package debug

import (
	"fmt"
	"runtime"
	"strings"
)

func Stack() (str string) {
	var name, file string
	var line int
	var pc [16]uintptr

	n := runtime.Callers(4, pc[:])
	for _, pc := range pc[:n] {
		fn := runtime.FuncForPC(pc)
		if fn == nil {
			continue
		}
		file, line = fn.FileLine(pc)
		name = fn.Name()
		if !strings.HasPrefix(name, "runtime.") {
			break
		}
	}

	switch {
	case name != "":
		str = fmt.Sprintf("%v:%v", name, line)
	case file != "":
		str = fmt.Sprintf("%v:%v", file, line)
	default:
		str = fmt.Sprintf("pc:%x", pc)
	}

	return
}