fix sapling activation height and consensus branch id

common/common.go

@@ -40,17 +40,34 @@ func GetSaplingInfo(rpcClient *rpcclient.Client) (int, int, string, string, int,
 
 	chainName := f.(map[string]interface{})["chain"].(string)
 
-	upgradeJSON := f.(map[string]interface{})["upgrades"]
-	saplingJSON := upgradeJSON.(map[string]interface{})["76b809bb"] // Sapling ID
-	saplingHeight := saplingJSON.(map[string]interface{})["activationheight"].(float64)
+	// DragonX has Sapling active from block 1 but sets NO_ACTIVATION_HEIGHT in
+	// chainparams, so dragonxd omits it from the upgrades map. Fall back to
+	// height 1 when the key is absent.
+	saplingHeight := float64(1)
+	upgradeJSON, ok := f.(map[string]interface{})["upgrades"]
+	if ok {
+		if upgradesMap, ok := upgradeJSON.(map[string]interface{}); ok {
+			if saplingJSON, ok := upgradesMap["76b809bb"]; ok {
+				saplingHeight = saplingJSON.(map[string]interface{})["activationheight"].(float64)
+			}
+		}
+	}
 
 	blockHeight := f.(map[string]interface{})["headers"].(float64)
 	difficulty := f.(map[string]interface{})["difficulty"].(float64)
 	longestchain := f.(map[string]interface{})["longestchain"].(float64)
 	notarized := f.(map[string]interface{})["notarized"].(float64)
 
-	consensus := f.(map[string]interface{})["consensus"]
-	branchID := consensus.(map[string]interface{})["nextblock"].(string)
+	// DragonX always uses Sapling consensus rules but CurrentEpochBranchId()
+	// returns Sprout (0) for full nodes because the activation heights are
+	// set to NO_ACTIVATION_HEIGHT. Override to the correct Sapling branch ID.
+	branchID := "76b809bb"
+	consensus, ok := f.(map[string]interface{})["consensus"]
+	if ok {
+		if nextblock, ok := consensus.(map[string]interface{})["nextblock"].(string); ok && nextblock != "00000000" {
+			branchID = nextblock
+		}
+	}
 
 	return int(saplingHeight), int(blockHeight), chainName, branchID, int(difficulty), int(longestchain), int(notarized), nil
 }