textui: Implement a reusable progress module

To replace all of the ad-hoc hacks

1 files changed, 88 insertions, 0 deletions

diff --git a/lib/textui/progress.go b/lib/textui/progress.go
new file mode 100644
index 0000000..7b3f63a
--- /dev/null
+++ b/lib/textui/progress.go
@@ -0,0 +1,88 @@
+// Copyright (C) 2022  Luke Shumaker <lukeshu@lukeshu.com>
+//
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+package textui
+
+import (
+	"context"
+	"fmt"
+	"sync/atomic"
+	"time"
+
+	"github.com/datawire/dlib/dlog"
+)
+
+type Stats interface {
+	comparable
+	fmt.Stringer
+}
+
+type Progress[T Stats] struct {
+	ctx      context.Context
+	lvl      dlog.LogLevel
+	interval time.Duration
+
+	cancel context.CancelFunc
+	done   chan struct{}
+
+	cur     atomic.Value // Value[T]
+	oldStat T
+	oldLine string
+}
+
+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
+}
+
+func (p *Progress[T]) Set(val T) {
+	if p.cur.Swap(val) == nil {
+		go p.run()
+	}
+}
+
+func (p *Progress[T]) Done() {
+	p.cancel()
+	<-p.done
+}
+
+func (p *Progress[T]) flush(force bool) {
+	cur := p.cur.Load().(T)
+	if !force && cur == p.oldStat {
+		return
+	}
+	defer func() { p.oldStat = cur }()
+
+	line := cur.String()
+	if !force && line == p.oldLine {
+		return
+	}
+	defer func() { p.oldLine = line }()
+
+	dlog.Log(p.ctx, p.lvl, line)
+}
+
+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)
+		}
+	}
+}