multi: handle trade suspension messages.

This adds the suspension handler to the client core.

client/core/core.go

@@ -60,6 +60,9 @@ type dexConnection struct {
 
 	tradeMtx sync.RWMutex
 	trades   map[order.OrderID]*trackedTrade
+
+	suspensionMtx   sync.RWMutex
+	suspensionEpoch uint64
 }
 
 // refreshMarkets rebuilds, saves, and returns the market map. The map itself
@@ -1085,6 +1088,24 @@ func (c *Core) Trade(pw string, form *TradeForm) (*Order, error) {
 		return nil, fmt.Errorf("unknown DEX %s", form.DEX)
 	}
 
+	dc.suspensionMtx.RLock()
+	suspensionEpoch := dc.suspensionEpoch
+	dc.suspensionMtx.RUnlock()
+
+	// TODO: (Refinement) instead of outrightly avoiding placing orders when
+	// a trade suspension is received, we need to decide whether a trade
+	// can be taken based on the block times of the blockchains involved
+	// in the trade.
+	//
+	// timeRemaining := time.Duration(int64(suspensionEpoch) - time.Now().Unix())
+
+	// Avoid placing an order if the connection is scheduled for a
+	// trade suspension.
+	if suspensionEpoch != 0 {
+		return nil, fmt.Errorf("order placement suspended due to impending"+
+			" trade suspension for dex %s", dc.acct.url)
+	}
+
 	rate, qty := form.Rate, form.Qty
 	if form.IsLimit && rate == 0 {
 		return nil, fmt.Errorf("zero-rate order not allowed")
@@ -1918,6 +1939,21 @@ func handleMatchProofMsg(_ *Core, dc *dexConnection, msg *msgjson.Message) error
 	return ob.ValidateMatchProof(note)
 }
 
+// handleTradeSuspensionMsg is called when a suspension message is received.
+func handleTradeSuspensionMsg(_ *Core, dc *dexConnection, msg *msgjson.Message) error {
+	var suspension msgjson.TradeSuspensionRequest
+	err := msg.Unmarshal(&suspension)
+	if err != nil {
+		return fmt.Errorf("trade suspension unmarshal error: %v", err)
+	}
+
+	dc.suspensionMtx.Lock()
+	dc.suspensionEpoch = suspension.Epoch
+	dc.suspensionMtx.Unlock()
+
+	return nil
+}
+
 // routeHandler is a handler for a message from the DEX.
 type routeHandler func(*Core, *dexConnection, *msgjson.Message) error
 
@@ -1928,7 +1964,7 @@ var reqHandlers = map[string]routeHandler{
 	msgjson.AuditRoute:       handleAuditRoute,
 	msgjson.RedemptionRoute:  handleRedemptionRoute,
 	msgjson.RevokeMatchRoute: nil,
-	msgjson.SuspensionRoute:  nil,
+	msgjson.SuspensionRoute:  handleTradeSuspensionMsg,
 }
 
 var noteHandlers = map[string]routeHandler{

client/core/core_test.go

@@ -2144,3 +2144,41 @@ func tMsgAudit(oid order.OrderID, mid order.MatchID, recipient string, val uint6
 	}
 	return audit, auditInfo
 }
+
+func TestHandleTradeSuspensionMsg(t *testing.T) {
+	rig := newTestRig()
+	payload := &msgjson.TradeSuspensionRequest{
+		Epoch:   uint64(time.Now().Add(time.Hour * 24).Unix()),
+		Persist: true,
+	}
+
+	req, _ := msgjson.NewRequest(rig.dc.NextID(), msgjson.SuspensionRoute, payload)
+	err := handleTradeSuspensionMsg(rig.core, rig.dc, req)
+	if err != nil {
+		t.Fatalf("[handleTradeSuspensionMsg] unexpected error: %v", err)
+	}
+
+	rig.dc.suspensionMtx.RLock()
+	epochSet := rig.dc.suspensionEpoch != 0
+	rig.dc.suspensionMtx.RUnlock()
+
+	if !epochSet {
+		t.Fatal("expected the trade suspension starting epoch set")
+	}
+
+	form := &TradeForm{
+		DEX:     tDexUrl,
+		IsLimit: true,
+		Sell:    true,
+		Base:    tDCR.ID,
+		Quote:   tBTC.ID,
+		Qty:     tDCR.LotSize * 10,
+		Rate:    tBTC.RateStep * 1000,
+		TifNow:  false,
+	}
+
+	_, err = rig.core.Trade(tPW, form)
+	if err == nil {
+		t.Fatalf("expected a trade suspension set error")
+	}
+}

dex/msgjson/types.go

@@ -689,6 +689,12 @@ type PreimageRequest struct {
 	CommitChecksum Bytes `json:"csum"`
 }
 
+// TradeSuspensionRequest is the server-origination trade suspension payload.
+type TradeSuspensionRequest struct {
+	Epoch   uint64 `json:"epoch"`
+	Persist bool   `json:"persist"`
+}
+
 // PreimageResponse is the client-originating preimage response payload.
 type PreimageResponse struct {
 	Preimage Bytes `json:"pimg"`