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1 // Package bfchroma provides an easy and extensible blackfriday renderer that
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2 // uses the chroma syntax highlighter to render code blocks.
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3 package bfchroma
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4
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5 import (
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6 "io"
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7
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8 "github.com/alecthomas/chroma/v2"
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9 "github.com/alecthomas/chroma/v2/formatters/html"
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10 "github.com/alecthomas/chroma/v2/lexers"
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11 "github.com/alecthomas/chroma/v2/styles"
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12 bf "github.com/russross/blackfriday/v2"
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13 )
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14
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15 // Option defines the functional option type
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16 type Option func(r *Renderer)
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17
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18 // Style is a function option allowing to set the style used by chroma
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19 // Default : "monokai"
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20 func Style(s string) Option {
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21 return func(r *Renderer) {
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22 r.Style = styles.Get(s)
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23 }
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24 }
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25
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26 // ChromaStyle is an option to directly set the style of the renderer using a
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27 // chroma style instead of a string
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28 func ChromaStyle(s *chroma.Style) Option {
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29 return func(r *Renderer) {
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30 r.Style = s
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31 }
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32 }
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33
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34 // WithoutAutodetect disables chroma's language detection when no codeblock
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35 // extra information is given. It will fallback to a sane default instead of
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36 // trying to detect the language.
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37 func WithoutAutodetect() Option {
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38 return func(r *Renderer) {
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39 r.Autodetect = false
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40 }
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41 }
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42
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43 // EmbedCSS will embed CSS needed for html.WithClasses() in beginning of the document
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44 func EmbedCSS() Option {
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45 return func(r *Renderer) {
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46 r.embedCSS = true
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47 }
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48 }
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49
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50 // ChromaOptions allows to pass Chroma html.Option such as Standalone()
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51 // WithClasses(), ClassPrefix(prefix)...
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52 func ChromaOptions(options ...html.Option) Option {
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53 return func(r *Renderer) {
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54 r.ChromaOptions = options
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55 }
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56 }
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57
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58 // Extend allows to specify the blackfriday renderer which is extended
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59 func Extend(br bf.Renderer) Option {
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60 return func(r *Renderer) {
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61 r.Base = br
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62 }
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63 }
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64
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65 // NewRenderer will return a new bfchroma renderer with sane defaults
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66 func NewRenderer(options ...Option) *Renderer {
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67 r := &Renderer{
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68 Base: bf.NewHTMLRenderer(bf.HTMLRendererParameters{
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69 Flags: bf.CommonHTMLFlags,
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70 }),
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71 Style: styles.Monokai,
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72 Autodetect: true,
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73 }
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74 for _, option := range options {
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75 option(r)
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76 }
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77 r.Formatter = html.New(r.ChromaOptions...)
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78 return r
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79 }
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80
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81 // RenderWithChroma will render the given text to the w io.Writer
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82 func (r *Renderer) RenderWithChroma(w io.Writer, text []byte, data bf.CodeBlockData) error {
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83 var lexer chroma.Lexer
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84
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85 // Determining the lexer to use
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86 if len(data.Info) > 0 {
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87 lexer = lexers.Get(string(data.Info))
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88 } else if r.Autodetect {
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89 lexer = lexers.Analyse(string(text))
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90 }
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91 if lexer == nil {
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92 lexer = lexers.Fallback
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93 }
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94
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95 // Tokenize the code
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96 iterator, err := lexer.Tokenise(nil, string(text))
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97 if err != nil {
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98 return err
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99 }
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100 return r.Formatter.Format(w, r.Style, iterator)
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101 }
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102
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103 // Renderer is a custom Blackfriday renderer that uses the capabilities of
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104 // chroma to highlight code with triple backtick notation
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105 type Renderer struct {
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106 Base bf.Renderer
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107 Autodetect bool
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108 ChromaOptions []html.Option
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109 Style *chroma.Style
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110 Formatter *html.Formatter
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111 embedCSS bool
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112 }
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113
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114 // RenderNode satisfies the Renderer interface
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115 func (r *Renderer) RenderNode(w io.Writer, node *bf.Node, entering bool) bf.WalkStatus {
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116 switch node.Type {
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117 case bf.Document:
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118 if entering && r.embedCSS {
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119 w.Write([]byte("<style>")) // nolint: errcheck
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120 r.Formatter.WriteCSS(w, r.Style) // nolint: errcheck
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121 w.Write([]byte("</style>")) // nolint: errcheck
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122 }
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123 return r.Base.RenderNode(w, node, entering)
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124 case bf.CodeBlock:
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125 if err := r.RenderWithChroma(w, node.Literal, node.CodeBlockData); err != nil {
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126 return r.Base.RenderNode(w, node, entering)
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127 }
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128 return bf.SkipChildren
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129 default:
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130 return r.Base.RenderNode(w, node, entering)
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131 }
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132 }
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133
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134 // RenderHeader satisfies the Renderer interface
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135 func (r *Renderer) RenderHeader(w io.Writer, ast *bf.Node) {
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136 r.Base.RenderHeader(w, ast)
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137 }
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138
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139 // RenderFooter satisfies the Renderer interface
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140 func (r *Renderer) RenderFooter(w io.Writer, ast *bf.Node) {
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141 r.Base.RenderFooter(w, ast)
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142 }
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143
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144 // ChromaCSS returns CSS used with chroma's html.WithClasses() option
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145 func (r *Renderer) ChromaCSS(w io.Writer) error {
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146 return r.Formatter.WriteCSS(w, r.Style)
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147 }
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