package main

// Acting on the package manager (novox/hq to-be 42 Phase 1, research 026/05): an upgrade, removing
// orphans, cleaning the cache.
//
// **A transaction is never this process's child.** A tool call is ended after twenty seconds, and an
// upgrade takes minutes; a pacman killed in the middle of a transaction leaves a half-upgraded machine
// and a lock. So a transaction runs as a transient unit of the service manager (`systemd-run`), started
// through sudo -n: it belongs to the machine, outlives the call, and logs to the journal, from which
// the tool answers what it did.

import (
	"fmt"
	"regexp"
	"strconv"
	"strings"
)

// DBLock is the file pacman holds while a transaction runs.
const DBLock = "/var/lib/pacman/db.lck"

// unitPrefix names every transient unit the module's tools start, so one is recognised as the mesh's.
const unitPrefix = "mesh-pacman-"

func (m *Machine) locked() bool {
	_, err := m.ReadFile(DBLock)
	return err == nil
}

// transaction starts pacman with these arguments as a transient unit, waiting for it when asked.
func (m *Machine) transaction(what string, wait bool, args ...string) (string, Ran, error) {
	if m.locked() {
		return "", Ran{}, fmt.Errorf("another pacman holds %s: a transaction is running, or one was killed and left its lock", DBLock)
	}
	unit := fmt.Sprintf("%s%s-%d", unitPrefix, what, m.Now().Unix())
	run := []string{"--unit=" + unit, "--description=pacman " + strings.Join(args, " ") + ", started by the mesh's pacman tools", "--quiet"}
	if wait {
		run = append(run, "--wait")
	}
	run = append(run, append([]string{"pacman"}, args...)...)
	r, err := m.RootRan("systemd-run", run...)
	if err == nil && !wait && r.Status != 0 {
		err = failure("systemd-run", "sudo", r)
	}
	return unit, r, err
}

// journal is the last lines a unit logged, read through sudo -n: the operator account need not be
// in a group that reads the system journal.
func (m *Machine) journal(unit string, n int) []string {
	out, err := m.Root("journalctl", "--no-pager", "-o", "cat", "-n", strconv.Itoa(n), "-u", unit)
	if err != nil {
		return []string{"(the journal could not be read: " + err.Error() + ")"}
	}
	return lines(out)
}

// Upgrade starts a full system upgrade as a transient unit and answers at once, with the
// distribution's news since the last upgrade; or, given a unit it started, answers how it went.
func (m *Machine) Upgrade(unit string, n int) (map[string]any, error) {
	if unit != "" {
		return m.UpgradeStatus(unit, n)
	}
	news := m.News("")
	started, _, err := m.transaction("upgrade", false, "-Syu", "--noconfirm")
	if err != nil {
		return nil, err
	}
	return map[string]any{
		"started": started,
		"follow":  "call pacman_upgrade with this unit to read how it goes",
		"news":    news,
	}, nil
}

var unitName = regexp.MustCompile(`^` + unitPrefix + `[a-z-]+-[0-9]+$`)

// UpgradeStatus is a transaction unit's state and the tail of what it logged.
func (m *Machine) UpgradeStatus(unit string, n int) (map[string]any, error) {
	if !unitName.MatchString(unit) {
		return nil, fmt.Errorf("%q is not a unit the pacman tools started", unit)
	}
	p, err := m.unitProps(unit, "LoadState", "ActiveState", "SubState", "Result", "ExecMainStatus")
	if err != nil {
		return nil, err
	}
	out := map[string]any{"unit": unit, "running": p["ActiveState"] == "active" || p["ActiveState"] == "activating", "log": m.journal(unit, n)}
	switch {
	case p["LoadState"] == "not-found":
		// A transient unit that finished well is let go by the service manager; one that failed stays.
		out["finished"], out["succeeded"] = true, true
	case p["ActiveState"] == "failed":
		out["finished"], out["succeeded"], out["exit_status"] = true, false, p["ExecMainStatus"]
	default:
		out["finished"] = !out["running"].(bool)
		out["succeeded"] = p["Result"] == "success" && p["ExecMainStatus"] == "0"
	}
	return out, nil
}

// RemoveOrphans removes the named orphans, or every one when all is said; a name that is not an
// orphan is refused, so this never removes a package something needs or someone chose. Their
// configuration files changed on the machine are kept by the package manager as .pacsave.
func (m *Machine) RemoveOrphans(names []string, all bool) (map[string]any, error) {
	listed, err := m.Orphans()
	if err != nil {
		return nil, err
	}
	orphans := map[string]bool{}
	var every []string
	for _, p := range listed["orphans"].([]map[string]string) {
		orphans[p["name"]] = true
		every = append(every, p["name"])
	}
	switch {
	case all && len(names) > 0:
		return nil, fmt.Errorf("name the orphans to remove, or say all — not both")
	case all:
		names = every
	case len(names) == 0:
		return nil, fmt.Errorf("name the orphans to remove (pacman_orphans lists them), or say all: true")
	}
	for _, n := range names {
		if !orphans[n] {
			return nil, fmt.Errorf("%s is not an orphan here, and is not removed", n)
		}
	}
	if len(names) == 0 {
		return map[string]any{"removed": []string{}, "note": "there are no orphans"}, nil
	}
	unit, r, err := m.transaction("remove-orphans", true, append([]string{"-Rs", "--noconfirm", "--"}, names...)...)
	if err != nil {
		if r.Status == 124 {
			return map[string]any{"unit": unit, "running": true, "note": "still running after the call's limit; it continues as its unit"}, nil
		}
		return nil, err
	}
	answer := map[string]any{"unit": unit, "log": m.journal(unit, 100)}
	if r.Status != 0 {
		answer["removed"] = []string{}
		answer["error"] = fmt.Sprintf("pacman failed with status %d; nothing is removed by a transaction that failed", r.Status)
		return answer, nil
	}
	answer["removed"] = names
	return answer, nil
}

// PkgCache is the package cache: its size, what cleaning would free, and its timer.
type PkgCache struct {
	Directory     string            `json:"directory"`
	Files         int               `json:"package_files"`
	Bytes         int64             `json:"bytes"`
	LeftDownloads int               `json:"interrupted_download_dirs"`
	Keep          int               `json:"keep"`
	Candidates    int               `json:"candidates"`
	Frees         string            `json:"frees"`
	Uninstalled   bool              `json:"uninstalled_only"`
	Cleaned       bool              `json:"cleaned"`
	Timer         map[string]string `json:"paccache_timer"`
	Said          string            `json:"said"`
}

// CacheDir is where pacman keeps what it downloaded.
const CacheDir = "/var/cache/pacman/pkg"

var (
	dryRun  = regexp.MustCompile(`finished dry run: (\d+) candidates \(disk space saved: ([^)]+)\)`)
	removed = regexp.MustCompile(`finished: (\d+) packages removed \(disk space saved: ([^)]+)\)`)
	noPrune = regexp.MustCompile(`no candidate packages found for pruning`)
)

// Cache reads the cache, says what paccache would remove keeping the last keep versions of each
// package (or only those of packages no longer installed), and with clean removes them.
func (m *Machine) Cache(keep int, uninstalled, clean bool) (PkgCache, error) {
	c := PkgCache{Directory: CacheDir, Keep: keep, Uninstalled: uninstalled}
	out, err := m.Out("find", CacheDir, "-mindepth", "1", "-maxdepth", "1", "-printf", "%y %s %f\n")
	if err != nil && strings.TrimSpace(out) == "" {
		return c, err
	}
	for _, l := range lines(out) {
		f := strings.SplitN(l, " ", 3)
		if len(f) != 3 {
			continue
		}
		switch {
		case f[0] == "d" && strings.HasPrefix(f[2], "download-"):
			c.LeftDownloads++
		case f[0] == "f":
			size, _ := strconv.ParseInt(f[1], 10, 64)
			c.Bytes += size
			if strings.Contains(f[2], ".pkg.tar") && !strings.HasSuffix(f[2], ".sig") {
				c.Files++
			}
		}
	}
	args := []string{"-k", strconv.Itoa(keep)}
	if uninstalled {
		args = append(args, "-u")
	}
	if clean {
		said, err := m.Root("paccache", append([]string{"-r"}, args...)...)
		if err != nil {
			return c, err
		}
		c.Cleaned, c.Said = true, firstLine(lastLines(said, 1))
		if x := removed.FindStringSubmatch(said); x != nil {
			c.Candidates, _ = strconv.Atoi(x[1])
			c.Frees = x[2]
		}
	} else {
		r := m.Run(bg(), "paccache", append([]string{"-d"}, args...)...)
		if r.Err != "" || r.Status != 0 && !noPrune.MatchString(r.Stdout+r.Stderr) {
			if r.Err == "ENOENT" {
				return c, fmt.Errorf("paccache is not installed: it comes with pacman-contrib, which this module declares")
			}
			return c, failure("paccache", "paccache", r)
		}
		c.Said = firstLine(lastLines(r.Stdout+r.Stderr, 1))
		if x := dryRun.FindStringSubmatch(r.Stdout + r.Stderr); x != nil {
			c.Candidates, _ = strconv.Atoi(x[1])
			c.Frees = x[2]
		}
	}
	if t, err := m.unitProps("paccache.timer", "ActiveState", "UnitFileState", "LastTriggerUSec", "NextElapseUSecRealtime"); err == nil {
		c.Timer = t
	}
	return c, nil
}

func lastLines(text string, n int) string {
	ls := lines(text)
	if len(ls) > n {
		ls = ls[len(ls)-n:]
	}
	return strings.Join(ls, "\n")
}