package utility

import (
	"bytes"
	"io"
	"log"
	"os/exec"
)

func ExecutePipe(outbuffer *bytes.Buffer, stack ...*exec.Cmd) (err error) {
	var errbuffer bytes.Buffer
	pipestack := make([]*io.PipeWriter, len(stack)-1)
	i := 0

	for ; i < len(stack)-1; i++ {
		stdinpipe, stdoutpipe := io.Pipe()
		stack[i].Stdout = stdoutpipe
		stack[i].Stderr = &errbuffer
		stack[i+1].Stdin = stdinpipe
		pipestack[i] = stdoutpipe
	}

	stack[i].Stdout = outbuffer
	stack[i].Stderr = &errbuffer

	if err := callpipe(stack, pipestack); err != nil {
		log.Fatalln(string(errbuffer.Bytes()), err)
	}

	return err
}

func callpipe(stack []*exec.Cmd, pipes []*io.PipeWriter) (err error) {
	if stack[0].Process == nil {
		if err = stack[0].Start(); err != nil {
			return err
		}
	}

	if len(stack) > 1 {
		if err = stack[1].Start(); err != nil {
			return err
		}
		defer func() {
			if err == nil {
				pipes[0].Close()
				err = callpipe(stack[1:], pipes[1:])
			}
		}()
	}

	return stack[0].Wait()
}