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highlight.go
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highlight.go
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package m
import (
"bytes"
"os"
"strings"
"github.com/alecthomas/chroma/v2"
"github.com/alecthomas/chroma/v2/lexers"
log "github.com/sirupsen/logrus"
)
// Files larger than this won't be highlighted
const MAX_HIGHLIGHT_SIZE int64 = 1024 * 1024
// Read and highlight a file using Chroma: https://github.com/alecthomas/chroma
//
// If force is true, file will always be highlighted. If force is false, files
// larger than MAX_HIGHLIGHT_SIZE will not be highlighted.
//
// Returns nil with no error if highlighting would be a no-op.
func highlight(filename string, force bool, style chroma.Style, formatter chroma.Formatter) (*string, error) {
// Highlight input file using Chroma:
// https://github.com/alecthomas/chroma
fileInfo, err := os.Stat(filename)
if err != nil {
return nil, err
}
if fileInfo.Size() > MAX_HIGHLIGHT_SIZE && !force {
log.Debugf("Not highlighting %s because it is %d bytes large, which is larger than moar's built-in highlighting limit of %d bytes",
filename, fileInfo.Size(), MAX_HIGHLIGHT_SIZE)
return nil, nil
}
lexer := lexers.Match(filename)
if lexer == nil {
// No highlighter available for this file type
return nil, nil
}
// FIXME: Can we test for the lexer implementation class instead? That
// should be more resilient towards this arbitrary string changing if we
// upgrade Chroma at some point.
if lexer.Config().Name == "plaintext" {
// This highlighter doesn't provide any highlighting, but not doing
// anything at all is cheaper and simpler, so we do that.
return nil, nil
}
// See: https://github.com/alecthomas/chroma#identifying-the-language
// FIXME: Do we actually need this? We should profile our reader performance
// with and without.
lexer = chroma.Coalesce(lexer)
contents, err := os.ReadFile(filename)
if err != nil {
return nil, err
}
iterator, err := lexer.Tokenise(nil, string(contents))
if err != nil {
return nil, err
}
var stringBuffer bytes.Buffer
err = formatter.Format(&stringBuffer, &style, iterator)
if err != nil {
return nil, err
}
highlighted := stringBuffer.String()
// If buffer ends with SGR Reset ("<ESC>[0m"), remove it. Chroma sometimes
// (always?) puts one of those by itself on the last line, making us believe
// there is one line too many.
sgrReset := "\x1b[0m"
trimmed := strings.TrimSuffix(highlighted, sgrReset)
return &trimmed, nil
}