package main

import (
	"flag"
	"fmt"
	"io"
	"os"
	"os/exec"
	"path/filepath"
	"time"
)

func parseArgs() (string, string, []string) {
	logDir := flag.String("logdir", "", "Log output directory (default=stderr)")
	flag.Parse()
	return *logDir, flag.Arg(0), flag.Args()[1:]
}

func execution(commandName string, args[] string, stdout, stderr io.Writer) (*os.ProcessState, error){
	cmd := exec.Command(commandName, args...)
	childStdout, _ := cmd.StdoutPipe()
	childStderr, _ := cmd.StderrPipe()

	go io.Copy(stdout, childStdout)
	go io.Copy(stderr, childStderr)

	err := cmd.Run()
	if err != nil {
		return nil, err
	}
	return cmd.ProcessState, nil
}

func initOut(logDir, commandName string) (stdout, stderr io.Writer, err error) {
	if logDir == "" {
		stdout = os.Stdout
		stderr = os.Stderr
	} else {
		ts := time.Now().Unix()

		stdoutFileName := fmt.Sprintf("%s-%v-stdout.log", commandName, ts)
		stdoutFile, err := os.Create(filepath.Join(logDir, stdoutFileName))
		if err != nil {
			return nil, nil, nil
		}
		stdout = io.MultiWriter(os.Stdout, stdoutFile)

		stderrFileName := fmt.Sprintf("%s-%v-stderr.log", commandName, ts)
		stderrFile, err := os.Create(filepath.Join(logDir, stderrFileName))
		if err != nil {
			return nil, nil, nil
		}
		stderr = io.MultiWriter(os.Stderr, stderrFile)
	}
	return
}

func main() {
	logDir, commnadName, args := parseArgs()
	stdout, stderr, err := initOut(logDir, commnadName)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Can`t create file : %v\n", err)
		os.Exit(1)
	}

	startTime := time.Now();
	ps, err := execution(commnadName, args, stdout, stderr)
	if err != nil {
		fmt.Fprintf(stderr, "Can`t exec command %s", commnadName)
		os.Exit(1)
	}
	exitTime := time.Now();
	fmt.Fprintln(stdout, ps.String())
	fmt.Fprintf(stdout, "wall clock time=%v system time=%v user time=%v\n",
		exitTime.Sub(startTime), ps.SystemTime(), ps.UserTime())
}