mox!

vendor/github.com/mjl-/xfmt/xfmt.go

@@ -0,0 +1,207 @@
+// Package xfmt reformats text, wrapping it while recognizing comments.
+package xfmt
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"strings"
+)
+
+// Config tells format how to reformat text.
+type Config struct {
+	MaxWidth      int      // Max width of content (excluding indenting), after which lines are wrapped.
+	BreakPrefixes []string // String prefixes that cause a line to break, instead of being merged into the previous line.
+}
+
+// Format reads text from r and writes reformatted text to w, according to
+// instructions in config. Lines ending with \r\n are formatted with \r\n as well.
+func Format(w io.Writer, r io.Reader, config Config) error {
+	f := &formatter{
+		in:     bufio.NewReader(r),
+		out:    bufio.NewWriter(w),
+		config: config,
+	}
+	return f.format()
+}
+
+type formatter struct {
+	in         *bufio.Reader
+	out        *bufio.Writer
+	config     Config
+	curLine    string
+	curLineend string
+}
+
+type parseError error
+
+func (f *formatter) format() (rerr error) {
+	defer func() {
+		e := recover()
+		if e != nil {
+			if pe, ok := e.(parseError); ok {
+				rerr = pe
+			} else {
+				panic(e)
+			}
+		}
+	}()
+
+	for {
+		line, end := f.gatherLine()
+		if line == "" && end == "" {
+			break
+		}
+		prefix, rem := parseLine(line)
+		for _, s := range f.splitLine(rem) {
+			f.write(prefix)
+			f.write(s)
+			f.write(end)
+		}
+	}
+	return f.out.Flush()
+
+}
+
+func (f *formatter) check(err error, action string) {
+	if err != nil {
+		panic(parseError(fmt.Errorf("%s: %s", action, err)))
+	}
+}
+
+func (f *formatter) write(s string) {
+	_, err := f.out.Write([]byte(s))
+	f.check(err, "write")
+}
+
+func (f *formatter) peekLine() (string, string) {
+	if f.curLine != "" || f.curLineend != "" {
+		return f.curLine, f.curLineend
+	}
+
+	line, err := f.in.ReadString('\n')
+	if err != io.EOF {
+		f.check(err, "read")
+	}
+	if line == "" {
+		return "", ""
+	}
+	if strings.HasSuffix(line, "\r\n") {
+		f.curLine, f.curLineend = line[:len(line)-2], "\r\n"
+	} else if strings.HasSuffix(line, "\n") {
+		f.curLine, f.curLineend = line[:len(line)-1], "\n"
+	} else {
+		f.curLine, f.curLineend = line, ""
+	}
+	return f.curLine, f.curLineend
+}
+
+func (f *formatter) consumeLine() {
+	if f.curLine == "" && f.curLineend == "" {
+		panic("bad")
+	}
+	f.curLine = ""
+	f.curLineend = ""
+}
+
+func (f *formatter) gatherLine() (string, string) {
+	var curLine, curLineend string
+	var curPrefix string
+
+	for {
+		line, end := f.peekLine()
+		if line == "" && end == "" {
+			break
+		}
+		if curLine == "" {
+			curLineend = end
+		}
+		prefix, rem := parseLine(line)
+		if prefix == "" && rem == "" {
+			if curLine == "" {
+				f.consumeLine()
+			}
+			break
+		}
+		if curLine != "" && (curPrefix != prefix || rem == "" || f.causeBreak(rem)) {
+			break
+		}
+		curPrefix = prefix
+		if curLine != "" {
+			curLine += " "
+		}
+		curLine += rem
+		f.consumeLine()
+		// Control at begin or end of line are not merged.
+		if curLine != "" && curLine[len(curLine)-1] < 0x20 {
+			break
+		}
+	}
+
+	return curPrefix + curLine, curLineend
+}
+
+func (f *formatter) causeBreak(s string) bool {
+	c := s[0]
+	if c < 0x20 {
+		return true
+	}
+	for _, ss := range f.config.BreakPrefixes {
+		if strings.HasPrefix(s, ss) {
+			return true
+		}
+	}
+
+	// Don't merge lines starting with eg "1. ".
+	for i, c := range s {
+		if c >= '0' && c <= '9' {
+			continue
+		}
+		if i > 0 && c == '.' && strings.HasPrefix(s[i:], ". ") {
+			return true
+		}
+		break
+	}
+	return false
+}
+
+func parseLine(s string) (string, string) {
+	orig := s
+	s = strings.TrimLeft(orig, " \t")
+	prefix := orig[:len(orig)-len(s)]
+	if strings.HasPrefix(s, "//") {
+		prefix += "//"
+		s = s[2:]
+	} else if strings.HasPrefix(s, "#") {
+		prefix += "#"
+		s = s[1:]
+	}
+	ns := strings.TrimLeft(s, " \t")
+	prefix += s[:len(s)-len(ns)]
+	s = ns
+	return prefix, s
+}
+
+func (f *formatter) splitLine(s string) []string {
+	if len(s) <= f.config.MaxWidth {
+		return []string{s}
+	}
+
+	line := ""
+	r := []string{}
+	for _, w := range strings.Split(s, " ") {
+		if line != "" && len(line)+1+len(w) > f.config.MaxWidth {
+			r = append(r, line)
+			line = w
+			continue
+		}
+		if line != "" {
+			line += " "
+		}
+		line += w
+	}
+	if line != "" {
+		r = append(r, line)
+	}
+	return r
+}