First code commit.

SparkRing.go

@@ -0,0 +1,68 @@
+package main
+
+type (
+	// SparkRing is a ring structure to draw a spark line in a terminal.
+	SparkRing struct {
+		Ring []float64
+		tail int
+	}
+)
+
+var (
+	steps = []rune{' ', '▁', '▂', '▃', '▄', '▅', '▆', '▇', '█'}
+)
+
+// NewSparkRing will instantiate a new SparkRing with a length of len.
+func NewSparkRing(len int) *SparkRing {
+	return &SparkRing{
+		Ring: make([]float64, len),
+	}
+}
+
+// Push will push a new value to the ring.
+func (s *SparkRing) Push(value float64) {
+	if s.tail >= len(s.Ring) {
+		s.tail = 0
+	}
+
+	s.Ring[s.tail] = value
+
+	s.tail++
+}
+
+// Max will return the maximum value stored in the ring.
+func (s *SparkRing) Max() float64 {
+	var max float64
+
+	for _, value := range s.Ring {
+		if value > max {
+			max = value
+		}
+	}
+
+	return max
+}
+
+// String will return the sparkline as a string.
+func (s *SparkRing) String() string {
+	ret := make([]rune, len(s.Ring))
+	stepSize := s.Max() / float64(len(steps))
+
+	for i, value := range s.Ring {
+		scaled := value / stepSize
+		pos := int(scaled - 0.5)
+
+		if pos > len(steps)-1 {
+			pos = len(steps) - 1
+		}
+
+		if pos < 0 {
+			pos = 0
+		}
+
+		l := len(s.Ring)
+		ret[(l+i-s.tail)%l] = steps[pos]
+	}
+
+	return string(ret)
+}