gno.land/p/samcrew/piechart/v0⧉

1// Package piechart provides functionality to render a pie chart as an SVG image.2// It takes a list of PieSlice objects, each representing a slice of the pie with a value,3// color, and label, and generates an SVG representation of the pie chart.4package piechart56import (7	"math"89	"gno.land/p/nt/svg/v0"10	"gno.land/p/nt/ufmt/v0"11	"gno.land/p/sunspirit/md/v0"12)1314type PieSlice struct {15	Value float6416	Color string17	Label string18}1920// Render creates an SVG pie chart from given slices (value, color and label).21// It returns an img svg markup as a string, including a markdown header if a non-empty title is provided.22func Render(slices []PieSlice, title string) string {23	// Validate input slices length24	if len(slices) == 0 {25		return "\npiechart fails: no data provided"26	}2728	const (29		canvasWidth  = 50030		canvasHeight = 20031		centerX      = 100.032		centerY      = 100.033		radius       = 80.034		legendX      = 21035		legendStartY = 3036		lineHeight   = 2637		squareSize   = 1638		fontSize     = 1639	)4041	canvas := svg.NewCanvas(canvasWidth, canvasHeight)4243	// Sum all values to compute slices proportions44	var total float6445	for _, s := range slices {46		total += s.Value47	}4849	// Draw pie slices and legend in one pass50	startAngle := -math.Pi / 251	for i, s := range slices {52		if s.Value > 0 {53			// --- PIE SLICE ---54			// Calculate angle span for current slice55			angle := (s.Value / total) * 2 * math.Pi56			endAngle := startAngle + angle5758			// Compute start and end points on the circle circumference59			cosStart, sinStart := math.Cos(startAngle), math.Sin(startAngle)60			cosEnd, sinEnd := math.Cos(endAngle), math.Sin(endAngle)61			x1 := centerX + radius*cosStart62			y1 := centerY + radius*sinStart63			x2 := centerX + radius*cosEnd64			y2 := centerY + radius*sinEnd6566			// Determine if the arc should be a large arc (> 180 degrees) (Arc direction)67			largeArcFlag := 068			if angle > math.Pi {69				largeArcFlag = 170			}7172			// Build the SVG path for the pie slice73			path := ufmt.Sprintf(74				"M%.2f,%.2f L%.2f,%.2f A%.2f,%.2f 0 %d 1 %.2f,%.2f Z",75				centerX, centerY, x1, y1, radius, radius, largeArcFlag, x2, y2,76			)7778			// Colored slice79			canvas.Append(svg.Path{80				D:    path,81				Fill: s.Color,82			})8384			startAngle = endAngle85		}8687		// --- LEGEND ---88		y := legendStartY + i*lineHeight89		// Colored square representing slice color90		canvas.Append(svg.Rectangle{91			X:      legendX,92			Y:      y - squareSize/2,93			Width:  squareSize,94			Height: squareSize,95			Fill:   s.Color,96		})9798		// Legend text showing label, value and percentage99		text := ufmt.Sprintf("%s: %.0f (%.1f%%)", s.Label, s.Value, s.Value*100/total)100		canvas.Append(svg.Text{101			X:    legendX + squareSize + 8,102			Y:    y + fontSize/3,103			Text: text,104			Fill: "#54595D",105			Attr: svg.BaseAttrs{106				Style: ufmt.Sprintf("font-family:'Inter var',sans-serif;font-size:%dpx;", fontSize),107			},108		})109	}110111	if title == "" {112		return canvas.Render("Pie Chart")113	}114	return md.H2(title) + canvas.Render("Pie Chart "+title)115}116