generator.go

package parser

import (
	"os"
	"strings"
)

// ToGemtext turns asl into gemtext.
func ToGemtext(asl ASL) string {
	var b strings.Builder

	asl.Visit(func(e Element) {
		switch e.Type() {

		case ElementTypes.Link():
			b.WriteString("=>")
			if e.URL() != "" {
				b.WriteString(" ")
				b.WriteString(e.URL())
			}

		case ElementTypes.Heading():
			switch e.Level() {
			case HeadingLevels.Heading():
				b.WriteString("#")
			case HeadingLevels.SubHeading():
				b.WriteString("##")
			case HeadingLevels.SubSubHeading():
				b.WriteString("###")
			}

		case ElementTypes.List():
			b.WriteString("*")

		case ElementTypes.Quote():
			b.WriteString(">")

		case ElementTypes.PreformatToggle():
			b.WriteString("```")

		}

		if e.Text() != "" &&
			e.Type() != ElementTypes.Text() &&
			e.Type() != ElementTypes.PreformatToggle() {
			b.WriteString(" ")
		}

		b.WriteString(e.Text())
		b.WriteString("\n")
	})

	return b.String()
}

// ToGemtextFile turns asl into gemtext, then writes it into the named file.
// Returns an error if there's an error while writing the file.
func ToGemtextFile(name string, asl ASL, perm os.FileMode) error {
	return os.WriteFile(name, []byte(ToGemtext(asl)), perm)
}

var escaper = strings.NewReplacer(
	"&", "&",
	`"`, """,
	"'", "'",
	"<", "&lt;",
	">", "&gt;",
)

// ToHTML turns asl into HTML.
func ToHTML(asl ASL) string {
	// Possible improvement for later:
	// If preformat block contains code (base this on the alt text), put code
	// inside code element (<pre><code>code</code></pre>) and highlight it using
	// https://github.com/alecthomas/chroma

	var b strings.Builder

	var prev Element = NewText("")
	isPreformattedMode := false
	preformatHasAltText := false

	asl.Visit(func(e Element) {
		if prev.Type() == ElementTypes.List() && e.Type() != ElementTypes.List() {
			b.WriteString("</ul>\n")
		}

		text := escaper.Replace(e.Text())
		switch e.Type() {

		case ElementTypes.Text():
			if isPreformattedMode {
				b.WriteString(text)
				break
			}
			if text == "" {
				b.WriteString("<br />")
			} else {
				b.WriteString("<p>")
				b.WriteString(text)
				b.WriteString("</p>")
			}

		case ElementTypes.Link():
			b.WriteString(`<p><a href="`)
			b.WriteString(e.URL())
			b.WriteString(`">`)
			if text == "" {
				b.WriteString(escaper.Replace(e.URL()))
			} else {
				b.WriteString(text)
			}
			b.WriteString("</a></p>")

		case ElementTypes.Heading():
			var open string
			var close string
			switch e.Level() {
			case HeadingLevels.Heading():
				open = "<h1>"
				close = "</h1>"
			case HeadingLevels.SubHeading():
				open = "<h2>"
				close = "</h2>"
			case HeadingLevels.SubSubHeading():
				open = "<h3>"
				close = "</h3>"
			}
			b.WriteString(open)
			b.WriteString(text)
			b.WriteString(close)

		case ElementTypes.List():
			if prev.Type() != ElementTypes.List() {
				b.WriteString("<ul>\n")
			}
			b.WriteString("<li>")
			b.WriteString(text)
			b.WriteString("</li>")

		case ElementTypes.Quote():
			b.WriteString("<blockquote><p>")
			b.WriteString(text)
			b.WriteString("</p></blockquote>")

		case ElementTypes.PreformatToggle():
			if isPreformattedMode {
				b.WriteString("</pre>")

				if preformatHasAltText {
					b.WriteString("</figure>")
				}
			} else {
				if text != "" {
					b.WriteString("<figure><figcaption>")
					b.WriteString(text)
					b.WriteString("</figcaption>")
				}

				b.WriteString("<pre>")
			}
			isPreformattedMode = !isPreformattedMode
			preformatHasAltText = text != ""

		}

		b.WriteString("\n")
		prev = e
	})

	if prev.Type() == ElementTypes.List() {
		b.WriteString("</ul>\n")
	}

	if isPreformattedMode {
		b.WriteString("</pre>")

		if preformatHasAltText {
			b.WriteString("</figure>")
		}

		b.WriteString("\n")
	}

	return b.String()
}

// ToHTMLFile turns asl into HTML, then writes it into the named file. Returns
// an error if there's an error while writing the file.
func ToHTMLFile(name string, asl ASL, perm os.FileMode) error {
	return os.WriteFile(name, []byte(ToHTML(asl)), perm)
}

// Possible functions to add later:
// ToGemtextBytes
//   Could be more performant
//   Prevents need for []byte conversion in ToGemtextFile
// ToHTMLBytes
//   Could be more performant
//   Prevents need for []byte conversion in ToHTMLFile
// ToMarkdown
//   How should the noncollapsing empty lines in gemtext be translated?
// ToMarkdownBytes
// ToMarkdownFile