package exec

import (
	"bufio"
	"io"
	"log"
	"os/exec"
	"strings"
)

type Executor interface {
	StartExecuteCommand(actionName string, command string, arg ...string) (*exec.Cmd, error)
	ExecuteCommand(actionName string, command string, arg ...string) error
	ExecuteCommandPipeline(actionName string, command string) (string, error)
	ExecuteCommandWithOutput(actionName string, command string, arg ...string) (string, error)
}

type CommandExecutor struct {
}

// Start a process and return immediately
func (*CommandExecutor) StartExecuteCommand(actionName string, command string, arg ...string) (*exec.Cmd, error) {
	cmd, stdout, stderr, err := startCommand(command, arg...)
	if err != nil {
		return cmd, createCommandError(err, actionName)
	}

	go logOutput(stdout, stderr)

	return cmd, nil
}

// Start a process and wait for its completion
func (*CommandExecutor) ExecuteCommand(actionName string, command string, arg ...string) error {
	cmd, stdout, stderr, err := startCommand(command, arg...)
	if err != nil {
		return createCommandError(err, actionName)
	}

	logOutput(stdout, stderr)

	if err := cmd.Wait(); err != nil {
		return createCommandError(err, actionName)
	}

	return nil
}

func (*CommandExecutor) ExecuteCommandWithOutput(actionName string, command string, arg ...string) (string, error) {
	logCommand(command, arg...)
	cmd := exec.Command(command, arg...)
	return runCommandWithOutput(actionName, cmd)
}

func (*CommandExecutor) ExecuteCommandPipeline(actionName string, command string) (string, error) {
	logCommand(command)
	cmd := exec.Command("bash", "-c", command)
	return runCommandWithOutput(actionName, cmd)
}

func startCommand(command string, arg ...string) (*exec.Cmd, io.ReadCloser, io.ReadCloser, error) {
	logCommand(command, arg...)

	cmd := exec.Command(command, arg...)
	stdout, _ := cmd.StdoutPipe()
	stderr, _ := cmd.StderrPipe()

	err := cmd.Start()

	return cmd, stdout, stderr, err
}

func logOutput(stdout, stderr io.ReadCloser) {
	if stdout == nil || stderr == nil {
		log.Printf("failed to collect stdout and stderr")
		return
	}

	// read command's stdout line by line and write it to the log
	in := bufio.NewScanner(io.MultiReader(stdout, stderr))
	lastLine := ""
	for in.Scan() {
		lastLine = in.Text()
		log.Printf(lastLine)
	}
}

func runCommandWithOutput(actionName string, cmd *exec.Cmd) (string, error) {
	output, err := cmd.Output()
	if err != nil {
		return "", createCommandError(err, actionName)
	}

	return strings.TrimSpace(string(output)), nil
}

func logCommand(command string, arg ...string) {
	log.Printf("Running command: %s %s", command, strings.Join(arg, " "))
}