/
renderer.go
201 lines (184 loc) · 5.07 KB
/
renderer.go
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// Package gemini contains an implementation of markdown => text/gemini
// renderer for github.com/gomarkdown/markdown.
package gemini
import (
"io"
"github.com/gomarkdown/markdown/ast"
)
var (
lineBreak = []byte{'\n'}
lineBreakByte byte = 0x0a
space = []byte{' '}
linkPrefix = []byte("=> ")
quotePrefix = []byte("> ")
)
// Renderer implements markdown.Renderer.
type Renderer struct{}
// NewRenderer returns a new Renderer.
func NewRenderer() Renderer {
return Renderer{}
}
func (r Renderer) link(w io.Writer, node *ast.Link, entering bool) {
if entering {
w.Write(linkPrefix)
w.Write(node.Destination)
if node.Title != nil {
w.Write(space)
w.Write(node.Title)
}
}
}
func (r Renderer) linkText(w io.Writer, node *ast.Link) {
for _, text := range node.Children {
// TODO: Renderer.linkText: link can contain subblocks
if l := text.AsLeaf(); l != nil {
w.Write(l.Literal)
}
}
}
func (r Renderer) imageText(w io.Writer, node *ast.Image) {
for _, text := range node.Children {
// TODO: Renderer.imageText: link can contain subblocks
if l := text.AsLeaf(); l != nil {
w.Write(l.Literal)
}
}
}
func (r Renderer) image(w io.Writer, node *ast.Image, entering bool) {
if entering {
w.Write(linkPrefix)
w.Write(node.Destination)
for _, sub := range node.Container.Children {
if l := sub.AsLeaf(); l != nil {
// TODO: Renderer.image: Markdown technically allows for
// links inside image titles, yet to think out how to
// render that :thinking:
w.Write(space)
w.Write(l.Literal)
}
}
}
}
func (r Renderer) blockquote(w io.Writer, node *ast.BlockQuote, entering bool) {
// TODO: Renderer.blockquote: needs support for subnode rendering;
// ideally to be merged with paragraph
if entering {
w.Write(quotePrefix)
if para, ok := node.Children[0].(*ast.Paragraph); ok {
for _, subnode := range para.Children {
if l := subnode.AsLeaf(); l != nil {
// TODO: Renderer.blockquote: rendering by byte is asking
// for optimizations
for _, b := range l.Literal {
w.Write([]byte{b})
if b == lineBreakByte {
w.Write(quotePrefix)
}
}
}
}
}
} else {
w.Write(lineBreak)
w.Write(lineBreak)
}
}
func (r Renderer) heading(w io.Writer, node *ast.Heading, entering bool) {
if entering {
// pad headings with the relevant number of #-s
heading := make([]byte, node.Level+1)
heading[len(heading)-1] = ' '
for i := 0; i < len(heading)-1; i++ {
heading[i] = '#'
}
w.Write(heading)
for _, text := range node.Children {
w.Write(text.AsLeaf().Literal)
}
} else {
w.Write(lineBreak)
w.Write(lineBreak)
}
}
func (r Renderer) paragraph(w io.Writer, node *ast.Paragraph, entering bool) {
if entering {
linkStack := make([]ast.Node, 0, len(node.Children))
onlyElement := len(node.Children) == 1
for _, child := range node.Children {
// only render links text in the paragraph if they're
// combined with some other text on page
if link, ok := child.(*ast.Link); ok {
if !(len(link.Children) > 1) && !onlyElement {
r.linkText(w, link)
}
linkStack = append(linkStack, link)
}
if image, ok := child.(*ast.Image); ok {
if !(len(image.Children) > 1) && !onlyElement {
r.imageText(w, image)
}
linkStack = append(linkStack, image)
}
if text, ok := child.(*ast.Text); ok {
r.text(w, text)
}
}
// render a links block after paragraph
if len(linkStack) > 0 {
w.Write(lineBreak)
w.Write(lineBreak)
for _, link := range linkStack {
if link, ok := link.(*ast.Link); ok {
r.link(w, link, true)
}
if image, ok := link.(*ast.Image); ok {
r.image(w, image, true)
}
w.Write(lineBreak)
}
}
} else {
w.Write(lineBreak)
w.Write(lineBreak)
}
}
func (r Renderer) code(w io.Writer, node *ast.Code, entering bool) {
// TODO: Renderer.code: no good way to test that yet
if entering {
w.Write([]byte("```\n"))
w.Write(node.Content)
} else {
w.Write([]byte("```\n\n"))
}
}
func (r Renderer) text(w io.Writer, node *ast.Text) {
w.Write(node.Literal)
}
// RenderNode implements Renderer.RenderNode().
func (r Renderer) RenderNode(w io.Writer, node ast.Node, entering bool) ast.WalkStatus {
// despite most of the subroutines here accepting entering, most of
// them don't really need an extra pass
switch node := node.(type) {
case *ast.BlockQuote:
r.blockquote(w, node, entering)
case *ast.Heading:
r.heading(w, node, entering)
case *ast.Paragraph:
// blockquote wraps paragraphs which makes for an extra render
if _, parentIsBlockQuote := node.Parent.(*ast.BlockQuote); !parentIsBlockQuote {
r.paragraph(w, node, entering)
}
case *ast.Code:
// TODO: *ast.Code render is likely to be merged into paragraph
r.code(w, node, entering)
}
return ast.GoToNext
}
// RenderHeader implements Renderer.RenderHeader().
func (r Renderer) RenderHeader(w io.Writer, node ast.Node) {
// likely doesn't need any code
}
// RenderFooter implements Renderer.RenderFooter().
func (r Renderer) RenderFooter(w io.Writer, node ast.Node) {
// likely doesn't need any code either
}