package html
import (
"fmt"
"html"
"io"
"sort"
"strings"
"github.com/alecthomas/chroma"
)
// Option sets an option of the HTML formatter.
type Option func(f *Formatter)
// Standalone configures the HTML formatter for generating a standalone HTML document.
func Standalone() Option { return func(f *Formatter) { f.standalone = true } }
// ClassPrefix sets the CSS class prefix.
func ClassPrefix(prefix string) Option { return func(f *Formatter) { f.prefix = prefix } }
// WithClasses emits HTML using CSS classes, rather than inline styles.
func WithClasses() Option { return func(f *Formatter) { f.classes = true } }
// TabWidth sets the number of characters for a tab. Defaults to 8.
func TabWidth(width int) Option { return func(f *Formatter) { f.tabWidth = width } }
// WithLineNumbers formats output with line numbers.
func WithLineNumbers() Option {
return func(f *Formatter) {
f.lineNumbers = true
}
}
// HighlightLines higlights the given line ranges with the Highlight style.
//
// A range is the beginning and ending of a range as 1-based line numbers, inclusive.
func HighlightLines(ranges [][2]int) Option {
return func(f *Formatter) {
f.highlightRanges = ranges
sort.Sort(f.highlightRanges)
}
}
// BaseLineNumber sets the initial number to start line numbering at. Defaults to 1.
func BaseLineNumber(n int) Option {
return func(f *Formatter) {
f.baseLineNumber = n
}
}
// New HTML formatter.
func New(options ...Option) *Formatter {
f := &Formatter{
baseLineNumber: 1,
}
for _, option := range options {
option(f)
}
return f
}
// Formatter that generates HTML.
type Formatter struct {
standalone bool
prefix string
classes bool
tabWidth int
lineNumbers bool
highlightRanges highlightRanges
baseLineNumber int
}
type highlightRanges [][2]int
func (h highlightRanges) Len() int { return len(h) }
func (h highlightRanges) Swap(i, j int) { h[i], h[j] = h[j], h[i] }
func (h highlightRanges) Less(i, j int) bool { return h[i][0] < h[j][0] }
func (f *Formatter) Format(w io.Writer, style *chroma.Style, iterator chroma.Iterator) (err error) {
defer func() {
if perr := recover(); perr != nil {
err = perr.(error)
}
}()
return f.writeHTML(w, style, iterator.Tokens())
}
func brightenOrDarken(colour chroma.Colour, factor float64) chroma.Colour {
if colour.Brightness() < 0.5 {
return colour.Brighten(factor)
}
return colour.Brighten(-factor)
}
// Ensure that style entries exist for highlighting, etc.
func (f *Formatter) restyle(style *chroma.Style) (*chroma.Style, error) {
builder := style.Builder()
bg := builder.Get(chroma.Background)
// If we don't have a line highlight colour, make one that is 10% brighter/darker than the background.
if !style.Has(chroma.LineHighlight) {
highlight := chroma.StyleEntry{Background: bg.Background}
highlight.Background = brightenOrDarken(highlight.Background, 0.1)
builder.AddEntry(chroma.LineHighlight, highlight)
}
// If we don't have line numbers, use the text colour but 20% brighter/darker
if !style.Has(chroma.LineNumbers) {
text := chroma.StyleEntry{Colour: bg.Colour}
text.Colour = brightenOrDarken(text.Colour, 0.5)
builder.AddEntry(chroma.LineNumbers, text)
}
return builder.Build()
}
// We deliberately don't use html/template here because it is two orders of magnitude slower (benchmarked).
//
// OTOH we need to be super careful about correct escaping...
func (f *Formatter) writeHTML(w io.Writer, style *chroma.Style, tokens []*chroma.Token) (err error) { // nolint: gocyclo
style, err = f.restyle(style)
if err != nil {
return err
}
css := f.styleToCSS(style)
if !f.classes {
for t, style := range css {
css[t] = compressStyle(style)
}
}
if f.standalone {
fmt.Fprint(w, "\n")
if f.classes {
fmt.Fprint(w, "")
}
fmt.Fprintf(w, "\n", f.styleAttr(css, chroma.Background))
}
fmt.Fprintf(w, "", f.styleAttr(css, chroma.Background))
lines := splitTokensIntoLines(tokens)
lineDigits := len(fmt.Sprintf("%d", len(lines)))
highlightIndex := 0
for index, tokens := range lines {
// 1-based line number.
line := f.baseLineNumber + index
highlight := false
for highlightIndex < len(f.highlightRanges) && line > f.highlightRanges[highlightIndex][1] {
highlightIndex++
}
if highlightIndex < len(f.highlightRanges) {
hrange := f.highlightRanges[highlightIndex]
if line >= hrange[0] && line <= hrange[1] {
highlight = true
}
}
if highlight {
fmt.Fprintf(w, "", f.styleAttr(css, chroma.LineHighlight))
}
if f.lineNumbers {
fmt.Fprintf(w, "%*d", f.styleAttr(css, chroma.LineNumbers), lineDigits, line)
}
for _, token := range tokens {
html := html.EscapeString(token.String())
attr := f.styleAttr(css, token.Type)
if attr != "" {
html = fmt.Sprintf("%s", attr, html)
}
fmt.Fprint(w, html)
}
if highlight {
fmt.Fprintf(w, "")
}
}
fmt.Fprint(w, "\n")
if f.standalone {
fmt.Fprint(w, "\n")
fmt.Fprint(w, "