textfmt/markdown.go

package textfmt

import (
	"bytes"
	"errors"
	"fmt"
	"io"
	"slices"
	"strings"
)

func escapeMarkdown(s string, additional ...rune) string {
	var (
		rr                                    []rune
		isNumberOnNewLine                     bool
		isLinkOpen, isLinkClosed, isLinkLabel bool
	)

	isNewLine := true
	r := []rune(s)
	for _, ri := range r {
		switch ri {
		case '\\', '`', '*', '_', '[', ']', '#', '<', '>':
			rr = append(rr, '\\', ri)
		default:
			switch {
			case isNewLine:
				switch ri {
				case '+', '-':
					rr = append(rr, '\\', ri)
				default:
					rr = append(rr, ri)
				}
			case isNumberOnNewLine:
				switch ri {
				case '.':
					rr = append(rr, '\\', ri)
				default:
					rr = append(rr, ri)
				}
			case isLinkClosed:
				switch ri {
				case '(':
					rr = append(rr, '\\', ri)
				default:
					rr = append(rr, ri)
				}
			case isLinkLabel:
				switch ri {
				case ')':
					rr = append(rr, '\\', ri)
				default:
					rr = append(rr, ri)
				}
			default:
				if slices.Contains(additional, ri) {
					rr = append(rr, '\\', ri)
				} else {
					rr = append(rr, ri)
				}
			}
		}

		isNumberOnNewLine = (isNewLine || isNumberOnNewLine) && ri >= '0' && ri <= '9'
		isNewLine = ri == '\n'
		isLinkOpen = !isLinkLabel && ri == '[' || isLinkOpen && ri != ']'
		isLinkClosed = isLinkOpen && ri == ']'
		isLinkLabel = isLinkClosed && ri == '(' || isLinkLabel && ri != ')'
	}

	return string(rr)
}

func mdTextToString(text Txt) (string, error) {
	var b bytes.Buffer
	w := mdWriter{w: &b, internal: true}
	renderMDText(&w, text)
	if w.err != nil {
		return "", w.err
	}

	return b.String(), nil
}

func mdCellTexts(rows []TableRow) ([][]string, error) {
	var texts [][]string
	for _, row := range rows {
		var rowTexts []string
		for _, cell := range row.cells {
			txt, err := mdTextToString(cell.text)
			if err != nil {
				return nil, err
			}

			rowTexts = append(rowTexts, txt)
		}

		texts = append(texts, rowTexts)
	}

	return texts, nil
}

func mdEnsureHeaderTexts(h []string) []string {
	var hh []string
	for _, t := range h {
		if strings.TrimSpace(t) == "" {
			t = "\\-"
		}

		hh = append(hh, t)
	}

	return hh
}

func renderMDText(w writer, text Txt) {
	if len(text.cat) > 0 {
		for i, tc := range text.cat {
			if i > 0 {
				w.write(" ")
			}

			renderMDText(w, tc)
		}

		return
	}

	text.text = singleLine(text.text)
	text.text = escapeMarkdown(text.text)
	text.link = singleLine(text.link)
	text.link = escapeMarkdown(text.link)
	if text.bold {
		w.write("**")
	}

	if text.italic {
		w.write("_")
	}

	defer func() {
		if text.italic {
			w.write("_")
		}

		if text.bold {
			w.write("**")
		}
	}()

	if text.link != "" {
		if text.text != "" {
			w.write("[")
			w.write(text.text)
			w.write("](")
			w.write(text.link)
			w.write(")")
			return
		}

		w.write(text.link)
		return
	}

	w.write(text.text)
}

func renderMDTitle(w writer, e Entry) {
	hashes := e.titleLevel + 1
	if hashes > 6 {
		hashes = 6
	}

	w.write(timesn("#", hashes), " ")
	renderMDText(w, e.text)
}

func renderMDParagraphIndent(w writer, e Entry) {
	txt, err := mdTextToString(e.text)
	if err != nil {
		w.setErr(err)
	}

	indentFirst := e.indent + e.indentFirst
	if e.wrapWidth > 0 {
		txt = wrap(txt, e.wrapWidth, indentFirst, e.indent)
	}

	writeLines(w, txt, indentFirst, e.indent)
}

func renderMDParagraph(w writer, e Entry) {
	e.indent = 0
	e.indentFirst = 0
	renderMDParagraphIndent(w, e)
}

func renderMDList(w writer, e Entry) {
	e.indent = 2
	e.indentFirst = -2
	if e.wrapWidth > 2 {
		e.wrapWidth -= 2
	}

	for i, item := range e.items {
		if i > 0 {
			w.write("\n")
		}

		w.write("- ")
		p := itemToParagraph(e, item.text)
		renderMDParagraphIndent(w, p)
	}
}

func renderMDNumberedList(w writer, e Entry) {
	maxDigits := numDigits(len(e.items))
	e.indent = maxDigits + 2
	e.indentFirst = 0 - maxDigits - 2
	if e.wrapWidth > maxDigits+2 {
		e.wrapWidth -= maxDigits + 2
	}

	for i, item := range e.items {
		if i > 0 {
			w.write("\n")
		}

		w.write(padRight(fmt.Sprintf("%d.", i+1), maxDigits+2))
		p := itemToParagraph(e, item.text)
		renderMDParagraphIndent(w, p)
	}
}

func renderMDDefinitions(w writer, e Entry) {
	for _, d := range e.definitions {
		e.items = append(
			e.items,
			Item(Cat(Text(fmt.Sprintf("%s:", d.name.text)), d.value)),
		)
	}

	renderMDList(w, e)
}

func renderMDNumberedDefinitions(w writer, e Entry) {
	for _, d := range e.definitions {
		e.items = append(
			e.items,
			Item(Cat(Text(fmt.Sprintf("%s:", d.name.text)), d.value)),
		)
	}

	renderMDNumberedList(w, e)
}

func renderMDTable(w writer, e Entry) {
	e.rows = normalizeTable(e.rows)
	e.rows = ensureHeader(e.rows)
	if len(e.rows) == 0 || len(e.rows[0].cells) == 0 {
		return
	}

	headerTexts, err := mdCellTexts(e.rows[:1])
	if err != nil {
		w.setErr(err)
		return
	}

	cellTexts, err := mdCellTexts(e.rows[1:])
	if err != nil {
		w.setErr(err)
		return
	}

	headerTexts[0] = mdEnsureHeaderTexts(headerTexts[0])
	columns := columnWidths(headerTexts)
	cellColumns := columnWidths(cellTexts)
	if len(cellColumns) > 0 {
		for i := range columns {
			if cellColumns[i] > columns[i] {
				columns[i] = cellColumns[i]
			}
		}
	}

	w.write("|")
	for i, h := range headerTexts[0] {
		w.write(" ", padRight(h, columns[i]))
		w.write(" |")
	}

	w.write("\n|")
	for _, c := range columns {
		w.write(timesn("-", c+1))
		w.write("-|")
	}

	for _, row := range cellTexts {
		w.write("\n|")
		for i, cell := range row {
			w.write(" ", padRight(cell, columns[i]))
			w.write(" |")
		}
	}
}

func renderMDCode(w writer, e Entry) {
	w.write("```\n")
	w.write(e.text.text)
	w.write("\n```")
}

func renderMDMultiple(w writer, s SyntaxItem) {
	s.topLevel = false
	s.multiple = false
	renderMDSyntaxItem(w, s)
	w.write("...")
}

func renderMDRequired(w writer, s SyntaxItem) {
	s.delimited = true
	s.topLevel = false
	s.required = false
	w.write("<")
	renderMDSyntaxItem(w, s)
	w.write(">")
}

func renderMDOptional(w writer, s SyntaxItem) {
	s.delimited = true
	s.topLevel = false
	s.optional = false
	w.write("[")
	renderMDSyntaxItem(w, s)
	w.write("]")
}

func renderMDSequence(w writer, s SyntaxItem) {
	if !s.delimited && !s.topLevel {
		w.write("(")
	}

	for i, item := range s.sequence {
		if i > 0 {
			w.write(" ")
		}

		item.delimited = false
		renderMDSyntaxItem(w, item)
	}

	if !s.delimited && !s.topLevel {
		w.write(")")
	}
}

func renderMDChoice(w writer, s SyntaxItem) {
	if !s.delimited && !s.topLevel {
		w.write("(")
	}

	for i, item := range s.choice {
		if i > 0 {
			separator := "|"
			if s.topLevel {
				separator = "\n"
			}

			w.write(separator)
		}

		item.delimited = false
		renderMDSyntaxItem(w, item)
	}

	if !s.delimited && !s.topLevel {
		w.write(")")
	}
}

func renderMDSymbol(w writer, s SyntaxItem) {
	w.write(escapeTeletype(s.symbol))
}

func renderMDSyntaxItem(w writer, s SyntaxItem) {
	switch {

	// foo...
	case s.multiple:
		renderMDMultiple(w, s)

	// <foo>
	case s.required:
		renderMDRequired(w, s)

	// [foo]
	case s.optional:
		renderMDOptional(w, s)

	// foo bar baz or (foo bar baz)
	case len(s.sequence) > 0:
		renderMDSequence(w, s)

	// foo|bar|baz or (foo|bar|baz)
	case len(s.choice) > 0:
		renderMDChoice(w, s)

	// foo
	default:
		renderMDSymbol(w, s)
	}
}

func renderMDSyntax(w writer, e Entry) {
	s := e.syntax
	s.topLevel = true
	w.write("```\n")
	renderMDSyntaxItem(w, s)
	w.write("\n```")
}

func renderMarkdown(out io.Writer, d Document) error {
	w := mdWriter{w: out}
	for i, e := range d.entries {
		if i > 0 {
			w.write("\n\n")
		}

		switch e.typ {
		case invalid:
			return errors.New("invalid entry")
		case title:
			renderMDTitle(&w, e)
		case paragraph:
			renderMDParagraph(&w, e)
		case list:
			renderMDList(&w, e)
		case numberedList:
			renderMDNumberedList(&w, e)
		case definitions:
			renderMDDefinitions(&w, e)
		case numberedDefinitions:
			renderMDNumberedDefinitions(&w, e)
		case table:
			renderMDTable(&w, e)
		case code:
			renderMDCode(&w, e)
		case syntax:
			renderMDSyntax(&w, e)
		}
	}

	if len(d.entries) > 0 {
		w.write("\n")
	}

	return w.err
}