Add WaitCondition* and Limit query options

WaitConditions are useful for efficient polling of livestatus.

query.go

@@ -8,6 +8,7 @@ import (
 	"net"
 	"strconv"
 	"strings"
+	"time"
 )
 
 // Query is a binding query instance.
@@ -49,6 +50,60 @@ func (q *Query) Negate() *Query {
 	return q
 }
 
+// Limit the query to n responses.
+func (q *Query) Limit(n int) *Query {
+	q.headers = append(q.headers, fmt.Sprintf("Limit: %d", n))
+	return q
+}
+
+// WaitObject sets the object within the queried table to wait on. For the table
+// hosts, hostgroups, servicegroups, contacts and contactgroups this is simply
+// the name of the object. For the table services it is the hostname followed
+// by a space followed by the service description
+func (q *Query) WaitObject(obj string) *Query {
+	q.headers = append(q.headers, "WaitObject: "+obj)
+	return q
+}
+
+// WaitCondition sets a new wait condition  to apply to the query.
+func (q *Query) WaitCondition(rule string) *Query {
+	q.headers = append(q.headers, "WaitCondition: "+rule)
+	return q
+}
+
+// WaitConditionAnd combines the n last wait conditions into a new wait
+// condition using a `And` operation.
+func (q *Query) WaitConditionAnd(n int) *Query {
+	q.headers = append(q.headers, fmt.Sprintf("WaitConditionAnd: %d", n))
+	return q
+}
+
+// WaitConditionOr combines the n last wait condition into a new wait condition
+// using a `Or` operation.
+func (q *Query) WaitConditionOr(n int) *Query {
+	q.headers = append(q.headers, fmt.Sprintf("WaitConditionOr: %d", n))
+	return q
+}
+
+// WaitConditionNegate negates the most recent wait condition.
+func (q *Query) WaitConditionNegate() *Query {
+	q.headers = append(q.headers, "WaitConditionNegate:")
+	return q
+}
+
+// WaitTrigger sets the nagios event that will trigger a check of
+// the wait condition.
+func (q *Query) WaitTrigger(event string) *Query {
+	q.headers = append(q.headers, "WaitTrigger: "+event)
+	return q
+}
+
+// WaitTimeout set a timeout for the wait condition.
+func (q *Query) WaitTimeout(t time.Duration) *Query {
+	q.headers = append(q.headers, fmt.Sprintf("WaitTimeout: %d", t/time.Millisecond))
+	return q
+}
+
 // Exec executes the query.
 func (q *Query) Exec() (*Response, error) {
 	resp := &Response{}