feat: highlight code blocks within answers

src/utils/syntax.go

@@ -0,0 +1,78 @@
+package utils
+
+import (
+	"bytes"
+	"html"
+	"io"
+	"regexp"
+	"strings"
+
+	"github.com/alecthomas/chroma/formatters"
+	"github.com/alecthomas/chroma/lexers"
+	"github.com/alecthomas/chroma/styles"
+)
+
+var plainFormattedCodeRegex = regexp.MustCompile(`(?s)<pre tabindex="0" class="chroma"><code>(.+?)</code></pre>`)
+
+func HighlightSyntaxViaContent(content string) (htmlOut string) {
+	content = html.UnescapeString(content)
+
+	fallbackOut := content
+
+	// identify the language
+	lexer := lexers.Analyse(content)
+	if lexer == nil {
+		// unable to identify, so just return the wrapped content
+		htmlOut = fallbackOut
+		return
+	}
+
+	style := styles.Get("xcode")
+	if style == nil {
+		style = styles.Fallback
+	}
+
+	formatter := formatters.Get("html")
+	if formatter == nil {
+		formatter = formatters.Fallback
+	}
+
+	iterator, err := lexer.Tokenise(nil, content)
+	if err != nil {
+		htmlOut = fallbackOut
+		return
+	}
+
+	b := bytes.NewBufferString("")
+	w := io.Writer(b)
+
+	err = formatter.Format(w, style, iterator)
+	if err != nil {
+		htmlOut = fallbackOut
+		return
+	}
+
+	// parse only the <pre><code>...</code></pre> part
+	htmlOut = b.String()
+	htmlOut = plainFormattedCodeRegex.FindString(htmlOut)
+
+	htmlOut = StripBlockTags(htmlOut)
+
+	// remove <pre tabindex="0" class="chroma">
+	htmlOut = strings.Replace(htmlOut, "<pre tabindex=\"0\" class=\"chroma\">", "", -1)
+
+	return
+}
+
+func StripBlockTags(content string) (result string) {
+	// strip all "<code>" tags
+	content = strings.Replace(content, "<code>", "", -1)
+	content = strings.Replace(content, "</code>", "", -1)
+	// and the <pre>
+	content = strings.Replace(content, "<pre>", "", -1)
+	content = strings.Replace(content, "</pre>", "", -1)
+
+	result = content
+
+	return
+}