POC: change error to receive err instead of format

client/asset/dcr/dcr.go

@@ -2444,7 +2444,7 @@ func (dcr *ExchangeWallet) sendRegFee(addr dcrutil.Address, regFee, netFeeRate u
 	}
 	coins, _, _, _, err := dcr.fund(enough)
 	if err != nil {
-		return nil, 0, fmt.Errorf("unable to pay registration fee of %s DCR with fee rate of %d atoms/byte: %w",
+		return nil, 0, fmt.Errorf("Unable to pay registration fee of %s DCR with fee rate of %d atoms/byte: %w",
 			amount(regFee), netFeeRate, err)
 	}
 	return dcr.sendCoins(addr, coins, regFee, netFeeRate, false)

client/core/errors.go

@@ -53,6 +53,10 @@ func (e *Error) Error() string {
 	return e.s
 }
 
+func (e *Error) Code() int {
+	return e.code
+}
+
 // newError is a constructor for a new Error.
 func newError(code int, s string, a ...interface{}) error {
 	return &Error{

client/webserver/api.go

@@ -4,6 +4,7 @@
 package webserver
 
 import (
+	"errors"
 	"fmt"
 	"net/http"
 	"time"
@@ -80,7 +81,7 @@ func (s *WebServer) apiRegister(w http.ResponseWriter, r *http.Request) {
 		Fee:     reg.Fee,
 	})
 	if err != nil {
-		s.writeAPIError(w, "registration error: %v", err)
+		s.writeAPIErrorPOC(w, err)
 		return
 	}
 	// There was no error paying the fee, but we must wait on confirmations
@@ -690,3 +691,21 @@ func (s *WebServer) writeAPIError(w http.ResponseWriter, format string, a ...int
 	}
 	writeJSON(w, resp, s.indent)
 }
+
+// writeAPIError logs the formatted error and sends a standardResponse with the
+// error message.
+func (s *WebServer) writeAPIErrorPOC(w http.ResponseWriter, err error) {
+	// log.Error(errMsg)
+	var cErr *core.Error
+	var code int
+	if errors.As(err, &cErr) {
+		code = cErr.Code()
+	}
+	resp := &standardResponse{
+		OK:   false,
+		Msg:  err.Error(),
+		Code: code,
+	}
+	log.Error(err.Error())
+	writeJSON(w, resp, s.indent)
+}

client/webserver/site/src/html/register.tmpl

@@ -89,6 +89,19 @@
       </div>
     </form>
 
+    {{- /* registration failed low balance. */ -}}
+    <form class="card mx-auto my-5 bg1 d-hide" id="failedRegForm">
+      <div class="bg2 px-2 py-1 text-center fs18">Insuficient funds</div>
+      <div class="p-4">
+        <div class="fs16">
+          Looks like you do not have enough funds for paying the fee in the
+          selected account. Please fund the account and try again.
+        </div>
+        <div class="fs15 pt-3 text-center d-hide errcolor" id="regFundsErr"></div>
+        <hr class="dashed mt-4">
+      </div>
+    </form>
+
   </div>
 </div>
 {{template "bottom"}}

client/webserver/site/src/js/register.js

@@ -6,6 +6,9 @@ import { NewWalletForm, bindOpenWallet, bind as bindForm } from './forms'
 const DCR_ID = 42
 const animationLength = 300
 
+// XXX: move code errors to a specific file?
+const sendFeeErr = 8;
+
 let app
 
 export default class RegistrationPage extends BasePage {
@@ -27,7 +30,7 @@ export default class RegistrationPage extends BasePage {
       'dexShowMore',
       // Form 5: Confirm DEX registration and pay fee
       'confirmRegForm', 'feeDisplay', 'dexDCRLotSize', 'appPass', 'submitConfirm', 'regErr',
-      'dexCertBox'
+      'dexCertBox', 'failedRegForm', 'regFundsErr'
     ])
 
     // Hide the form closers for the registration process.
@@ -86,7 +89,9 @@ export default class RegistrationPage extends BasePage {
     form1.style.right = '0'
     form2.style.right = -shift
     Doc.show(form2)
-    form2.querySelector('input').focus()
+    if (form2.querySelector('input')) {
+      form2.querySelector('input').focus()
+    }
     await Doc.animate(animationLength, progress => {
       form2.style.right = `${-shift + progress * shift}px`
     }, 'easeOutHard')
@@ -189,6 +194,14 @@ export default class RegistrationPage extends BasePage {
     const res = await postJSON('/api/register', registration)
     loaded()
     if (!app.checkResponse(res)) {
+      // show different form with no passphrase input in case of no funds.
+      if (res.code === sendFeeErr) {
+        await this.changeForm(page.confirmRegForm, page.failedRegForm)
+        page.regFundsErr.textContent = res.msg
+        Doc.show(page.regFundsErr)
+        return
+      }
+
       page.regErr.textContent = res.msg
       Doc.show(page.regErr)
       return

client/webserver/types.go

@@ -17,8 +17,9 @@ import (
 
 // standardResponse is a basic API response when no data needs to be returned.
 type standardResponse struct {
-	OK  bool   `json:"ok"`
-	Msg string `json:"msg,omitempty"`
+	OK   bool   `json:"ok"`
+	Msg  string `json:"msg,omitempty"`
+	Code int    `json:"code,omitempty"`
 }
 
 // simpleAck is a plain standardResponse with "ok" = true.