Merge pull request #5 from bbrks/add-prefix-and-suffix-support

Add prefix and suffix support

Author: bbrks

wrap.go

@@ -17,21 +17,46 @@ type Wrapper struct {
 	// Newline defines which characters should be used to split and create new lines.
 	// Default: "\n"
 	Newline string
+
+	// OutputLinePrefix is prepended to any output lines. This can be useful
+	// for wrapping code-comments and prefixing new lines with "// ".
+	// Default: ""
+	OutputLinePrefix string
+
+	// OutputLineSuffix is appended to any output lines.
+	// Default: ""
+	OutputLineSuffix string
+
+	// LimitIncludesPrefixSuffix can be set to false if you don't want prefixes
+	// and suffixes to be included in the length limits.
+	// Default: true
+	LimitIncludesPrefixSuffix bool
+
+	// TrimPrefix can be set to remove a prefix on each input line.
+	// This can be paired up with OutputPrefix to create a block of C-style
+	// comments (/* * */ ) from a long single-line comment.
+	// Default: ""
+	TrimInputPrefix string
+
+	// TrimSuffix can be set to remove a suffix on each input line.
+	// Default: ""
+	TrimInputSuffix string
 }
 
 // NewWrapper returns a new instance of a Wrapper initialised with defaults.
 func NewWrapper() Wrapper {
 	return Wrapper{
-		Breakpoints: defaultBreakpoints,
-		Newline:     defaultNewline,
+		Breakpoints:               defaultBreakpoints,
+		Newline:                   defaultNewline,
+		LimitIncludesPrefixSuffix: true,
 	}
 }
 
 // line will wrap a single line of text at the given length.
-// If limit is less than 1, the string remains unchanged.
+// If limit is less than 1, the string remains unwrapped.
 func (w Wrapper) line(s string, limit int) string {
 	if limit < 1 || len(s) < limit {
-		return s
+		return w.OutputLinePrefix + s + w.OutputLineSuffix
 	}
 
 	// Find the index of the last breakpoint within the limit.
@@ -42,20 +67,30 @@ func (w Wrapper) line(s string, limit int) string {
 		i = strings.IndexAny(s, w.Breakpoints)
 		// Nothing left to do!
 		if i < 0 {
-			return s
+			return w.OutputLinePrefix + s + w.OutputLineSuffix
 		}
 	}
 
 	// Recurse until we have nothing left to do.
-	return s[:i] + w.Newline + w.line(s[i+1:], limit)
+	return w.OutputLinePrefix + s[:i] + w.OutputLineSuffix + w.Newline + w.line(s[i+1:], limit)
 }
 
 // Wrap will wrap one or more lines of text at the given length.
-// If limit is less than 1, the string remains unchanged.
+// If limit is less than 1, the string remains unwrapped.
 func (w Wrapper) Wrap(s string, limit int) string {
+
+	// Subtract the length of the prefix and suffix from the limit
+	// so we don't break length limits when using them.
+	if w.LimitIncludesPrefixSuffix {
+		limit -= len(w.OutputLinePrefix) + len(w.OutputLineSuffix)
+	}
+
 	var ret string
 	for _, str := range strings.Split(s, w.Newline) {
+		str = strings.TrimPrefix(str, w.TrimInputPrefix)
+		str = strings.TrimSuffix(str, w.TrimInputSuffix)
 		ret += w.line(str, limit) + w.Newline
 	}
+
 	return ret
 }

wrap_test.go

@@ -21,6 +21,7 @@ var loremIpsums = []string{
 	"Curabitur tellus libero, feugiat vel mauris et, consequat auctor ipsum. Praesent sed pharetra dolor, at convallis lectus. Vivamus at ullamcorper sem. Sed euismod vel massa a dignissim. Proin auctor nibh at pretium facilisis. Ut aliquam erat lacus. Integer sit amet magna urna. Maecenas bibendum pretium mauris convallis semper. Nunc arcu tortor, pulvinar quis eros ut, mattis placerat tortor. Sed et lacus magna. Proin ultrices fermentum sem et placerat. Donec eget sapien mi. Maecenas maximus justo sed vulputate pulvinar. Class aptent taciti sociosqu ad litora torquent per conubia nostra, per inceptos himenaeos. Vestibulum accumsan, sapien sit amet suscipit dignissim, velit velit maximus elit, a cursus mi odio eu magna. Nunc nec fermentum nisi, non imperdiet purus.",
 	"Vestibulum convallis magna arcu, sagittis porta mi luctus sit amet. Nunc tellus magna, fermentum et mi vitae, consectetur vestibulum nulla. Fusce ornare, augue vitae tempor pellentesque, orci orci fringilla tortor, porta feugiat justo purus nec sem. Interdum et malesuada fames ac ante ipsum primis in faucibus. Nulla pellentesque sed odio in aliquam. Fusce sed molestie velit. Curabitur id quam ac felis accumsan vehicula quis in ex.",
 	"Duis ac ornare erat. Nulla in odio eget ante tristique dignissim a non erat. Sed non nisi vitae arcu dapibus porta vitae dignissim ante. Cras et fringilla turpis. Maecenas arcu nibh, tempus euismod pretium eget, hendrerit vitae arcu. Sed vel dolor quam. Etiam consequat sed dolor ut elementum. Quisque dictum tempor pretium. Sed eu sollicitudin mi, in commodo ante.",
+	"",
 }
 
 func TestWrapper_Wrap(t *testing.T) {
@@ -229,3 +230,24 @@ The girl was accident-prone, good-looking, quick-thinking, carbon-neutral, bad-t
 	// The girl was accident-prone, good-looking, quick-thinking, carbon-neutral, bad
 	// tempered, sport-mad, fair-haired, camera-ready, and finally open-mouthed.
 }
+
+func ExampleWrapper_Wrap_prefix() {
+	var loremIpsum = "/* Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed vulputate quam nibh, et faucibus enim gravida vel. Integer bibendum lectus et erat semper fermentum quis a risus. Fusce dignissim tempus metus non pretium. Nunc sagittis magna nec purus porttitor mollis. Pellentesque feugiat quam eget laoreet aliquet. Donec gravida congue massa, et sollicitudin turpis lacinia a. Fusce non tortor magna. Cras vel finibus tellus. */"
+
+	// Trim the single-line block comment symbols from each input line.
+	w.TrimInputPrefix = "/* "
+	w.TrimInputSuffix = " */"
+
+	// Prefix each new line with a single-line comment symbol.
+	w.OutputLinePrefix = "// "
+
+	// Wrap when lines exceed 80 chars.
+	fmt.Println(w.Wrap(loremIpsum, 80))
+	// Output:
+	// // Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed vulputate quam
+	// // nibh, et faucibus enim gravida vel. Integer bibendum lectus et erat semper
+	// // fermentum quis a risus. Fusce dignissim tempus metus non pretium. Nunc
+	// // sagittis magna nec purus porttitor mollis. Pellentesque feugiat quam eget
+	// // laoreet aliquet. Donec gravida congue massa, et sollicitudin turpis lacinia
+	// // a. Fusce non tortor magna. Cras vel finibus tellus.
+}