// Copyright 2023 Mikhail Klementev. All rights reserved.
// Use of this source code is governed by a AGPLv3 license
// (or later) that can be found in the LICENSE file.

package main

import (
	"errors"
	"fmt"
	"io/ioutil"
	"math"
	"math/rand"
	"os"
	"os/exec"
	"os/user"
	"regexp"
	"runtime"
	"strings"
	"time"

	"github.com/naoina/toml"
	"github.com/rs/zerolog/log"

	"code.dumpstack.io/tools/out-of-tree/config"
)

type KernelCmd struct {
	NoDownload bool  `help:"do not download qemu image while kernel generation"`
	UseHost    bool  `help:"also use host kernels"`
	Force      bool  `help:"force reinstall kernel"`
	NoHeaders  bool  `help:"do not install kernel headers"`
	Shuffle    bool  `help:"randomize kernels installation order"`
	Retries    int64 `help:"amount of tries for each kernel" default:"10"`

	List        KernelListCmd        `cmd:"" help:"list kernels"`
	Autogen     KernelAutogenCmd     `cmd:"" help:"generate kernels based on the current config"`
	Genall      KernelGenallCmd      `cmd:"" help:"generate all kernels for distro"`
	Install     KernelInstallCmd     `cmd:"" help:"install specific kernel"`
	ConfigRegen KernelConfigRegenCmd `cmd:"" help:"regenerate config"`
}

type KernelListCmd struct{}

func (cmd *KernelListCmd) Run(g *Globals) (err error) {
	kcfg, err := config.ReadKernelConfig(g.Config.Kernels)
	if err != nil {
		log.Debug().Err(err).Msg("read kernel config")
	}

	if len(kcfg.Kernels) == 0 {
		return errors.New("No kernels found")
	}

	for _, k := range kcfg.Kernels {
		fmt.Println(k.DistroType, k.DistroRelease, k.KernelRelease)
	}

	return
}

type KernelAutogenCmd struct {
	Max int64 `help:"download kernels from set defined by regex in release_mask, but no more than X for each of release_mask" default:"100500"`
}

func (cmd KernelAutogenCmd) Run(kernelCmd *KernelCmd, g *Globals) (err error) {
	ka, err := config.ReadArtifactConfig(g.WorkDir + "/.out-of-tree.toml")
	if err != nil {
		return
	}

	for _, sk := range ka.SupportedKernels {
		if sk.DistroRelease == "" {
			err = errors.New("Please set distro_release")
			return
		}

		err = generateKernels(sk,
			g.Config.Docker.Registry,
			g.Config.Docker.Commands,
			cmd.Max, kernelCmd.Retries,
			!kernelCmd.NoDownload,
			kernelCmd.Force,
			!kernelCmd.NoHeaders,
			kernelCmd.Shuffle,
		)
		if err != nil {
			return
		}
	}

	return updateKernelsCfg(kernelCmd.UseHost, !kernelCmd.NoDownload)
}

type KernelGenallCmd struct {
	Distro string `required:"" help:"distribution"`
	Ver    string `required:"" help:"distro version"`
}

func (cmd *KernelGenallCmd) Run(kernelCmd *KernelCmd, g *Globals) (err error) {
	distroType, err := config.NewDistroType(cmd.Distro)
	if err != nil {
		return
	}

	km := config.KernelMask{
		DistroType:    distroType,
		DistroRelease: cmd.Ver,
		ReleaseMask:   ".*",
	}
	err = generateKernels(km,
		g.Config.Docker.Registry,
		g.Config.Docker.Commands,
		math.MaxUint32, kernelCmd.Retries,
		!kernelCmd.NoDownload,
		kernelCmd.Force,
		!kernelCmd.NoHeaders,
		kernelCmd.Shuffle,
	)
	if err != nil {
		return
	}

	return updateKernelsCfg(kernelCmd.UseHost, !kernelCmd.NoDownload)
}

type KernelInstallCmd struct {
	Distro string `required:"" help:"distribution"`
	Ver    string `required:"" help:"distro version"`
	Kernel string `required:"" help:"kernel release mask"`
}

func (cmd *KernelInstallCmd) Run(kernelCmd *KernelCmd, g *Globals) (err error) {
	distroType, err := config.NewDistroType(cmd.Distro)
	if err != nil {
		return
	}

	km := config.KernelMask{
		DistroType:    distroType,
		DistroRelease: cmd.Ver,
		ReleaseMask:   cmd.Kernel,
	}
	err = generateKernels(km,
		g.Config.Docker.Registry,
		g.Config.Docker.Commands,
		math.MaxUint32, kernelCmd.Retries,
		!kernelCmd.NoDownload,
		kernelCmd.Force,
		!kernelCmd.NoHeaders,
		kernelCmd.Shuffle,
	)
	if err != nil {
		return
	}

	return updateKernelsCfg(kernelCmd.UseHost, !kernelCmd.NoDownload)
}

type KernelConfigRegenCmd struct{}

func (cmd *KernelConfigRegenCmd) Run(kernelCmd *KernelCmd, g *Globals) (err error) {
	return updateKernelsCfg(kernelCmd.UseHost, !kernelCmd.NoDownload)
}

func matchDebImagePkg(container, mask string) (pkgs []string, err error) {

	cmd := "apt-cache search --names-only '^linux-image-[0-9\\.\\-]*-generic' | awk '{ print $1 }'"

	// FIXME timeout should be in global out-of-tree config
	c, err := NewContainer(container, time.Hour)
	if err != nil {
		return
	}

	output, err := c.Run(tempDirBase, cmd)
	if err != nil {
		return
	}

	r, err := regexp.Compile("linux-image-" + mask)
	if err != nil {
		return
	}

	for _, pkg := range strings.Fields(output) {
		if r.MatchString(pkg) || strings.Contains(pkg, mask) {
			pkgs = append(pkgs, pkg)
		}
	}

	return
}

func matchCentOSDevelPkg(container, mask string, generic bool) (
	pkgs []string, err error) {

	cmd := "yum search kernel-devel --showduplicates | " +
		"grep '^kernel-devel' | cut -d ' ' -f 1"

	// FIXME timeout should be in global out-of-tree config
	c, err := NewContainer(container, time.Hour)
	if err != nil {
		return
	}

	output, err := c.Run(tempDirBase, cmd)
	if err != nil {
		return
	}

	r, err := regexp.Compile("kernel-devel-" + mask)
	if err != nil {
		return
	}

	for _, pkg := range strings.Fields(output) {
		if r.MatchString(pkg) || strings.Contains(pkg, mask) {
			pkgs = append(pkgs, pkg)
		}
	}

	return
}

func dockerImagePath(sk config.KernelMask) (path string, err error) {
	usr, err := user.Current()
	if err != nil {
		return
	}

	path = usr.HomeDir + "/.out-of-tree/containers/"
	path += sk.DistroType.String() + "/" + sk.DistroRelease
	return
}

func vsyscallAvailable() (available bool, err error) {
	if runtime.GOOS != "linux" {
		// Docker for non-Linux systems is not using the host
		// kernel but uses kernel inside a virtual machine, so
		// it builds by the Docker team with vsyscall support.
		available = true
		return
	}

	buf, err := ioutil.ReadFile("/proc/self/maps")
	if err != nil {
		return
	}

	available = strings.Contains(string(buf), "[vsyscall]")
	return
}

func generateBaseDockerImage(registry string, commands []config.DockerCommand,
	sk config.KernelMask) (err error) {

	imagePath, err := dockerImagePath(sk)
	if err != nil {
		return
	}
	dockerPath := imagePath + "/Dockerfile"

	d := "# BASE\n"

	// TODO move as function to container.go
	cmd := exec.Command(containerRuntime, "images", "-q", sk.DockerName())
	log.Debug().Msgf("run %v", cmd)

	rawOutput, err := cmd.CombinedOutput()
	if err != nil {
		return
	}

	if exists(dockerPath) && string(rawOutput) != "" {
		log.Info().Msgf("Base image for %s:%s found",
			sk.DistroType.String(), sk.DistroRelease)
		return
	}

	log.Info().Msgf("Base image for %s:%s not found, start generating",
		sk.DistroType.String(), sk.DistroRelease)
	os.MkdirAll(imagePath, os.ModePerm)

	d += "FROM "
	if registry != "" {
		d += registry + "/"
	}

	d += fmt.Sprintf("%s:%s\n",
		strings.ToLower(sk.DistroType.String()),
		sk.DistroRelease,
	)

	vsyscall, err := vsyscallAvailable()
	if err != nil {
		return
	}

	for _, c := range commands {
		d += "RUN " + c.Command + "\n"
	}

	switch sk.DistroType {
	case config.Ubuntu:
		d += "ENV DEBIAN_FRONTEND=noninteractive\n"
		d += "RUN apt-get update\n"
		d += "RUN apt-get install -y build-essential libelf-dev\n"
		d += "RUN apt-get install -y wget git\n"
		// Install a single kernel and headers to ensure all dependencies are cached
		d += "RUN export PKGNAME=$(apt-cache search --names-only '^linux-headers-[0-9\\.\\-]*-generic' | awk '{ print $1 }' | head -n 1); " +
			"apt-get install -y $PKGNAME $(echo $PKGNAME | sed 's/headers/image/'); " +
			"apt-get remove -y $PKGNAME $(echo $PKGNAME | sed 's/headers/image/')\n"
		if sk.DistroRelease >= "14.04" {
			d += "RUN apt-get install -y libseccomp-dev\n"
		}
		d += "RUN mkdir -p /lib/modules\n"
	case config.CentOS:
		if sk.DistroRelease < "7" && !vsyscall {
			log.Print("Old CentOS requires `vsyscall=emulate` " +
				"on the latest kernels")
			log.Print("Check out `A note about vsyscall` " +
				"at https://hub.docker.com/_/centos")
			log.Print("See also https://lwn.net/Articles/446528/")
			err = fmt.Errorf("vsyscall is not available")
			return
		} else if sk.DistroRelease == "8" {
			// CentOS 8 doesn't have Vault repos by default
			for _, repover := range []string{
				"8.0.1905", "8.1.1911", "8.2.2004", "8.3.2011", "8.4.2105", "8.5.2111",
			} {
				repo := fmt.Sprintf("[%s]\\nbaseurl=http://vault.centos.org/%s/BaseOS/$basearch/os/\\ngpgcheck=0", repover, repover)
				d += fmt.Sprintf("RUN echo -e '%s' >> /etc/yum.repos.d/CentOS-Vault.repo\n", repo)
			}
			d += "RUN sed -i 's/enabled=1/enabled=0/' /etc/yum.repos.d/*\n"
		}

		// enable rpms from old minor releases
		d += "RUN sed -i 's/enabled=0/enabled=1/' /etc/yum.repos.d/CentOS-Vault.repo\n"
		// do not remove old kernels
		d += "RUN sed -i 's;installonly_limit=;installonly_limit=100500;' /etc/yum.conf\n"
		d += "RUN yum -y update\n"

		d += "RUN yum -y groupinstall 'Development Tools'\n"

		if sk.DistroRelease < "8" {
			d += "RUN yum -y install deltarpm\n"
		} else {
			d += "RUN yum -y install grub2-tools-minimal " +
				"elfutils-libelf-devel\n"
		}

		var flags string
		if sk.DistroRelease >= "8" {
			flags = "--noautoremove"
		}

		// Cache kernel package dependencies
		d += "RUN export PKGNAME=$(yum search kernel-devel --showduplicates | grep '^kernel-devel' | cut -d ' ' -f 1 | head -n 1); " +
			"yum -y install $PKGNAME $(echo $PKGNAME | sed 's/-devel//'); " +
			fmt.Sprintf("yum -y remove $PKGNAME $(echo $PKGNAME | sed 's/-devel//') %s\n", flags)
	default:
		err = fmt.Errorf("%s not yet supported", sk.DistroType.String())
		return
	}

	d += "# END BASE\n\n"

	err = ioutil.WriteFile(dockerPath, []byte(d), 0644)
	if err != nil {
		return
	}

	c, err := NewContainer(sk.DockerName(), time.Hour)
	if err != nil {
		return
	}

	output, err := c.Build(imagePath)
	if err != nil {
		log.Error().Err(err).Msgf("Base image for %s:%s generating error",
			sk.DistroType.String(), sk.DistroRelease)
		log.Fatal().Msg(output)
		return
	}

	log.Info().Msgf("Base image for %s:%s generating success",
		sk.DistroType.String(), sk.DistroRelease)

	return
}

func installKernel(sk config.KernelMask, pkgname string, force, headers bool) (err error) {
	slog := log.With().
		Str("distro_type", sk.DistroType.String()).
		Str("distro_release", sk.DistroRelease).
		Str("pkg", pkgname).
		Logger()

	c, err := NewContainer(sk.DockerName(), time.Hour) // TODO conf
	if err != nil {
		return
	}

	moddirs, err := ioutil.ReadDir(c.Volumes.LibModules)
	if err != nil {
		return
	}

	for _, krel := range moddirs {
		if strings.Contains(pkgname, krel.Name()) {
			if force {
				slog.Info().Msg("Reinstall")
			} else {
				slog.Info().Msg("Already installed")
				return
			}
		}
	}

	volumes := c.Volumes

	c.Volumes.LibModules = ""
	c.Volumes.UsrSrc = ""
	c.Volumes.Boot = ""

	slog.Debug().Msgf("Installing kernel")

	cmd := "true"

	switch sk.DistroType {
	case config.Ubuntu:
		var headerspkg string
		if headers {
			headerspkg = strings.Replace(pkgname, "image", "headers", -1)
		}

		cmd += fmt.Sprintf(" && apt-get install -y %s %s", pkgname, headerspkg)
	case config.CentOS:
		imagepkg := strings.Replace(pkgname, "-devel", "", -1)

		version := strings.Replace(pkgname, "kernel-devel-", "", -1)

		if !headers {
			pkgname = ""
		}
		cmd += fmt.Sprintf(" && yum -y install %s %s", imagepkg,
			pkgname)

		cmd += fmt.Sprintf(" && dracut --add-drivers 'e1000 ext4' -f "+
			"/boot/initramfs-%s.img %s", version, version)
	default:
		err = fmt.Errorf("%s not yet supported", sk.DistroType.String())
		return
	}

	c.Args = append(c.Args, "-v", volumes.LibModules+":/target/lib/modules")
	c.Args = append(c.Args, "-v", volumes.UsrSrc+":/target/usr/src")
	c.Args = append(c.Args, "-v", volumes.Boot+":/target/boot")

	cmd += " && cp -r /boot /target/"
	cmd += " && cp -r /lib/modules /target/lib/"
	cmd += " && cp -r /usr/src /target/usr/"

	_, err = c.Run("", cmd)
	if err != nil {
		return
	}

	slog.Debug().Msgf("Success")
	return
}

func findKernelFile(files []os.FileInfo, kname string) (name string, err error) {
	for _, file := range files {
		if strings.HasPrefix(file.Name(), "vmlinuz") {
			if strings.Contains(file.Name(), kname) {
				name = file.Name()
				return
			}
		}
	}

	err = errors.New("cannot find kernel")
	return
}

func findInitrdFile(files []os.FileInfo, kname string) (name string, err error) {
	for _, file := range files {
		if strings.HasPrefix(file.Name(), "initrd") ||
			strings.HasPrefix(file.Name(), "initramfs") {

			if strings.Contains(file.Name(), kname) {
				name = file.Name()
				return
			}
		}
	}

	err = errors.New("cannot find kernel")
	return
}

func genRootfsImage(d containerImageInfo, download bool) (rootfs string, err error) {
	usr, err := user.Current()
	if err != nil {
		return
	}
	imageFile := d.Name + ".img"

	imagesPath := usr.HomeDir + "/.out-of-tree/images/"
	os.MkdirAll(imagesPath, os.ModePerm)

	rootfs = imagesPath + imageFile
	if !exists(rootfs) {
		if download {
			log.Info().Msgf("%v not available, start download", imageFile)
			err = downloadImage(imagesPath, imageFile)
		}
	}
	return
}

func updateKernelsCfg(host, download bool) (err error) {
	newkcfg := config.KernelConfig{}

	if host {
		// Get host kernels
		newkcfg, err = genHostKernels(download)
		if err != nil {
			return
		}
	}

	// Get docker kernels
	dockerImages, err := listContainerImages()
	if err != nil {
		return
	}

	for _, d := range dockerImages {
		err = listContainersKernels(d, &newkcfg, download)
		if err != nil {
			log.Print("gen kernels", d.Name, ":", err)
			continue
		}
	}

	stripkcfg := config.KernelConfig{}
	for _, nk := range newkcfg.Kernels {
		if !hasKernel(nk, stripkcfg) {
			stripkcfg.Kernels = append(stripkcfg.Kernels, nk)
		}
	}

	buf, err := toml.Marshal(&stripkcfg)
	if err != nil {
		return
	}

	buf = append([]byte("# Autogenerated\n# DO NOT EDIT\n\n"), buf...)

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

	// TODO move all cfg path values to one provider
	kernelsCfgPath := usr.HomeDir + "/.out-of-tree/kernels.toml"
	err = ioutil.WriteFile(kernelsCfgPath, buf, 0644)
	if err != nil {
		return
	}

	log.Info().Msgf("%s is successfully updated", kernelsCfgPath)
	return
}

func listContainersKernels(dii containerImageInfo, newkcfg *config.KernelConfig,
	download bool) (err error) {

	rootfs, err := genRootfsImage(dii, download)
	if err != nil {
		return
	}

	c, err := NewContainer(dii.Name, time.Hour)
	if err != nil {
		return
	}

	moddirs, err := ioutil.ReadDir(c.Volumes.LibModules)
	if err != nil {
		return
	}

	bootfiles, err := ioutil.ReadDir(c.Volumes.Boot)
	if err != nil {
		return
	}

	for _, krel := range moddirs {
		log.Debug().Msgf("generate config entry for %s", krel.Name())

		var kernelFile, initrdFile string
		kernelFile, err = findKernelFile(bootfiles, krel.Name())
		if err != nil {
			log.Warn().Msgf("cannot find kernel %s", krel.Name())
			continue
		}

		initrdFile, err = findInitrdFile(bootfiles, krel.Name())
		if err != nil {
			log.Warn().Msgf("cannot find initrd %s", krel.Name())
			continue
		}

		ki := config.KernelInfo{
			DistroType:    dii.DistroType,
			DistroRelease: dii.DistroRelease,
			KernelRelease: krel.Name(),
			ContainerName: dii.Name,

			KernelPath:  c.Volumes.Boot + "/" + kernelFile,
			InitrdPath:  c.Volumes.Boot + "/" + initrdFile,
			ModulesPath: c.Volumes.LibModules + "/" + krel.Name(),

			RootFS: rootfs,
		}
		newkcfg.Kernels = append(newkcfg.Kernels, ki)
	}

	for _, cmd := range []string{
		"find /boot -type f -exec chmod a+r {} \\;",
	} {
		_, err = c.Run(tempDirBase, cmd)
		if err != nil {
			return
		}
	}

	return
}

func hasKernel(ki config.KernelInfo, kcfg config.KernelConfig) bool {
	for _, sk := range kcfg.Kernels {
		if sk == ki {
			return true
		}
	}
	return false
}

func shuffleStrings(a []string) []string {
	// Fisher–Yates shuffle
	for i := len(a) - 1; i > 0; i-- {
		j := rand.Intn(i + 1)
		a[i], a[j] = a[j], a[i]
	}
	return a
}

func generateKernels(km config.KernelMask, registry string,
	commands []config.DockerCommand, max, retries int64,
	download, force, headers, shuffle bool) (err error) {

	log.Info().Msgf("Generating for kernel mask %v", km)

	_, err = genRootfsImage(containerImageInfo{Name: km.DockerName()},
		download)
	if err != nil {
		return
	}

	err = generateBaseDockerImage(registry, commands, km)
	if err != nil {
		return
	}

	var pkgs []string
	switch km.DistroType {
	case config.Ubuntu:
		pkgs, err = matchDebImagePkg(km.DockerName(), km.ReleaseMask)
	case config.CentOS:
		pkgs, err = matchCentOSDevelPkg(km.DockerName(),
			km.ReleaseMask, true)
	default:
		err = fmt.Errorf("%s not yet supported", km.DistroType.String())
	}
	if err != nil {
		return
	}

	if shuffle {
		pkgs = shuffleStrings(pkgs)
	}
	for i, pkg := range pkgs {
		if max <= 0 {
			log.Print("Max is reached")
			break
		}

		log.Info().Msgf("%d/%d %s", i+1, len(pkgs), pkg)

		var attempt int64
		for {
			attempt++

			err = installKernel(km, pkg, force, headers)
			if err == nil {
				max--
				break
			} else if attempt >= retries {
				log.Error().Err(err).Msg("install kernel")
				log.Debug().Msg("skip")
				break
			} else {
				log.Warn().Err(err).Msg("install kernel")
				time.Sleep(time.Second)
				log.Info().Msg("retry")
			}
		}
	}

	return
}