nix-amer/internal/instruction/copy.go

package instruction

import (
	"os"
	"strings"
)

type copy struct {
	raw string
	Src string
	Dst string
}

func (d *copy) Raw() string { return strings.Join([]string{"copy", d.raw}, " ") }

func (d *copy) Build(_args string) error {

	// 1. extract action (sub command)
	split := strings.Fields(_args)

	// 2. check syntax
	if len(split) != 2 {
		return ErrInvalidSyntax
	}

	d.Src = strings.Trim(split[0], " \t")
	d.Dst = strings.Trim(split[1], " \t")
	d.raw = _args
	return nil
}

func (d copy) Exec(ctx ExecutionContext) ([]byte, error) {

	// 1. fail if source file not found
	if _, err := os.Stat(d.Src); os.IsNotExist(err) {
		return nil, &FileError{"cannot find file", d.Src, err}
	}

	// 2. execute script
	if err := ctx.Executor.Command("cp", "-r", d.Src, d.Dst).Run(); err != nil {
		return nil, &FileError{"cannot copy to", d.Dst, err}
	}

	return nil, nil

}

func (d copy) DryRun(ctx ExecutionContext) ([]byte, error) {

	// 1. fail if source file not found
	if _, err := os.Stat(d.Src); os.IsNotExist(err) {
		return nil, &FileError{"cannot find file", d.Src, err}
	}

	// 2. if destination to create : try to create (then remove)
	fi, err := os.Stat(d.Dst)
	if os.IsNotExist(err) {

		file, err2 := os.OpenFile(d.Dst, os.O_APPEND|os.O_WRONLY|os.O_CREATE, os.FileMode(0777))
		if err2 != nil {
			return nil, &FileError{"cannot copy to", d.Dst, err2}
		}
		file.Close()

		if err2 := os.Remove(d.Dst); err2 != nil {
			return nil, &FileError{"cannot remove dry-run file", d.Dst, err2}
		}

		return nil, nil

	} else if fi != nil && fi.IsDir() {
		return nil, nil // no error if dir
	}

	// 3. if destination exists : check write permission
	file, err := os.OpenFile(d.Dst, os.O_APPEND|os.O_WRONLY, 0600)
	if err != nil {
		return nil, &FileError{"cannot copy to", d.Dst, err}
	}
	file.Close()

	return nil, nil

}