btcjson, main: Implement the getchaintips call

getchaintips call is implemented and the behavior mimics that of Bitcoin
Core. Resolves #1912.

btcjson/chainsvrresults.go

@@ -117,6 +117,19 @@ type GetBlockVerboseTxResult struct {
 	NextHash      string        `json:"nextblockhash,omitempty"`
 }
 
+// ChainTip is a single chain tip.
+type ChainTip struct {
+	Height    int32  `json:"height"`
+	Hash      string `json:"hash"`
+	BranchLen int32  `json:"branchlen"`
+	Status    string `json:"status"`
+}
+
+// GetChainTipsResult models the data from the getchaintips command.
+type GetChainTipsResult struct {
+	ChainTips []ChainTip `json:"chaintips"`
+}
+
 // GetChainTxStatsResult models the data from the getchaintxstats command.
 type GetChainTxStatsResult struct {
 	Time                   int64   `json:"time"`

rpcserver.go

@@ -146,6 +146,7 @@ var rpcHandlersBeforeInit = map[string]commandHandler{
 	"getblockhash":           handleGetBlockHash,
 	"getblockheader":         handleGetBlockHeader,
 	"getblocktemplate":       handleGetBlockTemplate,
+	"getchaintips":           handleGetChainTips,
 	"getcfilter":             handleGetCFilter,
 	"getcfilterheader":       handleGetCFilterHeader,
 	"getconnectioncount":     handleGetConnectionCount,
@@ -231,7 +232,6 @@ var rpcAskWallet = map[string]struct{}{
 // Commands that are currently unimplemented, but should ultimately be.
 var rpcUnimplemented = map[string]struct{}{
 	"estimatepriority": {},
-	"getchaintips":     {},
 	"getmempoolentry":  {},
 	"getnetworkinfo":   {},
 	"getwork":          {},
@@ -266,6 +266,7 @@ var rpcLimited = map[string]struct{}{
 	"getblockcount":         {},
 	"getblockhash":          {},
 	"getblockheader":        {},
+	"getchaintips":          {},
 	"getcfilter":            {},
 	"getcfilterheader":      {},
 	"getcurrentnet":         {},
@@ -2192,6 +2193,24 @@ func handleGetBlockTemplate(s *rpcServer, cmd interface{}, closeChan <-chan stru
 	}
 }
 
+// handleGetChainTips implements the getchaintips command.
+func handleGetChainTips(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
+	chainTips := s.cfg.Chain.ChainTips()
+
+	ret := btcjson.GetChainTipsResult{}
+	for _, chainTip := range chainTips {
+		ret.ChainTips = append(ret.ChainTips,
+			btcjson.ChainTip{
+				Height:    chainTip.Height,
+				Hash:      chainTip.BlockHash.String(),
+				BranchLen: chainTip.BranchLen,
+				Status:    chainTip.Status.String(),
+			})
+	}
+
+	return ret, nil
+}
+
 // handleGetCFilter implements the getcfilter command.
 func handleGetCFilter(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
 	if s.cfg.CfIndex == nil {

rpcserverhelp.go

@@ -347,6 +347,18 @@ var helpDescsEnUS = map[string]string{
 	"getblocktemplate--condition2": "mode=proposal, accepted",
 	"getblocktemplate--result1":    "An error string which represents why the proposal was rejected or nothing if accepted",
 
+	// GetChainTipsResult help.
+	"getchaintipsresult-chaintips": "The chaintips that this node is aware of",
+
+	// ChainTip help.
+	"chaintip-height":    "The height of the chain tip",
+	"chaintip-hash":      "The block hash of the chain tip",
+	"chaintip-branchlen": "Returns zero for main chain. Otherwise is the length of branch connecting the tip to the main chain",
+	"chaintip-status":    "Status of the chain. Returns \"active\" for the main chain",
+
+	// GetChainTipsCmd help.
+	"getchaintips--synopsis": "Returns information about all known tips in the block tree, including the main chain as well as orphaned branches.",
+
 	// GetCFilterCmd help.
 	"getcfilter--synopsis":  "Returns a block's committed filter given its hash.",
 	"getcfilter-filtertype": "The type of filter to return (0=regular)",
@@ -728,6 +740,7 @@ var rpcResultTypes = map[string][]interface{}{
 	"getblockheader":         {(*string)(nil), (*btcjson.GetBlockHeaderVerboseResult)(nil)},
 	"getblocktemplate":       {(*btcjson.GetBlockTemplateResult)(nil), (*string)(nil), nil},
 	"getblockchaininfo":      {(*btcjson.GetBlockChainInfoResult)(nil)},
+	"getchaintips":           {(*btcjson.GetChainTipsResult)(nil)},
 	"getcfilter":             {(*string)(nil)},
 	"getcfilterheader":       {(*string)(nil)},
 	"getconnectioncount":     {(*int32)(nil)},