poloniex: filter non-liquid and unused assets (#1185)

* poloniex: filter non-liquid and unused assets

* glorious: nits

---------

Co-authored-by: Ryan O'Hara-Reid <ryan.oharareid@thrasher.io>

exchanges/lbank/lbank_wrapper.go

@@ -99,7 +99,6 @@ func (l *Lbank) SetDefaults() {
 					kline.IntervalCapacity{Interval: kline.ThirtyMin},
 					kline.IntervalCapacity{Interval: kline.OneHour},
 					kline.IntervalCapacity{Interval: kline.FourHour},
-
 					// NOTE: The supported time intervals below are returned
 					// offset to the Asia/HongKong time zone. This may lead to
 					// issues with candle quality and conversion as the

exchanges/poloniex/poloniex_test.go

@@ -1061,3 +1061,11 @@ func TestGetAvailableTransferChains(t *testing.T) {
 		t.Fatal(err)
 	}
 }
+
+func TestFetchTradablePairs(t *testing.T) {
+	t.Parallel()
+	_, err := p.FetchTradablePairs(context.Background(), asset.Spot)
+	if err != nil {
+		t.Error(err)
+	}
+}

exchanges/poloniex/poloniex_wrapper.go

@@ -265,21 +265,25 @@ func (p *Poloniex) Run(ctx context.Context) {
 
 // FetchTradablePairs returns a list of the exchanges tradable pairs
 func (p *Poloniex) FetchTradablePairs(ctx context.Context, _ asset.Item) (currency.Pairs, error) {
+	// TODO: Upgrade to new API version for fetching operational pairs.
 	resp, err := p.GetTicker(ctx)
 	if err != nil {
 		return nil, err
 	}
 
-	pairs := make([]currency.Pair, len(resp))
-	var target int
-	for key := range resp {
+	pairs := make([]currency.Pair, 0, len(resp))
+	for key, info := range resp {
+		// Poloniex returns 0 for highest bid and lowest ask if support has been
+		// dropped from the front end. We don't want to add these pairs.
+		if info.HighestBid == 0 || info.LowestAsk == 0 {
+			continue
+		}
 		var pair currency.Pair
 		pair, err = currency.NewPairFromString(key)
 		if err != nil {
 			return nil, err
 		}
-		pairs[target] = pair
-		target++
+		pairs = append(pairs, pair)
 	}
 	return pairs, nil
 }