client/eth: PreRedeem

client/asset/eth/eth.go

@@ -416,7 +416,12 @@ func (eth *ExchangeWallet) estimateSwap(lots, lotSize, feeSuggestion uint64, nfo
 // PreRedeem generates an estimate of the range of redemption fees that could
 // be assessed.
 func (*ExchangeWallet) PreRedeem(req *asset.PreRedeemForm) (*asset.PreRedeem, error) {
-	return nil, asset.ErrNotImplemented
+	return &asset.PreRedeem{
+		Estimate: &asset.RedeemEstimate{
+			RealisticBestCase:  RedeemGas * req.FeeSuggestion,
+			RealisticWorstCase: RedeemGas * req.FeeSuggestion * req.Lots,
+		},
+	}, nil
 }
 
 // FundOrder selects coins for use in an order. The coins will be locked, and

client/asset/eth/eth_test.go

@@ -584,6 +584,30 @@ func TestPreSwap(t *testing.T) {
 	}
 }
 
+func TestPreRedeem(t *testing.T) {
+	node := &testNode{}
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	eth := &ExchangeWallet{
+		node: node,
+		ctx:  ctx,
+		log:  tLogger,
+		acct: new(accounts.Account),
+	}
+	preRedeem, err := eth.PreRedeem(&asset.PreRedeemForm{
+		LotSize:       123456,
+		Lots:          5,
+		FeeSuggestion: 100,
+	})
+	if err != nil {
+		t.Fatalf("unexpected PreRedeem error: %v", err)
+	}
+
+	if preRedeem.Estimate.RealisticBestCase >= preRedeem.Estimate.RealisticWorstCase {
+		t.Fatalf("best case > worst case")
+	}
+}
+
 func TestMaxOrder(t *testing.T) {
 	ethToGwei := func(eth uint64) uint64 {
 		return eth * dexeth.GweiFactor