From 86d31aacec9c1fc75799c9bcdecc3a342b8f5319 Mon Sep 17 00:00:00 2001
From: chihiro-h <chihiro-h@mercari.com>
Date: Sun, 1 Oct 2023 21:03:27 +0900
Subject: [PATCH] add: util for formatting bytes format

---
 internal/util.go      | 19 +++++++++++++++++++
 internal/util_test.go | 19 +++++++++++++++++++
 2 files changed, 38 insertions(+)
 create mode 100644 internal/util.go
 create mode 100644 internal/util_test.go

diff --git a/internal/util.go b/internal/util.go
new file mode 100644
index 0000000..bff5545
--- /dev/null
+++ b/internal/util.go
@@ -0,0 +1,19 @@
+package internal
+
+import (
+	"fmt"
+)
+
+// ref: https://yourbasic.org/golang/formatting-byte-size-to-human-readable-format/
+func formatBytes(b int64) string {
+	const unit = 1000
+	if b < unit {
+		return fmt.Sprintf("%d", b)
+	}
+	div, exp := int64(unit), 0
+	for n := b / unit; n >= unit; n /= unit {
+		div *= unit
+		exp++
+	}
+	return fmt.Sprintf("%.1f%c", float64(b)/float64(div), "KMGTPE"[exp])
+}
diff --git a/internal/util_test.go b/internal/util_test.go
new file mode 100644
index 0000000..54ace66
--- /dev/null
+++ b/internal/util_test.go
@@ -0,0 +1,19 @@
+package internal
+
+import "testing"
+
+func TestFormatBytes(t *testing.T) {
+	tests := map[int64]string{
+		999:       "999",
+		1024:      "1.0K",
+		1536:      "1.5K",
+		987654321: "987.7M",
+	}
+	for key, value := range tests {
+		got := formatBytes(key)
+		want := value
+		if got != want {
+			t.Fatalf("got: %v, want: %v\n", got, want)
+		}
+	}
+}