// Package osupdate is the agent's OS-update leg for the customer GUEST (`11-os-updates.md` §8 step 2, agent v0.140.0).
//
// It runs right after the night's successful whole-guest backup, while the backup goroutine still holds the host-wide
// heavy-op gate (so it never overlaps a backup or a restore-test, `11` C10), at most once per night. All root work is
// the wrapper `felhom-os-apply` (configs/, its own tests); this package only builds plans, calls the wrapper through
// sudo, judges health and reports to the hub.
//
// NO AUTOMATIC UNDO in this release (R-837, measured 2026-10-04): a customer guest cannot be snapshotted — PVE
// refuses any snapshot not named `vzdump` when the guest has host-path binds (mp8, mp9). A failed health check
// therefore stops, reports `health_failed` and the hub mails the operator; the whole-guest backup taken minutes
// earlier is the undo, by hand.
package osupdate

import (
	"context"
	"encoding/json"
	"fmt"
	"log/slog"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"sync"
	"time"

	"gitea.dooplex.hu/admin/felhom-agent/internal/hub"
	"gitea.dooplex.hu/admin/felhom-agent/internal/proxmox"
)

// WrapperPath is the pinned sudoers vector (configs/felhom-agent.sudoers FELHOM_OSAPPLY).
const WrapperPath = "/usr/local/sbin/felhom-os-apply"

// DefaultPlanDir is where plans are written (the sudoers glob names it).
const DefaultPlanDir = "/var/lib/felhom-agent/os"

// Package is one name=version with its origin.
type Package struct {
	Name    string `json:"name"`
	Version string `json:"version"`
	Origin  string `json:"origin"`
}

// Pending is one update the guest's sources offer (origin as apt names it, possibly several).
type Pending struct {
	Name   string   `json:"name"`
	From   string   `json:"from"`
	To     string   `json:"to"`
	Origin []string `json:"origin"`
}

// Container is one container's state as the wrapper saw it.
type Container struct {
	State  string `json:"state"`
	Health string `json:"health"` // healthy | unhealthy | starting | none
}

// Health is the guest's health snapshot (the wrapper's `health` object).
type Health struct {
	DockerOK   bool                 `json:"docker_ok"`
	NetworkOK  bool                 `json:"network_ok"`
	Controller string               `json:"controller"`
	Containers map[string]Container `json:"containers"`
}

// WrapperReport is the wrapper's OSAPPLY-REPORT object.
type WrapperReport struct {
	Mode                string          `json:"mode"`
	Refused             json.RawMessage `json:"refused"`
	Failed              json.RawMessage `json:"failed"`
	Upgraded            []Package       `json:"upgraded"`
	Installed           []Package       `json:"installed"`
	Pending             []Pending       `json:"pending"`
	RestartNeeded       []string        `json:"restart_needed"`
	DockerRestartNeeded bool            `json:"docker_restart_needed"`
	RebootNeeded        bool            `json:"reboot_needed"`
	HealthBefore        *Health         `json:"health_before"`
	HealthAfter         *Health         `json:"health_after"`
	Health              *Health         `json:"health"`
}

func (w WrapperReport) refused() bool { return len(w.Refused) > 0 && string(w.Refused) != "null" }
func (w WrapperReport) failed() bool  { return len(w.Failed) > 0 && string(w.Failed) != "null" }

// Report is what the hub receives (hub osupdates.Report — field-exact).
type Report struct {
	RunID               string          `json:"run_id"`
	Trigger             string          `json:"trigger"`
	Mode                string          `json:"mode"`
	Ring                int             `json:"ring"`
	ReleaseID           string          `json:"release_id"`
	Outcome             string          `json:"outcome"`
	Healthy             bool            `json:"healthy"`
	HealthReason        string          `json:"health_reason,omitempty"`
	VMID                int             `json:"vmid"`
	Upgraded            []Package       `json:"upgraded,omitempty"`
	Installed           []Package       `json:"installed,omitempty"`
	Pending             []Pending       `json:"pending,omitempty"`
	NotCovered          []string        `json:"not_covered,omitempty"`
	RestartNeeded       []string        `json:"restart_needed,omitempty"`
	DockerRestartNeeded bool            `json:"docker_restart_needed,omitempty"`
	RebootNeeded        bool            `json:"reboot_needed,omitempty"`
	Refused             json.RawMessage `json:"refused,omitempty"`
}

// Reporter posts a report to the hub (*hub.Client).
type Reporter interface {
	PostOSReport(ctx context.Context, body []byte) error
}

// Leg runs one OS-update pass for the customer guest.
type Leg struct {
	Runner     proxmox.Runner
	Hub        Reporter
	Logger     *slog.Logger
	PlanDir    string
	StatePath  string        // last night run (once per night)
	HealthWait time.Duration // how long health may take to come back (default 5 min)
	HealthPoll time.Duration // default 15 s
	MinGap     time.Duration // between night runs (default 20 h)
	Now        func() time.Time
	Sleep      func(context.Context, time.Duration)

	mu    sync.Mutex
	block *hub.WireOSUpdate
	have  bool
}

// OnDesiredState stores the hub's os_update block (desired.RawConsumer — store only, never block).
func (l *Leg) OnDesiredState(_ context.Context, resp *hub.DesiredStateResponse) {
	if resp == nil {
		return
	}
	l.mu.Lock()
	defer l.mu.Unlock()
	l.block, l.have = resp.DesiredState.OSUpdate, true
}

// Block returns the newest os_update block. No block (an older hub, or nothing fetched yet) = ring 1, ON, no
// release: the box reports and installs nothing.
func (l *Leg) Block() hub.WireOSUpdate {
	l.mu.Lock()
	defer l.mu.Unlock()
	if l.block == nil {
		return hub.WireOSUpdate{Ring: 1, Enabled: true}
	}
	return *l.block
}

// SetBlock sets the block directly (the selftest fetches the desired state itself).
func (l *Leg) SetBlock(b *hub.WireOSUpdate) {
	l.mu.Lock()
	defer l.mu.Unlock()
	l.block, l.have = b, true
}

func (l *Leg) now() time.Time {
	if l.Now != nil {
		return l.Now()
	}
	return time.Now()
}

func (l *Leg) log() *slog.Logger {
	if l.Logger != nil {
		return l.Logger
	}
	return slog.Default()
}

func (l *Leg) sleep(ctx context.Context, d time.Duration) {
	if l.Sleep != nil {
		l.Sleep(ctx, d)
		return
	}
	select {
	case <-ctx.Done():
	case <-time.After(d):
	}
}

// IsFast reports whether every origin apt names is Debian / Debian-Security (the fast lane, `11` C3).
func IsFast(origins []string) bool {
	if len(origins) == 0 {
		return false
	}
	for _, o := range origins {
		if o != "Debian" && o != "Debian-Security" {
			return false
		}
	}
	return true
}

func fastOrigin(origins []string) string {
	for _, o := range origins {
		if o == "Debian-Security" {
			return o
		}
	}
	return "Debian"
}

// HealthVerdict is THE health rule (`11` §5.4.1; pinned by TestHealthVerdict_*): after the run, docker answers, the
// guest's network resolves, the controller's own health check is `healthy`, and every container that was running
// before is running again — and healthy again if it was healthy before. "starting" is not yet healthy.
func HealthVerdict(before, after *Health) (bool, string) {
	if after == nil {
		return false, "no health reading"
	}
	if !after.DockerOK {
		return false, "docker does not answer"
	}
	if !after.NetworkOK {
		return false, "the guest cannot resolve deb.debian.org"
	}
	if after.Controller != "healthy" {
		return false, "the controller is " + after.Controller
	}
	if before == nil {
		return true, ""
	}
	names := make([]string, 0, len(before.Containers))
	for n := range before.Containers {
		names = append(names, n)
	}
	sort.Strings(names)
	for _, n := range names {
		b := before.Containers[n]
		if b.State != "running" {
			continue
		}
		a, ok := after.Containers[n]
		if !ok || a.State != "running" {
			return false, n + " was running and is not"
		}
		if b.Health == "healthy" && a.Health != "healthy" {
			return false, n + " was healthy and is " + a.Health
		}
	}
	return true, ""
}

// MergeBaseline is the health baseline from two readings: a container counts as running (and healthy) if EITHER
// reading saw it so. nil-safe. Pinned by TestHealth_BaselineIsTheStartOfTheLeg.
func MergeBaseline(a, b *Health) *Health {
	if a == nil {
		return b
	}
	if b == nil {
		return a
	}
	out := &Health{DockerOK: a.DockerOK && b.DockerOK, NetworkOK: a.NetworkOK && b.NetworkOK, Controller: b.Controller,
		Containers: map[string]Container{}}
	for _, h := range []*Health{a, b} {
		for n, c := range h.Containers {
			cur, seen := out.Containers[n]
			if !seen || (cur.State != "running" && c.State == "running") {
				out.Containers[n] = c
				continue
			}
			if c.State == "running" && c.Health == "healthy" {
				out.Containers[n] = c
			}
		}
	}
	return out
}

// call writes the plan and runs the wrapper once.
func (l *Leg) call(ctx context.Context, runID, mode string, vmid int, rel hub.WireOSRelease, pkgs []Package) (WrapperReport, error) {
	dir := l.PlanDir
	if dir == "" {
		dir = DefaultPlanDir
	}
	if err := os.MkdirAll(dir, 0o700); err != nil {
		return WrapperReport{}, fmt.Errorf("osupdate: plan dir: %w", err)
	}
	plan := map[string]any{"release_id": rel.ID, "layer": "guest", "lane": "fast", "vmid": vmid, "mode": mode,
		"snapshot": rel.Snapshot, "packages": pkgs}
	if pkgs == nil {
		plan["packages"] = []Package{}
	}
	b, _ := json.Marshal(plan)
	path := filepath.Join(dir, "plan-"+runID+"-"+mode+".json")
	if err := os.WriteFile(path, b, 0o600); err != nil {
		return WrapperReport{}, fmt.Errorf("osupdate: write plan: %w", err)
	}
	defer os.Remove(path)
	stdout, stderr, err := l.Runner.Run(ctx, WrapperPath, "--plan", path)
	for _, line := range strings.Split(strings.TrimSpace(string(stderr)), "\n") {
		if strings.HasPrefix(line, "os-apply: ") {
			l.log().Info("osupdate: wrapper", "line", line)
		}
	}
	var rep WrapperReport
	found := false
	for _, line := range strings.Split(string(stdout), "\n") {
		if strings.HasPrefix(line, "OSAPPLY-REPORT ") {
			if jerr := json.Unmarshal([]byte(strings.TrimPrefix(line, "OSAPPLY-REPORT ")), &rep); jerr == nil {
				found = true
			}
		}
	}
	if !found {
		return rep, fmt.Errorf("osupdate: wrapper gave no report (err %v): %s", err, strings.TrimSpace(string(stderr)))
	}
	return rep, nil // a refusal / failure is IN the report (exit 2 / 3), not an error here
}

// Run is one pass: inventory → (switch, ring, plan) → apply → health → report. trigger is "night" or "debug".
func (l *Leg) Run(ctx context.Context, vmid int, trigger string) Report {
	runID := l.now().UTC().Format("20060102T150405Z")
	blk := l.Block()
	rel := hub.WireOSRelease{ID: "ring0-" + runID}
	if blk.Ring == 1 {
		rel = hub.WireOSRelease{}
		if blk.Release != nil {
			rel = *blk.Release
		}
	}
	rep := Report{RunID: runID, Trigger: trigger, Ring: blk.Ring, VMID: vmid, ReleaseID: rel.ID, Mode: "inventory"}
	lg := l.log().With("run", runID, "vmid", vmid, "ring", blk.Ring, "trigger", trigger)

	if trigger == "night" && l.StatePath != "" {
		gap := l.MinGap
		if gap == 0 {
			gap = 20 * time.Hour
		}
		if b, err := os.ReadFile(l.StatePath); err == nil {
			if last, perr := time.Parse(time.RFC3339, strings.TrimSpace(string(b))); perr == nil && l.now().Sub(last) < gap {
				lg.Info("osupdate: skipped — already ran tonight", "last", last.UTC().Format(time.RFC3339))
				rep.Outcome = "skipped"
				return rep
			}
		}
	}
	lg.Info("osupdate: START", "enabled", blk.Enabled, "release", rel.ID)

	inv, err := l.call(ctx, runID, "inventory", vmid, rel, nil)
	if err != nil || inv.refused() || inv.failed() {
		rep.Outcome, rep.Refused = "refused", inv.Refused
		if err != nil {
			rep.Outcome, rep.HealthReason = "failed", err.Error()
		}
		return l.finish(ctx, lg, rep)
	}
	var plan []Package
	switch {
	case !blk.Enabled:
		rep.Outcome = "inventory"
		lg.Info("osupdate: switched OFF for this box — reporting only")
	case blk.Ring == 0:
		for _, p := range inv.Pending {
			if IsFast(p.Origin) {
				plan = append(plan, Package{Name: p.Name, Version: p.To, Origin: fastOrigin(p.Origin)})
			}
		}
	default:
		for _, p := range rel.Packages {
			plan = append(plan, Package{Name: p.Name, Version: p.Version, Origin: p.Origin})
		}
	}
	pkgNames := map[string]bool{}
	for _, p := range plan {
		pkgNames[p.Name] = true
	}
	if blk.Enabled && len(plan) == 0 {
		rep.Outcome = "nothing"
	}
	final := inv
	if blk.Enabled && len(plan) > 0 {
		rep.Mode = "apply"
		ap, err := l.call(ctx, runID, "apply", vmid, rel, plan)
		switch {
		case err != nil:
			rep.Outcome, rep.HealthReason = "failed", err.Error()
			return l.finish(ctx, lg, rep)
		case ap.refused():
			rep.Outcome, rep.Refused = "refused", ap.Refused
			return l.finish(ctx, lg, rep)
		case ap.failed():
			rep.Outcome, rep.Refused = "failed", ap.Failed
		}
		final = ap
		rep.Upgraded = ap.Upgraded
		if rep.Outcome == "" {
			if len(ap.Upgraded) == 0 {
				rep.Outcome = "nothing"
			} else {
				rep.Outcome = "applied"
			}
		}
		// Health: compare with what the guest looked like BEFORE the run; give restarted services time.
		wait, poll := l.HealthWait, l.HealthPoll
		if wait == 0 {
			wait = 5 * time.Minute
		}
		if poll == 0 {
			poll = 15 * time.Second
		}
		deadline := l.now().Add(wait)
		cur := ap.HealthAfter
		// The baseline is the guest as it was at the START of the leg (the inventory's reading) merged with the
		// apply's own "before": an app that stops at any point during the run counts. Found live 2026-10-04: an app
		// stopped between the inventory and the apply's own reading was taken as "stopped before" and ignored.
		base := MergeBaseline(inv.HealthAfter, ap.HealthBefore)
		for {
			ok, why := HealthVerdict(base, cur)
			rep.Healthy, rep.HealthReason = ok, why
			if ok || !l.now().Before(deadline) || ctx.Err() != nil {
				break
			}
			l.sleep(ctx, poll)
			hr, herr := l.call(ctx, runID, "health", vmid, rel, nil)
			if herr == nil && hr.Health != nil {
				cur = hr.Health
			}
		}
		if !rep.Healthy && rep.Outcome == "applied" {
			rep.Outcome = "health_failed"
		}
	} else {
		ok, why := HealthVerdict(nil, inv.HealthAfter)
		rep.Healthy, rep.HealthReason = ok, why
	}
	rep.Installed, rep.Pending = final.Installed, final.Pending
	rep.RestartNeeded, rep.DockerRestartNeeded, rep.RebootNeeded = final.RestartNeeded, final.DockerRestartNeeded, final.RebootNeeded
	rep.NotCovered = notCovered(final.Pending, blk.Ring, pkgNames)
	if trigger == "night" && l.StatePath != "" {
		_ = os.WriteFile(l.StatePath, []byte(l.now().UTC().Format(time.RFC3339)), 0o600)
	}
	return l.finish(ctx, lg, rep)
}

// notCovered lists pending updates no approved release covers: in ring 0 everything outside the fast lane; in
// ring 1 also every fast-lane update the release did not name.
func notCovered(pending []Pending, ring int, planned map[string]bool) []string {
	var out []string
	for _, p := range pending {
		if !IsFast(p.Origin) || (ring == 1 && !planned[p.Name]) {
			out = append(out, p.Name)
		}
	}
	return out
}

func (l *Leg) finish(ctx context.Context, lg *slog.Logger, rep Report) Report {
	lg.Info("osupdate: DONE", "outcome", rep.Outcome, "healthy", rep.Healthy, "reason", rep.HealthReason,
		"upgraded", len(rep.Upgraded), "pending", len(rep.Pending), "not_covered", len(rep.NotCovered), "restart_needed", len(rep.RestartNeeded))
	if l.Hub != nil {
		body, _ := json.Marshal(rep)
		rctx, cancel := context.WithTimeout(context.WithoutCancel(ctx), time.Minute)
		defer cancel()
		if err := l.Hub.PostOSReport(rctx, body); err != nil {
			lg.Warn("osupdate: reporting to the hub failed (the run itself is done)", "err", err)
		}
	}
	return rep
}