rpc: Handle `getinfo` locally in bitcoin-cli w/ `-getinfo`

This adds the infrastructure `BaseRequestHandler` class that takes care
of converting bitcoin-cli arguments into a JSON-RPC request object, and
converting the reply into a JSON object that can be shown as result.

This is subsequently used to handle the `-getinfo` option, which sends
a JSON-RPC batch request to the RPC server with
`["getnetworkinfo", "getblockchaininfo", "getwalletinfo"]`,
and after reply combines the result into what looks like a `getinfo`
result.

There have been some requests for a client-side `getinfo` and this
is my PoC of how to do it. If this is considered a good idea
some of the logic could be moved up to rpcclient.cpp and
used in the GUI console as well.

Extra-Author: Andrew Chow <achow101@gmail.com>

3 files changed, 127 insertions, 15 deletions

diff --git a/src/bitcoin-cli.cpp b/src/bitcoin-cli.cpp
index 3c94c99b3e..e21a269221 100644
--- a/src/bitcoin-cli.cpp
+++ b/src/bitcoin-cli.cpp
@@ -37,6 +37,7 @@ std::string HelpMessageCli()
     strUsage += HelpMessageOpt("-?", _("This help message"));
     strUsage += HelpMessageOpt("-conf=<file>", strprintf(_("Specify configuration file (default: %s)"), BITCOIN_CONF_FILENAME));
     strUsage += HelpMessageOpt("-datadir=<dir>", _("Specify data directory"));
+    strUsage += HelpMessageOpt("-getinfo", _("Get general information from the remote server. Note that unlike server-side RPC calls, the results of -getinfo is the result of multiple non-atomic requests. Some entries in the result may represent results from different states (e.g. wallet balance may be as of a different block from the chain state reported)"));
     AppendParamsHelpMessages(strUsage);
     strUsage += HelpMessageOpt("-named", strprintf(_("Pass named instead of positional arguments (default: %s)"), DEFAULT_NAMED));
     strUsage += HelpMessageOpt("-rpcconnect=<ip>", strprintf(_("Send commands to node running on <ip> (default: %s)"), DEFAULT_RPCCONNECT));
@@ -191,7 +192,96 @@ static void http_error_cb(enum evhttp_request_error err, void *ctx)
 }
 #endif
 
-static UniValue CallRPC(const std::string& strMethod, const UniValue& params)
+/** Class that handles the conversion from a command-line to a JSON-RPC request,
+ * as well as converting back to a JSON object that can be shown as result.
+ */
+class BaseRequestHandler
+{
+public:
+    virtual UniValue PrepareRequest(const std::string& method, const std::vector<std::string>& args) = 0;
+    virtual UniValue ProcessReply(const UniValue &batch_in) = 0;
+};
+
+/** Process getinfo requests */
+class GetinfoRequestHandler: public BaseRequestHandler
+{
+public:
+    const int ID_NETWORKINFO = 0;
+    const int ID_BLOCKCHAININFO = 1;
+    const int ID_WALLETINFO = 2;
+
+    /** Create a simulated `getinfo` request. */
+    UniValue PrepareRequest(const std::string& method, const std::vector<std::string>& args) override
+    {
+        UniValue result(UniValue::VARR);
+        result.push_back(JSONRPCRequestObj("getnetworkinfo", NullUniValue, ID_NETWORKINFO));
+        result.push_back(JSONRPCRequestObj("getblockchaininfo", NullUniValue, ID_BLOCKCHAININFO));
+        result.push_back(JSONRPCRequestObj("getwalletinfo", NullUniValue, ID_WALLETINFO));
+        return result;
+    }
+
+    /** Collect values from the batch and form a simulated `getinfo` reply. */
+    UniValue ProcessReply(const UniValue &batch_in) override
+    {
+        UniValue result(UniValue::VOBJ);
+        std::vector<UniValue> batch = JSONRPCProcessBatchReply(batch_in, 3);
+        // Errors in getnetworkinfo() and getblockchaininfo() are fatal, pass them on
+        // getwalletinfo() is allowed to fail in case there is no wallet.
+        if (!batch[ID_NETWORKINFO]["error"].isNull()) {
+            return batch[ID_NETWORKINFO];
+        }
+        if (!batch[ID_BLOCKCHAININFO]["error"].isNull()) {
+            return batch[ID_BLOCKCHAININFO];
+        }
+        result.pushKV("version", batch[ID_NETWORKINFO]["result"]["version"]);
+        result.pushKV("protocolversion", batch[ID_NETWORKINFO]["result"]["protocolversion"]);
+        if (!batch[ID_WALLETINFO].isNull()) {
+            result.pushKV("walletversion", batch[ID_WALLETINFO]["result"]["walletversion"]);
+            result.pushKV("balance", batch[ID_WALLETINFO]["result"]["balance"]);
+        }
+        result.pushKV("blocks", batch[ID_BLOCKCHAININFO]["result"]["blocks"]);
+        result.pushKV("timeoffset", batch[ID_NETWORKINFO]["result"]["timeoffset"]);
+        result.pushKV("connections", batch[ID_NETWORKINFO]["result"]["connections"]);
+        result.pushKV("proxy", batch[ID_NETWORKINFO]["result"]["networks"][0]["proxy"]);
+        result.pushKV("difficulty", batch[ID_BLOCKCHAININFO]["result"]["difficulty"]);
+        result.pushKV("testnet", UniValue(batch[ID_BLOCKCHAININFO]["result"]["chain"].get_str() == "test"));
+        if (!batch[ID_WALLETINFO].isNull()) {
+            result.pushKV("walletversion", batch[ID_WALLETINFO]["result"]["walletversion"]);
+            result.pushKV("balance", batch[ID_WALLETINFO]["result"]["balance"]);
+            result.pushKV("keypoololdest", batch[ID_WALLETINFO]["result"]["keypoololdest"]);
+            result.pushKV("keypoolsize", batch[ID_WALLETINFO]["result"]["keypoolsize"]);
+            if (!batch[ID_WALLETINFO]["result"]["unlocked_until"].isNull()) {
+                result.pushKV("unlocked_until", batch[ID_WALLETINFO]["result"]["unlocked_until"]);
+            }
+            result.pushKV("paytxfee", batch[ID_WALLETINFO]["result"]["paytxfee"]);
+        }
+        result.pushKV("relayfee", batch[ID_NETWORKINFO]["result"]["relayfee"]);
+        result.pushKV("warnings", batch[ID_NETWORKINFO]["result"]["warnings"]);
+        return JSONRPCReplyObj(result, NullUniValue, 1);
+    }
+};
+
+/** Process default single requests */
+class DefaultRequestHandler: public BaseRequestHandler {
+public:
+    UniValue PrepareRequest(const std::string& method, const std::vector<std::string>& args) override
+    {
+        UniValue params;
+        if(gArgs.GetBoolArg("-named", DEFAULT_NAMED)) {
+            params = RPCConvertNamedValues(method, args);
+        } else {
+            params = RPCConvertValues(method, args);
+        }
+        return JSONRPCRequestObj(method, params, 1);
+    }
+
+    UniValue ProcessReply(const UniValue &reply) override
+    {
+        return reply.get_obj();
+    }
+};
+
+static UniValue CallRPC(BaseRequestHandler *rh, const std::string& strMethod, const std::vector<std::string>& args)
 {
     std::string host;
     // In preference order, we choose the following for the port:
@@ -238,7 +328,7 @@ static UniValue CallRPC(const std::string& strMethod, const UniValue& params)
     evhttp_add_header(output_headers, "Authorization", (std::string("Basic ") + EncodeBase64(strRPCUserColonPass)).c_str());
 
     // Attach request data
-    std::string strRequest = JSONRPCRequestObj(strMethod, params, 1).write() + "\n";
+    std::string strRequest = rh->PrepareRequest(strMethod, args).write() + "\n";
     struct evbuffer* output_buffer = evhttp_request_get_output_buffer(req.get());
     assert(output_buffer);
     evbuffer_add(output_buffer, strRequest.data(), strRequest.size());
@@ -277,7 +367,7 @@ static UniValue CallRPC(const std::string& strMethod, const UniValue& params)
     UniValue valReply(UniValue::VSTR);
     if (!valReply.read(response.body))
         throw std::runtime_error("couldn't parse reply from server");
-    const UniValue& reply = valReply.get_obj();
+    const UniValue reply = rh->ProcessReply(valReply);
     if (reply.empty())
         throw std::runtime_error("expected reply to have result, error and id properties");
 
@@ -309,24 +399,25 @@ int CommandLineRPC(int argc, char *argv[])
                 args.push_back(line);
             }
         }
-        if (args.size() < 1) {
-            throw std::runtime_error("too few parameters (need at least command)");
-        }
-        std::string strMethod = args[0];
-        args.erase(args.begin()); // Remove trailing method name from arguments vector
-
-        UniValue params;
-        if(gArgs.GetBoolArg("-named", DEFAULT_NAMED)) {
-            params = RPCConvertNamedValues(strMethod, args);
+        std::unique_ptr<BaseRequestHandler> rh;
+        std::string method;
+        if (gArgs.GetBoolArg("-getinfo", false)) {
+            rh.reset(new GetinfoRequestHandler());
+            method = "";
         } else {
-            params = RPCConvertValues(strMethod, args);
+            rh.reset(new DefaultRequestHandler());
+            if (args.size() < 1) {
+                throw std::runtime_error("too few parameters (need at least command)");
+            }
+            method = args[0];
+            args.erase(args.begin()); // Remove trailing method name from arguments vector
         }
 
         // Execute and handle connection failures with -rpcwait
         const bool fWait = gArgs.GetBoolArg("-rpcwait", false);
         do {
             try {
-                const UniValue reply = CallRPC(strMethod, params);
+                const UniValue reply = CallRPC(rh.get(), method, args);
 
                 // Parse reply
                 const UniValue& result = find_value(reply, "result");
diff --git a/src/rpc/protocol.cpp b/src/rpc/protocol.cpp
index dc6bcec382..1f4ae75b18 100644
--- a/src/rpc/protocol.cpp
+++ b/src/rpc/protocol.cpp
@@ -19,7 +19,7 @@
  * JSON-RPC protocol.  Bitcoin speaks version 1.0 for maximum compatibility,
  * but uses JSON-RPC 1.1/2.0 standards for parts of the 1.0 standard that were
  * unspecified (HTTP errors and contents of 'error').
- * 
+ *
  * 1.0 spec: http://json-rpc.org/wiki/specification
  * 1.2 spec: http://jsonrpc.org/historical/json-rpc-over-http.html
  */
@@ -135,3 +135,22 @@ void DeleteAuthCookie()
     }
 }
 
+std::vector<UniValue> JSONRPCProcessBatchReply(const UniValue &in, size_t num)
+{
+    if (!in.isArray()) {
+        throw std::runtime_error("Batch must be an array");
+    }
+    std::vector<UniValue> batch(num);
+    for (size_t i=0; i<in.size(); ++i) {
+        const UniValue &rec = in[i];
+        if (!rec.isObject()) {
+            throw std::runtime_error("Batch member must be object");
+        }
+        size_t id = rec["id"].get_int();
+        if (id >= num) {
+            throw std::runtime_error("Batch member id larger than size");
+        }
+        batch[id] = rec;
+    }
+    return batch;
+}
diff --git a/src/rpc/protocol.h b/src/rpc/protocol.h
index 5c9c64f67d..bba7438c95 100644
--- a/src/rpc/protocol.h
+++ b/src/rpc/protocol.h
@@ -97,5 +97,7 @@ bool GenerateAuthCookie(std::string *cookie_out);
 bool GetAuthCookie(std::string *cookie_out);
 /** Delete RPC authentication cookie from disk */
 void DeleteAuthCookie();
+/** Parse JSON-RPC batch reply into a vector */
+std::vector<UniValue> JSONRPCProcessBatchReply(const UniValue &in, size_t num);
 
 #endif // BITCOIN_RPCPROTOCOL_H