55 lines
1.4 KiB
Go
55 lines
1.4 KiB
Go
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package main
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import (
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"bytes"
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"io"
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"strings"
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"unicode"
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"unicode/utf8"
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)
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// isTitle returns the title level if the lines seem to form a title,
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// zero otherwise. Input lines may inclide trailing newlines.
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func isTitle(line1, line2 []byte) int {
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// This is a very naïve method, we should target graphemes (thus at least
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// NFC normalize the lines first) and account for wide characters.
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diff := utf8.RuneCount(line1) - utf8.RuneCount(line2)
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if len(line2) < 2 || diff < -1 || diff > 1 {
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return 0
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}
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// "Don't be fooled by back-to-back delimited blocks."
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// Still gets fooled by other things, though.
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if bytes.IndexFunc(line1, func(r rune) bool {
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return unicode.IsLetter(r) || unicode.IsNumber(r)
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}) < 0 {
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return 0
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}
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// The underline must be homogenous.
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for _, r := range bytes.TrimRight(line2, "\r\n") {
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if r != line2[0] {
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return 0
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}
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}
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return 1 + strings.IndexByte("=-~^+", line2[0])
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}
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func writeLine(w *io.PipeWriter, cur, next []byte) []byte {
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if level := isTitle(cur, next); level > 0 {
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w.Write(append(bytes.Repeat([]byte{'='}, level), ' '))
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next = nil
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}
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w.Write(cur)
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return next
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}
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// ConvertTitles converts AsciiDoc two-line (underlined) titles to single-line.
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func ConvertTitles(w *io.PipeWriter, input []byte) {
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var last []byte
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for _, cur := range bytes.SplitAfter(input, []byte{'\n'}) {
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last = writeLine(w, last, cur)
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}
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writeLine(w, last, nil)
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}
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