package main

import (
	"fmt"
	"math/rand"
	"sync"
	"time"

	"github.com/vbauerster/mpb/v8"
	"github.com/vbauerster/mpb/v8/decor"
)

func main() {
	var wg sync.WaitGroup
	// passed wg will be accounted at p.Wait() call
	p := mpb.New(
		mpb.WithWaitGroup(&wg),
		mpb.WithWidth(16),
	)
	total, numBars := 101, 3
	wg.Add(numBars)

	for i := 0; i < numBars; i++ {
		name := fmt.Sprintf("Bar#%d:", i)
		bar := p.New(int64(total), condBuilder(i != 0),
			mpb.PrependDecorators(
				// simple name decorator
				decor.Name(name),
			),
			mpb.AppendDecorators(
				// replace ETA decorator with "done" message, OnComplete event
				decor.OnComplete(
					// ETA decorator with ewma age of 60
					decor.EwmaETA(decor.ET_STYLE_GO, 60), "done",
				),
			),
		)
		// simulating some work
		go func() {
			defer wg.Done()
			rng := rand.New(rand.NewSource(time.Now().UnixNano()))
			max := 100 * time.Millisecond
			for i := 0; i < total; i++ {
				// start variable is solely for EWMA calculation
				// EWMA's unit of measure is an iteration's duration
				start := time.Now()
				time.Sleep(time.Duration(rng.Intn(10)+1) * max / 10)
				// we need to call EwmaIncrement to fulfill ewma decorator's contract
				bar.EwmaIncrement(time.Since(start))
			}
		}()
	}
	// wait for passed wg and for all bars to complete and flush
	p.Wait()
}

func condBuilder(cond bool) mpb.BarFillerBuilder {
	return mpb.BarFillerBuilderFunc(func() mpb.BarFiller {
		if cond {
			// spinner Bar on cond
			frames := []string{"∙∙∙", "●∙∙", "∙●∙", "∙∙●", "∙∙∙"}
			return mpb.SpinnerStyle(frames...).Build()
		}
		return mpb.BarStyle().Lbound("╢").Filler("▌").Tip("▌").Padding("░").Rbound("╟").Build()
	})
}