// Package updates is the package-manager view: what can be upgraded, when the index
// was last refreshed, whether a reboot is pending, and the refresh/upgrade actions,
// which run as background tasks so their output can be followed live.
//
// Supported: apt (Debian, Ubuntu), dnf (Fedora, RHEL family), zypper (openSUSE, SLES),
// pacman (Arch) and apk (Alpine). All of them list, refresh, upgrade and install; pacman
// upgrades everything or nothing, because Arch doesn't support partial upgrades.
package updates

import (
	"bufio"
	"context"
	"errors"
	"os"
	"os/exec"
	"path/filepath"
	"regexp"
	"sort"
	"strings"
	"time"

	"hamlab/internal/priv"
	"hamlab/internal/tasks"
)

type Package struct {
	Name        string `json:"name"`
	Current     string `json:"current"`
	Candidate   string `json:"candidate"`
	Suite       string `json:"suite,omitempty"`
	Security    bool   `json:"security"`
	Description string `json:"description,omitempty"`
}

type Status struct {
	Manager       string    `json:"manager"` // apt | dnf | zypper | pacman | apk | ""
	CanUpgrade    bool      `json:"can_upgrade"`
	Selective     bool      `json:"selective"` // individual packages can be upgraded
	Packages      []Package `json:"packages"`
	SecurityCount int       `json:"security_count"`
	LastRefresh   int64     `json:"last_refresh,omitempty"` // unix ms
	LastUpgrade   int64     `json:"last_upgrade,omitempty"`
	RebootNeeded  bool      `json:"reboot_needed"`
	RebootPkgs    []string  `json:"reboot_pkgs"`
	AutoUpgrades  bool      `json:"auto_upgrades"`
	RunningTask   string    `json:"running_task,omitempty"`
	Sudo          bool      `json:"sudo"`
}

type Manager struct {
	sudo  bool
	tasks *tasks.Manager
	pm    string
}

func New(sudo bool, tm *tasks.Manager) *Manager {
	m := &Manager{sudo: sudo, tasks: tm}
	for _, pm := range []string{"apt-get", "dnf", "zypper", "pacman", "apk"} {
		if _, err := exec.LookPath(pm); err == nil {
			m.pm = strings.TrimSuffix(pm, "-get")
			break
		}
	}
	return m
}

func (m *Manager) sudoArgs(args ...string) []string {
	if m.sudo {
		return priv.Wrap(args...)
	}
	return args
}

func out(ctx context.Context, args ...string) (string, error) {
	ctx, cancel := context.WithTimeout(ctx, 60*time.Second)
	defer cancel()
	cmd := exec.CommandContext(ctx, args[0], args[1:]...)
	cmd.Env = append(os.Environ(), "LC_ALL=C", "DEBIAN_FRONTEND=noninteractive")
	b, err := cmd.Output()
	if err != nil {
		var ee *exec.ExitError
		if errors.As(err, &ee) && len(ee.Stderr) > 0 {
			return string(b), errors.New(strings.TrimSpace(string(ee.Stderr)))
		}
		return string(b), err
	}
	return string(b), nil
}

// newestMtime: the newest mtime among the paths matching any of the globs.
func newestMtime(globs ...string) int64 {
	var best int64
	for _, g := range globs {
		matches, _ := filepath.Glob(g)
		for _, m := range matches {
			if t := mtimeMs(m); t > best {
				best = t
			}
		}
	}
	return best
}

// dnfLastUpgrade: newest transaction in `dnf history` whose action includes an upgrade,
// else the newest transaction of any kind.
func dnfLastUpgrade(ctx context.Context) int64 {
	text, err := out(ctx, "dnf", "history", "list")
	if err != nil {
		return 0
	}
	re := regexp.MustCompile(`(\d{4}-\d{2}-\d{2} \d{2}:\d{2}:\d{2})\s+(\S+)`)
	var newest, upgrade int64
	for _, line := range strings.Split(text, "\n") {
		m := re.FindStringSubmatch(line)
		if m == nil {
			continue
		}
		t, err := time.ParseInLocation("2006-01-02 15:04:05", m[1], time.Local)
		if err != nil {
			continue
		}
		ms := t.UnixMilli()
		if ms > newest {
			newest = ms
		}
		if strings.Contains(m[2], "U") && ms > upgrade {
			upgrade = ms
		}
	}
	if upgrade > 0 {
		return upgrade
	}
	return newest
}

func mtimeMs(p string) int64 {
	st, err := os.Stat(p)
	if err != nil {
		return 0
	}
	return st.ModTime().UnixMilli()
}

// ---- status ----

func (m *Manager) Status(ctx context.Context) Status {
	s := Status{Manager: m.pm, Packages: []Package{}, RebootPkgs: []string{}, Sudo: m.sudo}
	if t, ok := m.tasks.RunningOf("updates"); ok {
		s.RunningTask = t.ID
	}
	s.CanUpgrade = m.sudo && m.pm != ""
	s.Selective = m.pm != "pacman"
	switch m.pm {
	case "apt":
		s.Packages = aptUpgradable(ctx)
		s.LastRefresh = mtimeMs("/var/lib/apt/periodic/update-success-stamp")
		if s.LastRefresh == 0 {
			s.LastRefresh = mtimeMs("/var/lib/apt/lists/partial")
		}
		if s.LastRefresh == 0 {
			s.LastRefresh = mtimeMs("/var/lib/apt/lists")
		}
		s.LastUpgrade = aptLastUpgrade()
		s.AutoUpgrades = aptAutoUpgrades(ctx)
	case "dnf":
		s.Packages = dnfUpgradable(ctx)
		s.LastRefresh = newestMtime("/var/cache/libdnf5/*/repodata", "/var/cache/dnf/*/repodata", "/var/cache/libdnf5", "/var/cache/dnf")
		s.LastUpgrade = dnfLastUpgrade(ctx)
	case "zypper":
		s.Packages = zypperUpgradable(ctx)
		s.LastRefresh = newestMtime("/var/cache/zypp/raw/*", "/var/cache/zypp/raw")
		s.LastUpgrade = mtimeMs("/var/log/zypp/history")
	case "pacman":
		s.Packages = pacmanUpgradable(ctx)
		s.LastRefresh = newestMtime("/var/lib/pacman/sync/*.db", "/var/lib/pacman/sync")
		s.LastUpgrade = pacmanLastUpgrade()
	case "apk":
		s.Packages = apkUpgradable(ctx)
		s.LastRefresh = newestMtime("/var/cache/apk/APKINDEX.*", "/var/lib/apk/APKINDEX.*")
		s.LastUpgrade = mtimeMs("/lib/apk/db/installed")
	}
	for _, p := range s.Packages {
		if p.Security {
			s.SecurityCount++
		}
	}
	if _, err := os.Stat("/run/reboot-required"); err == nil {
		s.RebootNeeded = true
		if b, err := os.ReadFile("/run/reboot-required.pkgs"); err == nil {
			for _, l := range strings.Split(strings.TrimSpace(string(b)), "\n") {
				if l = strings.TrimSpace(l); l != "" {
					s.RebootPkgs = append(s.RebootPkgs, l)
				}
			}
		}
	} else if m.pm != "apt" {
		s.RebootNeeded = kernelChanged()
	}
	return s
}

// kernelChanged: the running kernel isn't the newest installed one (dnf/pacman hosts).
func kernelChanged() bool {
	b, err := os.ReadFile("/proc/sys/kernel/osrelease")
	if err != nil {
		return false
	}
	running := strings.TrimSpace(string(b))
	ents, err := os.ReadDir("/lib/modules")
	if err != nil {
		return false
	}
	newest := ""
	for _, e := range ents {
		if e.Name() > newest {
			newest = e.Name()
		}
	}
	return newest != "" && newest != running
}

// ---- apt ----

var aptListRe = regexp.MustCompile(`^(\S+)/(\S+)\s+(\S+)\s+\S+\s+\[upgradable from: (\S+)\]`)

func aptUpgradable(ctx context.Context) []Package {
	text, _ := out(ctx, "apt", "list", "--upgradable")
	var pkgs []Package
	for _, line := range strings.Split(text, "\n") {
		m := aptListRe.FindStringSubmatch(line)
		if m == nil {
			continue
		}
		pkgs = append(pkgs, Package{Name: m[1], Suite: m[2], Candidate: m[3], Current: m[4],
			Security: strings.Contains(m[2], "security")})
	}
	if len(pkgs) == 0 {
		return []Package{}
	}
	// One apt-cache call for all the descriptions.
	args := append([]string{"apt-cache", "show", "--no-all-versions"}, names(pkgs)...)
	if text, err := out(ctx, args...); err == nil {
		desc := map[string]string{}
		cur := ""
		for _, line := range strings.Split(text, "\n") {
			if strings.HasPrefix(line, "Package: ") {
				cur = strings.TrimPrefix(line, "Package: ")
			} else if strings.HasPrefix(line, "Description-en: ") || strings.HasPrefix(line, "Description: ") {
				if _, ok := desc[cur]; !ok {
					_, v, _ := strings.Cut(line, ": ")
					desc[cur] = v
				}
			}
		}
		for i := range pkgs {
			pkgs[i].Description = desc[pkgs[i].Name]
		}
	}
	sort.Slice(pkgs, func(i, j int) bool { return pkgs[i].Name < pkgs[j].Name })
	return pkgs
}

func names(pkgs []Package) []string {
	n := make([]string, len(pkgs))
	for i, p := range pkgs {
		n[i] = p.Name
	}
	return n
}

// aptLastUpgrade: the Start-Date of the last history.log entry that upgraded something.
func aptLastUpgrade() int64 {
	f, err := os.Open("/var/log/apt/history.log")
	if err != nil {
		return 0
	}
	defer f.Close()
	var last, start string
	sc := bufio.NewScanner(f)
	sc.Buffer(make([]byte, 0, 64<<10), 8<<20)
	for sc.Scan() {
		l := sc.Text()
		switch {
		case strings.HasPrefix(l, "Start-Date: "):
			start = strings.TrimPrefix(l, "Start-Date: ")
		case strings.HasPrefix(l, "Upgrade: "):
			last = start
		}
	}
	if last == "" {
		return 0
	}
	t, err := time.ParseInLocation("2006-01-02  15:04:05", last, time.Local)
	if err != nil {
		return 0
	}
	return t.UnixMilli()
}

func aptAutoUpgrades(ctx context.Context) bool {
	text, _ := out(ctx, "apt-config", "dump", "APT::Periodic::Unattended-Upgrade")
	return strings.Contains(text, `"1"`)
}

// ---- dnf / zypper / pacman / apk ----

func dnfUpgradable(ctx context.Context) []Package {
	text, _ := out(ctx, "dnf", "-q", "check-update") // exit 100 when updates exist; output still parses
	var pkgs []Package
	for _, line := range strings.Split(text, "\n") {
		f := strings.Fields(line)
		if len(f) != 3 || !strings.Contains(f[0], ".") {
			continue
		}
		name := f[0][:strings.LastIndex(f[0], ".")]
		pkgs = append(pkgs, Package{Name: name, Candidate: f[1], Suite: f[2], Security: strings.Contains(f[2], "security")})
	}
	if pkgs == nil {
		return []Package{}
	}
	// check-update only names the candidate; one rpm query fills in what's installed.
	args := append([]string{"rpm", "-q", "--qf", `%{NAME} %|EPOCH?{%{EPOCH}:}:{}|%{VERSION}-%{RELEASE}\n`}, names(pkgs)...)
	if text, _ := out(ctx, args...); text != "" { // exits non-zero when any name isn't installed (new dependencies)
		cur := map[string]string{}
		for _, line := range strings.Split(text, "\n") {
			if f := strings.Fields(line); len(f) == 2 {
				cur[f[0]] = f[1] // several installed (kernels): the last listed is the newest
			}
		}
		for i := range pkgs {
			pkgs[i].Current = cur[pkgs[i].Name]
		}
	}
	return pkgs
}

func pacmanUpgradable(ctx context.Context) []Package {
	text, _ := out(ctx, "pacman", "-Qu")
	var pkgs []Package
	for _, line := range strings.Split(text, "\n") {
		f := strings.Fields(line) // name old -> new
		if len(f) == 4 && f[2] == "->" {
			pkgs = append(pkgs, Package{Name: f[0], Current: f[1], Candidate: f[3]})
		}
	}
	if pkgs == nil {
		return []Package{}
	}
	return pkgs
}

// zypperUpgradable parses the table `zypper list-updates` prints:
// S | Repository | Name | Current Version | Available Version | Arch
func zypperUpgradable(ctx context.Context) []Package {
	text, _ := out(ctx, "zypper", "--non-interactive", "--quiet", "list-updates")
	pkgs := []Package{}
	for _, line := range strings.Split(text, "\n") {
		f := strings.Split(line, "|")
		if len(f) < 5 || strings.TrimSpace(f[0]) != "v" {
			continue
		}
		repo := strings.TrimSpace(f[1])
		pkgs = append(pkgs, Package{Name: strings.TrimSpace(f[2]), Current: strings.TrimSpace(f[3]), Candidate: strings.TrimSpace(f[4]),
			Suite: repo, Security: strings.Contains(strings.ToLower(repo), "security")})
	}
	return pkgs
}

var apkVerRe = regexp.MustCompile(`^(.+)-([^-]+-r\d+)\s+<\s+(\S+)`)

// apkUpgradable parses `apk version -l '<'`: "musl-1.2.4-r2   < 1.2.5-r0".
func apkUpgradable(ctx context.Context) []Package {
	text, _ := out(ctx, "apk", "version", "-l", "<")
	pkgs := []Package{}
	for _, line := range strings.Split(text, "\n") {
		if m := apkVerRe.FindStringSubmatch(strings.TrimSpace(line)); m != nil {
			pkgs = append(pkgs, Package{Name: m[1], Current: m[2], Candidate: m[3]})
		}
	}
	return pkgs
}

// pacmanLastUpgrade: the timestamp of the last "upgraded" line in pacman.log.
func pacmanLastUpgrade() int64 {
	f, err := os.Open("/var/log/pacman.log")
	if err != nil {
		return 0
	}
	defer f.Close()
	last := ""
	sc := bufio.NewScanner(f)
	sc.Buffer(make([]byte, 0, 64<<10), 1<<20)
	for sc.Scan() {
		if l := sc.Text(); strings.Contains(l, "[ALPM] upgraded ") && strings.HasPrefix(l, "[") {
			if end := strings.IndexByte(l, ']'); end > 1 {
				last = l[1:end]
			}
		}
	}
	for _, layout := range []string{"2006-01-02T15:04:05-0700", "2006-01-02 15:04"} {
		if t, err := time.ParseInLocation(layout, last, time.Local); err == nil {
			return t.UnixMilli()
		}
	}
	return 0
}

// ---- actions ----

// Never starts with '-', so a name can't be read as an option by any of the managers.
var pkgNameRe = regexp.MustCompile(`^[A-Za-z0-9][A-Za-z0-9+._-]{0,127}$`)

func checkNames(pkgs []string) error {
	for _, p := range pkgs {
		if !pkgNameRe.MatchString(p) {
			return errors.New("bad package name: " + p)
		}
	}
	return nil
}

func (m *Manager) start(args ...string) (*tasks.Task, error) {
	if m.pm == "" {
		return nil, errors.New("no supported package manager on this host")
	}
	if !m.sudo {
		return nil, errors.New("needs root: run Ham Lab as root, or give its user passwordless sudo or doas")
	}
	if t, ok := m.tasks.RunningOf("updates"); ok {
		return nil, errors.New("another package task is running: " + t.Title)
	}
	full := priv.Wrap(append([]string{"env", "DEBIAN_FRONTEND=noninteractive", "APT_LISTCHANGES_FRONTEND=none", "LC_ALL=C"}, args...)...)
	cmd := exec.Command(full[0], full[1:]...)
	return m.tasks.Start("updates", strings.Join(args, " "), cmd)
}

func (m *Manager) Refresh() (*tasks.Task, error) {
	switch m.pm {
	case "apt":
		return m.start("apt-get", "update")
	case "dnf":
		return m.start("dnf", "-y", "makecache", "--refresh")
	case "zypper":
		return m.start("zypper", "--non-interactive", "refresh")
	case "pacman":
		return m.start("pacman", "-Sy", "--noconfirm")
	case "apk":
		return m.start("apk", "update")
	}
	return m.start()
}

// rolling reports a distro whose supported upgrade path is a full distribution upgrade.
func rolling() bool {
	b, _ := os.ReadFile("/etc/os-release")
	return strings.Contains(string(b), "tumbleweed") || strings.Contains(string(b), "microos")
}

// Upgrade upgrades everything, or only the named packages. Nothing here can block on a
// question: apt keeps the current config file on a conflict, the rest run non-interactive.
func (m *Manager) Upgrade(pkgs []string) (*tasks.Task, error) {
	if err := checkNames(pkgs); err != nil {
		return nil, err
	}
	all := len(pkgs) == 0
	var args []string
	switch m.pm {
	case "apt":
		args = []string{"apt-get", "-y", "-o", "Dpkg::Options::=--force-confdef", "-o", "Dpkg::Options::=--force-confold"}
		if all {
			args = append(args, "dist-upgrade")
		} else {
			args = append(args, "install", "--only-upgrade")
		}
	case "dnf":
		args = []string{"dnf", "-y", "upgrade"}
	case "zypper":
		args = []string{"zypper", "--non-interactive", "update"}
		if all && rolling() {
			args = []string{"zypper", "--non-interactive", "dist-upgrade"}
		}
	case "pacman":
		if !all {
			return nil, errors.New("pacman upgrades everything or nothing: Arch doesn't support partial upgrades")
		}
		args = []string{"pacman", "-Syu", "--noconfirm"}
	case "apk":
		args = []string{"apk", "upgrade"}
		if all {
			args = []string{"apk", "upgrade", "--update-cache"}
		}
	}
	return m.start(append(args, pkgs...)...)
}

// Install installs packages (used by other tabs for optional tooling like smartmontools).
func (m *Manager) Install(pkgs []string) (*tasks.Task, error) {
	if len(pkgs) == 0 {
		return nil, errors.New("no packages")
	}
	if err := checkNames(pkgs); err != nil {
		return nil, err
	}
	var args []string
	switch m.pm {
	case "apt":
		args = []string{"apt-get", "-y", "--no-install-recommends", "install"}
	case "dnf":
		args = []string{"dnf", "-y", "install"}
	case "zypper":
		args = []string{"zypper", "--non-interactive", "install", "--no-recommends"}
	case "pacman":
		args = []string{"pacman", "-S", "--noconfirm", "--needed"}
	case "apk":
		args = []string{"apk", "add"}
	}
	return m.start(append(args, pkgs...)...)
}

func (m *Manager) Changelog(ctx context.Context, pkg string) (string, error) {
	if !pkgNameRe.MatchString(pkg) {
		return "", errors.New("bad package name")
	}
	switch m.pm {
	case "apt":
		text, err := out(ctx, "apt-get", "changelog", "-qq", pkg)
		if len(text) > 64<<10 {
			text = text[:64<<10] + "\n…"
		}
		return text, err
	case "dnf":
		return out(ctx, "dnf", "-q", "changelog", pkg)
	}
	return "", errors.New("changelogs not available for " + m.pm)
}

// Power runs systemctl reboot / poweroff.
func (m *Manager) Power(ctx context.Context, action string) error {
	if action != "reboot" && action != "poweroff" {
		return errors.New("unknown power action")
	}
	_, err := out(ctx, m.sudoArgs("systemctl", action)...)
	return err
}