From 84cd68de7f225e795f390bfacd9fd1427601bb04 Mon Sep 17 00:00:00 2001
From: dudaodong <lanliddd.2007@163.com>
Date: Sun, 19 Feb 2023 12:34:39 +0800
Subject: [PATCH] fix: fix bugs of PadEnd and PadStart

---
 strutil/string.go          | 40 +++++++-------------------------------
 strutil/string_internal.go | 37 +++++++++++++++++++++++++++++++++++
 strutil/string_test.go     |  1 +
 3 files changed, 45 insertions(+), 33 deletions(-)

diff --git a/strutil/string.go b/strutil/string.go
index b527b09..80bcfa9 100644
--- a/strutil/string.go
+++ b/strutil/string.go
@@ -67,44 +67,18 @@ func LowerFirst(s string) string {
 	return string(r) + s[size:]
 }
 
-// PadEnd pads string on the right side if it's shorter than size.
-// Padding characters are truncated if they exceed size.
-// Play: https://go.dev/play/p/9xP8rN0vz--
-func PadEnd(source string, size int, padStr string) string {
-	len1 := len(source)
-	len2 := len(padStr)
-
-	if len1 >= size {
-		return source
-	}
-
-	fill := ""
-	if len2 >= size-len1 {
-		fill = padStr[0 : size-len1]
-	} else {
-		fill = strings.Repeat(padStr, size-len1)
-	}
-	return source + fill[0:size-len1]
-}
-
 // PadStart pads string on the left side if it's shorter than size.
 // Padding characters are truncated if they exceed size.
 // Play: https://go.dev/play/p/xpTfzArDfvT
 func PadStart(source string, size int, padStr string) string {
-	len1 := len(source)
-	len2 := len(padStr)
+	return padAtPosition(source, size, padStr, 1)
+}
 
-	if len1 >= size {
-		return source
-	}
-
-	fill := ""
-	if len2 >= size-len1 {
-		fill = padStr[0 : size-len1]
-	} else {
-		fill = strings.Repeat(padStr, size-len1)
-	}
-	return fill[0:size-len1] + source
+// PadEnd pads string on the right side if it's shorter than size.
+// Padding characters are truncated if they exceed size.
+// Play: https://go.dev/play/p/9xP8rN0vz--
+func PadEnd(source string, size int, padStr string) string {
+	return padAtPosition(source, size, padStr, 2)
 }
 
 // KebabCase coverts string to kebab-case, non letters and numbers will be ignored.
diff --git a/strutil/string_internal.go b/strutil/string_internal.go
index 2d4b54c..9ae2920 100644
--- a/strutil/string_internal.go
+++ b/strutil/string_internal.go
@@ -98,3 +98,40 @@ func toUpperAll(rs []rune) []rune {
 	}
 	return rs
 }
+
+// padWithPosition pads string
+func padAtPosition(str string, length int, padStr string, position int) string {
+	if len(str) >= length {
+		return str
+	}
+
+	if padStr == "" {
+		padStr = " "
+	}
+
+	length = length - len(str)
+	startPadLen := 0
+	if position == 0 {
+		startPadLen = length / 2
+	} else if position == 1 {
+		startPadLen = length
+	}
+	endPadLen := length - startPadLen
+
+	charLen := len(padStr)
+	leftPad := ""
+	cur := 0
+	for cur < startPadLen {
+		leftPad += string(padStr[cur%charLen])
+		cur++
+	}
+
+	cur = 0
+	rightPad := ""
+	for cur < endPadLen {
+		rightPad += string(padStr[cur%charLen])
+		cur++
+	}
+
+	return leftPad + str + rightPad
+}
diff --git a/strutil/string_test.go b/strutil/string_test.go
index 26ef3fd..6682ebc 100644
--- a/strutil/string_test.go
+++ b/strutil/string_test.go
@@ -171,6 +171,7 @@ func TestLowerFirst(t *testing.T) {
 func TestPadEnd(t *testing.T) {
 	assert := internal.NewAssert(t, "TestPadEnd")
 
+	assert.Equal("a ", PadEnd("a", 2, " "))
 	assert.Equal("a", PadEnd("a", 1, "b"))
 	assert.Equal("ab", PadEnd("a", 2, "b"))
 	assert.Equal("abcdmn", PadEnd("abcd", 6, "mno"))