package certs

import (
	"bytes"
	"context"
	"crypto/tls"
	"crypto/x509"
	"errors"
	"fmt"
	"io/fs"
	"log"
	"log/slog"
	"os"
	"path/filepath"
	"regexp"
	"slices"
	"strings"
	"sync"
	"sync/atomic"
	"time"

	legolog "github.com/go-acme/lego/v4/log"

	"jarl/internal/auth"
	"jarl/internal/engine"
	"jarl/internal/model"
	"jarl/internal/porkbun"
	"jarl/internal/store"
)

// Config configures the manager (acme and certificates in jarl.yaml).
type Config struct {
	Directory string // ACME directory URL
	Email     string
	AgreeTOS  bool
	EABKeyID  string
	EABHMAC   string
	Resolvers []string
	CABundle  string
	// Dir is where certificates with the dns use are written for named.
	Dir     string
	Version string
	// Porkbun publishes challenges for domains Porkbun serves (nil
	// without an API key); PorkbunAllows limits it to porkbun.domains.
	Porkbun       *porkbun.Client
	PorkbunAllows func(domain string) bool
	// CheckPropagation makes lego wait until every name server of the
	// zone serves the challenge before telling the CA (acme.check_propagation).
	CheckPropagation bool
	// PropagationTimeout is how long to wait for that (default 10 minutes).
	PropagationTimeout time.Duration
	// SkipPropagationCheck is !CheckPropagation (set by New).
	SkipPropagationCheck bool
}

// Manager keeps certificates current and serves jarld's own.
type Manager struct {
	cfg   Config
	store *store.Store
	eng   *engine.Engine
	log   *slog.Logger
	res   resolver

	// legoMu: lego keeps its DNS settings in package variables, so one
	// client works at a time. issueMu: one issue at a time.
	legoMu  sync.Mutex
	issueMu sync.Mutex

	web   atomic.Pointer[webCert]
	mu    sync.Mutex
	files map[int64]fileStamp // file-source certificates: what was read last
	kick  chan struct{}
	now   func() time.Time
	// issuing holds the names being obtained now, with when it started.
	issuing sync.Map
	// base is the context background issues run in (jarld's lifetime).
	base context.Context
}

type webCert struct {
	name string
	pair *tls.Certificate
}

type fileStamp struct {
	certMod, keyMod time.Time
	certSize        int64
}

// New returns a manager. Call Start before serving, then Run.
func New(cfg Config, st *store.Store, eng *engine.Engine, logger *slog.Logger) *Manager {
	if logger == nil {
		logger = slog.Default()
	}
	cfg.SkipPropagationCheck = !cfg.CheckPropagation
	m := &Manager{cfg: cfg, store: st, eng: eng, log: logger, res: resolver{servers: cfg.Resolvers},
		files: map[int64]fileStamp{}, kick: make(chan struct{}, 1), now: time.Now, base: context.Background()}
	// lego logs every step; keep it at debug level.
	legolog.Logger = log.New(slogWriter{logger}, "", 0)
	return m
}

type slogWriter struct{ l *slog.Logger }

func (w slogWriter) Write(p []byte) (int, error) {
	w.l.Debug("lego: " + strings.TrimSpace(string(p)))
	return len(p), nil
}

// Errors for the API.
var (
	ErrNotFound = errors.New("no such certificate")
	ErrConflict = errors.New("a certificate with that name exists")
)

// InputError is a request Jarl refuses.
type InputError struct{ Msg string }

func (e *InputError) Error() string { return e.Msg }

func inputErr(format string, a ...any) error { return &InputError{Msg: fmt.Sprintf(format, a...)} }

// Input creates or changes a certificate; nil fields are left alone.
type Input struct {
	Name      *string   `json:"name"`
	Source    *string   `json:"source"`
	Domains   *[]string `json:"domains"`
	CertFile  *string   `json:"cert_file"`
	KeyFile   *string   `json:"key_file"`
	Uses      *[]string `json:"uses"`
	Challenge *string   `json:"challenge"`
	KeyType   *string   `json:"key_type"`
	Comment   *string   `json:"comment"`
}

var nameRe = regexp.MustCompile(`^[a-z0-9][a-z0-9_-]{0,62}$`)
var labelRe = regexp.MustCompile(`^[a-z0-9_]([a-z0-9_-]{0,61}[a-z0-9_])?$`)

func normDomains(in []string) ([]string, error) {
	var out []string
	for _, d := range in {
		d = strings.ToLower(strings.TrimSuffix(strings.TrimSpace(d), "."))
		if d == "" {
			continue
		}
		labels := strings.Split(d, ".")
		if len(labels) < 2 {
			return nil, inputErr("%q isn't a domain name a CA will sign (it needs at least two labels)", d)
		}
		for i, l := range labels {
			if l == "*" && i == 0 {
				continue
			}
			if !labelRe.MatchString(l) {
				return nil, inputErr("%q isn't a valid domain name (a wildcard is only allowed as the first label: *.example.com)", d)
			}
		}
		if len(d) > 253 {
			return nil, inputErr("%q is too long", d)
		}
		if !slices.Contains(out, d) {
			out = append(out, d)
		}
	}
	if len(out) == 0 {
		return nil, inputErr("give at least one domain name")
	}
	if len(out) > 100 {
		return nil, inputErr("at most 100 names per certificate")
	}
	return out, nil
}

func (m *Manager) apply(c *model.Certificate, in Input, creating bool) error {
	if in.Name != nil {
		if !creating && *in.Name != c.Name {
			return inputErr("a certificate can't be renamed (its files for named are named after it): create a new one and delete this one")
		}
		c.Name = *in.Name
	}
	if !nameRe.MatchString(c.Name) {
		return inputErr("name %q: use lowercase letters, digits, - and _ (at most 63)", c.Name)
	}
	if in.Source != nil {
		if !creating && *in.Source != c.Source {
			return inputErr("a certificate's source can't change: create a new one")
		}
		c.Source = *in.Source
	}
	if c.Source == "" {
		c.Source = model.CertSourceACME
	}
	if in.Uses != nil {
		c.Uses = nil
		for _, u := range *in.Uses {
			u = strings.ToLower(strings.TrimSpace(u))
			if u != model.CertUseWeb && u != model.CertUseDNS {
				return inputErr("unknown use %q: web (jarld's HTTPS) or dns (for named: DNS over TLS and HTTPS)", u)
			}
			if !slices.Contains(c.Uses, u) {
				c.Uses = append(c.Uses, u)
			}
		}
		slices.Sort(c.Uses)
	}
	if c.Uses == nil {
		c.Uses = []string{}
	}
	if in.Comment != nil {
		c.Comment = *in.Comment
	}
	switch c.Source {
	case model.CertSourceACME:
		if in.CertFile != nil && *in.CertFile != "" || in.KeyFile != nil && *in.KeyFile != "" {
			return inputErr("cert_file and key_file are for --source file; Jarl keeps the files of certificates it obtains itself")
		}
		if in.Domains != nil {
			d, err := normDomains(*in.Domains)
			if err != nil {
				return err
			}
			c.Domains = d
		}
		if len(c.Domains) == 0 {
			return inputErr("give the domain names the certificate is for")
		}
		if in.Challenge != nil {
			c.Challenge = *in.Challenge
		}
		switch c.Challenge {
		case "":
			c.Challenge = model.ChallengeAuto
		case model.ChallengeAuto, model.ChallengeJarl, model.ChallengePorkbun:
		default:
			return inputErr("challenge must be auto, jarl or porkbun")
		}
		if in.KeyType != nil {
			c.KeyType = *in.KeyType
		}
		if c.KeyType == "" {
			c.KeyType = "ec256"
		}
		if !slices.Contains(KeyTypes, c.KeyType) {
			return inputErr("key type must be one of %s", strings.Join(KeyTypes, ", "))
		}
	case model.CertSourceFile:
		if in.Challenge != nil && *in.Challenge != "" || in.KeyType != nil && *in.KeyType != "" {
			return inputErr("challenge and key type are for certificates Jarl obtains (--source acme)")
		}
		if in.CertFile != nil {
			c.CertFile = *in.CertFile
		}
		if in.KeyFile != nil {
			c.KeyFile = *in.KeyFile
		}
		if !filepath.IsAbs(c.CertFile) || !filepath.IsAbs(c.KeyFile) {
			return inputErr("cert_file and key_file must be absolute paths (the full chain, and its key)")
		}
		c.Challenge, c.KeyType = "", ""
	default:
		return inputErr("source must be acme (Jarl obtains and renews it) or file (you renew it)")
	}
	return nil
}

// checkUses refuses a second certificate for jarld's HTTPS.
func (m *Manager) checkUses(ctx context.Context, c *model.Certificate) error {
	if !c.HasUse(model.CertUseWeb) {
		return nil
	}
	all, err := m.store.Certificates(ctx)
	if err != nil {
		return err
	}
	for _, o := range all {
		if o.ID != c.ID && o.HasUse(model.CertUseWeb) {
			return inputErr("certificate %s is already used for jarld's HTTPS; take the web use off it first (jarl cert update %s --use ...)", o.Name, o.Name)
		}
	}
	return nil
}

// List returns every certificate.
func (m *Manager) List(ctx context.Context) ([]*model.Certificate, error) {
	return m.store.Certificates(ctx)
}

// Get returns one certificate.
func (m *Manager) Get(ctx context.Context, name string) (*model.Certificate, error) {
	c, err := m.store.CertificateByName(ctx, name)
	if errors.Is(err, store.ErrNotFound) {
		return nil, ErrNotFound
	}
	return c, err
}

// Create adds a certificate. A file-source certificate is read at once;
// one Jarl obtains is left for Issue (or the background loop).
func (m *Manager) Create(ctx context.Context, in Input, p *auth.Principal) (*model.Certificate, error) {
	c := &model.Certificate{CreatedBy: p.Name(), UpdatedBy: p.Name()}
	if err := m.apply(c, in, true); err != nil {
		return nil, err
	}
	if err := m.checkUses(ctx, c); err != nil {
		return nil, err
	}
	if c.Source == model.CertSourceFile {
		if _, err := m.readFiles(c); err != nil {
			return nil, inputErr("%v", err)
		}
	}
	if err := m.store.CreateCertificate(ctx, c); err != nil {
		if errors.Is(err, store.ErrConflict) {
			return nil, ErrConflict
		}
		return nil, err
	}
	m.eng.Audit(ctx, p, "certificate.create", "certificate", c.ID, c.Name, "ok", describe(c))
	if c.Source == model.CertSourceFile {
		m.refreshFile(ctx, c, true)
	}
	return c, nil
}

// Update changes a certificate. New names or a new key type make one Jarl
// obtains due at once.
func (m *Manager) Update(ctx context.Context, name string, in Input, p *auth.Principal) (*model.Certificate, error) {
	c, err := m.Get(ctx, name)
	if err != nil {
		return nil, err
	}
	before := *c
	if err := m.apply(c, in, false); err != nil {
		return nil, err
	}
	if err := m.checkUses(ctx, c); err != nil {
		return nil, err
	}
	if before.HasUse(model.CertUseDNS) && !c.HasUse(model.CertUseDNS) && m.namedUses(ctx, m.FilesDir(c.Name)) {
		return nil, inputErr("named's configuration uses certificate %s (a tls statement names its files), so it keeps the dns use: take it out of named first (jarl encrypted-dns disable)", c.Name)
	}
	if c.Source == model.CertSourceFile && (c.CertFile != before.CertFile || c.KeyFile != before.KeyFile) {
		if _, err := m.readFiles(c); err != nil {
			return nil, inputErr("%v", err)
		}
	}
	if c.Source == model.CertSourceACME && c.CertPEM != "" && (!slices.Equal(c.Domains, before.Domains) || c.KeyType != before.KeyType) {
		now := m.now().UTC()
		c.RenewAt, c.Failures = &now, 0
	}
	c.UpdatedBy = p.Name()
	if err := m.store.UpdateCertificate(ctx, c); err != nil {
		return nil, err
	}
	m.eng.Audit(ctx, p, "certificate.update", "certificate", c.ID, c.Name, "ok", describe(c))
	if c.Source == model.CertSourceFile {
		m.mu.Lock()
		delete(m.files, c.ID)
		m.mu.Unlock()
		m.refreshFile(ctx, c, true)
	} else if c.CertPEM != "" {
		if err := m.deploy(ctx, c, []byte(c.CertPEM), []byte(c.KeyPEM)); err != nil {
			m.log.Warn("writing certificate files failed", "certificate", c.Name, "err", err)
		}
	}
	if before.HasUse(model.CertUseWeb) && !c.HasUse(model.CertUseWeb) {
		m.dropWeb(c.Name)
	}
	m.Kick()
	return c, nil
}

// Delete removes a certificate and its files for named.
func (m *Manager) Delete(ctx context.Context, name string, p *auth.Principal) error {
	c, err := m.Get(ctx, name)
	if err != nil {
		return err
	}
	if c.HasUse(model.CertUseDNS) && m.namedUses(ctx, m.FilesDir(c.Name)) {
		return inputErr("named's configuration uses certificate %s (a tls statement names its files): take it out first (jarl encrypted-dns disable, or remove the tls statement)", c.Name)
	}
	if err := m.store.DeleteCertificate(ctx, c.ID); err != nil {
		return err
	}
	m.dropWeb(c.Name)
	if err := m.removeFiles(c.Name); err != nil {
		m.log.Warn("removing certificate files failed", "certificate", c.Name, "err", err)
	}
	m.mu.Lock()
	delete(m.files, c.ID)
	m.mu.Unlock()
	m.eng.Audit(ctx, p, "certificate.delete", "certificate", c.ID, c.Name, "ok", "")
	return nil
}

func describe(c *model.Certificate) string {
	s := c.Source
	if c.Source == model.CertSourceACME {
		s += " " + strings.Join(c.Domains, " ") + ", challenge " + c.Challenge
	} else {
		s += " " + c.CertFile
	}
	if len(c.Uses) > 0 {
		s += ", uses " + strings.Join(c.Uses, ",")
	}
	return s
}

// Preview checks a new certificate's fields without saving it.
func (m *Manager) Preview(in Input) (*model.Certificate, error) {
	c := &model.Certificate{}
	if err := m.apply(c, in, true); err != nil {
		return nil, err
	}
	return c, nil
}

// Check works out where each name's challenge would go, without asking
// the CA for anything.
func (m *Manager) Check(ctx context.Context, c *model.Certificate) ([]Route, error) {
	if c.Source != model.CertSourceACME {
		return nil, inputErr("certificate %s is renewed by you (source file); there is nothing to check", c.Name)
	}
	st, err := m.store.LoadState(ctx)
	if err != nil {
		return nil, err
	}
	var out []Route
	for _, d := range c.Domains {
		out = append(out, m.route(ctx, st, c.Challenge, d, ""))
	}
	return out, nil
}

// IssueResult is the outcome of an issue.
type IssueResult struct {
	Certificate *model.Certificate `json:"certificate"`
	Routes      []Route            `json:"routes"`
}

// Issuing reports since when the certificate is being obtained (zero when
// it isn't).
func (m *Manager) Issuing(name string) time.Time {
	if v, ok := m.issuing.Load(name); ok {
		return v.(time.Time)
	}
	return time.Time{}
}

// IssueAsync starts obtaining a certificate in the background and returns
// at once: talking to the CA and waiting for every name server to serve
// the challenge can take minutes. Issuing tells when it is done; the
// outcome is in the certificate (last_success, last_error).
func (m *Manager) IssueAsync(ctx context.Context, name string, p *auth.Principal) (*model.Certificate, error) {
	c, err := m.Get(ctx, name)
	if err != nil {
		return nil, err
	}
	if c.Source == model.CertSourceFile {
		res, err := m.Issue(ctx, name, p)
		if res != nil {
			return res.Certificate, err
		}
		return nil, err
	}
	if _, busy := m.issuing.LoadOrStore(name, m.now()); busy {
		return c, nil
	}
	go func() {
		defer m.issuing.Delete(name)
		m.issue(m.base, c, p)
	}()
	return c, nil
}

// Issue obtains a new certificate for c now (a file-source certificate is
// reread instead).
func (m *Manager) Issue(ctx context.Context, name string, p *auth.Principal) (*IssueResult, error) {
	c, err := m.Get(ctx, name)
	if err != nil {
		return nil, err
	}
	if c.Source == model.CertSourceFile {
		m.mu.Lock()
		delete(m.files, c.ID)
		m.mu.Unlock()
		if err := m.refreshFile(ctx, c, true); err != nil {
			return &IssueResult{Certificate: c}, err
		}
		return &IssueResult{Certificate: c}, nil
	}
	return m.issue(ctx, c, p)
}

func (m *Manager) issue(ctx context.Context, c *model.Certificate, p *auth.Principal) (*IssueResult, error) {
	m.issueMu.Lock()
	defer m.issueMu.Unlock()
	// Reload: another issue may have finished while this one waited.
	if fresh, err := m.Get(ctx, c.Name); err == nil {
		c = fresh
	}
	var old *x509.Certificate
	if c.CertPEM != "" {
		if in, _, err := Inspect([]byte(c.CertPEM), []byte(c.KeyPEM)); err == nil {
			old = in.Leaf
		}
	}
	m.log.Info("obtaining certificate", "certificate", c.Name, "domains", strings.Join(c.Domains, " "), "by", p.Name())
	now := m.now().UTC()
	c.LastAttempt = &now
	res, routes, err := m.obtain(ctx, c, old)
	c.LastRoutes = nil
	for _, r := range routes {
		if r.Error == "" {
			c.LastRoutes = append(c.LastRoutes, r.String())
		}
	}
	var info *Info
	if err == nil {
		info, _, err = Inspect(res.Certificate, res.PrivateKey)
		if err != nil {
			err = fmt.Errorf("the CA's certificate is unusable: %w", err)
		}
	}
	if err != nil {
		c.Failures++
		c.LastError = err.Error()
		if serr := m.store.UpdateCertificate(ctx, c); serr != nil {
			m.log.Error("saving certificate state failed", "certificate", c.Name, "err", serr)
		}
		m.log.Warn("obtaining certificate failed", "certificate", c.Name, "failures", c.Failures, "err", err)
		m.eng.Audit(ctx, p, "certificate.issue", "certificate", c.ID, c.Name, "error", err.Error())
		return &IssueResult{Certificate: c, Routes: routes}, err
	}
	c.CertPEM, c.KeyPEM = string(res.Certificate), string(res.PrivateKey)
	setInfo(c, info)
	done := m.now().UTC()
	c.LastSuccess, c.Failures, c.LastError = &done, 0, ""
	at := twoThirds(info.NotBefore, info.NotAfter)
	c.RenewAt, c.ARICheckedAt = &at, nil
	if t, err := m.renewalInfo(ctx, c, info.Leaf); err == nil && t != nil {
		c.RenewAt, c.ARICheckedAt = t, &done
	}
	if err := m.store.UpdateCertificate(ctx, c); err != nil {
		return nil, err
	}
	m.log.Info("certificate obtained", "certificate", c.Name, "expires", info.NotAfter.Format(time.DateOnly), "renew_at", c.RenewAt.Format(time.RFC3339), "routes", strings.Join(c.LastRoutes, "; "))
	m.eng.Audit(ctx, p, "certificate.issue", "certificate", c.ID, c.Name, "ok", fmt.Sprintf("%s, valid until %s, from %s", strings.Join(info.Names, " "), info.NotAfter.Format(time.DateOnly), info.Issuer))
	if err := m.deploy(ctx, c, res.Certificate, res.PrivateKey); err != nil {
		m.log.Error("writing certificate files failed", "certificate", c.Name, "err", err)
		return &IssueResult{Certificate: c, Routes: routes}, fmt.Errorf("the certificate was obtained, but writing it for named failed: %w", err)
	}
	return &IssueResult{Certificate: c, Routes: routes}, nil
}

func setInfo(c *model.Certificate, in *Info) {
	nb, na := in.NotBefore.UTC(), in.NotAfter.UTC()
	c.Names, c.NotBefore, c.NotAfter, c.Issuer, c.Serial = in.Names, &nb, &na, in.Issuer, in.Serial
}

// readFiles reads a file-source certificate and checks it.
func (m *Manager) readFiles(c *model.Certificate) (*Info, error) {
	cert, err := os.ReadFile(c.CertFile)
	if err != nil {
		return nil, fileErr(err)
	}
	key, err := os.ReadFile(c.KeyFile)
	if err != nil {
		return nil, fileErr(err)
	}
	in, _, err := Inspect(cert, key)
	if err != nil {
		return nil, fmt.Errorf("%s and %s: %w", c.CertFile, c.KeyFile, err)
	}
	return in, nil
}

func fileErr(err error) error {
	if errors.Is(err, fs.ErrPermission) {
		return fmt.Errorf("%w: jarld runs as its own user (jarl) and must be able to read the certificate and its key; e.g. give the files group jarl (chgrp jarl FILE; chmod 640 FILE), or copy them somewhere it can read in your renewal hook", err)
	}
	return err
}

// refreshFile rereads a file-source certificate when its files changed
// (always with force) and deploys it.
func (m *Manager) refreshFile(ctx context.Context, c *model.Certificate, force bool) error {
	cs, err1 := os.Stat(c.CertFile)
	ks, err2 := os.Stat(c.KeyFile)
	var stamp fileStamp
	if err1 == nil && err2 == nil {
		stamp = fileStamp{certMod: cs.ModTime(), keyMod: ks.ModTime(), certSize: cs.Size()}
		m.mu.Lock()
		prev, ok := m.files[c.ID]
		m.mu.Unlock()
		if ok && prev == stamp && !force {
			return nil
		}
	}
	in, err := m.readFiles(c)
	now := m.now().UTC()
	c.LastAttempt = &now
	if err != nil {
		if c.LastError != err.Error() {
			m.log.Warn("reading certificate failed", "certificate", c.Name, "err", err)
		}
		c.LastError = err.Error()
		c.Failures = max(c.Failures, 1)
		m.store.UpdateCertificate(ctx, c)
		return err
	}
	if c.Serial != in.Serial {
		m.log.Info("certificate read", "certificate", c.Name, "file", c.CertFile, "expires", in.NotAfter.Format(time.DateOnly))
	}
	setInfo(c, in)
	c.Domains = in.Names
	c.LastSuccess, c.LastError, c.Failures = &now, "", 0
	if len(in.Warnings) > 0 {
		c.LastError = in.Warnings[0]
	}
	if err := m.store.UpdateCertificate(ctx, c); err != nil {
		return err
	}
	cert, _ := os.ReadFile(c.CertFile)
	key, _ := os.ReadFile(c.KeyFile)
	if err := m.deploy(ctx, c, cert, key); err != nil {
		return err
	}
	m.mu.Lock()
	m.files[c.ID] = stamp
	m.mu.Unlock()
	return nil
}

// FilesDir is where a certificate with the dns use is written for named.
func (m *Manager) FilesDir(name string) string { return filepath.Join(m.cfg.Dir, name) }

// Files names a certificate's files for named.
const (
	ChainFile = "fullchain.pem"
	KeyFile   = "privkey.pem"
)

// deploy puts a certificate where it is used: jarld's HTTPS and/or the
// files named reads. When those files change and named's configuration
// names them, named rereads it.
func (m *Manager) deploy(ctx context.Context, c *model.Certificate, cert, key []byte) error {
	_, pair, err := Inspect(cert, key)
	if err != nil {
		return err
	}
	if c.HasUse(model.CertUseWeb) {
		m.web.Store(&webCert{name: c.Name, pair: pair})
	} else {
		m.dropWeb(c.Name)
	}
	if !c.HasUse(model.CertUseDNS) {
		return m.removeFiles(c.Name)
	}
	dir := m.FilesDir(c.Name)
	changed := false
	for _, f := range []struct {
		name    string
		content []byte
		mode    fs.FileMode
	}{{ChainFile, cert, 0o644}, {KeyFile, key, 0o640}} {
		path := filepath.Join(dir, f.name)
		if old, err := os.ReadFile(path); err == nil && bytes.Equal(old, f.content) {
			continue
		}
		if err := m.eng.WriteFile(path, f.content, f.mode); err != nil {
			return err
		}
		changed = true
	}
	if changed && m.namedUses(ctx, dir) {
		if err := m.eng.Reconfig(ctx); err != nil {
			return fmt.Errorf("named didn't reread its configuration for the new certificate: %w", err)
		}
		m.log.Info("named rereads the new certificate", "certificate", c.Name)
	}
	return nil
}

// namedUses reports whether named's configuration names files in dir.
func (m *Manager) namedUses(ctx context.Context, dir string) bool {
	st, err := m.store.LoadState(ctx)
	if err != nil {
		return false
	}
	for _, o := range st.Options {
		if strings.Contains(o.Value, dir+"/") {
			return true
		}
	}
	return false
}

func (m *Manager) removeFiles(name string) error {
	if name == "" || strings.ContainsAny(name, "/.") {
		return nil
	}
	dir := m.FilesDir(name)
	if _, err := os.Stat(dir); err != nil {
		return nil
	}
	return os.RemoveAll(dir)
}

func (m *Manager) dropWeb(name string) {
	if w := m.web.Load(); w != nil && w.name == name {
		m.web.CompareAndSwap(w, nil)
	}
}

// WebCertificate is the certificate for jarld's HTTPS (nil when no
// certificate has the web use, or it has none yet).
func (m *Manager) WebCertificate() *tls.Certificate {
	if w := m.web.Load(); w != nil {
		return w.pair
	}
	return nil
}

// WebName is the name of the certificate jarld serves ("" for none).
func (m *Manager) WebName() string {
	if w := m.web.Load(); w != nil {
		return w.name
	}
	return ""
}

// HasWeb reports whether a certificate has the web use (whether or not
// it has been obtained yet).
func (m *Manager) HasWeb(ctx context.Context) bool {
	all, err := m.store.Certificates(ctx)
	if err != nil {
		return false
	}
	return slices.ContainsFunc(all, func(c *model.Certificate) bool { return c.HasUse(model.CertUseWeb) })
}

// Kick makes the loop look at the certificates now.
func (m *Manager) Kick() {
	select {
	case m.kick <- struct{}{}:
	default:
	}
}

// Start loads the certificates and puts them in place (jarld's HTTPS, the
// files for named). Call it before serving.
func (m *Manager) Start(ctx context.Context) {
	all, err := m.store.Certificates(ctx)
	if err != nil {
		m.log.Error("loading certificates failed", "err", err)
		return
	}
	for _, c := range all {
		switch {
		case c.Source == model.CertSourceFile:
			m.refreshFile(ctx, c, true)
		case c.CertPEM != "":
			if err := m.deploy(ctx, c, []byte(c.CertPEM), []byte(c.KeyPEM)); err != nil {
				m.log.Warn("putting certificate in place failed", "certificate", c.Name, "err", err)
			}
		}
	}
}

// Run renews certificates when they are due and rereads file-source ones
// when their files change, until ctx ends.
func (m *Manager) Run(ctx context.Context) {
	m.base = ctx
	select {
	case <-ctx.Done():
		return
	case <-time.After(20 * time.Second): // let jarld finish starting
	}
	for {
		m.Tick(ctx)
		t := time.NewTimer(10 * time.Minute)
		select {
		case <-ctx.Done():
			t.Stop()
			return
		case <-t.C:
		case <-m.kick:
			t.Stop()
		}
	}
}

// Tick does one round of the loop.
func (m *Manager) Tick(ctx context.Context) {
	all, err := m.store.Certificates(ctx)
	if err != nil {
		m.log.Error("loading certificates failed", "err", err)
		return
	}
	now := m.now()
	for _, c := range all {
		if ctx.Err() != nil {
			return
		}
		if c.Source == model.CertSourceFile {
			m.refreshFile(ctx, c, false)
			continue
		}
		if at := m.Due(c); !at.After(now) {
			if _, busy := m.issuing.LoadOrStore(c.Name, now); !busy {
				m.issue(ctx, c, auth.System)
				m.issuing.Delete(c.Name)
			}
			continue
		}
		// Ask the CA about the renewal window twice a day (it moves it
		// earlier when a certificate must be replaced, e.g. revoked).
		if c.CertPEM != "" && (c.ARICheckedAt == nil || now.Sub(*c.ARICheckedAt) > 12*time.Hour) {
			in, _, err := Inspect([]byte(c.CertPEM), []byte(c.KeyPEM))
			if err != nil {
				continue
			}
			t, err := m.renewalInfo(ctx, c, in.Leaf)
			checked := now.UTC()
			c.ARICheckedAt = &checked
			if err == nil && t != nil && (c.RenewAt == nil || !t.Equal(*c.RenewAt)) {
				m.log.Info("renewal time from the CA", "certificate", c.Name, "renew_at", t.Format(time.RFC3339))
				c.RenewAt = t
			}
			m.store.UpdateCertificate(ctx, c)
		}
	}
}

// Due is when c should be obtained (again): at once when it has no
// certificate yet or its names changed; else at its renewal time. After
// failures it waits 1, 2, 4 ... hours (at most a day) between attempts.
func (m *Manager) Due(c *model.Certificate) time.Time {
	var at time.Time
	switch {
	case c.CertPEM == "":
		at = c.CreatedAt
	case c.RenewAt != nil:
		at = *c.RenewAt
	case c.NotBefore != nil && c.NotAfter != nil:
		at = twoThirds(*c.NotBefore, *c.NotAfter)
	}
	if c.Failures > 0 && c.LastAttempt != nil {
		wait := time.Hour << min(c.Failures-1, 5)
		at = maxTime(at, c.LastAttempt.Add(min(wait, 24*time.Hour)))
	}
	return at
}

func maxTime(a, b time.Time) time.Time {
	if a.After(b) {
		return a
	}
	return b
}

// Status is a certificate's health.
type Status struct {
	State   string `json:"state"` // ok, pending, failing, expiring, expired
	Message string `json:"message,omitempty"`
}

// StatusOf says how c is doing.
func (m *Manager) StatusOf(c *model.Certificate) Status {
	now := m.now()
	if c.NotAfter == nil {
		if c.Failures > 0 {
			return Status{"failing", "not obtained yet: " + c.LastError}
		}
		return Status{"pending", "not obtained yet"}
	}
	left := c.NotAfter.Sub(now)
	life := c.NotAfter.Sub(*c.NotBefore)
	switch {
	case left <= 0:
		return Status{"expired", "expired on " + c.NotAfter.Format(time.DateOnly)}
	case c.Failures > 0 && c.Source == model.CertSourceACME:
		return Status{"failing", fmt.Sprintf("renewing failed %d times (next try %s): %s", c.Failures, m.Due(c).Local().Format("2 Jan 15:04"), c.LastError)}
	case c.Failures > 0:
		return Status{"failing", c.LastError}
	case left < life/6 || (c.Source == model.CertSourceFile && left < 14*24*time.Hour):
		return Status{"expiring", fmt.Sprintf("expires in %s (%s)", days(left), c.NotAfter.Format(time.DateOnly))}
	}
	return Status{"ok", ""}
}

func days(d time.Duration) string {
	n := int(d.Hours() / 24)
	if n == 1 {
		return "1 day"
	}
	if n < 1 {
		return fmt.Sprintf("%d hours", int(d.Hours()))
	}
	return fmt.Sprintf("%d days", n)
}

// AccountInfo is the ACME account as the API shows it.
type AccountInfo struct {
	Directory     string     `json:"directory"`
	Email         string     `json:"email,omitempty"`
	AgreeTOS      bool       `json:"agree_tos"`
	EAB           bool       `json:"eab"`
	Registered    bool       `json:"registered"`
	URI           string     `json:"uri,omitempty"`
	RegisteredAt  *time.Time `json:"registered_at,omitempty"`
	Porkbun       bool       `json:"porkbun"`
	Resolvers     []string   `json:"resolvers"`
	Dir           string     `json:"dir"`
	ActiveWebCert string     `json:"active_web_certificate,omitempty"`
}

// AccountInfo describes the ACME account and settings.
func (m *Manager) AccountInfo(ctx context.Context) AccountInfo {
	ai := AccountInfo{Directory: m.cfg.Directory, Email: m.cfg.Email, AgreeTOS: m.cfg.AgreeTOS, EAB: m.cfg.EABKeyID != "",
		Porkbun: m.cfg.Porkbun != nil, Resolvers: m.cfg.Resolvers, Dir: m.cfg.Dir, ActiveWebCert: m.WebName()}
	if a := m.account(ctx); a != nil && a.Directory == m.cfg.Directory && a.URI != "" {
		ai.Registered, ai.URI = true, a.URI
		t := a.RegisteredAt
		ai.RegisteredAt = &t
	}
	return ai
}