+package server
+
+import (
+ "encoding/json"
+ "net/http"
+ "reflect"
+ "strings"
+
+ "github.com/gin-gonic/gin"
+
+ "github.com/vapor/errors"
+)
+
+func Middleware(serverInstance interface{}) gin.HandlerFunc {
+ return func(c *gin.Context) {
+ // add Access-Control-Allow-Origin
+ c.Header("Access-Control-Allow-Origin", "*")
+ c.Header("Access-Control-Allow-Headers", "Content-Type")
+ c.Header("Access-Control-Allow-Methods", "POST, GET, OPTIONS")
+ if c.Request.Method == "OPTIONS" {
+ c.AbortWithStatus(http.StatusOK)
+ return
+ }
+
+ c.Set(serverLabel, serverInstance)
+ c.Next()
+ }
+}
+
+type handlerFun interface{}
+
+func HandlerMiddleware(handleFunc interface{}) func(*gin.Context) {
+ if err := validateFuncType(handleFunc); err != nil {
+ panic(err)
+ }
+
+ return func(context *gin.Context) {
+ handleRequest(context, handleFunc)
+ }
+}
+
+func validateFuncType(fun handlerFun) error {
+ ft := reflect.TypeOf(fun)
+ if ft.Kind() != reflect.Func || ft.IsVariadic() {
+ return errors.New("need nonvariadic func in " + ft.String())
+ }
+
+ if ft.NumIn() < 1 || ft.NumIn() > 3 {
+ return errors.New("need one or two or three parameters in " + ft.String())
+ }
+
+ if ft.In(0) != contextType {
+ return errors.New("the first parameter must point of context in " + ft.String())
+ }
+
+ if ft.NumIn() == 2 && ft.In(1).Kind() != reflect.Ptr {
+ return errors.New("the second parameter must point in " + ft.String())
+ }
+
+ if ft.NumIn() == 3 && ft.In(2) != paginationQueryType {
+ return errors.New("the third parameter of pagination must point of paginationQuery in " + ft.String())
+ }
+
+ if ft.NumOut() < 1 || ft.NumOut() > 2 {
+ return errors.New("the size of return value must one or two in " + ft.String())
+ }
+
+ // if has pagination, the first return value must slice or array
+ if ft.NumIn() == 3 && ft.Out(0).Kind() != reflect.Slice && ft.Out(0).Kind() != reflect.Array {
+ return errors.New("the first return value of pagination must slice of array in " + ft.String())
+ }
+
+ if !ft.Out(ft.NumOut() - 1).Implements(errorType) {
+ return errors.New("the last return value must error in " + ft.String())
+ }
+ return nil
+}
+
+// handleRequest get a handler function to process the request by request url
+func handleRequest(context *gin.Context, fun handlerFun) {
+ args, err := buildHandleFuncArgs(fun, context)
+ if err != nil {
+ respondErrorResp(context, err)
+ return
+ }
+
+ result := callHandleFunc(fun, args...)
+ if err := result[len(result)-1]; err != nil {
+ respondErrorResp(context, err.(error))
+ return
+ }
+
+ if exist := processPaginationIfPresent(fun, args, result, context); exist {
+ return
+ }
+
+ if len(result) == 1 {
+ respondSuccessResp(context, nil)
+ return
+ }
+
+ respondSuccessResp(context, result[0])
+}
+
+func buildHandleFuncArgs(fun handlerFun, context *gin.Context) ([]interface{}, error) {
+ args := []interface{}{context}
+
+ req, err := createHandleReqArg(fun, context)
+ if err != nil {
+ return nil, errors.Wrap(err, "createHandleReqArg")
+ }
+
+ if err := checkDisplayOrder(req); err != nil {
+ return nil, err
+ }
+
+ if req != nil {
+ args = append(args, req)
+ }
+
+ ft := reflect.TypeOf(fun)
+
+ // no pagination exists
+ if ft.NumIn() != 3 {
+ return args, nil
+ }
+
+ query, err := parsePagination(context)
+ if err != nil {
+ return nil, errors.Wrap(err, "ParsePagination")
+ }
+
+ args = append(args, query)
+ return args, nil
+}
+
+func createHandleReqArg(fun handlerFun, context *gin.Context) (interface{}, error) {
+ ft := reflect.TypeOf(fun)
+ if ft.NumIn() == 1 {
+ return nil, nil
+ }
+ argType := ft.In(1).Elem()
+
+ reqArg := reflect.New(argType).Interface()
+ if err := context.ShouldBindJSON(reqArg); err != nil {
+ return nil, errors.Wrap(err, "bind reqArg")
+ }
+
+ b, err := json.Marshal(reqArg)
+ if err != nil {
+ return nil, errors.Wrap(err, "json marshal")
+ }
+
+ context.Set(reqBodyLabel, string(b))
+
+ return reqArg, nil
+}
+
+func checkDisplayOrder(req interface{}) error {
+ if req == nil {
+ return nil
+ }
+
+ reqType := reflect.TypeOf(req).Elem()
+ reqVal := reflect.ValueOf(req).Elem()
+
+ for i := 0; i < reqType.NumField(); i++ {
+ field := reqType.Field(i)
+ if field.Type != reflect.TypeOf(Display{}) {
+ continue
+ }
+ display := reqVal.Field(i).Interface().(Display)
+
+ order := strings.Trim(display.Sorter.Order, "")
+ if order != "desc" && order != "asc" {
+ reqVal.Field(i).Set(reflect.ValueOf(Display{Filter: display.Filter, Sorter: Sorter{By: display.Sorter.By, Order: "desc"}}))
+ }
+ }
+ return nil
+}
+
+func callHandleFunc(fun handlerFun, args ...interface{}) []interface{} {
+ fv := reflect.ValueOf(fun)
+
+ params := make([]reflect.Value, len(args))
+ for i, arg := range args {
+ params[i] = reflect.ValueOf(arg)
+ }
+
+ rs := fv.Call(params)
+ result := make([]interface{}, len(rs))
+ for i, r := range rs {
+ result[i] = r.Interface()
+ }
+ return result
+}
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