Add function to create contribution history image

src/graphs/commit_chart.go

@@ -0,0 +1,71 @@
+package graphs
+
+import (
+	"fmt"
+	"image/color"
+
+	"gonum.org/v1/plot"
+	"gonum.org/v1/plot/plotter"
+	"gonum.org/v1/plot/vg"
+)
+
+func DrawCommitChart(commitsHistory []int, maxCommits int, width int, height int) error {
+	y := make([]float64, len(commitsHistory))
+	for i := range y {
+		y[i] = float64(commitsHistory[i])
+	}
+	x := make([]float64, len(commitsHistory))
+	for i := range x {
+		x[i] = float64(i-len(commitsHistory)) + 1
+	}
+
+	if len(x) != len(y) {
+		fmt.Println("x and y arrays must have the same length")
+	}
+
+	p := plot.New()
+
+	bgColor := color.RGBA{R: 51, G: 61, B: 79, A: 255}
+	p.BackgroundColor = bgColor
+
+	points := make(plotter.XYs, len(x))
+	for i := range x {
+		points[i].X = x[i]
+		points[i].Y = y[i]
+	}
+
+	line, err := plotter.NewLine(points)
+	if err != nil {
+		panic(err)
+	}
+	line.Color = color.RGBA{R: 0, G: 255, B: 0, A: 255}
+	p.Add(line)
+
+	p.Title.Text = "Contribution History"
+	p.X.Label.Text = "Days"
+	p.Y.Label.Text = "Commits"
+
+	p.X.Min = -366
+	p.X.Max = 5
+	p.Y.Min = -0
+	p.Y.Max = float64(maxCommits) + 5
+
+	white := color.White
+	p.Title.TextStyle.Color = white
+	p.X.Tick.Color = white
+	p.Y.Tick.Color = white
+	p.X.Label.TextStyle.Color = white
+	p.Y.Label.TextStyle.Color = white
+	p.X.Tick.Label.Color = white
+	p.Y.Tick.Label.Color = white
+	p.X.LineStyle.Color = white
+	p.Y.LineStyle.Color = white
+
+	p.X.Padding, p.Y.Padding = 0, 0
+
+	if err := p.Save(8*vg.Inch, 4*vg.Inch, "./images/commits_history.png"); err != nil {
+		panic(err)
+	}
+
+	return err
+}