be used to easily wrap any logger with Debugf method into the BasicLogger instance.
+type DebugLogger interface {
+	Debugf(string, ...interface{})
+}
+
+type debugLoggerAdapter struct {
+	logger DebugLogger
+}
+
+// DebugLoggerAdapter returns BasicLogger that calls underlying DebugLogger.Debugf.
+func DebugLoggerAdapter(logger DebugLogger) BasicLogger {
+	return &debugLoggerAdapter{logger: logger}
+}
+
+// Printf data in the log using DebugLogger.Debugf.
+func (l *debugLoggerAdapter) Printf(format string, v ...interface{}) {
+	l.logger.Debugf(format, v...)
+}
--- a/log_test.go
+++ b/log_test.go
@ -0,0 +1,24 @@
+package retailcrm
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+type wrappedLogger struct {
+	lastMessage string
+}
+
+func (w *wrappedLogger) Debugf(msg string, v ...interface{}) {
+	w.lastMessage = fmt.Sprintf(msg, v...)
+}
+
+func TestDebugLoggerAdapter_Printf(t *testing.T) {
+	wrapped := &wrappedLogger{}
+	logger := DebugLoggerAdapter(wrapped)
+	logger.Printf("Test message #%d", 1)
+
+	assert.Equal(t, "Test message #1", wrapped.lastMessage)
+}
--- a/marshaling.go
+++ b/marshaling.go
@ -0,0 +1,102 @@
+package retailcrm
+
+import (
+	"encoding/json"
+	"fmt"
+	"strconv"
+)
+
+func (t Tag) MarshalJSON() ([]byte, error) {
+	return json.Marshal(t.Name)
+}
+
+func (a *APIErrorsList) UnmarshalJSON(data []byte) error {
+	var i interface{}
+	var m APIErrorsList
+	if err := json.Unmarshal(data, &i); err != nil {
+		return err
+	}
+
+	switch e := i.(type) {
+	case map[string]interface{}:
+		m = make(APIErrorsList, len(e))
+		for idx, val := range e {
+			m[idx] = fmt.Sprint(val)
+		}
+	case []interface{}:
+		m = make(APIErrorsList, len(e))
+		for idx, val := range e {
+			m[strconv.Itoa(idx)] = fmt.Sprint(val)
+		}
+	}
+
+	*a = m
+	return nil
+}
+
+func (l *CustomFieldsList) UnmarshalJSON(data []byte) error {
+	var i interface{}
+	var m CustomFieldsList
+	if err := json.Unmarshal(data, &i); err != nil {
+		return err
+	}
+
+	switch e := i.(type) {
+	case map[string]interface{}:
+		m = make(CustomFieldsList, len(e))
+		for idx, val := range e {
+			m[idx] = fmt.Sprint(val)
+		}
+	case []interface{}:
+		m = make(CustomFieldsList, len(e))
+		for idx, val := range e {
+			m[strconv.Itoa(idx)] = fmt.Sprint(val)
+		}
+	}
+
+	*l = m
+	return nil
+}
+
+func (p *OrderPayments) UnmarshalJSON(data []byte) error {
+	var i interface{}
+	var m OrderPayments
+	if err := json.Unmarshal(data, &i); err != nil {
+		return err
+	}
+
+	switch e := i.(type) {
+	case map[string]interface{}:
+		m = make(OrderPayments, len(e))
+		for idx, val := range e {
+			var res OrderPayment
+			err := unmarshalMap(val.(map[string]interface{}), &res)
+			if err != nil {
+				return err
+			}
+			m[idx] = res
+		}
+	case []interface{}:
+		m = make(OrderPayments, len(e))
+		for idx, val := range e {
+			var res OrderPayment
+			err := unmarshalMap(val.(map[string]interface{}), &res)
+			if err != nil {
+				return err
+			}
+			m[strconv.Itoa(idx)] = res
+		}
+	}
+
+	*p = m
+	return nil
+}
+
+func unmarshalMap(m map[string]interface{}, v interface{}) (err error) {
+	var data []byte
+	data, err = json.Marshal(m)
+	if err != nil {
+		return err
+	}
+	return json.Unmarshal(data, v)
+}
--- a/marshaling_test.go
+++ b/marshaling_test.go
@ -0,0 +1,69 @@
+package retailcrm
+
+import (
+	"encoding/json"
+	"reflect"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestTag_MarshalJSON(t *testing.T) {
+	tags := []Tag{
+		{"first", "#3e89b6", false},
+		{"second", "#ffa654", false},
+	}
+	names := []byte(`["first","second"]`)
+	str, err := json.Marshal(tags)
+
+	if err != nil {
+		t.Errorf("%v", err.Error())
+	}
+
+	if !reflect.DeepEqual(str, names) {
+		t.Errorf("Marshaled: %#v\nExpected: %#v\n", str, names)
+	}
+}
+
+func TestAPIErrorsList_UnmarshalJSON(t *testing.T) {
+	var list APIErrorsList
+
+	require.NoError(t, json.Unmarshal([]byte(`["first", "second"]`), &list))
+	assert.Len(t, list, 2)
+	assert.Equal(t, list["0"], "first")
+	assert.Equal(t, list["1"], "second")
+
+	require.NoError(t, json.Unmarshal([]byte(`{"a": "first", "b": "second"}`), &list))
+	assert.Len(t, list, 2)
+	assert.Equal(t, list["a"], "first")
+	assert.Equal(t, list["b"], "second")
+}
+
+func TestCustomFieldsList_UnmarshalJSON(t *testing.T) {
+	var list CustomFieldsList
+
+	require.NoError(t, json.Unmarshal([]byte(`["first", "second"]`), &list))
+	assert.Len(t, list, 2)
+	assert.Equal(t, list["0"], "first")
+	assert.Equal(t, list["1"], "second")
+
+	require.NoError(t, json.Unmarshal([]byte(`{"a": "first", "b": "second"}`), &list))
+	assert.Len(t, list, 2)
+	assert.Equal(t, list["a"], "first")
+	assert.Equal(t, list["b"], "second")
+}
+
+func TestOrderPayments_UnmarshalJSON(t *testing.T) {
+	var list OrderPayments
+
+	require.NoError(t, json.Unmarshal([]byte(`[{"id": 1}, {"id": 2}]`), &list))
+	assert.Len(t, list, 2)
+	assert.Equal(t, list["0"], OrderPayment{ID: 1})
+	assert.Equal(t, list["1"], OrderPayment{ID: 2})
+
+	require.NoError(t, json.Unmarshal([]byte(`{"a": {"id": 1}, "b": {"id": 2}}`), &list))
+	assert.Len(t, list, 2)
+	assert.Equal(t, list["a"], OrderPayment{ID: 1})
+	assert.Equal(t, list["b"], OrderPayment{ID: 2})
+}
--- a/v5/request.go
+++ b/v5/request.go
@ -1,4 +1,4 @@
-package v5
+package retailcrm

 // CustomerRequest type.
 type CustomerRequest struct {
@ -177,8 +177,8 @@ type ProductsPropertiesRequest struct {
 type DeliveryTrackingRequest struct {
 	DeliveryID  string                  `json:"deliveryId,omitempty"`
 	TrackNumber string                  `json:"trackNumber,omitempty"`
-	History     []DeliveryHistoryRecord `json:"history,omitempty,brackets"`
-	ExtraData   map[string]string       `json:"extraData,omitempty,brackets"`
+	History     []DeliveryHistoryRecord `json:"history,omitempty"`
+	ExtraData   map[string]string       `json:"extraData,omitempty"`
 }

 // DeliveryShipmentsRequest type.
--- a/v5/response.go
+++ b/v5/response.go
@ -1,4 +1,4 @@
-package v5
+package retailcrm

 // SuccessfulResponse type.
 type SuccessfulResponse struct {
@ -20,7 +20,7 @@ type OrderCreateResponse struct {
 // OperationResponse type.
 type OperationResponse struct {
 	Success bool              `json:"success"`
-	Errors  map[string]string `json:"errors,omitempty"`
+	Errors  map[string]string `json:"ErrorsList,omitempty"`
 }

 // VersionResponse return available API versions.
@ -409,7 +409,7 @@ type ResponseInfo struct {

 // MgInfo type.
 type MgInfo struct {
-	EndpointUrl string `json:"endpointUrl"`
+	EndpointURL string `json:"endpointUrl"`
 	Token       string `json:"token"`
 }

--- a/v5/types.go
+++ b/v5/types.go
@ -1,4 +1,4 @@
-package v5
+package retailcrm

 import (
 	"encoding/json"
@ -19,6 +19,7 @@ type Client struct {
 	Key        string
 	Debug      bool
 	httpClient *http.Client
+	logger     BasicLogger
 }

 // Pagination type.
@ -154,7 +155,7 @@ type Customer struct {
 	BrowserID                    string           `json:"browserId,omitempty"`
 	MgCustomerID                 string           `json:"mgCustomerId,omitempty"`
 	PhotoURL                     string           `json:"photoUrl,omitempty"`
-	CustomFields                 map[string]string `json:"customFields,omitempty"`
+	CustomFields                 CustomFieldsList `json:"customFields,omitempty"`
 	Tags                         []Tag            `json:"tags,omitempty"`
 }

@ -166,7 +167,7 @@ type CorporateCustomer struct {
 	CreatedAt          string                     `json:"createdAt,omitempty"`
 	Vip                bool                       `json:"vip,omitempty"`
 	Bad                bool                       `json:"bad,omitempty"`
-	CustomFields       map[string]string          `json:"customFields,omitempty"`
+	CustomFields       CustomFieldsList           `json:"customFields,omitempty"`
 	PersonalDiscount   float32                    `json:"personalDiscount,omitempty"`
 	DiscountCardNumber string                     `json:"discountCardNumber,omitempty"`
 	ManagerID          int                        `json:"managerId,omitempty"`
@ -227,7 +228,7 @@ type Company struct {
 	CreatedAt    string           `json:"createdAt,omitempty"`
 	Contragent   *Contragent      `json:"contragent,omitempty"`
 	Address      *IdentifiersPair `json:"address,omitempty"`
-	CustomFields map[string]string `json:"customFields,omitempty"`
+	CustomFields CustomFieldsList `json:"customFields,omitempty"`
 }

 // CorporateCustomerNote type.
@ -272,6 +273,9 @@ type CorporateCustomerHistoryRecord struct {
 Order related types
 */

+type OrderPayments map[string]OrderPayment
+type CustomFieldsList map[string]string
+
 // Order type.
 type Order struct {
 	ID                            int               `json:"id,omitempty"`
@ -321,8 +325,8 @@ type Order struct {
 	Delivery                      *OrderDelivery    `json:"delivery,omitempty"`
 	Marketplace                   *OrderMarketplace `json:"marketplace,omitempty"`
 	Items                         []OrderItem       `json:"items,omitempty"`
-	CustomFields                  map[string]string       `json:"customFields,omitempty"`
-	Payments                      map[string]OrderPayment `json:"payments,omitempty"`
+	CustomFields                  CustomFieldsList  `json:"customFields,omitempty"`
+	Payments                      OrderPayments     `json:"payments,omitempty"`
 }

 // OrdersStatus type.
@ -378,8 +382,14 @@ type OrderDeliveryData struct {
 // UnmarshalJSON method.
 func (v *OrderDeliveryData) UnmarshalJSON(b []byte) error {
 	var additionalData map[string]interface{}
-	json.Unmarshal(b, &additionalData)
-	json.Unmarshal(b, &v.OrderDeliveryDataBasic)
+	err := json.Unmarshal(b, &additionalData)
+	if err != nil {
+		return err
+	}
+	err = json.Unmarshal(b, &v.OrderDeliveryDataBasic)
+	if err != nil {
+		return err
+	}
 	object := reflect.TypeOf(v.OrderDeliveryDataBasic)

 	for i := 0; i < object.NumField(); i++ {
@ -401,7 +411,10 @@ func (v *OrderDeliveryData) UnmarshalJSON(b []byte) error {
 func (v OrderDeliveryData) MarshalJSON() ([]byte, error) {
 	result := map[string]interface{}{}
 	data, _ := json.Marshal(v.OrderDeliveryDataBasic)
-	json.Unmarshal(data, &result)
+	err := json.Unmarshal(data, &result)
+	if err != nil {
+		return nil, err
+	}

 	for key, value := range v.AdditionalFields {
 		result[key] = value
@ -587,7 +600,7 @@ type User struct {
 	Phone      string      `json:"phone,omitempty"`
 	Status     string      `json:"status,omitempty"`
 	Groups     []UserGroup `json:"groups,omitempty"`
-	MgUserId   uint64      `json:"mgUserId,omitempty"`
+	MGUserID   uint64      `json:"mgUserId,omitempty"`
 }

 // UserGroup type.
@ -1054,7 +1067,7 @@ type Action struct {

 // MgTransport type.
 type MgTransport struct {
-	WebhookUrl string `json:"webhookUrl,omitempty"`
+	WebhookURL string `json:"webhookUrl,omitempty"`
 }

 // MgBot type.
@ -1072,7 +1085,7 @@ type CostRecord struct {
 	DateTo   string   `json:"dateTo,omitempty"`
 	Summ     float32  `json:"summ,omitempty"`
 	CostItem string   `json:"costItem,omitempty"`
-	UserId   int      `json:"userId,omitempty"`
+	UserID   int      `json:"userId,omitempty"`
 	Order    *Order   `json:"order,omitempty"`
 	Sites    []string `json:"sites,omitempty"`
 }
@ -1089,7 +1102,7 @@ type Cost struct {
 	CreatedAt string   `json:"createdAt,omitempty"`
 	CreatedBy string   `json:"createdBy,omitempty"`
 	Order     *Order   `json:"order,omitempty"`
-	UserId    int      `json:"userId,omitempty"`
+	UserID    int      `json:"userId,omitempty"`
 	Sites     []string `json:"sites,omitempty"`
 }

--- a/v5/types_test.go
+++ b/v5/types_test.go
@ -1,4 +1,4 @@
-package v5
+package retailcrm

 import (
 	"encoding/json"
--- a/v5/error.go
+++ b/v5/error.go
@ -1,32 +0,0 @@
-package v5
-
-import "encoding/json"
-
-// APIErrorsList struct.
-type APIErrorsList map[string]string
-
-// APIError struct.
-type APIError struct {
-	SuccessfulResponse
-	ErrorMsg string        `json:"errorMsg,omitempty"`
-	Errors   APIErrorsList `json:"errors,omitempty"`
-}
-
-func (e *APIError) Error() string {
-	return e.ErrorMsg
-}
-
-func NewAPIError(dataResponse []byte) error {
-	a := &APIError{}
-
-	if len(dataResponse) > 0 && dataResponse[0] == '<' {
-		a.ErrorMsg = "Account does not exist."
-		return a
-	}
-
-	if err := json.Unmarshal(dataResponse, a); err != nil {
-		return err
-	}
-
-	return a
-}
--- a/v5/error_test.go
+++ b/v5/error_test.go
@ -1,54 +0,0 @@
-package v5
-
-import (
-	"reflect"
-	"testing"
-
-	"golang.org/x/xerrors"
-)
-
-func TestFailure_ApiErrorsSlice(t *testing.T) {
-	b := []byte(`{"success": false,
-				"errorMsg": "Failed to activate module",
-				"errors": [
-					"Your account has insufficient funds to activate integration module",
-					"Test error"
-				]}`)
-	expected := APIErrorsList{
-		"0": "Your account has insufficient funds to activate integration module",
-		"1": "Test error",
-	}
-
-	var expEr *APIError
-	e := NewAPIError(b)
-
-	if xerrors.As(e, &expEr) {
-		if eq := reflect.DeepEqual(expEr.Errors, expected); eq != true {
-			t.Errorf("%+v", eq)
-		}
-	} else {
-		t.Errorf("Error must be type of APIError: %v", e)
-	}
-}
-
-func TestFailure_ApiErrorsMap(t *testing.T) {
-	b := []byte(`{"success": false,
-				"errorMsg": "Failed to activate module",
-				"errors": {"id": "ID must be an integer", "test": "Test error"}}`,
-	)
-	expected := APIErrorsList{
-		"id":   "ID must be an integer",
-		"test": "Test error",
-	}
-
-	var expEr *APIError
-	e := NewAPIError(b)
-
-	if xerrors.As(e, &expEr) {
-		if eq := reflect.DeepEqual(expEr.Errors, expected); eq != true {
-			t.Errorf("%+v", eq)
-		}
-	} else {
-		t.Errorf("Error must be type of APIError: %v", e)
-	}
-}
--- a/v5/marshaling.go
+++ b/v5/marshaling.go
@ -1,35 +0,0 @@
-package v5
-
-import (
-	"encoding/json"
-	"fmt"
-	"strconv"
-)
-
-func (t Tag) MarshalJSON() ([]byte, error) {
-	return json.Marshal(t.Name)
-}
-
-func (a *APIErrorsList) UnmarshalJSON(data []byte) error {
-	var i interface{}
-	var m map[string]string
-	if err := json.Unmarshal(data, &i); err != nil {
-		return err
-	}
-
-	switch e := i.(type) {
-	case map[string]interface{}:
-		m = make(map[string]string, len(e))
-		for idx, val := range e {
-			m[idx] = fmt.Sprint(val)
-		}
-	case []interface{}:
-		m = make(map[string]string, len(e))
-		for idx, val := range e {
-			m[strconv.Itoa(idx)] = fmt.Sprint(val)
-		}
-	}
-
-	*a = m
-	return nil
-}
--- a/v5/marshaling_test.go
+++ b/v5/marshaling_test.go
@ -1,24 +0,0 @@
-package v5
-
-import (
-	"encoding/json"
-	"reflect"
-	"testing"
-)
-
-func TestTag_MarshalJSON(t *testing.T) {
-	tags := []Tag{
-		{"first", "#3e89b6", false},
-		{"second", "#ffa654", false},
-	}
-	names := []byte(`["first","second"]`)
-	str, err := json.Marshal(tags)
-
-	if err != nil {
-		t.Errorf("%v", err.Error())
-	}
-
-	if !reflect.DeepEqual(str, names) {
-		t.Errorf("Marshaled: %#v\nExpected: %#v\n", str, names)
-	}
-}