1 files changed, 87 insertions, 0 deletions
diff --git a/pkg/plot/barchart.go b/pkg/plot/barchart.go
new file mode 100644
index 0000000..cb6c95c
--- /dev/null
+++ b/pkg/plot/barchart.go
@@ -0,0 +1,87 @@
+package plot
+
+import (
+	"bytes"
+	"math"
+
+	"github.com/sgreben/jp/pkg/draw"
+)
+
+// BarChart is a bar chart
+type BarChart struct {
+	draw.Canvas
+	BarPaddingX int
+}
+
+// NewBarChart returns a new bar chart
+func NewBarChart(canvas draw.Canvas) *BarChart {
+	chart := new(BarChart)
+	chart.Canvas = canvas
+	chart.BarPaddingX = 1
+	return chart
+}
+
+// Draw implements Chart
+func (c *BarChart) Draw(data *DataTable) string {
+	minY := math.Inf(1)
+	maxY := math.Inf(-1)
+	for _, row := range data.Rows {
+		for _, y := range row {
+			if y < minY {
+				minY = y
+			}
+			if y > maxY {
+				maxY = y
+			}
+		}
+	}
+	paddingX := 4
+	paddingY := 3
+	chartHeight := c.Size().Height - paddingY*c.RuneSize().Height
+	chartWidth := c.Size().Width - 2*paddingX*c.RuneSize().Width
+	scaleY := float64(chartHeight) / maxY
+	barPaddedWidth := chartWidth / len(data.Columns)
+	barWidth := barPaddedWidth - (c.BarPaddingX * c.RuneSize().Width)
+	if barPaddedWidth < c.RuneSize().Width {
+		barPaddedWidth = c.RuneSize().Width
+	}
+	if barWidth < c.RuneSize().Width {
+		barWidth = c.RuneSize().Width
+	}
+
+	scaleY = float64(chartHeight) / maxY
+
+	for i, group := range data.Columns {
+		barLeft := paddingX*c.RuneSize().Width + barPaddedWidth*i
+		barRight := barLeft + barWidth
+
+		y := data.Rows[0][i]
+		barHeight := y * scaleY
+		barBottom := (paddingY - 1) * c.RuneSize().Height
+		barTop := barBottom + int(barHeight)
+
+		for x := barLeft; x < barRight; x++ {
+			for y := barBottom; y < barTop; y++ {
+				c.Set(y, x)
+			}
+		}
+
+		// Group label
+		barMiddle := (barLeft + barRight) / 2
+		c.GetBuffer().WriteCenter(0, barMiddle/c.RuneSize().Width, []rune(group))
+
+		// Count label
+		countLabelY := int(math.Ceil(float64(barTop)/float64(c.RuneSize().Height))) * c.RuneSize().Height
+
+		if countLabelY <= barBottom && y > 0 {
+			c.GetBuffer().SetRow(barTop/c.RuneSize().Height, barLeft/c.RuneSize().Width, barRight/c.RuneSize().Width, '▁')
+			countLabelY = 3 * c.RuneSize().Height
+		}
+
+		c.GetBuffer().WriteCenter(countLabelY/c.RuneSize().Height, barMiddle/c.RuneSize().Width, Ff(y))
+	}
+
+	b := bytes.NewBuffer(nil)
+	c.GetBuffer().Render(b)
+	return b.String()
+}