keybase/cmd.go

package keybase

import (
	"context"
	"fmt"
	"io"
	"os/exec"
)

// apiCmd holds the pipes that connect to an executed command
type apiCmd struct {
	Stderr    io.ReadCloser
	Stdin     io.WriteCloser
	Stdout    io.ReadCloser
	startFunc func() error
}

type cmd interface {
	Start() error
	Stdin() io.WriteCloser
	Stdout() io.ReadCloser
	Stderr() io.ReadCloser
}

type defaultCmd struct {
	apiCmd *apiCmd
}

func (c *defaultCmd) Start() error {
	return c.apiCmd.startFunc()
}

func (c *defaultCmd) Stdin() io.WriteCloser {
	return c.apiCmd.Stdin
}

func (c *defaultCmd) Stdout() io.ReadCloser {
	return c.apiCmd.Stdout
}

func (c *defaultCmd) Stderr() io.ReadCloser {
	return c.apiCmd.Stderr
}

var _ cmd = &defaultCmd{}

func newApiCmd(ctx context.Context, execCmd string, args ...string) (cmd, error) {
	var err error

	// create a new apiCmd
	cmd := &apiCmd{}

	// set up the command
	api := exec.CommandContext(ctx, execCmd, args...)

	// an empty start func for failures
	cmd.startFunc = func() error { return nil }

	// hook up the stderr pipe
	if cmd.Stderr, err = api.StderrPipe(); err != nil {
		return nil, fmt.Errorf("failed to get pipe: %v", err)
	}

	// hook up the stdout pipe
	if cmd.Stdout, err = api.StdoutPipe(); err != nil {
		return nil, fmt.Errorf("failed to get pipe: %v", err)
	}

	// hook up the stdin pipe
	if cmd.Stdin, err = api.StdinPipe(); err != nil {
		return nil, fmt.Errorf("failed to get pipe: %v", err)
	}

	// create an anonymous function to start the commands
	cmd.startFunc = func() error {
		if err := api.Start(); err != nil {
			return fmt.Errorf("failed to start command: %v", err)
		}
		return nil
	}

	return &defaultCmd{cmd}, nil
}