custom currency validator

api/account.go

@@ -10,7 +10,7 @@ import (
 
 type createAccountRequest struct {
 	Owner    string `json:"owner" binding:"required"`
-	Currency string `json:"currency" binding:"required,oneof=USD EUR CAD"`
+	Currency string `json:"currency" binding:"required,currency"`
 }
 
 func (server *Server) createAccount(ctx *gin.Context) {

api/server.go

@@ -2,6 +2,8 @@ package api
 
 import (
 	"github.com/gin-gonic/gin"
+	"github.com/gin-gonic/gin/binding"
+	"github.com/go-playground/validator/v10"
 	db "github.com/techschool/simplebank/db/sqlc"
 )
 
@@ -16,6 +18,10 @@ func NewServer(store db.Store) *Server {
 	server := &Server{store: store}
 	router := gin.Default()
 
+	if v, ok := binding.Validator.Engine().(*validator.Validate); ok {
+		v.RegisterValidation("currency", validCurrency)
+	}
+
 	router.POST("/accounts", server.createAccount)
 	router.GET("/accounts/:id", server.getAccount)
 	router.GET("/accounts", server.listAccounts)

api/transfer.go

@@ -11,24 +11,8 @@ import (
 type transferRequest struct {
 	FromAccountID int64  `json:"from_account_id" binding:"required,min=1"`
 	ToAccountID   int64  `json:"to_account_id" binding:"required,min=1"`
-	Amount        int64  `json:"amount" binding:"required,min=1"`
-	Currency      string `json:"currency" binding:"required,oneof=USD EUR CAD"`
-}
-
-func (server *Server) goodAccountCurrency(ctx *gin.Context, accountID int64, currency string) bool {
-	account, err := server.store.GetAccount(ctx, accountID)
-	if err != nil {
-		ctx.JSON(http.StatusInternalServerError, errorResponse(err))
-		return false
-	}
-
-	if account.Currency != currency {
-		err := fmt.Errorf("account [%d] currency mismatch: %s vs %s", account.ID, account.Currency, currency)
-		ctx.JSON(http.StatusBadRequest, errorResponse(err))
-		return false
-	}
-
-	return true
+	Amount        int64  `json:"amount" binding:"required,gt=0"`
+	Currency      string `json:"currency" binding:"required,currency"`
 }
 
 func (server *Server) createTransfer(ctx *gin.Context) {
@@ -38,11 +22,11 @@ func (server *Server) createTransfer(ctx *gin.Context) {
 		return
 	}
 
-	if !server.goodAccountCurrency(ctx, req.FromAccountID, req.Currency) {
+	if !server.sameAccountCurrency(ctx, req.FromAccountID, req.Currency) {
 		return
 	}
 
-	if !server.goodAccountCurrency(ctx, req.ToAccountID, req.Currency) {
+	if !server.sameAccountCurrency(ctx, req.ToAccountID, req.Currency) {
 		return
 	}
 
@@ -60,3 +44,19 @@ func (server *Server) createTransfer(ctx *gin.Context) {
 
 	ctx.JSON(http.StatusOK, result)
 }
+
+func (server *Server) sameAccountCurrency(ctx *gin.Context, accountID int64, currency string) bool {
+	account, err := server.store.GetAccount(ctx, accountID)
+	if err != nil {
+		ctx.JSON(http.StatusInternalServerError, errorResponse(err))
+		return false
+	}
+
+	if account.Currency != currency {
+		err := fmt.Errorf("account [%d] currency mismatch: %s vs %s", account.ID, account.Currency, currency)
+		ctx.JSON(http.StatusBadRequest, errorResponse(err))
+		return false
+	}
+
+	return true
+}

api/validator.go

@@ -0,0 +1,18 @@
+package api
+
+import (
+	"github.com/go-playground/validator/v10"
+)
+
+var supportedCurrencies = map[string]bool{
+	"USD": true,
+	"EUR": true,
+	"CAD": true,
+}
+
+var validCurrency validator.Func = func(fieldLevel validator.FieldLevel) bool {
+	if currency, ok := fieldLevel.Field().Interface().(string); ok {
+		return supportedCurrencies[currency]
+	}
+	return false
+}

go.mod

@@ -4,8 +4,10 @@ go 1.15
 
 require (
 	github.com/gin-gonic/gin v1.6.3
+	github.com/go-playground/validator/v10 v10.2.0
 	github.com/golang/mock v1.4.4
 	github.com/lib/pq v1.8.0
 	github.com/spf13/viper v1.7.1
 	github.com/stretchr/testify v1.6.1
+	github.com/vektah/gqlparser v1.3.1
 )

go.sum

@@ -15,8 +15,11 @@ github.com/BurntSushi/toml v0.3.1 h1:WXkYYl6Yr3qBf1K79EBnL4mak0OimBfB0XUf9Vl28OQ
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
 github.com/BurntSushi/xgb v0.0.0-20160522181843-27f122750802/go.mod h1:IVnqGOEym/WlBOVXweHU+Q+/VP0lqqI8lqeDx9IjBqo=
 github.com/OneOfOne/xxhash v1.2.2/go.mod h1:HSdplMjZKSmBqAxg5vPj2TmRDmfkzw+cTzAElWljhcU=
+github.com/agnivade/levenshtein v1.0.1 h1:3oJU7J3FGFmyhn8KHjmVaZCN5hxTr7GxgRue+sxIXdQ=
+github.com/agnivade/levenshtein v1.0.1/go.mod h1:CURSv5d9Uaml+FovSIICkLbAUZ9S4RqaHDIsdSBg7lM=
 github.com/alecthomas/template v0.0.0-20160405071501-a0175ee3bccc/go.mod h1:LOuyumcjzFXgccqObfd/Ljyb9UuFJ6TxHnclSeseNhc=
 github.com/alecthomas/units v0.0.0-20151022065526-2efee857e7cf/go.mod h1:ybxpYRFXyAe+OPACYpWeL0wqObRcbAqCMya13uyzqw0=
+github.com/andreyvit/diff v0.0.0-20170406064948-c7f18ee00883/go.mod h1:rCTlJbsFo29Kk6CurOXKm700vrz8f0KW0JNfpkRJY/8=
 github.com/armon/circbuf v0.0.0-20150827004946-bbbad097214e/go.mod h1:3U/XgcO3hCbHZ8TKRvWD2dDTCfh9M9ya+I9JpbB7O8o=
 github.com/armon/go-metrics v0.0.0-20180917152333-f0300d1749da/go.mod h1:Q73ZrmVTwzkszR9V5SSuryQ31EELlFMUz1kKyl939pY=
 github.com/armon/go-radix v0.0.0-20180808171621-7fddfc383310/go.mod h1:ufUuZ+zHj4x4TnLV4JWEpy2hxWSpsRywHrMgIH9cCH8=
@@ -179,6 +182,7 @@ github.com/rogpeppe/fastuuid v0.0.0-20150106093220-6724a57986af/go.mod h1:XWv6So
 github.com/rogpeppe/go-internal v1.3.0/go.mod h1:M8bDsm7K2OlrFYOpmOWEs/qY81heoFRclV5y23lUDJ4=
 github.com/ryanuber/columnize v0.0.0-20160712163229-9b3edd62028f/go.mod h1:sm1tb6uqfes/u+d4ooFouqFdy9/2g9QGwK3SQygK0Ts=
 github.com/sean-/seed v0.0.0-20170313163322-e2103e2c3529/go.mod h1:DxrIzT+xaE7yg65j358z/aeFdxmN0P9QXhEzd20vsDc=
+github.com/sergi/go-diff v1.0.0/go.mod h1:0CfEIISq7TuYL3j771MWULgwwjU+GofnZX9QAmXWZgo=
 github.com/sirupsen/logrus v1.2.0/go.mod h1:LxeOpSwHxABJmUn/MG1IvRgCAasNZTLOkJPxbbu5VWo=
 github.com/smartystreets/assertions v0.0.0-20180927180507-b2de0cb4f26d h1:zE9ykElWQ6/NYmHa3jpm/yHnI4xSofP+UP6SpjHcSeM=
 github.com/smartystreets/assertions v0.0.0-20180927180507-b2de0cb4f26d/go.mod h1:OnSkiWE9lh6wB0YB77sQom3nweQdgAjqCqsofrRNTgc=
@@ -212,6 +216,8 @@ github.com/ugorji/go v1.1.7 h1:/68gy2h+1mWMrwZFeD1kQialdSzAb432dtpeJ42ovdo=
 github.com/ugorji/go v1.1.7/go.mod h1:kZn38zHttfInRq0xu/PH0az30d+z6vm202qpg1oXVMw=
 github.com/ugorji/go/codec v1.1.7 h1:2SvQaVZ1ouYrrKKwoSk2pzd4A9evlKJb9oTL+OaLUSs=
 github.com/ugorji/go/codec v1.1.7/go.mod h1:Ax+UKWsSmolVDwsd+7N3ZtXu+yMGCf907BLYF3GoBXY=
+github.com/vektah/gqlparser v1.3.1 h1:8b0IcD3qZKWJQHSzynbDlrtP3IxVydZ2DZepCGofqfU=
+github.com/vektah/gqlparser v1.3.1/go.mod h1:bkVf0FX+Stjg/MHnm8mEyubuaArhNEqfQhF+OTiAL74=
 github.com/xiang90/probing v0.0.0-20190116061207-43a291ad63a2/go.mod h1:UETIi67q53MR2AWcXfiuqkDkRtnGDLqkBTpCHuJHxtU=
 go.etcd.io/bbolt v1.3.2/go.mod h1:IbVyRI1SCnLcuJnV2u8VeU0CEYM7e686BmAb1XKL+uU=
 go.opencensus.io v0.21.0/go.mod h1:mSImk1erAIZhrmZN+AvHh14ztQfjbGwt4TtuofqLduU=
@@ -288,6 +294,7 @@ golang.org/x/time v0.0.0-20190308202827-9d24e82272b4/go.mod h1:tRJNPiyCQ0inRvYxb
 golang.org/x/tools v0.0.0-20180221164845-07fd8470d635/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 golang.org/x/tools v0.0.0-20190114222345-bf090417da8b/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
+golang.org/x/tools v0.0.0-20190125232054-d66bd3c5d5a6/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 golang.org/x/tools v0.0.0-20190226205152-f727befe758c/go.mod h1:9Yl7xja0Znq3iFh3HoIrodX9oNMXvdceNzlUR8zjMvY=
 golang.org/x/tools v0.0.0-20190311212946-11955173bddd/go.mod h1:LCzVGOaR6xXOjkQ3onu1FJEFr0SW1gC7cKk1uF8kGRs=
 golang.org/x/tools v0.0.0-20190312151545-0bb0c0a6e846/go.mod h1:LCzVGOaR6xXOjkQ3onu1FJEFr0SW1gC7cKk1uF8kGRs=