More SVG fun

utils/PieChart.go

@@ -0,0 +1,118 @@
+package utils
+
+import (
+	"fmt"
+	"math"
+)
+
+// PieChart ...
+type PieChart struct {
+	Title  string
+	Slices []*PieChartSlice
+}
+
+// PieChartSlice ...
+type PieChartSlice struct {
+	From  float64
+	To    float64
+	Title string
+	Color string
+}
+
+// coords returns the coordinates for the given percentage.
+func coords(percent float64) (float64, float64) {
+	x := math.Cos(2 * math.Pi * percent)
+	y := math.Sin(2 * math.Pi * percent)
+	return x, y
+}
+
+// SVGSlicePath creates a path string for a slice in a pie chart.
+func SVGSlicePath(from float64, to float64) string {
+	x1, y1 := coords(from)
+	x2, y2 := coords(to)
+
+	largeArc := "0"
+
+	if to-from > 0.5 {
+		largeArc = "1"
+	}
+
+	return fmt.Sprintf("M %.3f %.3f A 1 1 0 %s 1 %.3f %.3f L 0 0", x1, y1, largeArc, x2, y2)
+}
+
+// NewPieChart ...
+func NewPieChart(title string, data map[string]float64) *PieChart {
+	return &PieChart{
+		Title:  title,
+		Slices: ToPieChartSlices(data),
+	}
+}
+
+// ToPieChartSlices ...
+func ToPieChartSlices(data map[string]float64) []*PieChartSlice {
+	if len(data) == 0 {
+		return nil
+	}
+
+	dataSorted := []*AnalyticsItem{}
+	sum := 0.0
+
+	for key, value := range data {
+		sum += value
+
+		item := &AnalyticsItem{
+			Key:   key,
+			Value: value,
+		}
+
+		if len(dataSorted) == 0 {
+			dataSorted = append(dataSorted, item)
+			continue
+		}
+
+		found := false
+
+		for i := 0; i < len(dataSorted); i++ {
+			if value >= dataSorted[i].Value {
+				// Append empty element
+				dataSorted = append(dataSorted, nil)
+
+				// Move all elements after index "i" 1 position up
+				copy(dataSorted[i+1:], dataSorted[i:])
+
+				// Set value for index "i"
+				dataSorted[i] = item
+
+				// Set flag
+				found = true
+
+				// Leave loop
+				break
+			}
+		}
+
+		if !found {
+			dataSorted = append(dataSorted, item)
+		}
+	}
+
+	slices := []*PieChartSlice{}
+	current := 0.0
+	hueOffset := 0.0
+	hueScaling := 60.0
+
+	for _, item := range dataSorted {
+		percentage := float64(item.Value) / sum
+
+		slices = append(slices, &PieChartSlice{
+			From:  current,
+			To:    current + percentage,
+			Title: fmt.Sprintf("%s (%d%%)", item.Key, int(percentage*100+0.5)),
+			Color: fmt.Sprintf("hsl(%.2f, 75%%, 50%%)", current*hueScaling+hueOffset),
+		})
+
+		current += percentage
+	}
+
+	return slices
+}