1package decor
2
3import (
4	"sort"
5	"sync"
6
7	"github.com/VividCortex/ewma"
8)
9
10type threadSafeMovingAverage struct {
11	ewma.MovingAverage
12	mu sync.Mutex
13}
14
15func (s *threadSafeMovingAverage) Add(value float64) {
16	s.mu.Lock()
17	s.MovingAverage.Add(value)
18	s.mu.Unlock()
19}
20
21func (s *threadSafeMovingAverage) Value() float64 {
22	s.mu.Lock()
23	defer s.mu.Unlock()
24	return s.MovingAverage.Value()
25}
26
27func (s *threadSafeMovingAverage) Set(value float64) {
28	s.mu.Lock()
29	s.MovingAverage.Set(value)
30	s.mu.Unlock()
31}
32
33// NewThreadSafeMovingAverage converts provided ewma.MovingAverage
34// into thread safe ewma.MovingAverage.
35func NewThreadSafeMovingAverage(average ewma.MovingAverage) ewma.MovingAverage {
36	if tsma, ok := average.(*threadSafeMovingAverage); ok {
37		return tsma
38	}
39	return &threadSafeMovingAverage{MovingAverage: average}
40}
41
42type medianWindow [3]float64
43
44func (s *medianWindow) Len() int           { return len(s) }
45func (s *medianWindow) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
46func (s *medianWindow) Less(i, j int) bool { return s[i] < s[j] }
47
48func (s *medianWindow) Add(value float64) {
49	s[0], s[1] = s[1], s[2]
50	s[2] = value
51}
52
53func (s *medianWindow) Value() float64 {
54	tmp := *s
55	sort.Sort(&tmp)
56	return tmp[1]
57}
58
59func (s *medianWindow) Set(value float64) {
60	for i := 0; i < len(s); i++ {
61		s[i] = value
62	}
63}
64
65// NewMedian is fixed last 3 samples median MovingAverage.
66func NewMedian() ewma.MovingAverage {
67	return NewThreadSafeMovingAverage(new(medianWindow))
68}
69