shelly/lib.go

package shelly

import (
	"errors"
	"fmt"
	"log"
	"os/exec"
	"strings"
	"sync"
)

type Mode int

func (m Mode) String() string {
	switch m {
	case MODE_NORMAL:
		return "NORMAL"
	case MODE_STR:
		return "STR"
	case MODE_ESCAPE:
		return "ESCAPE"
	case MODE_ESCAPE_STR:
		return "ESCAPE_STR"
	}

	return "UNKNOWN"
}

const (
	MODE_NORMAL Mode = iota
	MODE_STR
	MODE_ESCAPE
	MODE_ESCAPE_STR
)

type LineType int

const (
	LINETYPE_SERIAL LineType = iota
	LINETYPE_PARALLEL
	LINETYPE_COMMENT
)

// Opts tells Exec how to behave
// Opts.Await will inform whether its call should wait for all parallel started jobs to finish
// Opts.SetupProc will customize the processes before execution - Eg.: setting out and err
type Opts struct {
	Await     bool
	SetupProc func(cmd *exec.Cmd)
}

// Line represents a line to be executed by the shell.
// Can be separated by \n our ; - in case of serial execution. & will be used to identify parallel execution
type Line struct {
	Tokens []string
	LType  LineType
}

// Tokens will break the string into tokens - It can be later organized in command lines and alikes
func Tokens(str string) ([]string, error) {
	params := make([]string, 0)
	sb := strings.Builder{}
	mode := MODE_NORMAL
	for i, a := range str {
		switch a {
		case ' ', '\t', '\r':
			switch mode {
			case MODE_NORMAL:
				if sb.Len() > 0 {
					params = append(params, sb.String())
				}
				sb = strings.Builder{}
			case MODE_STR:
				sb.WriteRune(a)
			default:
				return nil, errors.New(fmt.Sprintf("Error at char %d - cant add space here. Mode: %s", i, mode.String()))
			}
		case '\n':
			switch mode {
			case MODE_NORMAL:
				if sb.Len() > 0 {
					params = append(params, sb.String())
				}
				params = append(params, "\n")
				sb = strings.Builder{}
			case MODE_STR:
				sb.WriteRune(a)
			default:
				return nil, errors.New(fmt.Sprintf("Error at char %d - cant add new line here. Mode: %s", i, mode.String()))
			}
		case '"':
			switch mode {
			case MODE_NORMAL:
				if sb.Len() > 0 {
					params = append(params, sb.String())
				}
				sb = strings.Builder{}
				mode = MODE_STR
			case MODE_STR:
				params = append(params, sb.String())
				sb = strings.Builder{}
				mode = MODE_NORMAL
			case MODE_ESCAPE:
				sb.WriteRune(a)
				mode = MODE_NORMAL
			case MODE_ESCAPE_STR:
				sb.WriteRune(a)
				mode = MODE_STR
			}
		case '\\':
			switch mode {
			case MODE_NORMAL:
				mode = MODE_ESCAPE
			case MODE_STR:
				mode = MODE_ESCAPE_STR
			case MODE_ESCAPE:
				sb.WriteString("\\")
				mode = MODE_NORMAL
			case MODE_ESCAPE_STR:
				sb.WriteString("\\")
				mode = MODE_STR
			}
		default:
			switch mode {
			case MODE_NORMAL:
				sb.WriteRune(a)
			case MODE_STR:
				sb.WriteRune(a)
			case MODE_ESCAPE:
				sb.WriteString("\\" + string(a))
				mode = MODE_NORMAL
			case MODE_ESCAPE_STR:
				sb.WriteString("\\" + string(a))
				mode = MODE_STR
			}

		}
	}
	if mode != MODE_NORMAL {
		return nil, errors.New("Unterminated String")
	}
	if sb.Len() > 0 {
		params = append(params, sb.String())
	}

	return params, nil
}

// Lines will call Tokens first, and reorg them in executable lines
func Lines(str string) ([]Line, error) {
	ret := make([]Line, 0)
	tokens, err := Tokens(str)
	if err != nil {
		return nil, err
	}
	line := Line{
		Tokens: make([]string, 0),
		LType:  LINETYPE_SERIAL,
	}
	for _, tk := range tokens {
		switch tk {
		case "\n", ";":
			if len(line.Tokens) > 0 {
				if strings.HasPrefix(line.Tokens[0], "#") {
					line.LType = LINETYPE_COMMENT
				} else {
					line.LType = LINETYPE_SERIAL
				}
				ret = append(ret, line)
			}
			line = Line{
				Tokens: make([]string, 0),
			}
		case "&":
			if len(line.Tokens) > 0 {
				if strings.HasPrefix(line.Tokens[0], "#") {
					line.LType = LINETYPE_COMMENT
				} else {
					line.LType = LINETYPE_PARALLEL
				}
				ret = append(ret, line)
			}
			line = Line{
				Tokens: make([]string, 0),
			}
		default:
			line.Tokens = append(line.Tokens, tk)
		}
	}
	if len(line.Tokens) > 0 {
		ret = append(ret, line)
	}
	return ret, nil
}

// Exec will call Lines and execute one by one
func Exec(str string, opts ...*Opts) error {

	var opt *Opts
	if opts != nil && len(opts) > 0 {
		opt = opts[0]
	}

	if opt.SetupProc == nil {
		opt.SetupProc = func(cmd *exec.Cmd) {

		}
	}

	prepCmd := func(l Line) *exec.Cmd {
		cmd := exec.Command(l.Tokens[0], l.Tokens[1:]...)
		cmd.Stdout = log.Writer()
		cmd.Stderr = log.Writer()
		opt.SetupProc(cmd)
		return cmd
	}

	wg := sync.WaitGroup{}
	lines, err := Lines(str)

	if err != nil {
		return err
	}
	for _, l := range lines {

		switch l.LType {
		case LINETYPE_COMMENT:
			continue
		case LINETYPE_SERIAL:
			cmd := prepCmd(l)
			err = cmd.Run()
			if err != nil {
				return err
			}
		case LINETYPE_PARALLEL:
			go func(l Line) {
				cmd := prepCmd(l)
				wg.Add(1)
				err = cmd.Run()
				wg.Done()
			}(l)
		}

	}

	if opt.Await {
		wg.Wait()
	}

	return nil

}