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// Copyright (C) 2022-2023 Luke Shumaker <lukeshu@lukeshu.com>
//
// SPDX-License-Identifier: GPL-2.0-or-later
package textui
import (
"context"
"fmt"
"time"
"git.lukeshu.com/go/typedsync"
"github.com/datawire/dlib/dlog"
)
type Stats interface {
comparable
fmt.Stringer
}
// Progress helps display to the user the ongoing progress of a long
// task.
//
// There are few usage requirements to watch out for:
//
// - .Set() must have been called at least once before you call
// .Done(). The easiest way to ensure this is to call .Set right
// after creating the progress, or right before calling .Done(). I
// advise against counting on a loop to have called .Set() at least
// once.
type Progress[T Stats] struct {
ctx context.Context //nolint:containedctx // captured for separate goroutine
lvl dlog.LogLevel
interval time.Duration
cancel context.CancelFunc
done chan struct{}
cur typedsync.Value[T]
oldStat T
oldLine string
// This isn't a functional part, but is useful for helping us
// to detect misuse.
last time.Time
}
func NewProgress[T Stats](ctx context.Context, lvl dlog.LogLevel, interval time.Duration) *Progress[T] {
ctx, cancel := context.WithCancel(ctx)
ret := &Progress[T]{
ctx: ctx,
lvl: lvl,
interval: interval,
cancel: cancel,
done: make(chan struct{}),
}
return ret
}
// Set update the Progress. Rate-limiting prevents this from being
// expensive, or from spamming the user; it is reasonably safe to call
// .Set in a tight inner loop.
//
// It is safe to call Set concurrently.
func (p *Progress[T]) Set(val T) {
if _, hadOld := p.cur.Swap(val); !hadOld {
go p.run()
}
}
// Done closes the Progress; it flushes out one last status update (if
// nescessary), and releases resources associated with the Progress.
//
// It is safe to call Done multiple times, or concurrently.
//
// It will panic if Done is called without having called Set at least
// once.
func (p *Progress[T]) Done() {
p.cancel()
if _, started := p.cur.Load(); !started {
panic("textui.Progress: .Done called without ever calling .Set")
}
<-p.done
}
func (p *Progress[T]) flush(force bool) {
// Check how long it's been since we last printed something.
// If this grows too big, it probably means that either the
// program deadlocked or that we forgot to call .Done().
now := time.Now()
if !p.last.IsZero() && now.Sub(p.last) > Tunable(2*time.Minute) {
dlog.Error(p.ctx, "stale Progress")
panic("stale Progress")
}
// Load the data to print.
cur, ok := p.cur.Load()
if !ok {
panic("should not happen")
}
if !force && cur == p.oldStat {
return
}
defer func() { p.oldStat = cur }()
// Format the data as text.
line := cur.String()
if !force && line == p.oldLine {
return
}
defer func() { p.oldLine = line }()
// Print.
dlog.Log(p.ctx, p.lvl, line)
p.last = now
}
func (p *Progress[T]) run() {
p.flush(true)
ticker := time.NewTicker(p.interval)
for {
select {
case <-p.ctx.Done():
ticker.Stop()
p.flush(false)
close(p.done)
return
case <-ticker.C:
p.flush(false)
}
}
}
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