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package main
import (
"bufio"
"errors"
"flag"
"fmt"
"io"
"log"
"os"
"reflect"
"strings"
"github.com/mvertes/parscan/interpreter"
"github.com/mvertes/parscan/lang/golang"
"github.com/mvertes/parscan/scanner"
)
type Interpreter interface {
Eval(string) (reflect.Value, error)
}
func main() {
log.SetFlags(log.Lshortfile)
if err := run(os.Args[1:]); err != nil {
log.Fatal(err)
}
}
// isatty returns true if the input stream is a tty (i.e. a character device).
func isatty(in io.Reader) bool {
s, ok := in.(interface{ Stat() (os.FileInfo, error) })
if !ok {
return false
}
stat, err := s.Stat()
return err == nil && stat.Mode()&os.ModeCharDevice != 0
}
// repl executes an interactive line oriented Read Eval Print Loop (REPL).
func repl(interp Interpreter, in io.Reader) (err error) {
liner := bufio.NewScanner(in)
text, prompt := "", "> "
fmt.Print(prompt)
for liner.Scan() {
text += liner.Text()
res, err := interp.Eval(text + "\n")
switch {
case err == nil:
if res.IsValid() {
fmt.Println(": ", res)
}
text, prompt = "", "> "
case errors.Is(err, scanner.ErrBlock):
prompt = ">> "
default:
fmt.Println("Error:", err)
text, prompt = "", "> "
}
fmt.Print(prompt)
}
return err
}
func run(arg []string) (err error) {
var str string
rflag := flag.NewFlagSet("run", flag.ContinueOnError)
rflag.Usage = func() {
fmt.Println("Usage: parscan run [options] [path] [args]")
fmt.Println("Options:")
rflag.PrintDefaults()
}
rflag.StringVar(&str, "e", "", "string to eval")
if err = rflag.Parse(arg); err != nil {
return err
}
args := rflag.Args()
intpr := interpreter.NewInterpreter(scanner.NewScanner(golang.GoSpec))
var in io.Reader
if str != "" {
in = strings.NewReader(str)
} else {
in = os.Stdin
}
if len(args) > 0 {
if in, err = os.Open(arg[0]); err != nil {
return err
}
if i2, ok := in.(io.ReadCloser); ok {
defer i2.Close()
}
}
if isatty(in) {
return repl(intpr, in)
}
buf, err := io.ReadAll(in)
if err != nil {
return err
}
_, err = intpr.Eval(string(buf))
return err
}
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