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// Package wordwrap provides methods for wrapping the contents of a string
package wordwrap
import (
"bytes"
"github.com/mattn/go-runewidth"
"unicode"
)
// WrapString wraps the given string within lim width in characters.
//
// Wrapping is currently naive and only happens at white-space. A future
// version of the library will implement smarter wrapping. This means that
// pathological cases can dramatically reach past the limit, such as a very
// long word.
func WrapString(s string, lim uint) string {
// Initialize a buffer with a slightly larger size to account for breaks
init := make([]byte, 0, len(s))
buf := bytes.NewBuffer(init)
var current uint
var wordBuf, spaceBuf bytes.Buffer
var wordWidth, spaceWidth int
for _, char := range s {
if char == '\n' {
if wordBuf.Len() == 0 {
if current+uint(spaceWidth) > lim {
current = 0
} else {
current += uint(spaceWidth)
spaceBuf.WriteTo(buf)
spaceWidth += runewidth.StringWidth(buf.String())
}
spaceBuf.Reset()
spaceWidth = 0
} else {
current += uint(spaceWidth + wordWidth)
spaceBuf.WriteTo(buf)
spaceBuf.Reset()
wordBuf.WriteTo(buf)
wordBuf.Reset()
spaceWidth = 0
wordWidth = 0
}
buf.WriteRune(char)
current = 0
} else if unicode.IsSpace(char) {
if spaceBuf.Len() == 0 || wordBuf.Len() > 0 {
current += uint(spaceWidth + wordWidth)
spaceBuf.WriteTo(buf)
spaceBuf.Reset()
wordBuf.WriteTo(buf)
wordBuf.Reset()
spaceWidth = 0
wordWidth = 0
}
spaceBuf.WriteRune(char)
spaceWidth += runewidth.RuneWidth(char)
} else {
wordBuf.WriteRune(char)
wordWidth += runewidth.RuneWidth(char)
if current+uint(spaceWidth+wordWidth) > lim && uint(wordWidth) < lim {
buf.WriteRune('\n')
current = 0
spaceBuf.Reset()
spaceWidth = 0
}
}
}
if wordBuf.Len() == 0 {
if current+uint(spaceWidth) <= lim {
spaceBuf.WriteTo(buf)
}
} else {
spaceBuf.WriteTo(buf)
wordBuf.WriteTo(buf)
}
return buf.String()
}
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