restic-manager/internal/server/http/ui_handlers.go

package http

import (
	"crypto/rand"
	"encoding/base64"
	"encoding/json"
	"errors"
	"io/fs"
	"log/slog"
	stdhttp "net/http"
	"strings"
	"time"

	"github.com/coder/websocket"
	"github.com/go-chi/chi/v5"

	"gitea.dcglab.co.uk/steve/restic-manager/internal/api"
	"gitea.dcglab.co.uk/steve/restic-manager/internal/auth"
	"gitea.dcglab.co.uk/steve/restic-manager/internal/server/ui"
	"gitea.dcglab.co.uk/steve/restic-manager/internal/server/ws"
	"gitea.dcglab.co.uk/steve/restic-manager/internal/store"
	"gitea.dcglab.co.uk/steve/restic-manager/web"
)

// ----- static assets (Tailwind CSS, future favicon, etc) -------------

// staticHandler serves files embedded under web/static/ at /static/*.
// Returns 404 for anything missing rather than the fs default 500.
func staticHandler() stdhttp.Handler {
	sub, err := fs.Sub(web.FS, "static")
	if err != nil {
		// Embed.FS panics live at compile time; if Sub fails the binary
		// is genuinely broken — surface it loudly.
		panic("web: static subtree missing: " + err.Error())
	}
	return stdhttp.StripPrefix("/static/", stdhttp.FileServer(stdhttp.FS(sub)))
}

// ----- session helpers ------------------------------------------------

// sessionUser resolves the request's session cookie to a User, or
// (nil, nil) if the cookie is missing/expired/invalid. A non-nil
// error means an underlying store failure; treat that as 500.
func (s *Server) sessionUser(r *stdhttp.Request) (*ui.User, error) {
	c, err := r.Cookie(sessionCookieName)
	if err != nil {
		return nil, nil
	}
	sess, err := s.deps.Store.LookupSession(r.Context(), auth.HashToken(c.Value))
	if err != nil {
		// Treat "not found" / "expired" as "no session", not as fatal.
		if errors.Is(err, store.ErrNotFound) {
			return nil, nil
		}
		return nil, err
	}
	u, err := s.deps.Store.GetUserByID(r.Context(), sess.UserID)
	if err != nil {
		if errors.Is(err, store.ErrNotFound) {
			return nil, nil
		}
		return nil, err
	}
	return &ui.User{ID: u.ID, Username: u.Username, Role: string(u.Role)}, nil
}

// requireUIUser resolves the session and 303-redirects to /login if
// there isn't one. Returns nil + emits the redirect when unauthed.
// (HTML twin of jobs.go's API-style requireUser, which returns 401.)
func (s *Server) requireUIUser(w stdhttp.ResponseWriter, r *stdhttp.Request) *ui.User {
	u, err := s.sessionUser(r)
	if err != nil {
		stdhttp.Error(w, "internal", stdhttp.StatusInternalServerError)
		return nil
	}
	if u == nil {
		stdhttp.Redirect(w, r, "/login", stdhttp.StatusSeeOther)
		return nil
	}
	return u
}

// baseView populates the fields the nav partial needs on every
// authenticated page.
func (s *Server) baseView(u *ui.User, active string) ui.ViewData {
	return ui.ViewData{
		User:    u,
		Active:  active,
		Version: s.version(),
	}
}

// version returns the binary's build version — passed in via Deps so
// cmd/server's `var version` ends up here.
func (s *Server) version() string {
	if s.deps.Version != "" {
		return s.deps.Version
	}
	return "dev"
}

// ----- handlers -------------------------------------------------------

// dashboardPage is the data the dashboard template renders against.
type dashboardPage struct {
	Hosts     []store.Host
	HostCount int
	Summary   store.FleetSummary
}

// handleUIDashboard is the root page. Auth-gated; falls through to
// /login if there is no session.
func (s *Server) handleUIDashboard(w stdhttp.ResponseWriter, r *stdhttp.Request) {
	u := s.requireUIUser(w, r)
	if u == nil {
		return
	}

	hosts, err := s.deps.Store.ListHosts(r.Context())
	if err != nil {
		slog.Error("ui dashboard: list hosts", "err", err)
		stdhttp.Error(w, "internal", stdhttp.StatusInternalServerError)
		return
	}
	summary, err := s.deps.Store.FleetSummary(r.Context())
	if err != nil {
		slog.Error("ui dashboard: fleet summary", "err", err)
		stdhttp.Error(w, "internal", stdhttp.StatusInternalServerError)
		return
	}

	view := s.baseView(u, "dashboard")
	view.OpenAlerts = summary.OpenAlerts
	view.Page = dashboardPage{
		Hosts:     hosts,
		HostCount: len(hosts),
		Summary:   summary,
	}
	if err := s.deps.UI.Render(w, "dashboard", view); err != nil {
		slog.Error("ui: render dashboard", "err", err)
		stdhttp.Error(w, "internal", stdhttp.StatusInternalServerError)
	}
}

// handleUIRunBackup and handleUIInitRepo are stubbed during the P2
// redesign data-model rewrite. The dashboard per-host Run-now button
// is going away (operator clicks into host detail then a per-source-
// group Run-now), and Init-repo becomes implicit at host enrolment
// (auto-init dispatched server-side). Phase 4 of the redesign wires
// the new per-source-group Run-now via /hosts/{id}/source-groups/{gid}/run.

func (s *Server) handleUIRunBackup(w stdhttp.ResponseWriter, r *stdhttp.Request) {
	stdhttp.Error(w,
		"per-host Run-now is being replaced by per-source-group Run-now — see P2 redesign Phase 4",
		stdhttp.StatusNotImplemented)
}

func (s *Server) handleUIInitRepo(w stdhttp.ResponseWriter, r *stdhttp.Request) {
	stdhttp.Error(w,
		"manual Init-repo is being replaced by auto-init at host enrolment — see P2 redesign Phase 6",
		stdhttp.StatusNotImplemented)
}

// addHostPage carries the Add-host form state. The result-state
// (showing the install command + htpasswd snippet) lives at
// /hosts/pending/{token} and uses pendingHostPage instead, so the
// operator can refresh / bookmark / come back later — the password
// is decrypted from the still-alive token row on every render
// rather than living only in a one-shot rendered response.
type addHostPage struct {
	// Form fields — pre-populate the form on a re-render after a
	// validation error.
	Hostname     string
	Tags         string
	RepoURL      string
	RepoUsername string
	Paths        string
	ServerURL    string
	Error        string
}

// pendingHostPage is the GET /hosts/pending/{token} view. Lives
// for as long as the token does (1h ttl); once the agent enrols,
// the handler redirects to /hosts/{host_id} and this page is gone.
type pendingHostPage struct {
	Token             string
	ServerURL         string
	ExpiresAt         time.Time
	RepoURL           string
	RepoUsername      string
	RepoPassword      string
	InitialPaths      []string
}

// handleUIAddHostGet renders the empty Add host form.
func (s *Server) handleUIAddHostGet(w stdhttp.ResponseWriter, r *stdhttp.Request) {
	u := s.requireUIUser(w, r)
	if u == nil {
		return
	}
	view := s.baseView(u, "dashboard")
	view.Title = "Add host · restic-manager"
	view.Page = addHostPage{ServerURL: s.publicURL(r)}
	if err := s.deps.UI.Render(w, "add_host", view); err != nil {
		slog.Error("ui: render add_host", "err", err)
		stdhttp.Error(w, "internal", stdhttp.StatusInternalServerError)
	}
}

// handleUIAddHostPost validates the form, mints the enrolment token
// (with encrypted repo creds), and 303-redirects to the persistent
// pending-host page. On validation errors we re-render the form
// with the operator's typed input intact and a banner.
func (s *Server) handleUIAddHostPost(w stdhttp.ResponseWriter, r *stdhttp.Request) {
	u := s.requireUIUser(w, r)
	if u == nil {
		return
	}
	if err := r.ParseForm(); err != nil {
		stdhttp.Error(w, "bad request", stdhttp.StatusBadRequest)
		return
	}
	page := addHostPage{
		Hostname:     strings.TrimSpace(r.PostForm.Get("hostname")),
		Tags:         strings.TrimSpace(r.PostForm.Get("tags")),
		RepoURL:      strings.TrimSpace(r.PostForm.Get("repo_url")),
		RepoUsername: strings.TrimSpace(r.PostForm.Get("repo_username")),
		Paths:        r.PostForm.Get("paths"),
		ServerURL:    s.publicURL(r),
	}
	repoPassword := r.PostForm.Get("repo_password")

	if page.Hostname == "" {
		page.Error = "Hostname is required."
	} else if page.RepoURL == "" {
		page.Error = "Repo URL is required so the agent can back up the moment it comes online."
	}

	if page.Error == "" && repoPassword == "" {
		gen, err := generateRepoPassword()
		if err != nil {
			slog.Error("ui add_host: generate repo password", "err", err)
			page.Error = "Couldn’t generate a password — see the server log for details."
		} else {
			repoPassword = gen
		}
	}

	// Default repo username to the hostname when the operator left it
	// blank. With rest-server's --private-repos this is what the URL
	// path segment is expected to be anyway, and an htpasswd entry
	// always needs *some* user — defaulting saves the operator from
	// landing on a pending page with a half-formed snippet.
	repoUsername := page.RepoUsername
	if repoUsername == "" {
		repoUsername = page.Hostname
	}

	if page.Error == "" {
		token, _, err := s.mintEnrollmentToken(r.Context(), page.RepoURL, repoUsername, repoPassword, splitPaths(page.Paths))
		switch err {
		case nil:
			stdhttp.Redirect(w, r, "/hosts/pending/"+token, stdhttp.StatusSeeOther)
			return
		case errMissingRepoCreds:
			page.Error = "Repo URL and password are both required."
		default:
			slog.Error("ui add_host: mint token", "err", err)
			page.Error = "Couldn’t mint a token — see the server log for details."
		}
	}

	view := s.baseView(u, "dashboard")
	view.Title = "Add host · restic-manager"
	view.Page = page
	w.WriteHeader(stdhttp.StatusUnprocessableEntity)
	if err := s.deps.UI.Render(w, "add_host", view); err != nil {
		slog.Error("ui: render add_host", "err", err)
	}
}

// handleUIPendingHost serves the durable Add-host result page —
// shown after a successful POST /hosts/new and reachable until the
// agent enrols (the page redirects to /hosts/{id} once that
// happens) or the token expires (1h ttl). The password is
// re-decrypted from the encrypted token row on every render so
// the operator can refresh, bookmark, navigate away and come back.
func (s *Server) handleUIPendingHost(w stdhttp.ResponseWriter, r *stdhttp.Request) {
	u := s.requireUIUser(w, r)
	if u == nil {
		return
	}
	rawToken := chi.URLParam(r, "token")
	if rawToken == "" {
		stdhttp.NotFound(w, r)
		return
	}
	tokHash := auth.HashToken(rawToken)

	status, err := s.deps.Store.GetEnrollmentTokenStatus(r.Context(), tokHash)
	if err != nil {
		stdhttp.Redirect(w, r, "/hosts/new", stdhttp.StatusSeeOther)
		return
	}
	if status.ConsumedHost != nil {
		stdhttp.Redirect(w, r, "/hosts/"+*status.ConsumedHost, stdhttp.StatusSeeOther)
		return
	}
	if time.Now().After(status.ExpiresAt) {
		stdhttp.Redirect(w, r, "/hosts/new", stdhttp.StatusSeeOther)
		return
	}

	att, err := s.deps.Store.GetEnrollmentTokenAttachments(r.Context(), tokHash)
	if err != nil {
		slog.Warn("ui pending: load attachments", "err", err)
		stdhttp.Redirect(w, r, "/hosts/new", stdhttp.StatusSeeOther)
		return
	}
	page := pendingHostPage{
		Token:        rawToken,
		ServerURL:    s.publicURL(r),
		ExpiresAt:    status.ExpiresAt,
		InitialPaths: att.InitialPaths,
	}
	if att.EncRepoCreds != "" {
		plain, err := s.deps.AEAD.Decrypt(att.EncRepoCreds, []byte("token:"+tokHash))
		if err != nil {
			slog.Error("ui pending: decrypt creds", "err", err)
		} else {
			var blob repoCredsBlob
			if err := json.Unmarshal(plain, &blob); err == nil {
				page.RepoURL = blob.RepoURL
				page.RepoUsername = blob.RepoUsername
				page.RepoPassword = blob.RepoPassword
			}
		}
	}

	view := s.baseView(u, "dashboard")
	view.Title = "Pending host · restic-manager"
	view.Page = page
	if err := s.deps.UI.Render(w, "pending_host", view); err != nil {
		slog.Error("ui: render pending_host", "err", err)
		stdhttp.Error(w, "internal", stdhttp.StatusInternalServerError)
	}
}

// handleUIPendingAwaiting is the polled fragment that the pending-
// host page swaps in every couple of seconds to detect "agent
// connected". Returns either the still-awaiting partial (with the
// HTMX poll trigger preserved) or the connected partial (no poll —
// includes a meta-refresh to /hosts/{id} so the operator lands on
// the host detail).
func (s *Server) handleUIPendingAwaiting(w stdhttp.ResponseWriter, r *stdhttp.Request) {
	if u := s.requireUIUser(w, r); u == nil {
		return
	}
	rawToken := chi.URLParam(r, "token")
	if rawToken == "" {
		stdhttp.Error(w, "missing token", stdhttp.StatusBadRequest)
		return
	}
	status, err := s.deps.Store.GetEnrollmentTokenStatus(r.Context(), auth.HashToken(rawToken))
	page := awaitingFragment{Token: rawToken, ExpiresAt: status.ExpiresAt}
	switch {
	case errors.Is(err, store.ErrNotFound):
		page.State = "expired"
	case err != nil:
		slog.Warn("ui awaiting: lookup", "err", err)
		page.State = "expired"
	case status.ConsumedHost != nil:
		page.State = "connected"
		page.HostID = *status.ConsumedHost
		if h, err := s.deps.Store.GetHost(r.Context(), *status.ConsumedHost); err == nil {
			page.HostName = h.Name
			page.LastSeenAt = h.LastSeenAt
		}
	case time.Now().After(status.ExpiresAt):
		page.State = "expired"
	default:
		page.State = "awaiting"
	}
	if err := s.deps.UI.RenderPartial(w, "awaiting_agent", ui.ViewData{Page: page}); err != nil {
		slog.Error("ui: render awaiting_agent", "err", err)
		stdhttp.Error(w, "internal", stdhttp.StatusInternalServerError)
	}
}

// awaitingFragment carries the state for the polled awaiting-agent
// partial. State == awaiting | connected | expired drives both the
// copy block and whether HTMX keeps polling.
type awaitingFragment struct {
	State      string
	Token      string
	ExpiresAt  time.Time
	HostID     string
	HostName   string
	LastSeenAt *time.Time
}

// hostDetailPage carries everything the host detail template needs.
type hostDetailPage struct {
	Host      store.Host
	Snapshots []store.Snapshot
	// SnapshotsShown is the number rendered (we cap at ~50 for the
	// first slice; pagination lands when it matters).
	SnapshotsShown int
}

// handleUIHostDetail is the host detail page (snapshots tab by default).
// Auth-gated. 404 if the host id is unknown.
func (s *Server) handleUIHostDetail(w stdhttp.ResponseWriter, r *stdhttp.Request) {
	u := s.requireUIUser(w, r)
	if u == nil {
		return
	}
	hostID := chi.URLParam(r, "id")
	if hostID == "" {
		stdhttp.NotFound(w, r)
		return
	}
	host, err := s.deps.Store.GetHost(r.Context(), hostID)
	if err != nil {
		if errors.Is(err, store.ErrNotFound) {
			stdhttp.NotFound(w, r)
			return
		}
		slog.Error("ui host detail: get host", "host_id", hostID, "err", err)
		stdhttp.Error(w, "internal", stdhttp.StatusInternalServerError)
		return
	}
	snaps, err := s.deps.Store.ListSnapshotsByHost(r.Context(), hostID)
	if err != nil {
		slog.Error("ui host detail: list snapshots", "host_id", hostID, "err", err)
		stdhttp.Error(w, "internal", stdhttp.StatusInternalServerError)
		return
	}
	const cap = 50
	shown := snaps
	if len(shown) > cap {
		shown = shown[:cap]
	}

	view := s.baseView(u, "dashboard")
	view.Title = host.Name + " · restic-manager"
	view.Page = hostDetailPage{
		Host:           *host,
		Snapshots:      shown,
		SnapshotsShown: len(shown),
	}
	if err := s.deps.UI.Render(w, "host_detail", view); err != nil {
		slog.Error("ui: render host_detail", "err", err)
		stdhttp.Error(w, "internal", stdhttp.StatusInternalServerError)
	}
}

// generateRepoPassword returns a 24-byte URL-safe random string for
// use as a per-host rest-server password. URL-safe alphabet keeps
// it shell-safe inside single quotes — important since the operator
// pastes it into an `htpasswd -i` invocation on the rest-server.
func generateRepoPassword() (string, error) {
	var buf [24]byte
	if _, err := rand.Read(buf[:]); err != nil {
		return "", err
	}
	return base64.RawURLEncoding.EncodeToString(buf[:]), nil
}

// splitPaths parses the textarea content into a clean []string —
// one path per line, leading/trailing whitespace trimmed, blanks
// dropped.
func splitPaths(s string) []string {
	out := []string{}
	for _, line := range strings.Split(s, "\n") {
		if p := strings.TrimSpace(line); p != "" {
			out = append(out, p)
		}
	}
	return out
}

// publicURL is what the operator should paste into the install
// command. Prefers RM_BASE_URL (set by the operator's reverse
// proxy config) and falls back to scheme + Host of the inbound
// request — useful for local smoke without a proxy.
func (s *Server) publicURL(r *stdhttp.Request) string {
	if s.deps.Cfg.BaseURL != "" {
		return strings.TrimRight(s.deps.Cfg.BaseURL, "/")
	}
	scheme := "http"
	if r.TLS != nil || r.Header.Get("X-Forwarded-Proto") == "https" {
		scheme = "https"
	}
	return scheme + "://" + r.Host
}

// jobDetailPage carries everything the live-log template renders.
type jobDetailPage struct {
	Job      store.Job
	Host     store.Host
	Logs     []store.JobLogLine
	NextSeq  int64
	IsActive bool // true while status is queued|running
}

// handleUIJobDetail renders the live job log view (snapshot of any
// already-persisted log lines + an empty stream container the JS
// fills via the WS).
func (s *Server) handleUIJobDetail(w stdhttp.ResponseWriter, r *stdhttp.Request) {
	u := s.requireUIUser(w, r)
	if u == nil {
		return
	}
	jobID := chi.URLParam(r, "id")
	if jobID == "" {
		stdhttp.NotFound(w, r)
		return
	}
	job, err := s.deps.Store.GetJob(r.Context(), jobID)
	if err != nil {
		if errors.Is(err, store.ErrNotFound) {
			stdhttp.NotFound(w, r)
			return
		}
		stdhttp.Error(w, "internal", stdhttp.StatusInternalServerError)
		return
	}
	host, err := s.deps.Store.GetHost(r.Context(), job.HostID)
	if err != nil {
		stdhttp.Error(w, "internal", stdhttp.StatusInternalServerError)
		return
	}
	logs, err := s.deps.Store.ListJobLogs(r.Context(), jobID, 0, 0)
	if err != nil {
		stdhttp.Error(w, "internal", stdhttp.StatusInternalServerError)
		return
	}
	var nextSeq int64
	if n := len(logs); n > 0 {
		nextSeq = logs[n-1].Seq
	}

	view := s.baseView(u, "dashboard")
	view.Title = job.Kind + " · " + host.Name + " · restic-manager"
	view.Page = jobDetailPage{
		Job:      *job,
		Host:     *host,
		Logs:     logs,
		NextSeq:  nextSeq,
		IsActive: job.Status == "queued" || job.Status == "running",
	}
	if err := s.deps.UI.Render(w, "job_detail", view); err != nil {
		slog.Error("ui: render job_detail", "err", err)
		stdhttp.Error(w, "internal", stdhttp.StatusInternalServerError)
	}
}

// handleJobStream is the browser-side WS endpoint. Auth is via the
// session cookie (the HTTP layer does the lookup before upgrading).
// On connect we subscribe to JobHub for the given job_id; the
// subscriber goroutine pumps fan-out messages to the client until
// the job finishes or the browser navigates away.
//
// Messages on the wire are the same api.Envelope shape as on the
// agent side, so the client-side JS can switch on env.type the
// same way our Go code does.
func (s *Server) handleJobStream(w stdhttp.ResponseWriter, r *stdhttp.Request) {
	if u, _ := s.sessionUser(r); u == nil {
		stdhttp.Error(w, "unauthorized", stdhttp.StatusUnauthorized)
		return
	}
	jobID := chi.URLParam(r, "id")
	if jobID == "" {
		stdhttp.Error(w, "missing job id", stdhttp.StatusBadRequest)
		return
	}
	if _, err := s.deps.Store.GetJob(r.Context(), jobID); err != nil {
		stdhttp.NotFound(w, r)
		return
	}

	conn, err := websocket.Accept(w, r, &websocket.AcceptOptions{
		InsecureSkipVerify: true, // Origin checks pointless for a same-origin browser hop.
	})
	if err != nil {
		slog.Warn("ws browser accept failed", "job_id", jobID, "err", err)
		return
	}
	defer func() { _ = conn.Close(websocket.StatusNormalClosure, "") }()

	// Wrap so we get the same Send semantics as the agent path.
	c := ws.NewConn("browser-"+jobID, conn)

	// Register first so future broadcasts reach us, then re-fetch the
	// job to close the late-subscriber race: a fast-failing job can
	// finish (DB write + Broadcast) before the browser's WS hop
	// completes, leaving the JS waiting forever for a job.finished
	// that already passed. If the job is already terminal here, prime
	// the subscriber with a synthetic job.finished so the JS reloads.
	sub := s.deps.JobHub.Register(jobID)
	if cur, gerr := s.deps.Store.GetJob(r.Context(), jobID); gerr == nil && isTerminalJobStatus(cur.Status) {
		if env, ferr := buildSyntheticJobFinished(cur); ferr == nil {
			sub.Send(env)
		}
	}
	sub.Run(r.Context(), c)
}

func isTerminalJobStatus(s string) bool {
	switch api.JobStatus(s) {
	case api.JobSucceeded, api.JobFailed, api.JobCancelled:
		return true
	}
	return false
}

func buildSyntheticJobFinished(job *store.Job) (api.Envelope, error) {
	var fin time.Time
	if job.FinishedAt != nil {
		fin = *job.FinishedAt
	}
	exit := 0
	if job.ExitCode != nil {
		exit = *job.ExitCode
	}
	errMsg := ""
	if job.Error != nil {
		errMsg = *job.Error
	}
	return api.Marshal(api.MsgJobFinished, "", api.JobFinishedPayload{
		JobID:      job.ID,
		Status:     api.JobStatus(job.Status),
		ExitCode:   exit,
		FinishedAt: fin,
		Stats:      job.Stats,
		Error:      errMsg,
	})
}

// userByID fetches the full store.User the UI session represents.
// Returns the user, ok-flag, error. Used by handlers that need the
// store-side row (e.g. for audit_log.user_id) rather than just the
// projected ui.User.
func (s *Server) userByID(r *stdhttp.Request, id string) (*store.User, bool, error) {
	u, err := s.deps.Store.GetUserByID(r.Context(), id)
	if err != nil {
		if errors.Is(err, store.ErrNotFound) {
			return nil, false, nil
		}
		return nil, false, err
	}
	return u, true, nil
}

// handleUILoginGet renders the login form. If the user is already
// signed in we redirect them home — login is for the unauthenticated.
func (s *Server) handleUILoginGet(w stdhttp.ResponseWriter, r *stdhttp.Request) {
	if u, _ := s.sessionUser(r); u != nil {
		stdhttp.Redirect(w, r, "/", stdhttp.StatusSeeOther)
		return
	}
	view := ui.ViewData{Version: s.version()}
	if err := s.deps.UI.Render(w, "login", view); err != nil {
		slog.Error("ui: render login", "err", err)
		stdhttp.Error(w, "internal", stdhttp.StatusInternalServerError)
	}
}

// handleUILoginPost consumes the form, validates, mints a session,
// and either redirects to / on success or re-renders the form with
// an error banner on failure.
func (s *Server) handleUILoginPost(w stdhttp.ResponseWriter, r *stdhttp.Request) {
	if err := r.ParseForm(); err != nil {
		stdhttp.Error(w, "bad request", stdhttp.StatusBadRequest)
		return
	}
	username := r.PostForm.Get("username")
	password := r.PostForm.Get("password")

	if _, err := s.authenticateAndSession(w, r, username, password); err != nil {
		// Re-render the form. Single generic message — see
		// authenticateAndSession's note on not leaking user existence.
		view := ui.ViewData{
			Version:  s.version(),
			Username: username,
			Error:    "Invalid username or password.",
		}
		w.WriteHeader(stdhttp.StatusUnauthorized)
		if err := s.deps.UI.Render(w, "login", view); err != nil {
			slog.Error("ui: render login (post-fail)", "err", err)
		}
		return
	}
	stdhttp.Redirect(w, r, "/", stdhttp.StatusSeeOther)
}

// handleUILogoutPost is the form-submit twin of /api/auth/logout. It
// drops the session cookie and redirects to /login.
func (s *Server) handleUILogoutPost(w stdhttp.ResponseWriter, r *stdhttp.Request) {
	if c, err := r.Cookie(sessionCookieName); err == nil {
		_ = s.deps.Store.DeleteSession(r.Context(), auth.HashToken(c.Value))
	}
	stdhttp.SetCookie(w, &stdhttp.Cookie{
		Name:     sessionCookieName,
		Value:    "",
		Path:     "/",
		MaxAge:   -1,
		HttpOnly: true,
		Secure:   s.deps.Cfg.CookieSecure,
		SameSite: stdhttp.SameSiteLaxMode,
	})
	stdhttp.Redirect(w, r, "/login", stdhttp.StatusSeeOther)
}