1 files changed, 932 insertions, 0 deletions

diff --git a/vendor/github.com/yuin/goldmark/renderer/html/html.go b/vendor/github.com/yuin/goldmark/renderer/html/html.go
new file mode 100644
index 0000000..7bf2ab8
--- /dev/null
+++ b/vendor/github.com/yuin/goldmark/renderer/html/html.go
@@ -0,0 +1,932 @@
+package html
+
+import (
+        "bytes"
+        "fmt"
+        "strconv"
+        "unicode/utf8"
+
+        "github.com/yuin/goldmark/ast"
+        "github.com/yuin/goldmark/renderer"
+        "github.com/yuin/goldmark/util"
+)
+
+// A Config struct has configurations for the HTML based renderers.
+type Config struct {
+        Writer              Writer
+        HardWraps           bool
+        EastAsianLineBreaks bool
+        XHTML               bool
+        Unsafe              bool
+}
+
+// NewConfig returns a new Config with defaults.
+func NewConfig() Config {
+        return Config{
+                Writer:              DefaultWriter,
+                HardWraps:           false,
+                EastAsianLineBreaks: false,
+                XHTML:               false,
+                Unsafe:              false,
+        }
+}
+
+// SetOption implements renderer.NodeRenderer.SetOption.
+func (c *Config) SetOption(name renderer.OptionName, value interface{}) {
+        switch name {
+        case optHardWraps:
+                c.HardWraps = value.(bool)
+        case optEastAsianLineBreaks:
+                c.EastAsianLineBreaks = value.(bool)
+        case optXHTML:
+                c.XHTML = value.(bool)
+        case optUnsafe:
+                c.Unsafe = value.(bool)
+        case optTextWriter:
+                c.Writer = value.(Writer)
+        }
+}
+
+// An Option interface sets options for HTML based renderers.
+type Option interface {
+        SetHTMLOption(*Config)
+}
+
+// TextWriter is an option name used in WithWriter.
+const optTextWriter renderer.OptionName = "Writer"
+
+type withWriter struct {
+        value Writer
+}
+
+func (o *withWriter) SetConfig(c *renderer.Config) {
+        c.Options[optTextWriter] = o.value
+}
+
+func (o *withWriter) SetHTMLOption(c *Config) {
+        c.Writer = o.value
+}
+
+// WithWriter is a functional option that allow you to set the given writer to
+// the renderer.
+func WithWriter(writer Writer) interface {
+        renderer.Option
+        Option
+} {
+        return &withWriter{writer}
+}
+
+// HardWraps is an option name used in WithHardWraps.
+const optHardWraps renderer.OptionName = "HardWraps"
+
+type withHardWraps struct {
+}
+
+func (o *withHardWraps) SetConfig(c *renderer.Config) {
+        c.Options[optHardWraps] = true
+}
+
+func (o *withHardWraps) SetHTMLOption(c *Config) {
+        c.HardWraps = true
+}
+
+// WithHardWraps is a functional option that indicates whether softline breaks
+// should be rendered as '<br>'.
+func WithHardWraps() interface {
+        renderer.Option
+        Option
+} {
+        return &withHardWraps{}
+}
+
+// EastAsianLineBreaks is an option name used in WithEastAsianLineBreaks.
+const optEastAsianLineBreaks renderer.OptionName = "EastAsianLineBreaks"
+
+type withEastAsianLineBreaks struct {
+}
+
+func (o *withEastAsianLineBreaks) SetConfig(c *renderer.Config) {
+        c.Options[optEastAsianLineBreaks] = true
+}
+
+func (o *withEastAsianLineBreaks) SetHTMLOption(c *Config) {
+        c.EastAsianLineBreaks = true
+}
+
+// WithEastAsianLineBreaks is a functional option that indicates whether softline breaks
+// between east asian wide characters should be ignored.
+func WithEastAsianLineBreaks() interface {
+        renderer.Option
+        Option
+} {
+        return &withEastAsianLineBreaks{}
+}
+
+// XHTML is an option name used in WithXHTML.
+const optXHTML renderer.OptionName = "XHTML"
+
+type withXHTML struct {
+}
+
+func (o *withXHTML) SetConfig(c *renderer.Config) {
+        c.Options[optXHTML] = true
+}
+
+func (o *withXHTML) SetHTMLOption(c *Config) {
+        c.XHTML = true
+}
+
+// WithXHTML is a functional option indicates that nodes should be rendered in
+// xhtml instead of HTML5.
+func WithXHTML() interface {
+        Option
+        renderer.Option
+} {
+        return &withXHTML{}
+}
+
+// Unsafe is an option name used in WithUnsafe.
+const optUnsafe renderer.OptionName = "Unsafe"
+
+type withUnsafe struct {
+}
+
+func (o *withUnsafe) SetConfig(c *renderer.Config) {
+        c.Options[optUnsafe] = true
+}
+
+func (o *withUnsafe) SetHTMLOption(c *Config) {
+        c.Unsafe = true
+}
+
+// WithUnsafe is a functional option that renders dangerous contents
+// (raw htmls and potentially dangerous links) as it is.
+func WithUnsafe() interface {
+        renderer.Option
+        Option
+} {
+        return &withUnsafe{}
+}
+
+// A Renderer struct is an implementation of renderer.NodeRenderer that renders
+// nodes as (X)HTML.
+type Renderer struct {
+        Config
+}
+
+// NewRenderer returns a new Renderer with given options.
+func NewRenderer(opts ...Option) renderer.NodeRenderer {
+        r := &Renderer{
+                Config: NewConfig(),
+        }
+
+        for _, opt := range opts {
+                opt.SetHTMLOption(&r.Config)
+        }
+        return r
+}
+
+// RegisterFuncs implements NodeRenderer.RegisterFuncs .
+func (r *Renderer) RegisterFuncs(reg renderer.NodeRendererFuncRegisterer) {
+        // blocks
+
+        reg.Register(ast.KindDocument, r.renderDocument)
+        reg.Register(ast.KindHeading, r.renderHeading)
+        reg.Register(ast.KindBlockquote, r.renderBlockquote)
+        reg.Register(ast.KindCodeBlock, r.renderCodeBlock)
+        reg.Register(ast.KindFencedCodeBlock, r.renderFencedCodeBlock)
+        reg.Register(ast.KindHTMLBlock, r.renderHTMLBlock)
+        reg.Register(ast.KindList, r.renderList)
+        reg.Register(ast.KindListItem, r.renderListItem)
+        reg.Register(ast.KindParagraph, r.renderParagraph)
+        reg.Register(ast.KindTextBlock, r.renderTextBlock)
+        reg.Register(ast.KindThematicBreak, r.renderThematicBreak)
+
+        // inlines
+
+        reg.Register(ast.KindAutoLink, r.renderAutoLink)
+        reg.Register(ast.KindCodeSpan, r.renderCodeSpan)
+        reg.Register(ast.KindEmphasis, r.renderEmphasis)
+        reg.Register(ast.KindImage, r.renderImage)
+        reg.Register(ast.KindLink, r.renderLink)
+        reg.Register(ast.KindRawHTML, r.renderRawHTML)
+        reg.Register(ast.KindText, r.renderText)
+        reg.Register(ast.KindString, r.renderString)
+}
+
+func (r *Renderer) writeLines(w util.BufWriter, source []byte, n ast.Node) {
+        l := n.Lines().Len()
+        for i := 0; i < l; i++ {
+                line := n.Lines().At(i)
+                r.Writer.RawWrite(w, line.Value(source))
+        }
+}
+
+// GlobalAttributeFilter defines attribute names which any elements can have.
+var GlobalAttributeFilter = util.NewBytesFilter(
+        []byte("accesskey"),
+        []byte("autocapitalize"),
+        []byte("autofocus"),
+        []byte("class"),
+        []byte("contenteditable"),
+        []byte("dir"),
+        []byte("draggable"),
+        []byte("enterkeyhint"),
+        []byte("hidden"),
+        []byte("id"),
+        []byte("inert"),
+        []byte("inputmode"),
+        []byte("is"),
+        []byte("itemid"),
+        []byte("itemprop"),
+        []byte("itemref"),
+        []byte("itemscope"),
+        []byte("itemtype"),
+        []byte("lang"),
+        []byte("part"),
+        []byte("role"),
+        []byte("slot"),
+        []byte("spellcheck"),
+        []byte("style"),
+        []byte("tabindex"),
+        []byte("title"),
+        []byte("translate"),
+)
+
+func (r *Renderer) renderDocument(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
+        // nothing to do
+        return ast.WalkContinue, nil
+}
+
+// HeadingAttributeFilter defines attribute names which heading elements can have
+var HeadingAttributeFilter = GlobalAttributeFilter
+
+func (r *Renderer) renderHeading(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
+        n := node.(*ast.Heading)
+        if entering {
+                _, _ = w.WriteString("<h")
+                _ = w.WriteByte("0123456"[n.Level])
+                if n.Attributes() != nil {
+                        RenderAttributes(w, node, HeadingAttributeFilter)
+                }
+                _ = w.WriteByte('>')
+        } else {
+                _, _ = w.WriteString("</h")
+                _ = w.WriteByte("0123456"[n.Level])
+                _, _ = w.WriteString(">\n")
+        }
+        return ast.WalkContinue, nil
+}
+
+// BlockquoteAttributeFilter defines attribute names which blockquote elements can have
+var BlockquoteAttributeFilter = GlobalAttributeFilter.Extend(
+        []byte("cite"),
+)
+
+func (r *Renderer) renderBlockquote(w util.BufWriter, source []byte, n ast.Node, entering bool) (ast.WalkStatus, error) {
+        if entering {
+                if n.Attributes() != nil {
+                        _, _ = w.WriteString("<blockquote")
+                        RenderAttributes(w, n, BlockquoteAttributeFilter)
+                        _ = w.WriteByte('>')
+                } else {
+                        _, _ = w.WriteString("<blockquote>\n")
+                }
+        } else {
+                _, _ = w.WriteString("</blockquote>\n")
+        }
+        return ast.WalkContinue, nil
+}
+
+func (r *Renderer) renderCodeBlock(w util.BufWriter, source []byte, n ast.Node, entering bool) (ast.WalkStatus, error) {
+        if entering {
+                _, _ = w.WriteString("<pre><code>")
+                r.writeLines(w, source, n)
+        } else {
+                _, _ = w.WriteString("</code></pre>\n")
+        }
+        return ast.WalkContinue, nil
+}
+
+func (r *Renderer) renderFencedCodeBlock(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
+        n := node.(*ast.FencedCodeBlock)
+        if entering {
+                _, _ = w.WriteString("<pre><code")
+                language := n.Language(source)
+                if language != nil {
+                        _, _ = w.WriteString(" class=\"language-")
+                        r.Writer.Write(w, language)
+                        _, _ = w.WriteString("\"")
+                }
+                _ = w.WriteByte('>')
+                r.writeLines(w, source, n)
+        } else {
+                _, _ = w.WriteString("</code></pre>\n")
+        }
+        return ast.WalkContinue, nil
+}
+
+func (r *Renderer) renderHTMLBlock(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
+        n := node.(*ast.HTMLBlock)
+        if entering {
+                if r.Unsafe {
+                        l := n.Lines().Len()
+                        for i := 0; i < l; i++ {
+                                line := n.Lines().At(i)
+                                r.Writer.SecureWrite(w, line.Value(source))
+                        }
+                } else {
+                        _, _ = w.WriteString("<!-- raw HTML omitted -->\n")
+                }
+        } else {
+                if n.HasClosure() {
+                        if r.Unsafe {
+                                closure := n.ClosureLine
+                                r.Writer.SecureWrite(w, closure.Value(source))
+                        } else {
+                                _, _ = w.WriteString("<!-- raw HTML omitted -->\n")
+                        }
+                }
+        }
+        return ast.WalkContinue, nil
+}
+
+// ListAttributeFilter defines attribute names which list elements can have.
+var ListAttributeFilter = GlobalAttributeFilter.Extend(
+        []byte("start"),
+        []byte("reversed"),
+        []byte("type"),
+)
+
+func (r *Renderer) renderList(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
+        n := node.(*ast.List)
+        tag := "ul"
+        if n.IsOrdered() {
+                tag = "ol"
+        }
+        if entering {
+                _ = w.WriteByte('<')
+                _, _ = w.WriteString(tag)
+                if n.IsOrdered() && n.Start != 1 {
+                        fmt.Fprintf(w, " start=\"%d\"", n.Start)
+                }
+                if n.Attributes() != nil {
+                        RenderAttributes(w, n, ListAttributeFilter)
+                }
+                _, _ = w.WriteString(">\n")
+        } else {
+                _, _ = w.WriteString("</")
+                _, _ = w.WriteString(tag)
+                _, _ = w.WriteString(">\n")
+        }
+        return ast.WalkContinue, nil
+}
+
+// ListItemAttributeFilter defines attribute names which list item elements can have.
+var ListItemAttributeFilter = GlobalAttributeFilter.Extend(
+        []byte("value"),
+)
+
+func (r *Renderer) renderListItem(w util.BufWriter, source []byte, n ast.Node, entering bool) (ast.WalkStatus, error) {
+        if entering {
+                if n.Attributes() != nil {
+                        _, _ = w.WriteString("<li")
+                        RenderAttributes(w, n, ListItemAttributeFilter)
+                        _ = w.WriteByte('>')
+                } else {
+                        _, _ = w.WriteString("<li>")
+                }
+                fc := n.FirstChild()
+                if fc != nil {
+                        if _, ok := fc.(*ast.TextBlock); !ok {
+                                _ = w.WriteByte('\n')
+                        }
+                }
+        } else {
+                _, _ = w.WriteString("</li>\n")
+        }
+        return ast.WalkContinue, nil
+}
+
+// ParagraphAttributeFilter defines attribute names which paragraph elements can have.
+var ParagraphAttributeFilter = GlobalAttributeFilter
+
+func (r *Renderer) renderParagraph(w util.BufWriter, source []byte, n ast.Node, entering bool) (ast.WalkStatus, error) {
+        if entering {
+                if n.Attributes() != nil {
+                        _, _ = w.WriteString("<p")
+                        RenderAttributes(w, n, ParagraphAttributeFilter)
+                        _ = w.WriteByte('>')
+                } else {
+                        _, _ = w.WriteString("<p>")
+                }
+        } else {
+                _, _ = w.WriteString("</p>\n")
+        }
+        return ast.WalkContinue, nil
+}
+
+func (r *Renderer) renderTextBlock(w util.BufWriter, source []byte, n ast.Node, entering bool) (ast.WalkStatus, error) {
+        if !entering {
+                if _, ok := n.NextSibling().(ast.Node); ok && n.FirstChild() != nil {
+                        _ = w.WriteByte('\n')
+                }
+        }
+        return ast.WalkContinue, nil
+}
+
+// ThematicAttributeFilter defines attribute names which hr elements can have.
+var ThematicAttributeFilter = GlobalAttributeFilter.Extend(
+        []byte("align"),   // [Deprecated]
+        []byte("color"),   // [Not Standardized]
+        []byte("noshade"), // [Deprecated]
+        []byte("size"),    // [Deprecated]
+        []byte("width"),   // [Deprecated]
+)
+
+func (r *Renderer) renderThematicBreak(w util.BufWriter, source []byte, n ast.Node, entering bool) (ast.WalkStatus, error) {
+        if !entering {
+                return ast.WalkContinue, nil
+        }
+        _, _ = w.WriteString("<hr")
+        if n.Attributes() != nil {
+                RenderAttributes(w, n, ThematicAttributeFilter)
+        }
+        if r.XHTML {
+                _, _ = w.WriteString(" />\n")
+        } else {
+                _, _ = w.WriteString(">\n")
+        }
+        return ast.WalkContinue, nil
+}
+
+// LinkAttributeFilter defines attribute names which link elements can have.
+var LinkAttributeFilter = GlobalAttributeFilter.Extend(
+        []byte("download"),
+        // []byte("href"),
+        []byte("hreflang"),
+        []byte("media"),
+        []byte("ping"),
+        []byte("referrerpolicy"),
+        []byte("rel"),
+        []byte("shape"),
+        []byte("target"),
+)
+
+func (r *Renderer) renderAutoLink(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
+        n := node.(*ast.AutoLink)
+        if !entering {
+                return ast.WalkContinue, nil
+        }
+        _, _ = w.WriteString(`<a href="`)
+        url := n.URL(source)
+        label := n.Label(source)
+        if n.AutoLinkType == ast.AutoLinkEmail && !bytes.HasPrefix(bytes.ToLower(url), []byte("mailto:")) {
+                _, _ = w.WriteString("mailto:")
+        }
+        _, _ = w.Write(util.EscapeHTML(util.URLEscape(url, false)))
+        if n.Attributes() != nil {
+                _ = w.WriteByte('"')
+                RenderAttributes(w, n, LinkAttributeFilter)
+                _ = w.WriteByte('>')
+        } else {
+                _, _ = w.WriteString(`">`)
+        }
+        _, _ = w.Write(util.EscapeHTML(label))
+        _, _ = w.WriteString(`</a>`)
+        return ast.WalkContinue, nil
+}
+
+// CodeAttributeFilter defines attribute names which code elements can have.
+var CodeAttributeFilter = GlobalAttributeFilter
+
+func (r *Renderer) renderCodeSpan(w util.BufWriter, source []byte, n ast.Node, entering bool) (ast.WalkStatus, error) {
+        if entering {
+                if n.Attributes() != nil {
+                        _, _ = w.WriteString("<code")
+                        RenderAttributes(w, n, CodeAttributeFilter)
+                        _ = w.WriteByte('>')
+                } else {
+                        _, _ = w.WriteString("<code>")
+                }
+                for c := n.FirstChild(); c != nil; c = c.NextSibling() {
+                        segment := c.(*ast.Text).Segment
+                        value := segment.Value(source)
+                        if bytes.HasSuffix(value, []byte("\n")) {
+                                r.Writer.RawWrite(w, value[:len(value)-1])
+                                r.Writer.RawWrite(w, []byte(" "))
+                        } else {
+                                r.Writer.RawWrite(w, value)
+                        }
+                }
+                return ast.WalkSkipChildren, nil
+        }
+        _, _ = w.WriteString("</code>")
+        return ast.WalkContinue, nil
+}
+
+// EmphasisAttributeFilter defines attribute names which emphasis elements can have.
+var EmphasisAttributeFilter = GlobalAttributeFilter
+
+func (r *Renderer) renderEmphasis(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
+        n := node.(*ast.Emphasis)
+        tag := "em"
+        if n.Level == 2 {
+                tag = "strong"
+        }
+        if entering {
+                _ = w.WriteByte('<')
+                _, _ = w.WriteString(tag)
+                if n.Attributes() != nil {
+                        RenderAttributes(w, n, EmphasisAttributeFilter)
+                }
+                _ = w.WriteByte('>')
+        } else {
+                _, _ = w.WriteString("</")
+                _, _ = w.WriteString(tag)
+                _ = w.WriteByte('>')
+        }
+        return ast.WalkContinue, nil
+}
+
+func (r *Renderer) renderLink(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
+        n := node.(*ast.Link)
+        if entering {
+                _, _ = w.WriteString("<a href=\"")
+                if r.Unsafe || !IsDangerousURL(n.Destination) {
+                        _, _ = w.Write(util.EscapeHTML(util.URLEscape(n.Destination, true)))
+                }
+                _ = w.WriteByte('"')
+                if n.Title != nil {
+                        _, _ = w.WriteString(` title="`)
+                        r.Writer.Write(w, n.Title)
+                        _ = w.WriteByte('"')
+                }
+                if n.Attributes() != nil {
+                        RenderAttributes(w, n, LinkAttributeFilter)
+                }
+                _ = w.WriteByte('>')
+        } else {
+                _, _ = w.WriteString("</a>")
+        }
+        return ast.WalkContinue, nil
+}
+
+// ImageAttributeFilter defines attribute names which image elements can have.
+var ImageAttributeFilter = GlobalAttributeFilter.Extend(
+        []byte("align"),
+        []byte("border"),
+        []byte("crossorigin"),
+        []byte("decoding"),
+        []byte("height"),
+        []byte("importance"),
+        []byte("intrinsicsize"),
+        []byte("ismap"),
+        []byte("loading"),
+        []byte("referrerpolicy"),
+        []byte("sizes"),
+        []byte("srcset"),
+        []byte("usemap"),
+        []byte("width"),
+)
+
+func (r *Renderer) renderImage(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
+        if !entering {
+                return ast.WalkContinue, nil
+        }
+        n := node.(*ast.Image)
+        _, _ = w.WriteString("<img src=\"")
+        if r.Unsafe || !IsDangerousURL(n.Destination) {
+                _, _ = w.Write(util.EscapeHTML(util.URLEscape(n.Destination, true)))
+        }
+        _, _ = w.WriteString(`" alt="`)
+        _, _ = w.Write(nodeToHTMLText(n, source))
+        _ = w.WriteByte('"')
+        if n.Title != nil {
+                _, _ = w.WriteString(` title="`)
+                r.Writer.Write(w, n.Title)
+                _ = w.WriteByte('"')
+        }
+        if n.Attributes() != nil {
+                RenderAttributes(w, n, ImageAttributeFilter)
+        }
+        if r.XHTML {
+                _, _ = w.WriteString(" />")
+        } else {
+                _, _ = w.WriteString(">")
+        }
+        return ast.WalkSkipChildren, nil
+}
+
+func (r *Renderer) renderRawHTML(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
+        if !entering {
+                return ast.WalkSkipChildren, nil
+        }
+        if r.Unsafe {
+                n := node.(*ast.RawHTML)
+                l := n.Segments.Len()
+                for i := 0; i < l; i++ {
+                        segment := n.Segments.At(i)
+                        _, _ = w.Write(segment.Value(source))
+                }
+                return ast.WalkSkipChildren, nil
+        }
+        _, _ = w.WriteString("<!-- raw HTML omitted -->")
+        return ast.WalkSkipChildren, nil
+}
+
+func (r *Renderer) renderText(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
+        if !entering {
+                return ast.WalkContinue, nil
+        }
+        n := node.(*ast.Text)
+        segment := n.Segment
+        if n.IsRaw() {
+                r.Writer.RawWrite(w, segment.Value(source))
+        } else {
+                value := segment.Value(source)
+                r.Writer.Write(w, value)
+                if n.HardLineBreak() || (n.SoftLineBreak() && r.HardWraps) {
+                        if r.XHTML {
+                                _, _ = w.WriteString("<br />\n")
+                        } else {
+                                _, _ = w.WriteString("<br>\n")
+                        }
+                } else if n.SoftLineBreak() {
+                        if r.EastAsianLineBreaks && len(value) != 0 {
+                                sibling := node.NextSibling()
+                                if sibling != nil && sibling.Kind() == ast.KindText {
+                                        if siblingText := sibling.(*ast.Text).Text(source); len(siblingText) != 0 {
+                                                thisLastRune := util.ToRune(value, len(value)-1)
+                                                siblingFirstRune, _ := utf8.DecodeRune(siblingText)
+                                                if !(util.IsEastAsianWideRune(thisLastRune) &&
+                                                        util.IsEastAsianWideRune(siblingFirstRune)) {
+                                                        _ = w.WriteByte('\n')
+                                                }
+                                        }
+                                }
+                        } else {
+                                _ = w.WriteByte('\n')
+                        }
+                }
+        }
+        return ast.WalkContinue, nil
+}
+
+func (r *Renderer) renderString(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
+        if !entering {
+                return ast.WalkContinue, nil
+        }
+        n := node.(*ast.String)
+        if n.IsCode() {
+                _, _ = w.Write(n.Value)
+        } else {
+                if n.IsRaw() {
+                        r.Writer.RawWrite(w, n.Value)
+                } else {
+                        r.Writer.Write(w, n.Value)
+                }
+        }
+        return ast.WalkContinue, nil
+}
+
+var dataPrefix = []byte("data-")
+
+// RenderAttributes renders given node's attributes.
+// You can specify attribute names to render by the filter.
+// If filter is nil, RenderAttributes renders all attributes.
+func RenderAttributes(w util.BufWriter, node ast.Node, filter util.BytesFilter) {
+        for _, attr := range node.Attributes() {
+                if filter != nil && !filter.Contains(attr.Name) {
+                        if !bytes.HasPrefix(attr.Name, dataPrefix) {
+                                continue
+                        }
+                }
+                _, _ = w.WriteString(" ")
+                _, _ = w.Write(attr.Name)
+                _, _ = w.WriteString(`="`)
+                // TODO: convert numeric values to strings
+                _, _ = w.Write(util.EscapeHTML(attr.Value.([]byte)))
+                _ = w.WriteByte('"')
+        }
+}
+
+// A Writer interface writes textual contents to a writer.
+type Writer interface {
+        // Write writes the given source to writer with resolving references and unescaping
+        // backslash escaped characters.
+        Write(writer util.BufWriter, source []byte)
+
+        // RawWrite writes the given source to writer without resolving references and
+        // unescaping backslash escaped characters.
+        RawWrite(writer util.BufWriter, source []byte)
+
+        // SecureWrite writes the given source to writer with replacing insecure characters.
+        SecureWrite(writer util.BufWriter, source []byte)
+}
+
+var replacementCharacter = []byte("\ufffd")
+
+// A WriterConfig struct has configurations for the HTML based writers.
+type WriterConfig struct {
+        // EscapedSpace is an option that indicates that a '\' escaped half-space(0x20) should not be rendered.
+        EscapedSpace bool
+}
+
+// A WriterOption interface sets options for HTML based writers.
+type WriterOption func(*WriterConfig)
+
+// WithEscapedSpace is a WriterOption indicates that a '\' escaped half-space(0x20) should not be rendered.
+func WithEscapedSpace() WriterOption {
+        return func(c *WriterConfig) {
+                c.EscapedSpace = true
+        }
+}
+
+type defaultWriter struct {
+        WriterConfig
+}
+
+// NewWriter returns a new Writer.
+func NewWriter(opts ...WriterOption) Writer {
+        w := &defaultWriter{}
+        for _, opt := range opts {
+                opt(&w.WriterConfig)
+        }
+        return w
+}
+
+func escapeRune(writer util.BufWriter, r rune) {
+        if r < 256 {
+                v := util.EscapeHTMLByte(byte(r))
+                if v != nil {
+                        _, _ = writer.Write(v)
+                        return
+                }
+        }
+        _, _ = writer.WriteRune(util.ToValidRune(r))
+}
+
+func (d *defaultWriter) SecureWrite(writer util.BufWriter, source []byte) {
+        n := 0
+        l := len(source)
+        for i := 0; i < l; i++ {
+                if source[i] == '\u0000' {
+                        _, _ = writer.Write(source[i-n : i])
+                        n = 0
+                        _, _ = writer.Write(replacementCharacter)
+                        continue
+                }
+                n++
+        }
+        if n != 0 {
+                _, _ = writer.Write(source[l-n:])
+        }
+}
+
+func (d *defaultWriter) RawWrite(writer util.BufWriter, source []byte) {
+        n := 0
+        l := len(source)
+        for i := 0; i < l; i++ {
+                v := util.EscapeHTMLByte(source[i])
+                if v != nil {
+                        _, _ = writer.Write(source[i-n : i])
+                        n = 0
+                        _, _ = writer.Write(v)
+                        continue
+                }
+                n++
+        }
+        if n != 0 {
+                _, _ = writer.Write(source[l-n:])
+        }
+}
+
+func (d *defaultWriter) Write(writer util.BufWriter, source []byte) {
+        escaped := false
+        var ok bool
+        limit := len(source)
+        n := 0
+        for i := 0; i < limit; i++ {
+                c := source[i]
+                if escaped {
+                        if util.IsPunct(c) {
+                                d.RawWrite(writer, source[n:i-1])
+                                n = i
+                                escaped = false
+                                continue
+                        }
+                        if d.EscapedSpace && c == ' ' {
+                                d.RawWrite(writer, source[n:i-1])
+                                n = i + 1
+                                escaped = false
+                                continue
+                        }
+                }
+                if c == '\x00' {
+                        d.RawWrite(writer, source[n:i])
+                        d.RawWrite(writer, replacementCharacter)
+                        n = i + 1
+                        escaped = false
+                        continue
+                }
+                if c == '&' {
+                        pos := i
+                        next := i + 1
+                        if next < limit && source[next] == '#' {
+                                nnext := next + 1
+                                if nnext < limit {
+                                        nc := source[nnext]
+                                        // code point like #x22;
+                                        if nnext < limit && nc == 'x' || nc == 'X' {
+                                                start := nnext + 1
+                                                i, ok = util.ReadWhile(source, [2]int{start, limit}, util.IsHexDecimal)
+                                                if ok && i < limit && source[i] == ';' && i-start < 7 {
+                                                        v, _ := strconv.ParseUint(util.BytesToReadOnlyString(source[start:i]), 16, 32)
+                                                        d.RawWrite(writer, source[n:pos])
+                                                        n = i + 1
+                                                        escapeRune(writer, rune(v))
+                                                        continue
+                                                }
+                                                // code point like #1234;
+                                        } else if nc >= '0' && nc <= '9' {
+                                                start := nnext
+                                                i, ok = util.ReadWhile(source, [2]int{start, limit}, util.IsNumeric)
+                                                if ok && i < limit && i-start < 8 && source[i] == ';' {
+                                                        v, _ := strconv.ParseUint(util.BytesToReadOnlyString(source[start:i]), 10, 32)
+                                                        d.RawWrite(writer, source[n:pos])
+                                                        n = i + 1
+                                                        escapeRune(writer, rune(v))
+                                                        continue
+                                                }
+                                        }
+                                }
+                        } else {
+                                start := next
+                                i, ok = util.ReadWhile(source, [2]int{start, limit}, util.IsAlphaNumeric)
+                                // entity reference
+                                if ok && i < limit && source[i] == ';' {
+                                        name := util.BytesToReadOnlyString(source[start:i])
+                                        entity, ok := util.LookUpHTML5EntityByName(name)
+                                        if ok {
+                                                d.RawWrite(writer, source[n:pos])
+                                                n = i + 1
+                                                d.RawWrite(writer, entity.Characters)
+                                                continue
+                                        }
+                                }
+                        }
+                        i = next - 1
+                }
+                if c == '\\' {
+                        escaped = true
+                        continue
+                }
+                escaped = false
+        }
+        d.RawWrite(writer, source[n:])
+}
+
+// DefaultWriter is a default instance of the Writer.
+var DefaultWriter = NewWriter()
+
+var bDataImage = []byte("data:image/")
+var bPng = []byte("png;")
+var bGif = []byte("gif;")
+var bJpeg = []byte("jpeg;")
+var bWebp = []byte("webp;")
+var bSvg = []byte("svg+xml;")
+var bJs = []byte("javascript:")
+var bVb = []byte("vbscript:")
+var bFile = []byte("file:")
+var bData = []byte("data:")
+
+// IsDangerousURL returns true if the given url seems a potentially dangerous url,
+// otherwise false.
+func IsDangerousURL(url []byte) bool {
+        if bytes.HasPrefix(url, bDataImage) && len(url) >= 11 {
+                v := url[11:]
+                if bytes.HasPrefix(v, bPng) || bytes.HasPrefix(v, bGif) ||
+                        bytes.HasPrefix(v, bJpeg) || bytes.HasPrefix(v, bWebp) ||
+                        bytes.HasPrefix(v, bSvg) {
+                        return false
+                }
+                return true
+        }
+        return bytes.HasPrefix(url, bJs) || bytes.HasPrefix(url, bVb) ||
+                bytes.HasPrefix(url, bFile) || bytes.HasPrefix(url, bData)
+}
+
+func nodeToHTMLText(n ast.Node, source []byte) []byte {
+        var buf bytes.Buffer
+        for c := n.FirstChild(); c != nil; c = c.NextSibling() {
+                if s, ok := c.(*ast.String); ok && s.IsCode() {
+                        buf.Write(s.Text(source))
+                } else if !c.HasChildren() {
+                        buf.Write(util.EscapeHTML(c.Text(source)))
+                } else {
+                        buf.Write(nodeToHTMLText(c, source))
+                }
+        }
+        return buf.Bytes()
+}