Add methods to retrieve products and inventory data

Implemented `GetProductByArticle` to fetch product details by article. Added `GetRemainsAndPlanresidues` to obtain inventory balances for categories. These enhancements improve the API's capability to manage product and inventory information.

api/api.go

@@ -13,7 +13,10 @@ type Method interface {
 	GetParentCategories() ([]model.Category, error)
 	GetCategories() ([]model.Category, error)
 	GetTreeCategories() ([]model.TreeCategories, error)
+
 	GetProducts() ([]model.Product, error)
+	GetProductByArticle(article string) (model.Product, error)
+	GetRemainsAndPlanresidues() ([]model.ShortProduct, error)
 }
 
 func NewApi(credentials client.Credentials) Method {

api/products.go

@@ -1,8 +1,12 @@
 package api
 
-import "gitea.24example.ru/spavelit/bpiek/model"
+import (
+	"errors"
+	"gitea.24example.ru/spavelit/bpiek/model"
+)
 
 var products []model.Product
+var remainsAndPlanresidues []model.ShortProduct
 
 func (a *Api) GetProducts() ([]model.Product, error) {
 
@@ -29,3 +33,57 @@ func (a *Api) GetProducts() ([]model.Product, error) {
 
 	return products, nil
 }
+
+func (a *Api) GetProductByArticle(article string) (model.Product, error) {
+	apiResponse, err := a.Client.HTTPClient.
+		R().
+		SetResult(&model.Product{}).
+		Get("client/products/" + article)
+
+	if err != nil {
+		return model.Product{}, err
+	}
+
+	if apiResponse.StatusCode() != 200 {
+		return model.Product{}, errors.New(
+			"error getting product by article: " + article)
+	}
+
+	return apiResponse.Result().(model.Product), nil
+}
+
+func (a *Api) GetRemainsAndPlanresidues() ([]model.ShortProduct, error) {
+	if len(remainsAndPlanresidues) != 0 {
+		return remainsAndPlanresidues, nil
+	}
+
+	parentCategories, err := a.GetParentCategories()
+
+	if err != nil {
+		return nil, err
+	}
+
+	for _, category := range parentCategories {
+		apiResponse, err := a.Client.HTTPClient.
+			R().
+			SetResult(&model.RemainsAndPlanresiduesResponse{}).
+			Get("client/category/" + category.Slug + "/balances-json")
+
+		if err != nil {
+			return nil, err
+		}
+
+		if apiResponse.StatusCode() != 200 {
+			return nil, errors.New("file remains and planresidues not found")
+		}
+
+		result := apiResponse.Result().(model.RemainsAndPlanresiduesResponse)
+
+		if len(result.Products) != 0 {
+			remainsAndPlanresidues = append(remainsAndPlanresidues, result.Products...)
+		}
+	}
+
+	return remainsAndPlanresidues, nil
+
+}