package dependencies

import (
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"regexp"
	"runtime"
	"strings"

	"github.com/blang/semver"
	"github.com/juju/errors"

	"git.home.m-and-m.ovh/mderasse/boot/helpers"

	log "github.com/sirupsen/logrus"
)

// minimum minor required for the app to work
const minimumGolangVersion = "1.18.4"

// installation directory for fresh install.
// will be prefixed by $HOME
const defaultGolangInstallDir = "/local/go"

var regexGolangVersion = regexp.MustCompile(`^go version go(\d+\.\d+\.\d+)`)

type Golang struct{}

// regroup all golang dependencies function

// GetName
func (g Golang) GetName() string {
	return "Golang"
}

// GetMinimumVersion
func (g Golang) GetMinimumVersion() string {
	return minimumGolangVersion
}

// IsInstalled
func (g Golang) IsInstalled() (bool, error) {

	_, err := g.GetBinaryPath()
	if err != nil && !errors.Is(err, exec.ErrNotFound) {
		return false, errors.Trace(err)
	} else if err != nil && errors.Is(err, exec.ErrNotFound) {
		return false, nil
	}

	return true, nil
}

// GetBinaryPath
func (g Golang) GetBinaryPath() (string, error) {
	log.Debug("looking for golang binary")

	path, err := exec.LookPath("go")
	if err != nil {
		return "", errors.Trace(err)
	}

	log.Debug("found golang binary in", path)

	return path, nil
}

// GetVersion
func (g Golang) GetVersion() (string, error) {

	isInstalled, err := g.IsInstalled()
	if err != nil {
		return "", errors.Trace(err)
	}

	if !isInstalled {
		return "", errors.NotFoundf("golang is not installed on the system")
	}

	binaryPath, err := g.GetBinaryPath()
	if err != nil {
		return "", errors.Trace(err)
	}

	log.Debug("executing go version command")

	cmd := exec.Command(binaryPath, "version")
	stdout, err := cmd.Output()
	if err != nil {
		return "", errors.Trace(err)
	}
	cleanOut := strings.TrimSpace(string(stdout))

	log.Debugf("go version returned %s", cleanOut)

	parseOutput := regexGolangVersion.FindStringSubmatch(cleanOut)
	if len(parseOutput) != 2 {
		return "", errors.NotSupportedf("failed to parse golang version output: %s", cleanOut)
	}

	return parseOutput[1], nil
}

// IsVersionSupported
func (g Golang) IsVersionSupported() (bool, error) {

	isInstalled, err := g.IsInstalled()
	if err != nil {
		return false, errors.Trace(err)
	}
	if !isInstalled {
		return false, nil
	}

	version, err := g.GetVersion()
	if err != nil {
		return false, errors.Trace(err)
	}

	installedVersion, err := semver.Make(version)
	if err != nil {
		return false, errors.Trace(err)
	}

	requiredVersion, _ := semver.Make(minimumGolangVersion)
	if err != nil {
		return false, errors.Trace(err)
	}

	if installedVersion.LT(requiredVersion) {
		return false, nil
	}

	return true, nil
}

// CanBeInstalled
func (g Golang) CanBeInstalled() bool {
	return true
}

// DescribeInstall
func (g Golang) DescribeInstall(path string) string {

	commands := []string{
		"The following commands will be executed",
		fmt.Sprintf("rm -rf %s/* ", path),
		fmt.Sprintf("curl %s | tar --strip-components=1 -C %s -zxf -", g.getDownloadUrl(), path),
	}

	return strings.Join(commands, "\n")
}

// Install
func (g Golang) Install(path string) error {

	err := helpers.RemoveDirectoryContent(path)
	if err != nil {
		log.Warnf("fail to delete content of directory %s", path)
	}

	downloadUrl := g.getDownloadUrl()
	content, err := downloadFile(downloadUrl)
	if err != nil {
		log.Warnf("fail to download file from %s", downloadUrl)
		return errors.Trace(err)
	}

	gzipReader, err := unGzip(content)
	if err != nil {
		log.Warnf("fail to un-gzip downloaded file from %s, error:", downloadUrl)
		return errors.Trace(err)
	}

	// XXX: unTar should take a subdir
	err = unTar(gzipReader, "go/", path)
	if err != nil {
		log.Warnf("fail to un-tar downloaded file from %s", downloadUrl)
		return errors.Trace(err)
	}

	return nil
}

// DescribePostInstall
func (g Golang) DescribePostInstall(path string) string {

	descriptions := []string{
		`For your environment to work correctly, we will add if needed the following environment variable to your .bashrc:

	export GOPATH=\"$HOME/go\"`,
		fmt.Sprintf("	export GOROOT=\"%s\"", path),
		`	"PATH=\"$GOROOT/bin:$GOPATH/bin:$PATH\"

You will have to reopen a new terminal to apply the changes or execute the following command:

	source $HOME/.bashrc

`,
	}

	return strings.Join(descriptions, "\n")
}

// PostInstall
func (g Golang) PostInstall(path string) error {

	lineBashRc := []string{
		"# Golang - Added by gouik",
	}

	gopath := os.Getenv("GOPATH")
	createGoPath := false
	if gopath == "" {
		lineBashRc = append(lineBashRc, "export GOPATH=\"$HOME/go\"")
		createGoPath = true
	}

	goroot := os.Getenv("GOROOT")
	if goroot == "" {
		lineBashRc = append(lineBashRc, fmt.Sprintf("export GOROOT=\"%s\"", path))
	}

	// checking if go binary is found after installation
	// if not it's probably not in the path
	isInstalled, err := g.IsInstalled()
	if err != nil {
		return errors.Trace(err)
	}

	if !isInstalled {
		lineBashRc = append(lineBashRc, "PATH=\"$GOROOT/bin:$GOPATH/bin:$PATH\"")
	}

	homeDir, err := os.UserHomeDir()
	if err != nil {
		return errors.Trace(err)
	}

	if len(lineBashRc) > 1 {
		log.Debug("Adding env variable to .bashrc")

		fh, err := os.OpenFile(
			filepath.Join(homeDir, ".bashrc"),
			os.O_APPEND|os.O_CREATE|os.O_WRONLY,
			0644,
		)
		if err != nil {
			return errors.Trace(err)
		}
		defer fh.Close()

		_, err = fh.WriteString(
			fmt.Sprintf("\n\n%s\n", strings.Join(lineBashRc, "\n")),
		)
		if err != nil {
			return errors.Trace(err)
		}
	}

	if createGoPath {

		log.Debug("creating gopath directory")

		err = helpers.CheckAndCreateDir(filepath.Join(homeDir, "go"))
		if err != nil {
			return errors.Trace(err)
		}
	}

	return nil
}

// GetInstallDirectory will try to find the current golang directory. If it doesn't exist or if it's in a
// not userspace directory, it will provide the "default"
// It doesn't mean that the directory is "writable"
func (g Golang) GetInstallDirectory() (string, error) {

	homeDir, err := os.UserHomeDir()
	if err != nil {
		return "", errors.Trace(err)
	}

	isInstalled, err := g.IsInstalled()
	if err != nil {
		return "", errors.Trace(err)
	}

	// concat default install dir with home and we have our path
	if !isInstalled {
		return filepath.Join(homeDir, defaultGolangInstallDir), nil
	}

	// now let's play and find the current install path
	binaryPath, err := g.GetBinaryPath()
	if err != nil {
		return "", errors.Trace(err)
	}

	log.Debug("executing go env GOROOT command")

	cmd := exec.Command(binaryPath, "env", "GOROOT")
	stdout, err := cmd.Output()
	if err != nil {
		return "", errors.Trace(err)
	}
	cleanOut := strings.TrimSpace(string(stdout))

	if !strings.Contains(cleanOut, homeDir) {
		return filepath.Join(homeDir, defaultGolangInstallDir), nil
	}

	return cleanOut, nil
}

func (g Golang) getDownloadUrl() string {

	return fmt.Sprintf("https://dl.google.com/go/go%s.%s-%s.tar.gz", minimumGolangVersion, runtime.GOOS, runtime.GOARCH)
}