package container // https://github.com/docker/cli/blob/master/cli/command/container/exec.go

import (
	"context"
	"errors"
	"fmt"
	"io"

	"github.com/docker/cli/cli"
	"github.com/docker/cli/cli/command"
	"github.com/docker/docker/api/types"
	apiclient "github.com/docker/docker/client"
	"github.com/sirupsen/logrus"
)

// RunExec runs a command on a remote container. io.Writer corresponds to the
// command output.
func RunExec(dockerCli command.Cli, client *apiclient.Client, containerID string,
	execConfig *types.ExecConfig) (io.Writer, error) {
	ctx := context.Background()

	// We need to check the tty _before_ we do the ContainerExecCreate, because
	// otherwise if we error out we will leak execIDs on the server (and
	// there's no easy way to clean those up). But also in order to make "not
	// exist" errors take precedence we do a dummy inspect first.
	if _, err := client.ContainerInspect(ctx, containerID); err != nil {
		return nil, err
	}
	if !execConfig.Detach {
		if err := dockerCli.In().CheckTty(execConfig.AttachStdin, execConfig.Tty); err != nil {
			return nil, err
		}
	}

	response, err := client.ContainerExecCreate(ctx, containerID, *execConfig)
	if err != nil {
		return nil, err
	}

	execID := response.ID
	if execID == "" {
		return nil, errors.New("exec ID empty")
	}

	if execConfig.Detach {
		execStartCheck := types.ExecStartCheck{
			Detach: execConfig.Detach,
			Tty:    execConfig.Tty,
		}
		return nil, client.ContainerExecStart(ctx, execID, execStartCheck)
	}
	return interactiveExec(ctx, dockerCli, client, execConfig, execID)
}

func interactiveExec(ctx context.Context, dockerCli command.Cli, client *apiclient.Client,
	execConfig *types.ExecConfig, execID string) (io.Writer, error) {
	// Interactive exec requested.
	var (
		out, stderr io.Writer
		in          io.ReadCloser
	)

	if execConfig.AttachStdin {
		in = dockerCli.In()
	}
	if execConfig.AttachStdout {
		out = dockerCli.Out()
	}
	if execConfig.AttachStderr {
		if execConfig.Tty {
			stderr = dockerCli.Out()
		} else {
			stderr = dockerCli.Err()
		}
	}

	execStartCheck := types.ExecStartCheck{
		Tty: execConfig.Tty,
	}
	resp, err := client.ContainerExecAttach(ctx, execID, execStartCheck)
	if err != nil {
		return out, err
	}
	defer resp.Close()

	errCh := make(chan error, 1)

	go func() {
		defer close(errCh)
		errCh <- func() error {
			streamer := hijackedIOStreamer{
				streams:      dockerCli,
				inputStream:  in,
				outputStream: out,
				errorStream:  stderr,
				resp:         resp,
				tty:          execConfig.Tty,
				detachKeys:   execConfig.DetachKeys,
			}

			return streamer.stream(ctx)
		}()
	}()

	if execConfig.Tty && dockerCli.In().IsTerminal() {
		if err := MonitorTtySize(ctx, client, dockerCli, execID, true); err != nil {
			fmt.Fprintln(dockerCli.Err(), "Error monitoring TTY size:", err)
		}
	}

	if err := <-errCh; err != nil {
		logrus.Debugf("Error hijack: %s", err)
		return out, err
	}

	return out, getExecExitStatus(ctx, client, execID)
}

func getExecExitStatus(ctx context.Context, client apiclient.ContainerAPIClient, execID string) error {
	resp, err := client.ContainerExecInspect(ctx, execID)
	if err != nil {
		// If we can't connect, then the daemon probably died.
		if !apiclient.IsErrConnectionFailed(err) {
			return err
		}
		return cli.StatusError{StatusCode: -1}
	}
	status := resp.ExitCode
	if status != 0 {
		return cli.StatusError{StatusCode: status}
	}
	return nil
}