plot.go

package slackactivity

import (
	"fmt"
	"time"

	"github.com/slack-go/slack"
	"gonum.org/v1/plot"
	"gonum.org/v1/plot/plotter"
	"gonum.org/v1/plot/plotutil"
	"gonum.org/v1/plot/vg"
)

func GeneratePlot(
	counts []MessageCount,
	channel slack.Channel,
	imageHeight int,
	imageWidth int,
	outputPath string,
) error {
	values := make(plotter.Values, len(counts))
	for i, r := range counts {
		values[i] = float64(r.Count)
	}

	p := plot.New()
	p.Title.Text = channel.Name + " [reported at " + time.Now().Format("2006/01/02") + " ]"
	barwidth := float64(imageWidth / len(counts))
	w := vg.Points(barwidth)

	bars, err := plotter.NewBarChart(values, w)
	if err != nil {
		return fmt.Errorf("NewBarChart failed: %w", err)
	}

	bars.LineStyle.Width = vg.Length(0)
	bars.Color = plotutil.Color(1)
	bars.XMin = float64(-1 * len(counts))
	p.Add(bars)

	if err := p.Save(vg.Length(imageWidth), vg.Length(imageHeight), outputPath); err != nil {
		return fmt.Errorf("plot.Save failed: %w", err)
	}

	return nil
}