codegen: add interpreter tests

Also simplify project structure. The executable is now produced in
the root directory. Work in progress.

1 files changed, 71 insertions, 0 deletions

diff --git a/main.go b/main.go
new file mode 100644
index 0000000..037614c
--- /dev/null
+++ b/main.go
@@ -0,0 +1,71 @@
+package main
+
+import (
+	"bufio"
+	"errors"
+	"fmt"
+	"io"
+	"log"
+	"os"
+
+	"github.com/gnolang/parscan/codegen"
+	"github.com/gnolang/parscan/lang/golang"
+	"github.com/gnolang/parscan/scanner"
+	"github.com/gnolang/parscan/vm0"
+)
+
+type Interpreter interface {
+	Eval(string) (any, error)
+}
+
+func main() {
+	log.SetFlags(log.Lshortfile)
+	var interp Interpreter = vm0.New(golang.GoParser)
+	if len(os.Args) > 1 && os.Args[1] == "1" {
+		interp = codegen.NewInterpreter(golang.GoParser)
+		interp.(*codegen.Interpreter).AddSym(fmt.Println, "println")
+	}
+	in := os.Stdin
+
+	if isatty(in) {
+		// Provide an interactive line oriented Read Eval Print Loop (REPL).
+		liner := bufio.NewScanner(in)
+		text, prompt := "", "> "
+		fmt.Print(prompt)
+		for liner.Scan() {
+			text += liner.Text()
+			res, err := interp.Eval(text + "\n")
+			if err == nil {
+				if res != nil {
+					fmt.Println(": ", res)
+				}
+				text, prompt = "", "> "
+			} else if errors.Is(err, scanner.ErrBlock) {
+				prompt = ">> "
+			} else {
+				fmt.Println("Error:", err)
+				text, prompt = "", "> "
+			}
+			fmt.Print(prompt)
+		}
+		return
+	}
+
+	buf, err := io.ReadAll(in)
+	if err != nil {
+		log.Fatal(err)
+	}
+	if _, err := interp.Eval(string(buf)); 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
+}