// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
// See LICENSE.txt for license information.

package upgrader

import (
	"archive/tar"
	"bytes"
	"compress/gzip"
	_ "embed"
	"fmt"
	"io"
	"net/http"
	"os"
	"os/user"
	"path"
	"runtime"
	"strconv"
	"strings"
	"sync"
	"sync/atomic"
	"syscall"

	"github.com/pkg/errors"
	"golang.org/x/crypto/openpgp" //nolint:staticcheck

	"github.com/mattermost/mattermost/server/public/model"
	"github.com/mattermost/mattermost/server/public/shared/mlog"
)

//go:embed pubkey.gpg
var mattermostBuildPublicKeys []byte

var (
	upgradePercentage int64
	m                 sync.Mutex
	upgradeError      error
	upgrading         int32
)

type writeCounter struct {
	total int64
	read  int64
}

func (wc *writeCounter) Write(p []byte) (int, error) {
	n := len(p)
	wc.read += int64(n)

	if wc.total <= 0 {
		// skip the percentage calculation for invalid totals
		setUpgradePercentage(50)
		return n, nil
	}

	percentage := (wc.read * 100) / wc.total
	if percentage == 0 {
		percentage = 1
	} else if percentage >= 100 {
		percentage = 99
	}

	setUpgradePercentage(percentage)

	return n, nil
}

func getUpgradePercentage() int64 {
	return atomic.LoadInt64(&upgradePercentage)
}

func setUpgradePercentage(to int64) {
	atomic.StoreInt64(&upgradePercentage, to)
}

func getUpgradeError() error {
	m.Lock()
	defer m.Unlock()

	return upgradeError
}

func setUpgradeError(err error) {
	m.Lock()
	defer m.Unlock()

	upgradeError = err
}

func getCurrentVersionTgzURL() string {
	version := model.CurrentVersion
	if strings.HasPrefix(model.BuildNumber, version+"-rc") {
		version = model.BuildNumber
	}

	return "https://releases.mattermost.com/" + version + "/mattermost-" + version + "-linux-amd64.tar.gz"
}

func verifySignature(filename string, sigfilename string, publicKey []byte) error {
	keyring, err := openpgp.ReadArmoredKeyRing(bytes.NewReader(publicKey))
	if err != nil {
		mlog.Debug("Unable to load the public key to verify the file signature", mlog.Err(err))
		return NewInvalidSignature()
	}

	mattermost_tar, err := os.Open(filename)
	if err != nil {
		mlog.Debug("Unable to open the Mattermost .tar file to verify the file signature", mlog.Err(err))
		return NewInvalidSignature()
	}

	signature, err := os.Open(sigfilename)
	if err != nil {
		mlog.Debug("Unable to open the Mattermost .sig file verify the file signature", mlog.Err(err))
		return NewInvalidSignature()
	}

	_, err = openpgp.CheckDetachedSignature(keyring, mattermost_tar, signature)
	if err != nil {
		mlog.Debug("Unable to verify the Mattermost file signature", mlog.Err(err))
		return NewInvalidSignature()
	}
	return nil
}

func canIWriteTheExecutable() error {
	executablePath, err := os.Executable()
	if err != nil {
		return errors.New("error getting the path of the executable")
	}
	executableInfo, err := os.Stat(path.Dir(executablePath))
	if err != nil {
		return errors.New("error getting the executable info")
	}
	stat, ok := executableInfo.Sys().(*syscall.Stat_t)
	if !ok {
		return errors.New("error getting the executable info")
	}
	fileUID := int(stat.Uid)
	fileUser, err := user.LookupId(strconv.Itoa(fileUID))
	if err != nil {
		return errors.New("error getting the executable info")
	}

	mattermostUID := os.Getuid()
	mattermostUser, err := user.LookupId(strconv.Itoa(mattermostUID))
	if err != nil {
		return errors.New("error getting the executable info")
	}

	mode := executableInfo.Mode()
	if fileUID != mattermostUID && mode&(1<<1) == 0 && mode&(1<<7) == 0 {
		return NewInvalidPermissions("invalid-user-and-permission", path.Dir(executablePath), mattermostUser.Username, fileUser.Username)
	}

	if fileUID != mattermostUID && mode&(1<<1) == 0 && mode&(1<<7) != 0 {
		return NewInvalidPermissions("invalid-user", path.Dir(executablePath), mattermostUser.Username, fileUser.Username)
	}

	if fileUID == mattermostUID && mode&(1<<7) == 0 {
		return NewInvalidPermissions("invalid-permission", path.Dir(executablePath), mattermostUser.Username, fileUser.Username)
	}
	return nil
}

func canIUpgrade() error {
	if runtime.GOARCH != "amd64" {
		return NewInvalidArch()
	}
	if runtime.GOOS != "linux" {
		return NewInvalidArch()
	}
	return canIWriteTheExecutable()
}

func CanIUpgradeToE0() error {
	if err := canIUpgrade(); err != nil {
		return errors.Wrap(err, "unable to upgrade from TE to E0")
	}
	if model.BuildEnterpriseReady == "true" {
		mlog.Warn("Unable to upgrade from TE to E0. The server is already running E0.")
		return errors.New("you cannot upgrade your server from TE to E0 because you are already running Mattermost Enterprise Edition")
	}
	return nil
}

func UpgradeToE0() error {
	if !atomic.CompareAndSwapInt32(&upgrading, 0, 1) {
		mlog.Warn("Trying to upgrade while another upgrade is running")
		return errors.New("another upgrade is already running")
	}
	defer atomic.CompareAndSwapInt32(&upgrading, 1, 0)

	setUpgradePercentage(1)
	setUpgradeError(nil)

	executablePath, err := os.Executable()
	if err != nil {
		setUpgradeError(errors.New("error getting the executable path"))
		mlog.Error("Unable to get the path of the Mattermost executable", mlog.Err(err))
		setUpgradePercentage(0)
		return err
	}

	filename, err := download(getCurrentVersionTgzURL())
	if err != nil {
		if filename != "" {
			os.Remove(filename)
		}
		setUpgradeError(fmt.Errorf("error downloading the new Mattermost server binary file (percentage: %d)", getUpgradePercentage()))
		mlog.Error("Unable to download the Mattermost server binary file", mlog.Int("percentage", getUpgradePercentage()), mlog.String("url", getCurrentVersionTgzURL()), mlog.Err(err))
		setUpgradePercentage(0)
		return err
	}
	defer os.Remove(filename)

	sigfilename, err := download(getCurrentVersionTgzURL() + ".sig")
	if err != nil {
		if sigfilename != "" {
			os.Remove(sigfilename)
		}
		setUpgradeError(errors.New("error downloading the signature file of the new server"))
		mlog.Error("Unable to download the signature file of the new Mattermost server", mlog.String("url", getCurrentVersionTgzURL()+".sig"), mlog.Err(err))
		setUpgradePercentage(0)
		return err
	}
	defer os.Remove(sigfilename)

	err = verifySignature(filename, sigfilename, mattermostBuildPublicKeys)
	if err != nil {
		setUpgradeError(errors.New("unable to verify the signature of the downloaded file"))
		mlog.Error("Unable to verify the signature of the downloaded file", mlog.Err(err))
		setUpgradePercentage(0)
		return err
	}

	err = extractBinary(executablePath, filename)
	if err != nil {
		setUpgradeError(err)
		mlog.Error("Unable to extract the binary from the downloaded file", mlog.Err(err))
		setUpgradePercentage(0)
		return err
	}

	setUpgradePercentage(100)
	return nil
}

func UpgradeToE0Status() (int64, error) {
	return getUpgradePercentage(), getUpgradeError()
}

func download(url string) (string, error) {
	resp, err := http.Get(url)
	if err != nil {
		return "", err
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		io.Copy(io.Discard, resp.Body)
		return "", errors.Errorf("error downloading file %s: %s", url, resp.Status)
	}

	out, err := os.CreateTemp("", "*_mattermost.tar.gz")
	if err != nil {
		return "", err
	}
	defer out.Close()

	counter := &writeCounter{total: resp.ContentLength}
	_, err = io.Copy(out, io.TeeReader(resp.Body, counter))
	if err != nil {
		return "", err
	}

	return out.Name(), nil
}

func getFilePermissionsOrDefault(filename string, def os.FileMode) os.FileMode {
	file, err := os.Open(filename)
	if err != nil {
		mlog.Warn("Unable to get the file permissions", mlog.String("filename", filename), mlog.Err(err))
		return def
	}
	defer file.Close()

	fileStats, err := file.Stat()
	if err != nil {
		mlog.Warn("Unable to get the file permissions", mlog.String("filename", filename), mlog.Err(err))
		return def
	}
	return fileStats.Mode()
}

func extractBinary(executablePath string, filename string) error {
	gzipStream, err := os.Open(filename)
	if err != nil {
		return err
	}

	uncompressedStream, err := gzip.NewReader(gzipStream)
	if err != nil {
		return err
	}

	tarReader := tar.NewReader(uncompressedStream)

	for {
		header, err := tarReader.Next()

		if err == io.EOF {
			return errors.New("unable to find the Mattermost binary in the downloaded version")
		}

		if err != nil {
			return err
		}

		if header.Typeflag == tar.TypeReg && header.Name == "mattermost/bin/mattermost" {
			permissions := getFilePermissionsOrDefault(executablePath, 0755)
			tmpFile, err := os.CreateTemp(path.Dir(executablePath), "*")
			if err != nil {
				return err
			}
			tmpFileName := tmpFile.Name()
			os.Remove(tmpFileName)
			err = os.Rename(executablePath, tmpFileName)
			if err != nil {
				return err
			}
			outFile, err := os.Create(executablePath)
			if err != nil {
				err2 := os.Rename(tmpFileName, executablePath)
				if err2 != nil {
					mlog.Fatal("Unable to restore the backup of the executable file. Restore the executable file manually.")
					return errors.Wrap(err2, "critical error: unable to upgrade the binary or restore the old binary version. Please restore it manually")
				}
				return err
			}
			defer outFile.Close()
			if _, err = io.Copy(outFile, tarReader); err != nil {
				err2 := os.Remove(executablePath)
				if err2 != nil {
					mlog.Fatal("Unable to restore the backup of the executable file. Restore the executable file manually.")
					return errors.Wrap(err2, "critical error: unable to upgrade the binary or restore the old binary version. Please restore it manually")
				}

				err2 = os.Rename(tmpFileName, executablePath)
				if err2 != nil {
					mlog.Fatal("Unable to restore the backup of the executable file. Restore the executable file manually.")
					return errors.Wrap(err2, "critical error: unable to upgrade the binary or restore the old binary version. Please restore it manually")
				}
				return err
			}
			err = os.Remove(tmpFileName)
			if err != nil {
				mlog.Warn("Unable to clean up the binary backup file.", mlog.Err(err))
			}
			err = os.Chmod(executablePath, permissions)
			if err != nil {
				mlog.Warn("Unable to set the correct permissions for the file.", mlog.Err(err))
			}
			break
		}
	}
	return nil
}