package main

import (
	"bufio"
	_ "embed"
	"errors"
	"flag"
	"fmt"
	"os"
	"os/exec"
	"os/user"
	"strconv"
	"syscall"
)

const usage = `workspace - Use a containerized workspace

COMMANDS

dump-init-files: Dump emacs/bash init files to home directory, overwriting existing files.
                 List of files: ~/.bash_aliases, ~/.emacs, ~/.custom.el
`

//go:embed emacs/init.el
var initLisp string

//go:embed emacs/custom.el
var customLisp string

//go:embed bash/bash_aliases
var bashAliases string

var ErrAddUserFailExit = errors.New("useradd command returned no-zero exit code")
var ErrAddGroupFailExit = errors.New("groupadd command returned no-zero exit code")

func AddUser(username string, uid string) error {
	cmd := exec.Command(
		"useradd",
		"--no-create-home",
		"--uid", uid,
		"--user-group",
		username,
	)

	output, err := cmd.CombinedOutput()
	if err != nil {
		return fmt.Errorf(
			"Error adding user: %w. Process error: %w. Process output: %s",
			ErrAddUserFailExit,
			err,
			output,
		)
	}

	return nil
}

func AddGroup(name string, gid string) error {
	cmd := exec.Command(
		"groupadd",
		"--gid", gid,
		name,
	)

	output, err := cmd.CombinedOutput()
	if err != nil {
		return fmt.Errorf(
			"Error adding group: %w. Process error: %w. Process output: %s",
			ErrAddGroupFailExit,
			err,
			output,
		)
	}

	return nil
}

func EntryPoint(command []string) error {
	if len(command) == 0 {
		command = []string{"/bin/bash", "-i"}
	}

	uidString := os.Getenv("WORKSPACE_USER")
	uid, err := strconv.Atoi(uidString)
	if err != nil {
		return fmt.Errorf(
			"Failed to parse UID from WORKSPACE_USER env var with contents \"%s\". Error: %w",
			os.Getenv("WORKSPACE_USER"),
			err,
		)
	}

	dockerGidString := os.Getenv("WORKSPACE_DOCKER_GID")
	dockerGid, err := strconv.Atoi(dockerGidString)
	if err != nil {
		return fmt.Errorf(
			"Failed to parse GID from WORKSPACE_DOCKER_GID env var with contents \"%s\". Error: %w",
			os.Getenv("WORKSPACE_DOCKER_GID"),
			err,
		)
	}

	err = AddUser(os.Getenv("WORKSPACE_USERNAME"), uidString)
	if err != nil {
		return err
	}

	err = AddGroup("docker", dockerGidString)
	if err != nil {
		return err
	}

	err = syscall.Setgroups([]int{dockerGid})
	if err != nil {
		return err
	}

	err = syscall.Setgid(int(uid))
	if err != nil {
		return err
	}

	err = syscall.Setuid(int(uid))
	if err != nil {
		return err
	}

	path, err := exec.LookPath(command[0])
	if err != nil {
		return err
	}

	SetEnvVars()

	return syscall.Exec(path, command, os.Environ())
}

func Run(detach bool, mounts []string, command []string) error {
	workDir, err := os.Getwd()
	if err != nil {
		return err
	}

	curUser, err := user.Current()
	if err != nil {
		return err
	}

	home := os.Getenv("HOME")
	dockerGroup, err := user.LookupGroup("docker")
	if err != nil {
		return err
	}

	dockerCommand := []string{
		"/bin/docker", "run", "--network=host",
		"--workdir=" + workDir,
		"-e", "DISPLAY=" + os.Getenv("DISPLAY"),
		"-e", "WORKSPACE_USER=" + curUser.Uid,
		"-e", "WORKSPACE_USERNAME=" + curUser.Username,
		"-e", "WORKSPACE_DOCKER_GID=" + dockerGroup.Gid,
		"-e", "HOME=" + home,
		"-h", os.Getenv("HOSTNAME"),
		"-v", "/var/run/docker.sock:/var/run/docker.sock",
		"-v", "/etc/hosts:/etc/hosts:ro",
		"-v", "/etc/resolv.conf:/etc/resolv.conf:ro",
		"-v", home + ":" + home,
		"-e", "SSH_AGENT_LAUNCHER=" + os.Getenv("SSH_AGENT_LAUNCHER"),
		"-e", "SSH_AUTH_SOCK=" + os.Getenv("SSH_AUTH_SOCK"),
		"-e", "PULSE_SERVER=unix:/run/user/" + curUser.Uid + "/pulse/native",
		"-e", "DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/" + curUser.Uid + "/bus",
		"-e", "TERM=" + os.Getenv("TERM"),
		"-v", "/tmp/.X11-unix:/tmp/.X11-unix",
		"-v", "/run/user/" + curUser.Uid + ":/run/user/" + curUser.Uid,
		"-v", "/dev/snd",
	}

	if detach {
		dockerCommand = append(dockerCommand, "--detach")
	}

	if fileInfo, _ := os.Stdout.Stat(); (fileInfo.Mode() & os.ModeCharDevice) != 0 {
		dockerCommand = append(dockerCommand, "-ti")
	}

	for _, mount := range mounts {
		dockerCommand = append(dockerCommand, "-v", mount+":"+mount)
	}

	fileInfo, err := os.Lstat(home)
	if err != nil {
		return fmt.Errorf(
			"Failed to determine whether home directory is a symbolic link: %w",
			err,
		)
	}

	if fileInfo.Mode()&os.ModeSymlink == os.ModeSymlink {
		destination, err := os.Readlink(home)
		if err != nil {
			return fmt.Errorf(
				"Failed to determine whether home directory is a symbolic link: %w",
				err,
			)
		}

		dockerCommand = append(dockerCommand, "-v", destination+":"+destination)
	}

	dockerCommand = append(dockerCommand, "hugotty/workspace:latest")
	dockerCommand = append(dockerCommand, command...)

	return syscall.Exec(dockerCommand[0], dockerCommand, os.Environ())
}

func SetEnvVars() {
	home := os.Getenv("HOME")
	os.Setenv("PATH", home+"/bin:"+os.Getenv("PATH"))
	os.Setenv("PATH", home+"/dotfiles/bin:"+os.Getenv("PATH"))

	// PHP
	os.Setenv("PATH", home+"/.config/composer/vendor/bin:"+os.Getenv("PATH"))

	// Node
	os.Setenv("PATH", home+"/.npm_packages/bin:"+os.Getenv("PATH"))

	// Perl
	os.Setenv("PATH", home+"/perl5/perlbrew/bin:"+os.Getenv("PATH"))

	// Rust
	os.Setenv("PATH", home+"/.cargo/bin:"+os.Getenv("PATH"))

	// Locally installed python packages
	os.Setenv("PATH", home+"/.local/bin:"+os.Getenv("PATH"))

	// Home for virtualenvs
	os.Setenv("WORKON_HOME", home+"/.local/share/virtualenvs")

	// GO Stuff
	os.Setenv("GOPATH", home+"/go")
	os.Setenv("PATH", home+"/go/bin:"+os.Getenv("PATH"))
	os.Setenv("GOPRIVATE", "git.snorba.art")
}

func DumpStringToFile(data string, path string) error {
	file, err := os.Create(path)
	if err != nil {
		return err
	}

	writer := bufio.NewWriter(file)
	_, err = writer.WriteString(data)
	if err != nil {
		return err
	}

	return writer.Flush()
}

func main() {
	var cmd string
	if len(os.Args) > 1 {
		cmd = os.Args[1]
	}

	var detach bool
	run := flag.NewFlagSet("run", flag.ExitOnError)
	run.BoolVar(
		&detach,
		"detach",
		false,
		"Whether or not to detach from the container after running the command",
	)

	var mounts arrayFlag
	run.Var(&mounts, "mount", "Directory to mount inside the workspace container")

	switch cmd {
	case "entrypoint":
		err := EntryPoint(os.Args[2:])
		if err != nil {
			fmt.Println("error executing entrypoint command", err)
			os.Exit(1)
		}

	case "run":
		err := run.Parse(os.Args[2:])
		if err != nil {
			fmt.Println(err)
			os.Exit(1)
		}

		err = Run(detach, mounts, run.Args())
		if err != nil {
			fmt.Println("error running command in container", err)
			os.Exit(1)
		}
	case "dump-init-files":
		home := os.Getenv("HOME")

		files := map[string]string{
			home + "/.emacs":        initLisp,
			home + "/.custom.el":    customLisp,
			home + "/.bash_aliases": bashAliases,
		}

		for file, contents := range files {
			fmt.Fprintln(os.Stderr, "Dumping to "+file)
			err := DumpStringToFile(contents, file)
			if err != nil {
				fmt.Fprintln(os.Stderr, err)
				os.Exit(1)
			}
		}
	default:
		fmt.Println(usage)
		fmt.Println("run COMMAND: Start workspace container and run COMMAND within it")
		run.Usage()
	}
}