Refactor into reusable libraries

4 files changed, 74 insertions, 29 deletions

diff --git a/progress-bar.go b/cmd/progress-bar/progress-bar.go
index 0b1cefe..65079ef 100644
--- a/progress-bar.go
+++ b/cmd/progress-bar/progress-bar.go
@@ -8,19 +8,14 @@ import (
 	"os"
 	"os/exec"
 	"strconv"
-	"strings"
 	"time"
 
-	"golang.org/x/term"
+	"gitlab.com/rhogenson/progress-bar/progress"
 )
 
 var n = flag.Duration("n", 2*time.Minute, "polling interval")
 
 func run() error {
-	cols, _, err := term.GetSize(int(os.Stdout.Fd()))
-	if err != nil {
-		return err
-	}
 	args := flag.Args()
 	if len(args) < 2 {
 		return errors.New("usage error")
@@ -31,11 +26,7 @@ func run() error {
 		return fmt.Errorf("max: %s", err)
 	}
 	cmd := args[1:]
-	type measurement struct {
-		t time.Time
-		i int
-	}
-	var measurements []measurement
+	bar := progress.New(maxVal)
 	for i := 0; ; i++ {
 		outputBytes, err := exec.Command(cmd[0], cmd[1:]...).Output()
 		if err != nil {
@@ -47,22 +38,8 @@ func run() error {
 			fmt.Println(err)
 			continue
 		}
-		p := output * cols / maxVal
-		if i > 0 {
-			fmt.Print("\033[2F\033[J")
-		}
-		fmt.Printf("%s>\n", strings.Repeat("=", max(p-1, 0)))
-		measurements = append(measurements, measurement{time.Now(), output})
-		if len(measurements) > 20 {
-			measurements = measurements[1:]
-		}
-		deltaT := measurements[len(measurements)-1].t.Sub(measurements[0].t)
-		delta := measurements[len(measurements)-1].i - measurements[0].i
-		if delta == 0 {
-			fmt.Println()
-		} else {
-			fmt.Printf("ETA: %s\n", time.Duration(float64(maxVal-output)/float64(delta)*float64(deltaT)).Round(time.Second))
-		}
+		bar.Set(output)
+		bar.Print()
 		time.Sleep(*n)
 	}
 }
diff --git a/go.mod b/go.mod
index 8d19cf8..9531fa9 100644
--- a/go.mod
+++ b/go.mod
@@ -1,7 +1,10 @@
-module gitlab.com/rhogenson/progress-bar
+module gitlab.com/rhogenson/progress-bar/progress
 
 go 1.24.1
 
-require golang.org/x/term v0.28.0
+require (
+	gitlab.com/rhogenson/vecdeque v0.0.0-20250405201931-eb7fb2bc95c6
+	golang.org/x/term v0.28.0
+)
 
 require golang.org/x/sys v0.29.0 // indirect
diff --git a/go.sum b/go.sum
index f05f63b..4af7e2b 100644
--- a/go.sum
+++ b/go.sum
@@ -1,3 +1,5 @@
+gitlab.com/rhogenson/vecdeque v0.0.0-20250405201931-eb7fb2bc95c6 h1:S1vSZ4W5v+eL/ayT5M4RDqPUHlAN2SKl/x65O9D4jPo=
+gitlab.com/rhogenson/vecdeque v0.0.0-20250405201931-eb7fb2bc95c6/go.mod h1:i++skCmDHJAQbyC5LqvJbehbEGCiO8EkrsPon6h0Jgo=
 golang.org/x/sys v0.29.0 h1:TPYlXGxvx1MGTn2GiZDhnjPA9wZzZeGKHHmKhHYvgaU=
 golang.org/x/sys v0.29.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/term v0.28.0 h1:/Ts8HFuMR2E6IP/jlo7QVLZHggjKQbhu/7H0LJFr3Gg=
diff --git a/progress.go b/progress.go
new file mode 100644
index 0000000..7660605
--- /dev/null
+++ b/progress.go
@@ -0,0 +1,63 @@
+package progress
+
+import (
+	"fmt"
+	"os"
+	"strings"
+	"time"
+
+	"gitlab.com/rhogenson/vecdeque"
+	"golang.org/x/term"
+)
+
+const measurements = 20
+
+type measurement struct {
+	t time.Time
+	i int
+}
+
+type Bar struct {
+	max          int
+	measurements vecdeque.DQ[measurement]
+	cols         int
+}
+
+func New(max int) *Bar {
+	b := &Bar{max: max}
+	b.measurements.Grow(measurements)
+	return b
+}
+
+func (b *Bar) Set(i int) {
+	if b.measurements.Len() == measurements {
+		b.measurements.PopFront()
+	}
+	b.measurements.PushBack(measurement{time.Now(), i})
+}
+
+func (b *Bar) Print() {
+	first := b.measurements.Get(0)
+	last := b.measurements.Get(b.measurements.Len() - 1)
+	deltaT := last.t.Sub(first.t)
+	delta := last.i - first.i
+	eta := time.Duration(-1)
+	if delta != 0 {
+		eta = time.Duration(float64(b.max-last.i) / float64(delta) * float64(deltaT))
+	}
+
+	if b.cols == 0 {
+		var err error
+		if b.cols, _, err = term.GetSize(int(os.Stderr.Fd())); err != nil {
+			fmt.Fprintf(os.Stderr, "Warning: unable to determine terminal size: %s\n", err)
+		}
+	} else {
+		p := last.i * b.cols / b.max
+		fmt.Fprintf(os.Stderr, "\033[2F\033[J%s>\n", strings.Repeat("=", max(p-1, 0)))
+	}
+	if eta < 0 {
+		fmt.Fprintln(os.Stderr, "ETA: calculating...")
+	} else {
+		fmt.Fprintf(os.Stderr, "ETA: %s\n", eta.Round(time.Second))
+	}
+}