github.com/graemephi/kahugo@v0.62.3-0.20211121071557-d78c0423784d/markup/highlight/highlight.go (about)

     1  // Copyright 2019 The Hugo Authors. All rights reserved.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  // http://www.apache.org/licenses/LICENSE-2.0
     7  //
     8  // Unless required by applicable law or agreed to in writing, software
     9  // distributed under the License is distributed on an "AS IS" BASIS,
    10  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    11  // See the License for the specific language governing permissions and
    12  // limitations under the License.
    13  
    14  package highlight
    15  
    16  import (
    17  	"fmt"
    18  	gohtml "html"
    19  	"io"
    20  	"strings"
    21  
    22  	"github.com/alecthomas/chroma"
    23  	"github.com/alecthomas/chroma/formatters/html"
    24  	"github.com/alecthomas/chroma/lexers"
    25  	"github.com/alecthomas/chroma/styles"
    26  	hl "github.com/yuin/goldmark-highlighting"
    27  )
    28  
    29  func New(cfg Config) Highlighter {
    30  	return Highlighter{
    31  		cfg: cfg,
    32  	}
    33  }
    34  
    35  type Highlighter struct {
    36  	cfg Config
    37  }
    38  
    39  func (h Highlighter) Highlight(code, lang, optsStr string) (string, error) {
    40  	if optsStr == "" {
    41  		return highlight(code, lang, h.cfg)
    42  	}
    43  
    44  	cfg := h.cfg
    45  	if err := applyOptionsFromString(optsStr, &cfg); err != nil {
    46  		return "", err
    47  	}
    48  
    49  	return highlight(code, lang, cfg)
    50  }
    51  
    52  func highlight(code, lang string, cfg Config) (string, error) {
    53  	w := &strings.Builder{}
    54  	var lexer chroma.Lexer
    55  	if lang != "" {
    56  		lexer = lexers.Get(lang)
    57  	}
    58  
    59  	if lexer == nil && cfg.GuessSyntax {
    60  		lexer = lexers.Analyse(code)
    61  		if lexer == nil {
    62  			lexer = lexers.Fallback
    63  		}
    64  		lang = strings.ToLower(lexer.Config().Name)
    65  	}
    66  
    67  	if lexer == nil {
    68  		wrapper := getPreWrapper(lang)
    69  		fmt.Fprint(w, wrapper.Start(true, ""))
    70  		fmt.Fprint(w, gohtml.EscapeString(code))
    71  		fmt.Fprint(w, wrapper.End(true))
    72  		return w.String(), nil
    73  	}
    74  
    75  	style := styles.Get(cfg.Style)
    76  	if style == nil {
    77  		style = styles.Fallback
    78  	}
    79  	lexer = chroma.Coalesce(lexer)
    80  
    81  	iterator, err := lexer.Tokenise(nil, code)
    82  	if err != nil {
    83  		return "", err
    84  	}
    85  
    86  	options := cfg.ToHTMLOptions()
    87  	options = append(options, getHtmlPreWrapper(lang))
    88  
    89  	formatter := html.New(options...)
    90  
    91  	fmt.Fprint(w, `<div class="highlight">`)
    92  	if err := formatter.Format(w, style, iterator); err != nil {
    93  		return "", err
    94  	}
    95  	fmt.Fprint(w, `</div>`)
    96  
    97  	return w.String(), nil
    98  }
    99  
   100  func GetCodeBlockOptions() func(ctx hl.CodeBlockContext) []html.Option {
   101  	return func(ctx hl.CodeBlockContext) []html.Option {
   102  		var language string
   103  		if l, ok := ctx.Language(); ok {
   104  			language = string(l)
   105  		}
   106  		return []html.Option{
   107  			getHtmlPreWrapper(language),
   108  		}
   109  	}
   110  }
   111  
   112  func getPreWrapper(language string) preWrapper {
   113  	return preWrapper{language: language}
   114  }
   115  
   116  func getHtmlPreWrapper(language string) html.Option {
   117  	return html.WithPreWrapper(getPreWrapper(language))
   118  }
   119  
   120  type preWrapper struct {
   121  	language string
   122  }
   123  
   124  func (p preWrapper) Start(code bool, styleAttr string) string {
   125  	var language string
   126  	if code {
   127  		language = p.language
   128  	}
   129  	w := &strings.Builder{}
   130  	WritePreStart(w, language, styleAttr)
   131  	return w.String()
   132  }
   133  
   134  func WritePreStart(w io.Writer, language, styleAttr string) {
   135  	fmt.Fprintf(w, `<pre tabindex="0"%s>`, styleAttr)
   136  	fmt.Fprint(w, "<code")
   137  	if language != "" {
   138  		fmt.Fprint(w, ` class="language-`+language+`"`)
   139  		fmt.Fprint(w, ` data-lang="`+language+`"`)
   140  	}
   141  	fmt.Fprint(w, ">")
   142  }
   143  
   144  const preEnd = "</code></pre>"
   145  
   146  func (p preWrapper) End(code bool) string {
   147  	return preEnd
   148  }
   149  
   150  func WritePreEnd(w io.Writer) {
   151  	fmt.Fprint(w, preEnd)
   152  }