tramp-blog/commands/shell/subshell.go

package shell

import (
	"bytes"
	"io"
	"log"
)

type SubshellParameters struct{}

func (p *SubshellParameters) SubParsers() []Parser {
	return []Parser{
		&BaseParser{
			parameters: &StatementParameters{},
		},
	}
}

func (p *SubshellParameters) Enter(i *CharIterator) error {
	return i.Next()
}

func (p *SubshellParameters) Supports(charsBefore []rune, r rune) bool {
	if r == '(' {
		return len(charsBefore) == 0 ||
			countBackslashSuffixes(charsBefore)%2 == 0
	}

	return false
}

func (p *SubshellParameters) ShouldLeave(charsBefore []rune, r rune) bool {
	if r == ')' {
		return len(charsBefore) == 0 ||
			countBackslashSuffixes(charsBefore)%2 == 0
	}

	return false
}

func (p *SubshellParameters) MakeToken() Token {
	return &Subshell{}
}

type Subshell struct {
	BaseToken
}

func (s *Subshell) Evaluate(state State, stdin io.Reader, stdout io.Writer, stderr io.Writer) uint8 {
	var ret uint8

	for _, token := range s.Tokens() {
		if eval, ok := token.(Evalable); ok {
			ret = state.Eval(eval, stdin, stdout, stderr)
		} else {
			logstr := "shell: Unexpected token: " + token.String()
			log.Println(logstr)
			stderr.Write([]byte(logstr))

			return 2
		}
	}

	return ret
}

type Backtick struct {
	BaseToken
}

type BacktickParameters struct{}

func (p *BacktickParameters) MakeToken() Token {
	return &Backtick{}
}

func (p *BacktickParameters) Enter(i *CharIterator) error {
	return i.Next()
}

func (p *BacktickParameters) Supports(charsBefore []rune, r rune) bool {
	if r == '`' {
		return len(charsBefore) == 0 ||
			countBackslashSuffixes(charsBefore)%2 == 0
	}

	return false
}

func (p *BacktickParameters) ShouldLeave(charsBefore []rune, r rune) bool {
	if r == '`' {
		return len(charsBefore) == 0 ||
			countBackslashSuffixes(charsBefore)%2 == 0
	}

	return false
}

func (b *Backtick) Expand(state State, stdin io.Reader, stderr io.Writer) ([]string, uint8) {
	var ret uint8
	stdout := bytes.NewBuffer([]byte{})

	for _, token := range b.Tokens() {
		if eval, ok := token.(Evalable); ok {
			ret = state.Eval(eval, stdin, stdout, stderr)
		} else {
			logstr := "shell: Unexpected token: " + token.String()
			log.Println(logstr)
			stderr.Write([]byte(logstr))
		}
	}

	return []string{stdout.String()}, ret
}

func (p *BacktickParameters) SubParsers() []Parser {
	return []Parser{
		&BaseParser{
			parameters: &StatementInsideBacktickparameters{},
		},
	}
}

type StatementInsideBacktickparameters struct {
	StatementParameters
}

// Note: this is a bit of a hack. There is no way to know whether the new
// backtick is supposed to open a new backtick statement within the backtick, or
// close the current one. At least not in the current implementation that
// doesn't allow us to look ahead. Which means that backticks inside backticks
// are not supported.
func (p *StatementInsideBacktickparameters) ShouldLeave(charsBefore []rune, r rune) bool {
	if r == '\n' || r == ';' || r == ')' || r == '`' {
		return countBackslashSuffixes(charsBefore)%2 == 0
	}

	return false
}

func (p *StatementInsideBacktickparameters) Leave(i *CharIterator) error {
	if i.Current() == '`' {
		return i.Previous()
	}

	return nil
}