routing: Fill in the `getroute` functionality

Copied the JSON-request parsing from `pay.c`, passing through to
`gossipd`, filling the reply with the `route_hop` serialization, and
serializing as JSON-RPC response.

lightningd/gossip/gossip.c

@@ -451,11 +451,30 @@ static struct io_plan *release_peer(struct io_conn *conn, struct daemon *daemon,
 		      "Unknown peer %"PRIu64, unique_id);
 }
 
-static struct io_plan *getroute(struct io_conn *conn, struct daemon *daemon, u8 *msg)
+static struct io_plan *getroute_req(struct io_conn *conn, struct daemon *daemon,
+				    u8 *msg)
 {
-	return next_req_in(conn, daemon);
-}
+	tal_t *tmpctx = tal_tmpctx(msg);
+	struct pubkey source, destination;
+	u32 msatoshi;
+	u16 riskfactor;
+	u8 *out;
+	struct route_hop *hops;
+
+	fromwire_gossip_getroute_request(msg, NULL, &source, &destination,
+					 &msatoshi, &riskfactor);
+	status_trace("Trying to find a route from %s to %s for %d msatoshi",
+		     pubkey_to_hexstr(tmpctx, &source),
+		     pubkey_to_hexstr(tmpctx, &destination), msatoshi);
+
+	hops = get_route(tmpctx, daemon->rstate, &source, &destination,
+			 msatoshi, 1);
 
+	out = towire_gossip_getroute_reply(msg, hops);
+	tal_free(tmpctx);
+	daemon_conn_send(&daemon->master, out);
+	return daemon_conn_read_next(conn, &daemon->master);
+}
 
 static struct io_plan *getnodes(struct io_conn *conn, struct daemon *daemon)
 {
@@ -500,7 +519,7 @@ static struct io_plan *recv_req(struct io_conn *conn, struct daemon_conn *master
 		return getnodes(conn, daemon);
 
 	case WIRE_GOSSIP_GETROUTE_REQUEST:
-		return getroute(conn, daemon, daemon->msg_in);
+		return getroute_req(conn, daemon, daemon->master.msg_in);
 
 	case WIRE_GOSSIPCTL_RELEASE_PEER_REPLY:
 	case WIRE_GOSSIP_GETNODES_REPLY:

lightningd/gossip_control.c

@@ -221,8 +221,73 @@ static const struct json_command getnodes_command = {
     "Returns a list of all nodes that we know about"};
 AUTODATA(json_command, &getnodes_command);
 
+static bool json_getroute_reply(struct subd *gossip, const u8 *reply, const int *fds,
+				struct command *cmd)
+{
+	struct json_result *response;
+	struct route_hop *hops;
+	size_t i;
+
+	fromwire_gossip_getroute_reply(reply, reply, NULL, &hops);
+
+	if (tal_count(hops) == 0) {
+		command_fail(cmd, "Could not find a route");
+		return true;
+	}
+
+	response = new_json_result(cmd);
+	json_object_start(response, NULL);
+	json_array_start(response, "route");
+	for (i=0; i<tal_count(hops); i++) {
+		json_object_start(response, NULL);
+		json_add_pubkey(response, "id", &hops[i].nodeid);
+		json_add_u64(response, "msatoshi", hops[i].amount);
+		json_add_num(response, "delay", hops[i].delay);
+		json_object_end(response);
+	}
+	json_array_end(response);
+	json_object_end(response);
+	command_success(cmd, response);
+	return true;
+}
+
 static void json_getroute(struct command *cmd, const char *buffer, const jsmntok_t *params)
 {
+	struct pubkey id;
+	jsmntok_t *idtok, *msatoshitok, *riskfactortok;
+	u64 msatoshi;
+	double riskfactor;
+	struct lightningd *ld = ld_from_dstate(cmd->dstate);
+	if (!json_get_params(buffer, params,
+			     "id", &idtok,
+			     "msatoshi", &msatoshitok,
+			     "riskfactor", &riskfactortok,
+			     NULL)) {
+		command_fail(cmd, "Need id, msatoshi and riskfactor");
+		return;
+	}
+
+	if (!pubkey_from_hexstr(buffer + idtok->start,
+				idtok->end - idtok->start, &id)) {
+		command_fail(cmd, "Invalid id");
+		return;
+	}
+
+	if (!json_tok_u64(buffer, msatoshitok, &msatoshi)) {
+		command_fail(cmd, "'%.*s' is not a valid number",
+			     (int)(msatoshitok->end - msatoshitok->start),
+			     buffer + msatoshitok->start);
+		return;
+	}
+
+	if (!json_tok_double(buffer, riskfactortok, &riskfactor)) {
+		command_fail(cmd, "'%.*s' is not a valid double",
+			     (int)(riskfactortok->end - riskfactortok->start),
+			     buffer + riskfactortok->start);
+		return;
+	}
+	u8 *req = towire_gossip_getroute_request(cmd, &cmd->dstate->id, &id, msatoshi, riskfactor*1000);
+	subd_req(ld->gossip, req, -1, 0, json_getroute_reply, cmd);
 }
 
 static const struct json_command getroute_command = {