common: Add an Event module (#169)

2 files changed, 175 insertions, 0 deletions

diff --git a/common/event.go b/common/event.go
new file mode 100644
index 0000000..4c11d62
--- /dev/null
+++ b/common/event.go
@@ -0,0 +1,83 @@
+// Copyright 2018 The dexon-consensus-core Authors
+// This file is part of the dexon-consensus-core library.
+//
+// The dexon-consensus-core library is free software: you can redistribute it
+// and/or modify it under the terms of the GNU Lesser General Public License as
+// published by the Free Software Foundation, either version 3 of the License,
+// or (at your option) any later version.
+//
+// The dexon-consensus-core library is distributed in the hope that it will be
+// useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
+// General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the dexon-consensus-core library. If not, see
+// <http://www.gnu.org/licenses/>.
+
+package common
+
+import (
+	"container/heap"
+	"time"
+)
+
+type timeEventFn func(time.Time)
+
+type timeEvent struct {
+	t  time.Time
+	fn timeEventFn
+}
+
+// timeEvents implements a Min-Heap structure.
+type timeEvents []timeEvent
+
+func (h timeEvents) Len() int           { return len(h) }
+func (h timeEvents) Less(i, j int) bool { return h[i].t.Before(h[j].t) }
+func (h timeEvents) Swap(i, j int)      { h[i], h[j] = h[j], h[i] }
+func (h *timeEvents) Push(x interface{}) {
+	*h = append(*h, x.(timeEvent))
+}
+func (h *timeEvents) Pop() interface{} {
+	old := *h
+	n := len(old)
+	x := old[n-1]
+	*h = old[0 : n-1]
+	return x
+}
+
+// Event implements the Observer pattern.
+type Event struct {
+	timeEvents timeEvents
+}
+
+// NewEvent creates a new event instance.
+func NewEvent() *Event {
+	te := timeEvents{}
+	heap.Init(&te)
+	return &Event{
+		timeEvents: te,
+	}
+}
+
+// RegisterTime to get notified on and after specific time.
+func (e *Event) RegisterTime(t time.Time, fn timeEventFn) {
+	heap.Push(&e.timeEvents, timeEvent{
+		t:  t,
+		fn: fn,
+	})
+}
+
+// NotifyTime and trigger function callback.
+func (e *Event) NotifyTime(t time.Time) {
+	if len(e.timeEvents) == 0 {
+		return
+	}
+	for !t.Before(e.timeEvents[0].t) {
+		te := heap.Pop(&e.timeEvents).(timeEvent)
+		te.fn(t)
+		if len(e.timeEvents) == 0 {
+			return
+		}
+	}
+}
diff --git a/common/event_test.go b/common/event_test.go
new file mode 100644
index 0000000..ca44ddb
--- /dev/null
+++ b/common/event_test.go
@@ -0,0 +1,92 @@
+// Copyright 2018 The dexon-consensus-core Authors
+// This file is part of the dexon-consensus-core library.
+//
+// The dexon-consensus-core library is free software: you can redistribute it
+// and/or modify it under the terms of the GNU Lesser General Public License as
+// published by the Free Software Foundation, either version 3 of the License,
+// or (at your option) any later version.
+//
+// The dexon-consensus-core library is distributed in the hope that it will be
+// useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
+// General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the dexon-consensus-core library. If not, see
+// <http://www.gnu.org/licenses/>.
+
+package common
+
+import (
+	"math/rand"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/suite"
+)
+
+type EventTestSuite struct {
+	suite.Suite
+}
+
+func (s *EventTestSuite) TestTimeEvent() {
+	event := NewEvent()
+	now := time.Now()
+	triggered := make(chan int, 100)
+	trigger := func(id int) func(t time.Time) {
+		return func(t time.Time) {
+			triggered <- id
+		}
+	}
+	event.RegisterTime(now.Add(100*time.Millisecond), trigger(0))
+	event.NotifyTime(now)
+	s.Len(triggered, 0)
+	event.NotifyTime(now.Add(150 * time.Millisecond))
+	s.Len(triggered, 1)
+	triggered = make(chan int, 100)
+	event.NotifyTime(now.Add(150 * time.Millisecond))
+	s.Len(triggered, 0)
+
+	event.RegisterTime(now.Add(100*time.Millisecond), trigger(0))
+	event.RegisterTime(now.Add(100*time.Millisecond), trigger(0))
+	event.RegisterTime(now.Add(100*time.Millisecond), trigger(0))
+	event.RegisterTime(now.Add(100*time.Millisecond), trigger(0))
+	event.NotifyTime(now.Add(150 * time.Millisecond))
+	s.Len(triggered, 4)
+
+	triggered = make(chan int, 100)
+	for i := 0; i < 10; i++ {
+		event.RegisterTime(now.Add(time.Duration(100+i*10)*time.Millisecond),
+			trigger(i))
+	}
+	event.NotifyTime(now.Add(130 * time.Millisecond))
+	s.Require().Len(triggered, 4)
+	for i := 0; i < 4; i++ {
+		j := <-triggered
+		s.Equal(i, j)
+	}
+
+	event = NewEvent()
+	triggered = make(chan int, 100)
+	nums := make([]int, 10)
+	for i := range nums {
+		nums[i] = i
+	}
+	rand.Shuffle(len(nums), func(i, j int) {
+		nums[i], nums[j] = nums[j], nums[i]
+	})
+	for _, i := range nums {
+		event.RegisterTime(now.Add(time.Duration(100+i*10)*time.Millisecond),
+			trigger(i))
+	}
+	event.NotifyTime(now.Add(130 * time.Millisecond))
+	s.Require().Len(triggered, 4)
+	for i := 0; i < 4; i++ {
+		j := <-triggered
+		s.Equal(i, j)
+	}
+}
+
+func TestEvent(t *testing.T) {
+	suite.Run(t, new(EventTestSuite))
+}