package main

import (
	"fmt"
	"strings"
	"time"
)

type TickPrinter struct {
	Message  chan func() string
	msg      func() string
	lastLen  int
	Interval time.Duration
	stop     chan struct{}
	flush    chan struct{}
}

func NewTickPrinter(interval time.Duration) *TickPrinter {
	return &TickPrinter{
		Message: make(chan func() string),
		msg: func() string {
			return time.Now().Format("15:04:05")
		},
		stop:     make(chan struct{}),
		flush:    make(chan struct{}),
		Interval: interval,
	}
}

func (t *TickPrinter) Start() {
	ticker := time.NewTicker(t.Interval)
	for {
		select {
		case <-t.flush:
			fmt.Printf("\n")
			t.Print()
		case <-ticker.C:
			t.Print()
		case msg := <-t.Message:
			t.msg = msg
		case <-t.stop:
			return
		}
	}
}

func (t *TickPrinter) Stop() {
	close(t.stop)
	time.Sleep(t.Interval)
	fmt.Printf("\n")
}

func (t *TickPrinter) Flush() {
	t.flush <- struct{}{}
}

func (t *TickPrinter) Print() {
	fmt.Printf("\r%s", strings.Repeat(" ", t.lastLen))
	msg := t.msg()
	l := len(msg)
	if len(msg) < t.lastLen {
		msg += strings.Repeat(" ", t.lastLen-len(msg))
	}
	t.lastLen = l
	fmt.Printf("\r%s", msg)
}