add: get user balance endpoint

internal/service/api/handlers/get_balance.go

@@ -0,0 +1,30 @@
+package handlers
+
+import (
+	"net/http"
+
+	"github.com/ethereum/go-ethereum/accounts/abi/bind"
+	"github.com/rarimo/evm-airdrop-svc/internal/service/api"
+	"github.com/rarimo/evm-airdrop-svc/internal/service/api/models"
+	"github.com/rarimo/evm-airdrop-svc/internal/service/api/requests"
+	"gitlab.com/distributed_lab/ape"
+	"gitlab.com/distributed_lab/ape/problems"
+)
+
+func GetBalance(w http.ResponseWriter, r *http.Request) {
+	req, err := requests.NewGetBalanceRequest(r)
+	if err != nil {
+		api.Log(r).WithError(err).Error("failed to parse request")
+		ape.RenderErr(w, problems.BadRequest(err)...)
+		return
+	}
+
+	balance, err := api.ERC20Permit(r).BalanceOf(&bind.CallOpts{}, req.Address)
+	if err != nil {
+		api.Log(r).WithError(err).Error("failed to get user balance")
+		ape.RenderErr(w, problems.InternalError())
+		return
+	}
+
+	ape.Render(w, models.NewBalanceResponse(req.Address.String(), balance))
+}

internal/service/api/models/token.go

@@ -0,0 +1,21 @@
+package models
+
+import (
+	"math/big"
+
+	"github.com/rarimo/evm-airdrop-svc/resources"
+)
+
+func NewBalanceResponse(addr string, amount *big.Int) resources.BalanceResponse {
+	return resources.BalanceResponse{
+		Data: resources.Balance{
+			Key: resources.Key{
+				ID:   addr,
+				Type: resources.TOKEN,
+			},
+			Attributes: resources.BalanceAttributes{
+				Amount: amount,
+			},
+		},
+	}
+}

internal/service/api/requests/get_balance.go

@@ -0,0 +1,32 @@
+package requests
+
+import (
+	"net/http"
+
+	"github.com/ethereum/go-ethereum/common"
+	validation "github.com/go-ozzo/ozzo-validation/v4"
+	"gitlab.com/distributed_lab/logan/v3/errors"
+	"gitlab.com/distributed_lab/urlval"
+)
+
+type GetUserBalanceRequest struct {
+	Address common.Address `url:"address"`
+}
+
+func NewGetBalanceRequest(r *http.Request) (GetUserBalanceRequest, error) {
+	var req GetUserBalanceRequest
+
+	if err := urlval.Decode(r.URL.Query(), &req); err != nil {
+		return req, validation.Errors{
+			"query": errors.Wrap(err, "failed to decode url"),
+		}.Filter()
+	}
+
+	return req, req.validate()
+}
+
+func (r *GetUserBalanceRequest) validate() error {
+	return validation.Errors{
+		"/address": validation.Validate(r.Address, validation.Required),
+	}.Filter()
+}

internal/service/router.go

@@ -55,6 +55,10 @@ func Run(ctx context.Context, cfg *config.Config) {
 
 			r.Post("/permit-hash", handlers.BuildPermitHash)
 		})
+
+		r.Route("/token", func(r chi.Router) {
+			r.Get("/balance", handlers.GetBalance)
+		})
 	})
 
 	cfg.Log().Info("Service started")