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main.go
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main.go
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package main
import (
"bytes"
"flag"
"fmt"
"io"
"os"
"github.com/alecthomas/chroma"
"github.com/alecthomas/chroma/formatters"
"github.com/alecthomas/chroma/lexers"
"github.com/alecthomas/chroma/styles"
)
const version = "0.0.3"
var (
number_f = flag.Bool("number", false, "line number flag")
theme = flag.String("theme", "monokai", "highlights theme name")
language = flag.String("language", "", "file language")
)
type withNumberWriter struct {
writer io.Writer
lineNumber uint32
buffer *bytes.Buffer
}
func (wnw *withNumberWriter) Write(b []byte) (n int, err error) {
if !bytes.Contains(b, []byte{'\n'}) {
wnw.buffer.Write(b)
return len(b), nil
}
var p []byte
if wnw.buffer.Len() > 0 {
p = wnw.buffer.Bytes()
wnw.buffer.Reset()
}
p = append(p, b...)
ln := []byte(fmt.Sprintf("%4d| ", wnw.lineNumber))
if _, err = wnw.writer.Write(append(ln, p...)); err != nil {
return len(b), err
}
wnw.lineNumber++
return len(b), nil
}
func newWithNumber(w io.Writer) *withNumberWriter {
return &withNumberWriter{w, 1, new(bytes.Buffer)}
}
func main() {
flag.Usage = func() {
fmt.Fprintln(os.Stderr, "Usage: golang-cat [options...] filepath")
flag.PrintDefaults()
}
flag.Parse()
if flag.NArg() != 1 {
flag.Usage()
os.Exit(1)
}
bytes, err := os.ReadFile(flag.Arg(0))
if err != nil {
fmt.Println(err)
os.Exit(1)
}
if err := printText(&bytes); err != nil {
fmt.Println(err)
os.Exit(1)
}
}
func printText(text *[]byte) (err error) {
var w io.Writer
w = os.Stdout
if *number_f {
w = newWithNumber(w)
}
var lexer chroma.Lexer
if *language != "" {
lexer = lexers.Get(*language)
} else {
lexer = lexers.Analyse(string(*text))
}
if lexer == nil {
lexer = lexers.Fallback
}
style := styles.Get(*theme)
if style == nil {
style = styles.Fallback
}
formatter := formatters.Get("terminal256")
if formatter == nil {
formatter = formatters.Fallback
}
iterator, err := lexer.Tokenise(nil, string(*text))
if err != nil {
return err
}
return formatter.Format(w, style, iterator)
}