ZDDC/zddc/cmd/zddc-server/main.go

package main

import (
	"context"
	"errors"
	"fmt"
	"log/slog"
	"net/http"
	"os"
	"os/signal"
	"path/filepath"
	"sort"
	"strings"
	"syscall"
	"time"

	"codeberg.org/VARASYS/ZDDC/zddc/internal/apps"
	"codeberg.org/VARASYS/ZDDC/zddc/internal/archive"
	"codeberg.org/VARASYS/ZDDC/zddc/internal/auth"
	"codeberg.org/VARASYS/ZDDC/zddc/internal/cache"
	"codeberg.org/VARASYS/ZDDC/zddc/internal/config"
	"codeberg.org/VARASYS/ZDDC/zddc/internal/convert"
	appfs "codeberg.org/VARASYS/ZDDC/zddc/internal/fs"
	"codeberg.org/VARASYS/ZDDC/zddc/internal/handler"
	"codeberg.org/VARASYS/ZDDC/zddc/internal/policy"
	"codeberg.org/VARASYS/ZDDC/zddc/internal/tlsutil"
	"codeberg.org/VARASYS/ZDDC/zddc/internal/zddc"

	"github.com/klauspost/compress/gzhttp"
	"gopkg.in/natefinch/lumberjack.v2"
)

// version is the binary's own version, injected at build time via
// `-ldflags="-X main.version=..."`. Defaults to "dev" for unreleased
// builds; release pipelines pass the result of `git describe --tags`.
var version = "dev"

func main() {
	// --print-rego: dump a bundled reference Rego policy and exit.
	// Cheap escape hatch for operators standing up an external OPA who want
	// a parity-tested baseline as a starting point for customization.
	//
	//   --print-rego               → standard cascade (commercial default)
	//   --print-rego=standard      → same
	//   --print-rego=federal       → parent-deny-is-absolute (NIST AC-6)
	for _, a := range os.Args[1:] {
		switch a {
		case "--print-rego", "--print-rego=standard":
			fmt.Print(policy.ReferenceRego)
			return
		case "--print-rego=federal":
			fmt.Print(policy.FederalRego)
			return
		case "show-defaults", "--show-defaults":
			// Dump the embedded baseline .zddc to stdout. Pipe into a
			// real file (e.g. $ZDDC_ROOT/.zddc) to start from the
			// shipped defaults and edit; the on-disk copy then
			// participates in the cascade alongside the embedded
			// layer (both contribute; child wins). To ignore the
			// embedded layer entirely after exporting, set
			// `inherit: false` at the top of the exported file.
			_, _ = os.Stdout.Write(zddc.EmbeddedDefaultsBytes())
			return
		}
	}

	cfg, err := config.Load(os.Args[1:])
	if errors.Is(err, config.ErrHelpRequested) {
		config.Usage(os.Stderr)
		os.Exit(0)
	}
	if errors.Is(err, config.ErrVersionRequested) {
		printVersions(os.Stdout)
		os.Exit(0)
	}
	if err != nil {
		fmt.Fprintf(os.Stderr, "configuration error: %v\n\nRun with --help for usage.\n", err)
		os.Exit(1)
	}

	logRing := setupLogger(cfg.LogLevel)

	embedded := apps.EmbeddedVersions()
	slog.Info("zddc-server starting",
		"version", version,
		"root", cfg.Root,
		"addr", cfg.Addr,
		"embedded_apps", embeddedVersionsForLog(embedded))

	// Probe the container runtime for the MD→{docx,html,pdf} endpoint.
	// Non-fatal: if the host has no podman/docker (or the remote
	// socket is unreachable in sidecar mode), conversion requests
	// return 503 and everything else keeps working. The probe installs
	// the package-level Runner when an engine is found; the configured
	// image refs are pulled lazily on first conversion via
	// `--pull=missing` so there's no manual setup beyond installing
	// podman or docker.
	//
	// SetRemoteURL + SetScratchDir must run BEFORE Probe so the probe
	// can hit the sidecar socket when one is configured.
	convert.SetImages(cfg.ConvertPandocImage, cfg.ConvertChromiumImage)
	convert.SetRemoteURL(cfg.ConvertPodmanSocket)
	convert.SetScratchDir(cfg.ConvertScratchDir)
	probeCtx, probeCancel := context.WithTimeout(context.Background(), 5*time.Second)
	convert.Probe(probeCtx, cfg.ConvertEngine)
	probeCancel()
	convert.ConfigureLimits(cfg.ConvertMemMiB, cfg.ConvertCPUs, cfg.ConvertPIDs, cfg.ConvertTimeout)

	// Client mode short-circuit: when cfg.Upstream is set, this binary
	// runs as a downstream proxy/cache/mirror rather than a master.
	// The master-side machinery below (archive index, watcher, apps
	// server, policy decider, ACL middleware, token store) is all
	// skipped — every request flows through the cache layer, which
	// forwards to upstream and (in cache/mirror modes) persists the
	// response under cfg.Root.
	if cfg.Upstream != "" {
		runClient(cfg)
		return
	}

	// Build archive index
	slog.Info("building archive index...")
	start := time.Now()
	idx, err := archive.BuildIndex(cfg.Root)
	if err != nil {
		slog.Error("failed to build archive index", "err", err)
		os.Exit(1)
	}
	slog.Info("archive index built", "duration", time.Since(start))

	// Apps fetch+cache subsystem.
	appsServer, err := setupApps(cfg)
	if err != nil {
		slog.Error("failed to set up apps subsystem", "err", err)
		os.Exit(1)
	}

	// TLS config
	tlsCfg, useTLS, err := tlsutil.TLSConfig(cfg)
	if err != nil {
		slog.Error("failed to configure TLS", "err", err)
		os.Exit(1)
	}

	// Context for graceful shutdown
	ctx, cancel := signal.NotifyContext(context.Background(), syscall.SIGTERM, syscall.SIGINT)
	defer cancel()

	// Start file-system watcher (best-effort live updates; misses cross-client
	// writes on SMB/CIFS mounts since inotify only sees local-kernel events).
	watcher, err := archive.NewWatcher(cfg.Root, idx)
	if err != nil {
		slog.Warn("failed to start filesystem watcher (index will not auto-update)", "err", err)
	} else {
		go func() {
			if err := watcher.Start(ctx); err != nil && ctx.Err() == nil {
				slog.Error("watcher error", "err", err)
			}
		}()
	}

	// Periodic full re-scan. Required when the served root is an SMB/CIFS
	// share (Azure Files, etc.) — fsnotify sees only events the local kernel
	// generates, so writes from other clients to the share are invisible to
	// the watcher above. A periodic full walk closes that gap.
	if cfg.ArchiveRescanInterval > 0 {
		go runPeriodicRescan(ctx, cfg.Root, idx, cfg.ArchiveRescanInterval)
	} else {
		slog.Info("archive periodic rescan disabled (interval=0)")
	}


	// HTTP handler
	mux := http.NewServeMux()
	// Middleware chain (outermost → innermost):
	//   ACLMiddleware     — extract email from cfg.EmailHeader, store in
	//                       request context. Outermost so the email is
	//                       available to AccessLogMiddleware (Go's context
	//                       propagates DOWN the chain via r.WithContext, not
	//                       UP — so AccessLog can't read a context value set
	//                       by an inner middleware after next.ServeHTTP
	//                       returns).
	//   AccessLogMiddleware — structured per-request log; reads email from
	//                       the context the outer ACL middleware set.
	//   CORSMiddleware    — Origin / preflight handling.
	//   dispatch          — the actual request handler.
	auditLogger := setupAccessAuditLog(cfg.AccessLog)

	// Construct the policy decider once at startup. ZDDC_OPA_URL=internal
	// (default) routes decisions through the in-process Go evaluator;
	// http(s):// or unix:// values send each decision to an external
	// OPA-compatible server (federal customers, custom Rego policies).
	deciderCfg := policy.Config{
		URL:         cfg.OPAURL,
		FailOpen:    cfg.OPAFailOpen,
		CacheTTL:    cfg.OPACacheTTL,
		CascadeMode: cfg.CascadeMode,
	}
	// Translate "0" (operator opt-out) to "disable cache" (negative TTL is
	// the policy package's sentinel for "skip the wrapper").
	if deciderCfg.CacheTTL == 0 {
		deciderCfg.CacheTTL = -1
	}
	decider, err := policy.New(deciderCfg)
	if err != nil {
		slog.Error("invalid OPA URL", "url", cfg.OPAURL, "err", err)
		os.Exit(1)
	}
	// --no-auth swaps the configured decider for one that allows
	// everything. Logged at warn level so an operator who set this
	// inadvertently sees it on every restart.
	if cfg.NoAuth {
		decider = policy.AllowAllDecider{}
		slog.Warn("--no-auth enabled: ACL enforcement is disabled. Every request is permitted regardless of .zddc rules.")
	}
	slog.Info("policy decider ready",
		"mode", policyModeLabel(cfg.OPAURL),
		"url", cfg.OPAURL,
		"cache_ttl", cfg.OPACacheTTL,
		"cascade_mode", cfg.CascadeMode,
		"no_auth", cfg.NoAuth)

	// Token store: bearer-token issuance and validation.
	// Persists under <ZDDC_ROOT>/.zddc.d/tokens/ — already excluded
	// from public listings (fs.ListDirectory dot-prefix filter) and
	// direct serving (dispatch's reserved-prefix guard). Failures here
	// are non-fatal: token-based auth is opt-in per request, and
	// header-based auth keeps working without it.
	tokens, err := auth.NewStore(cfg.Root)
	if err != nil {
		slog.Warn("could not initialise token store; bearer-token auth disabled", "err", err)
		tokens = nil
	}

	// Innermost handler: dispatch.
	var inner http.Handler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		dispatch(cfg, idx, logRing, appsServer, tokens, w, r)
	})
	inner = handler.CORSMiddleware(cfg, inner)
	// HSTS only when zddc-server itself is the TLS-terminating endpoint.
	// Behind an upstream proxy terminating TLS (cfg.TLSMode=="none"), the
	// proxy is responsible for HSTS — adding it here would conflict.
	if useTLS {
		inner = handler.HSTSMiddleware(inner)
	}
	inner = handler.AccessLogMiddleware(auditLogger, inner)
	inner = handler.ACLMiddleware(cfg, decider, tokens, inner)
	mux.Handle("/", inner)

	gzWrapper, err := newGzipWrapper()
	if err != nil {
		slog.Error("gzhttp wrapper init", "err", err)
		os.Exit(1)
	}

	srv := &http.Server{
		Addr:      cfg.Addr,
		Handler:   gzWrapper(mux),
		TLSConfig: tlsCfg,
		// Conservative timeouts. ReadHeaderTimeout caps how long a slow
		// client can hold the connection before sending request headers
		// (the slowloris vector). Read/Write timeouts cap full-request
		// processing — directory listings + tool HTML serving complete
		// in milliseconds even with gzip, so 60s is generous. IdleTimeout
		// is the keep-alive ceiling between requests on the same conn.
		ReadHeaderTimeout: 10 * time.Second,
		ReadTimeout:       60 * time.Second,
		WriteTimeout:      60 * time.Second,
		IdleTimeout:       120 * time.Second,
	}

	// Serve in goroutine
	if useTLS {
		go func() {
			slog.Info("listening", "addr", cfg.Addr, "tls", true)
			if err := srv.ListenAndServeTLS("", ""); err != nil && err != http.ErrServerClosed {
				slog.Error("server error", "err", err)
				cancel()
			}
		}()
	} else {
		go func() {
			slog.Info("listening", "addr", cfg.Addr, "tls", false)
			if err := srv.ListenAndServe(); err != nil && err != http.ErrServerClosed {
				slog.Error("server error", "err", err)
				cancel()
			}
		}()
	}

	<-ctx.Done()
	slog.Info("shutting down...")

	shutdownCtx, shutdownCancel := context.WithTimeout(context.Background(), 30*time.Second)
	defer shutdownCancel()
	if err := srv.Shutdown(shutdownCtx); err != nil {
		slog.Error("shutdown error", "err", err)
	}
	slog.Info("stopped")
}

// runClient is the entry point when cfg.Upstream is set — a separate
// lifecycle from the master-side main(), with no archive index, no
// apps server, no watcher, no policy decider, no ACL middleware, no
// token store. The cache layer (zddc/internal/cache) is the entire
// request handler; AccessLog + HSTS + gzip wrap it the same way they
// wrap dispatch in master mode.
func runClient(cfg config.Config) {
	cacheLayer, err := cache.New(cfg)
	if err != nil {
		slog.Error("client mode init failed", "err", err)
		os.Exit(1)
	}
	slog.Info("client mode active",
		"upstream", cacheLayer.Upstream(),
		"mode", cacheLayer.Mode(),
		"no_auth", cfg.NoAuth,
		"skip_tls_verify", cfg.SkipTLSVerify)
	if cfg.NoAuth {
		slog.Warn("--no-auth enabled: incoming requests are not ACL-checked locally; trusting upstream's filtering.")
	}

	// Mirror walker: only constructed when --mode=mirror with at least
	// one subtree (config validation ensures a default of "/" applies
	// when the operator opted into mirror without specifying). Hooks
	// itself into cacheLayer.onAccess; no further wiring needed here.
	if cfg.Mode == "mirror" && len(cfg.MirrorSubtree) > 0 {
		sched, err := cache.NewMirrorScheduler(cacheLayer, cfg.MirrorSubtree, cfg.MirrorMinInterval, 0)
		if err != nil {
			slog.Error("mirror scheduler init failed", "err", err)
			os.Exit(1)
		}
		if sched != nil {
			slog.Info("mirror walker armed",
				"subtrees", sched.Subtrees(),
				"min_interval", sched.MinInterval())
		}
	}

	// Outbox: persist + replay offline writes. Only enabled in cache
	// or mirror modes (proxy mode doesn't persist anything by design).
	// A failure here is non-fatal: writes still flow live, but
	// transport errors return 503 instead of being queued.
	ctx, cancel := signal.NotifyContext(context.Background(), syscall.SIGTERM, syscall.SIGINT)
	defer cancel()

	if cfg.Mode != "proxy" {
		outbox, err := cache.NewOutbox(cacheLayer)
		if err != nil {
			slog.Warn("outbox init failed; offline writes will return 503", "err", err)
		} else {
			cacheLayer.SetOutbox(outbox)
			pending, _ := outbox.Pending()
			slog.Info("outbox ready", "dir", outbox.Dir(), "pending_at_startup", len(pending))
			go outbox.RunReplayLoop(ctx)
		}
	}

	tlsCfg, useTLS, err := tlsutil.TLSConfig(cfg)
	if err != nil {
		slog.Error("failed to configure TLS", "err", err)
		os.Exit(1)
	}

	auditLogger := setupAccessAuditLog(cfg.AccessLog)

	var inner http.Handler = cacheLayer
	inner = handler.CORSMiddleware(cfg, inner)
	if useTLS {
		inner = handler.HSTSMiddleware(inner)
	}
	inner = handler.AccessLogMiddleware(auditLogger, inner)

	mux := http.NewServeMux()
	mux.Handle("/", inner)

	gzWrapper, err := newGzipWrapper()
	if err != nil {
		slog.Error("gzhttp wrapper init", "err", err)
		os.Exit(1)
	}
	srv := &http.Server{
		Addr:              cfg.Addr,
		Handler:           gzWrapper(mux),
		TLSConfig:         tlsCfg,
		ReadHeaderTimeout: 10 * time.Second,
		ReadTimeout:       60 * time.Second,
		WriteTimeout:      60 * time.Second,
		IdleTimeout:       120 * time.Second,
	}

	if useTLS {
		go func() {
			slog.Info("listening", "addr", cfg.Addr, "tls", true, "client_mode", true)
			if err := srv.ListenAndServeTLS("", ""); err != nil && err != http.ErrServerClosed {
				slog.Error("server error", "err", err)
				cancel()
			}
		}()
	} else {
		go func() {
			slog.Info("listening", "addr", cfg.Addr, "tls", false, "client_mode", true)
			if err := srv.ListenAndServe(); err != nil && err != http.ErrServerClosed {
				slog.Error("server error", "err", err)
				cancel()
			}
		}()
	}

	<-ctx.Done()
	slog.Info("shutting down...")
	shutdownCtx, shutdownCancel := context.WithTimeout(context.Background(), 30*time.Second)
	defer shutdownCancel()
	if err := srv.Shutdown(shutdownCtx); err != nil {
		slog.Error("shutdown error", "err", err)
	}
	slog.Info("stopped")
}

// setupAccessAuditLog constructs a slog.Logger writing JSON lines to a
// size-rotated file at the operator-configured path. Returns nil if no
// path is configured (operator opted out via --access-log=) —
// AccessLogMiddleware then logs only to stderr.
//
// Auto-creates the parent directory (mode 0750) if missing, so the
// default path of <ZDDC_ROOT>/.zddc.d/logs/access-<host>.log "just
// works" on a fresh deployment without operator setup.
//
// Every record is tagged with `host` (os.Hostname). When multiple
// zddc-server replicas serve the same dataset (and write to the same
// .zddc.d/logs/ directory via per-host filenames), the host field also
// makes downstream-aggregated streams disambiguable.
//
// Rotation: lumberjack — 100 MB per file, 10 backups, 90-day max age,
// gzip compression on rotated files.
//
// File-permission posture: lumberjack creates new logs with mode 0600
// (running user only). For multi-user audit access, the operator should
// use group-readable parent directory permissions and either chmod the
// log out-of-band or run a forwarder that has its own read access.
// policyModeLabel collapses cfg.OPAURL to a one-word mode label for the
// startup log so operators can grep for the active decider quickly.
func policyModeLabel(opaURL string) string {
	switch {
	case opaURL == "" || strings.EqualFold(opaURL, "internal"):
		return "internal"
	case strings.HasPrefix(opaURL, "unix://"):
		return "external-unix"
	case strings.HasPrefix(opaURL, "https://"):
		return "external-https"
	case strings.HasPrefix(opaURL, "http://"):
		return "external-http"
	default:
		return "unknown"
	}
}

func setupAccessAuditLog(path string) *slog.Logger {
	if path == "" {
		return nil
	}
	if err := os.MkdirAll(filepath.Dir(path), 0o750); err != nil {
		slog.Error("could not create access-log directory; falling back to stderr-only",
			"dir", filepath.Dir(path), "err", err)
		return nil
	}
	rotator := &lumberjack.Logger{
		Filename:   path,
		MaxSize:    100, // megabytes per file before rotation
		MaxBackups: 10,
		MaxAge:     90, // days
		Compress:   true,
	}
	host, _ := os.Hostname()
	if host == "" {
		host = "unknown"
	}
	// JSON handler — line-delimited JSON is the format every standard
	// log shipper (Vector, Loki promtail, fluentbit, journalbeat) parses
	// natively, and stays grep-friendly for ad-hoc inspection.
	h := slog.NewJSONHandler(rotator, &slog.HandlerOptions{Level: slog.LevelInfo})
	slog.Info("access log file enabled",
		"path", path, "host", host,
		"max_size_mb", 100, "max_backups", 10, "max_age_days", 90)
	return slog.New(h).With("host", host)
}

// newGzipWrapper builds the gzip middleware applied to the entire mux.
// MinSize(1024) skips compressing tiny responses where the framing
// overhead exceeds the savings (304 Not Modified, error pages, small
// JSON listings under ~1 KB). The wrapper honors Accept-Encoding (passes
// through unchanged when the client doesn't advertise gzip), appends
// Vary: Accept-Encoding automatically, and passes through 304s untouched.
// Yields ~75% size reduction on the larger embedded HTML responses
// (browse: ~2 MB → a few hundred KB on the wire).
//
// Extracted so tests can construct an equivalent wrapper without going
// through the full main() server boot.
func newGzipWrapper() (func(http.Handler) http.HandlerFunc, error) {
	return gzhttp.NewWrapper(gzhttp.MinSize(1024))
}

// setupApps creates the cache + fetcher + server. No seeding, no refresh,
// no admin UI — the server fetches once on first request, caches forever
// in <ZDDC_ROOT>/_app/, and falls back to the embedded HTML on any failure.
func setupApps(cfg config.Config) (*apps.Server, error) {
	cache, err := apps.NewCache(filepath.Join(cfg.Root, apps.CacheDirName))
	if err != nil {
		return nil, fmt.Errorf("create cache: %w", err)
	}
	fetcher := apps.NewFetcher(cache, slog.Default())

	// Apps signing pubkey. Resolution order, highest priority first:
	//   1. --apps-pubkey / ZDDC_APPS_PUBKEY (path to PEM file)
	//   2. apps_pubkey: inline PEM in the root <ZDDC_ROOT>/.zddc file
	//      (root-only — same trust-anchor treatment as admins:)
	//   3. nothing → URL-fetched apps refuse-by-default; only embedded
	//      + local-path apps work
	//
	// Same posture as TLS certificates: zddc-server bakes nothing in.
	// Operators using zddc.varasys.io's canonical channels download
	// pubkey.pem from there and either configure the path via env/flag
	// or paste the PEM contents inline into root .zddc.
	switch {
	case cfg.AppsPubKey != "":
		pub, err := apps.LoadPubKey(cfg.AppsPubKey)
		if err != nil {
			return nil, fmt.Errorf("apps-pubkey: %w", err)
		}
		fetcher.VerifyKey = pub
		slog.Info("apps signing pubkey loaded", "source", "env/flag", "path", cfg.AppsPubKey)
	default:
		// Fall back to apps_pubkey: in root .zddc.
		rootZddc, err := zddc.ParseFile(filepath.Join(cfg.Root, ".zddc"))
		if err == nil && rootZddc.AppsPubKey != "" {
			pub, err := apps.ParsePubKeyPEM([]byte(rootZddc.AppsPubKey))
			if err != nil {
				return nil, fmt.Errorf("root .zddc apps_pubkey: %w", err)
			}
			fetcher.VerifyKey = pub
			slog.Info("apps signing pubkey loaded", "source", "root .zddc apps_pubkey")
		} else {
			slog.Warn("apps-pubkey not configured; URL-fetched apps will be refused (only embedded + local-path apps will work). " +
				"Set --apps-pubkey, ZDDC_APPS_PUBKEY, or apps_pubkey: in the root .zddc file to a PEM Ed25519 public key you trust.")
		}
	}

	return apps.NewServer(cfg.Root, cache, fetcher, version), nil
}

// printVersions writes the binary version + the build label of every app
// embedded into the binary. Called by --version and reused for the
// startup log line.
func printVersions(w *os.File) {
	fmt.Fprintf(w, "zddc-server %s\n\n", version)
	embedded := apps.EmbeddedVersions()
	if len(embedded) == 0 {
		fmt.Fprintln(w, "Embedded tools: (none — run `sh build.sh` to populate)")
		return
	}
	fmt.Fprintln(w, "Embedded tools:")
	keys := make([]string, 0, len(embedded))
	for k := range embedded {
		keys = append(keys, k)
	}
	sort.Strings(keys)
	for _, k := range keys {
		fmt.Fprintf(w, "  %-12s %s\n", k, embedded[k])
	}
}

// embeddedVersionsForLog formats the embedded-versions map as a single
// short string suitable for the startup `log/slog` line. Sorted by app
// name for stable output.
func embeddedVersionsForLog(embedded map[string]string) string {
	if len(embedded) == 0 {
		return "(none)"
	}
	keys := make([]string, 0, len(embedded))
	for k := range embedded {
		keys = append(keys, k)
	}
	sort.Strings(keys)
	parts := make([]string, 0, len(keys))
	for _, k := range keys {
		// Strip any " · timestamp · sha" suffix so the log line stays compact;
		// operators who want full detail run `zddc-server --version`.
		v := embedded[k]
		if i := strings.Index(v, " "); i > 0 {
			v = v[:i]
		}
		parts = append(parts, k+"="+v)
	}
	return strings.Join(parts, " ")
}

// serveSpecializedNoSlash handles a GET/HEAD request to a directory
// URL without a trailing slash by serving the directory's cascade-
// declared default_tool — the "specialized app" half of the slash/
// no-slash routing convention. (The slash half is DirTool, resolved
// in handler.ServeDirectory; it defaults to "browse".) Works for both
// real on-disk directories and purely-virtual ones (default_tool may
// come from an ancestor's paths: tree).
//
// Returns true once it has written a response. Returns false when
// there is nothing specialized to serve — no default_tool, or
// default_tool=tables with no matching table spec, or the tool isn't
// available at this path — so the caller falls through to its own
// fallback (landing at a project root, then a 302 to the slash form
// where DirTool/browse renders the listing).
//
// ACL is enforced here against dirAbs's effective policy, so every
// default_tool route is gated identically regardless of which call
// site reached it. dirAbs is the directory's filesystem path (it need
// not exist on disk); urlPath is the request URL path; email is the
// authenticated user (may be empty).
func serveSpecializedNoSlash(cfg config.Config, appsSrv *apps.Server, w http.ResponseWriter, r *http.Request, dirAbs, urlPath, email string) bool {
	app := apps.DefaultAppAt(cfg.Root, dirAbs)
	if app == "" {
		return false
	}
	chain, _ := zddc.EffectivePolicy(cfg.Root, dirAbs)
	if allowed, _ := policy.AllowFromChain(r.Context(), handler.DeciderFromContext(r), chain, email, urlPath); !allowed {
		http.Error(w, "Forbidden", http.StatusForbidden)
		return true
	}
	if app == "tables" {
		// tables isn't an apps-subsystem app — it's the table view,
		// served by handler.ServeTable from a synthesized
		// <dir>/table.html request (which also resolves the embedded
		// default-MDL spec for archive/<party>/mdl). No spec → caller
		// falls through.
		if tr := handler.RecognizeTableRequest(cfg.Root, http.MethodGet, urlPath+"/table.html"); tr != nil {
			handler.ServeTable(cfg, tr, w, r)
			return true
		}
		return false
	}
	if appsSrv != nil && apps.AppAvailableAt(cfg.Root, dirAbs, app) {
		appsSrv.Serve(w, r, app, chain, dirAbs)
		return true
	}
	return false
}

// splitZipPath detects a "<…>.zip/<member>" URL: a path where some
// ancestor segment resolves to a regular .zip file on disk and there's
// a tail segment after it (or a trailing slash). On a match it returns
// the zip's absolute filesystem path and the slash-separated member
// path inside the zip ("" when the URL is "<…>.zip/" with nothing
// after). ok is false for everything else — including "<…>.zip" with
// no trailing slash (that's a plain file download, handled downstream).
//
// Segments are stat'd one at a time against cfg.Root; case-folding has
// already been applied to on-disk segments by appfs.ResolveCanonical
// upstream, so the .zip segment matches by exact name here. The
// per-segment os.Stat walk is gated by a cheap ".zip/" substring check
// at the call site, so it never runs for ordinary requests.
func splitZipPath(fsRoot, urlPath string) (zipAbs, member string, ok bool) {
	trimmed := strings.Trim(urlPath, "/")
	if trimmed == "" {
		return "", "", false
	}
	segs := strings.Split(trimmed, "/")
	cur := fsRoot
	for i, seg := range segs {
		cur = filepath.Join(cur, seg)
		if cur != fsRoot && !strings.HasPrefix(cur, fsRoot+string(filepath.Separator)) {
			return "", "", false
		}
		info, err := os.Stat(cur)
		if err != nil {
			return "", "", false // a segment doesn't exist on disk — not a zip path
		}
		if info.IsDir() {
			continue
		}
		// cur is a non-directory. Only a regular .zip file with a tail
		// (or trailing slash) is "browse into the zip"; anything else
		// falls through to the normal file path.
		if !info.Mode().IsRegular() || !strings.EqualFold(filepath.Ext(seg), ".zip") {
			return "", "", false
		}
		if i < len(segs)-1 {
			return cur, strings.Join(segs[i+1:], "/"), true
		}
		// Last segment is the .zip itself: only a trailing slash means
		// "browse into it" (member == root); a bare "<…>.zip" is a file.
		if strings.HasSuffix(urlPath, "/") {
			return cur, "", true
		}
		return "", "", false
	}
	return "", "", false
}

// dispatch routes a request to the appropriate handler.
func dispatch(cfg config.Config, idx *archive.Index, ring *handler.LogRing, appsSrv *apps.Server, tokens *auth.Store, w http.ResponseWriter, r *http.Request) {
	// URL paths are case-insensitive: resolve each segment against the
	// on-disk casing under cfg.Root, preferring the all-lowercase
	// variant when multiple case variants exist (lowercase is the
	// project-wide canonical case for folders). The walk stops at the
	// first segment that doesn't exist on disk so virtual prefixes
	// (.profile, .archive, .tokens) and 404 paths flow through with
	// their tail preserved verbatim. Downstream handlers see the
	// canonical r.URL.Path; the access log captures the as-typed path
	// before this rewrite.
	if absPath, canonical, ok := appfs.ResolveCanonical(cfg.Root, r.URL.Path); ok {
		_ = absPath
		// Restore trailing slash so directory routing (which redirects
		// no-trailing-slash requests) keeps its existing semantics.
		if strings.HasSuffix(r.URL.Path, "/") && !strings.HasSuffix(canonical, "/") && canonical != "/" {
			canonical += "/"
		}
		if canonical != r.URL.Path {
			r.URL.Path = canonical
			r.URL.RawPath = ""
		}
	}

	urlPath := r.URL.Path
	email := handler.EmailFromContext(r)

	// Profile routes — the page itself is reachable to anyone (anonymous
	// included); admin-only sub-resources (whoami / config / logs /
	// projects / .zddc editor) keep their existing per-resource 404
	// existence-leakage gates inside ServeProfile.
	if urlPath == handler.ProfilePathPrefix || strings.HasPrefix(urlPath, handler.ProfilePathPrefix+"/") {
		handler.ServeProfile(cfg, ring, idx, w, r)
		return
	}

	// Token self-service: HTML page at /.tokens, JSON API at
	// /.api/tokens. Both routes require an authenticated user (the
	// existing email middleware injects the email from upstream auth).
	// Both routes refuse to serve when no token store is available
	// (e.g. NewStore failed at startup) — handled inside the handlers.
	if urlPath == handler.TokensPathPrefix || urlPath == handler.TokensPathPrefix+"/" {
		handler.ServeTokensPage(cfg, tokens, w, r)
		return
	}
	if urlPath == handler.TokensAPIPathPrefix || strings.HasPrefix(urlPath, handler.TokensAPIPathPrefix+"/") {
		handler.ServeTokensAPI(cfg, tokens, w, r)
		return
	}

	// Auth check endpoints — machine-only forward_auth targets used by
	// upstream proxies (e.g. the dev-shell pod's Caddy in front of
	// code-server) to gate routes on root-admin status. Handled before
	// the reserved-prefix guard below so the .auth namespace passes
	// through without being 404'd by the dot-prefix rule.
	if urlPath == handler.AuthPathPrefix+"/admin" {
		handler.ServeAuthAdmin(cfg, w, r)
		return
	}

	// Project list API: GET / with Accept: application/json
	if urlPath == "/" {
		accept := r.Header.Get("Accept")
		if strings.Contains(accept, "application/json") {
			handler.ServeProjectList(cfg, w, r)
			return
		}
	}

	// Split path into segments
	segments := strings.Split(strings.Trim(urlPath, "/"), "/")

	// Per-directory .zddc editor: <dir>/.zddc.html is a virtual URL
	// served by the existing form-based editor (same handler that
	// powers /.profile/zddc/edit?path=<dir>). Routed BEFORE the
	// dot-prefix guard so the leaf segment isn't 404'd. The handler
	// itself gates on hasAnyAdminScope; non-admins see 404.
	if handler.IsZddcEditorRequest(urlPath) {
		handler.ServeZddcEditorAtPath(cfg, w, r)
		return
	}

	// Raw .zddc YAML view: <dir>/.zddc is reachable at every depth
	// and returns the on-disk file's bytes (Content-Type: application/yaml)
	// or — when no file exists — a synthetic placeholder body with a
	// cascade summary so the user can see what's effective here.
	// GET/HEAD only; writes go through the admin-gated .zddc.html
	// form. Also carved out of the dot-prefix guard.
	if handler.IsZddcFileRequest(urlPath) {
		handler.ServeZddcFile(cfg, w, r)
		return
	}

	// Reserve dot-prefixed path segments. The listing pipeline already hides
	// hidden entries (internal/fs/tree.go:90, projectshandler.go:40),
	// but direct URL access would still serve them. 404 here so hidden trees
	// like /srv/.devshell (the in-image dev-shell's persistent home dir on
	// the same Azure Files PVC as served data) cannot be fetched. The
	// recognized virtual prefixes (.profile handled above, cfg.IndexPath
	// handled below) are explicitly allowed through.
	//
	// Also reserve the apps cache directory (`_app`): the cached HTML files
	// there must be served via the apps resolver (with proper headers and
	// ACL), never raw at /_app/...html. The apps cache stays reserved
	// even with ?hidden=1 — its files must go through the resolver for
	// proper ETag/MIME/X-ZDDC-Source headers.
	//
	// ?hidden=1 on a GET/HEAD relaxes the dot-prefix guard for everything
	// EXCEPT _app. The ACL chain on the resolved path is still the gate;
	// anyone who couldn't list this hidden file via fs.ListDirectory
	// can't reach it via direct URL either. Write methods stay blocked
	// from hidden paths (the file API has its own segment check that
	// the ?hidden flag does NOT relax).
	hiddenOK := r.URL.Query().Has("hidden") &&
		(r.Method == http.MethodGet || r.Method == http.MethodHead)
	for _, seg := range segments {
		if seg == "" {
			continue
		}
		if seg == apps.CacheDirName {
			http.NotFound(w, r)
			return
		}
		if !strings.HasPrefix(seg, ".") && !strings.HasPrefix(seg, "_") {
			continue
		}
		if seg == cfg.IndexPath {
			continue
		}
		if hiddenOK {
			continue
		}
		http.NotFound(w, r)
		return
	}

	// Check for .archive segment in the path. .archive is project-scoped
	// and addressed at exactly one depth — /<project>/.archive/... — even
	// though offline-built HTML files reference siblings via
	// "../.archive/<tracking>.html" from arbitrary depths. Any deeper form
	// (/<project>/<sub>/.../.archive/...) gets a 302 to the project-rooted
	// canonical so anchored links and bookmarks normalize to a single
	// stable URL per tracking number. The redirect target preserves the
	// path tail after .archive/ verbatim and the query string; browsers
	// preserve the fragment automatically across redirects.
	//
	// .archive is read-only: only GET/HEAD reach the handler. Anything
	// else (PUT/POST/DELETE) returns 405 here, before the file API would
	// otherwise see the request. This avoids the 302→GET silent-method-
	// downgrade trap and makes the contract explicit.
	for i, seg := range segments {
		if seg != cfg.IndexPath {
			continue
		}
		if r.Method != http.MethodGet && r.Method != http.MethodHead {
			w.Header().Set("Allow", "GET, HEAD")
			http.Error(w, "Method Not Allowed", http.StatusMethodNotAllowed)
			return
		}
		// segments[0] is the project; segments[i] is .archive. i==0
		// means /.archive/... at the very root, with no project to
		// scope by — 404 (a tracking-number reference must be project-
		// rooted; cross-project tracking-number collisions otherwise
		// silently pick a winner).
		if i == 0 {
			http.NotFound(w, r)
			return
		}
		project := segments[0]
		var filename string
		if i+1 < len(segments) {
			filename = strings.Join(segments[i+1:], "/")
		}
		// Canonicalize anything below /<project>/.archive/. Building
		// the target by hand (rather than re-encoding) keeps any
		// already-encoded characters in the original URL.RawPath
		// trailing segments intact for the browser to follow.
		if i > 1 {
			target := "/" + project + "/" + cfg.IndexPath + "/" + filename
			if r.URL.RawQuery != "" {
				target += "?" + r.URL.RawQuery
			}
			http.Redirect(w, r, target, http.StatusFound)
			return
		}
		handler.ServeArchive(cfg, idx, w, r, project, filename)
		return
	}

	// Tables-system intercept: *.table.html is a virtual URL that the
	// table handler renders inline, reading rows from a directory of
	// *.yaml files declared in the directory's .zddc tables: map.
	// Discovery is .zddc-declarative — no auto-mount on file presence —
	// so RecognizeTableRequest returns nil whenever there's no matching
	// declaration and the URL falls through to the static-file path
	// (or to the form intercept below for *.form.html / *.yaml.html).
	//
	// One exception: archive/<party>/mdl.table.html falls back to the
	// embedded default MDL spec when no operator declaration exists.
	// RecognizeTableRequest implements that fallback internally.
	if tableReq := handler.RecognizeTableRequest(cfg.Root, r.Method, urlPath); tableReq != nil {
		handler.ServeTable(cfg, tableReq, w, r)
		return
	}

	// Form-system intercept: *.form.html and *.yaml.html under a sibling form
	// folder are virtual URLs that the form handler renders inline, reading
	// the underlying *.form.yaml spec (and, for re-edit, the *.yaml data) from
	// disk. RecognizeFormRequest returns nil when the spec doesn't exist, so
	// non-form .html URLs fall through to the static-file path below.
	if formReq := handler.RecognizeFormRequest(cfg.Root, r.Method, urlPath); formReq != nil {
		handler.ServeForm(cfg, formReq, w, r)
		return
	}

	// Zip-as-directory intercept: a "<…>.zip/<member>" URL is a virtual
	// surface over a real .zip file on disk — GET "<…>.zip/" lists the
	// members, GET "<…>.zip/member.pdf" extracts and streams that one
	// member, so a client never has to download the whole archive. The
	// bare "<…>.zip" (no trailing slash) is NOT matched here and falls
	// through to the normal file path (a plain download). Like .archive,
	// a zip carries no .zddc of its own — ACL is the chain of the
	// directory CONTAINING the zip. Read-only: write methods are
	// rejected before ServeFileAPI could try to create a path under a
	// file. (The os.Stat walk in splitZipPath is gated by this cheap
	// substring check, so it doesn't run for ordinary requests.)
	if strings.Contains(strings.ToLower(urlPath), ".zip/") {
		if zipAbs, member, ok := splitZipPath(cfg.Root, urlPath); ok {
			if handler.IsWriteMethod(r.Method) {
				w.Header().Set("Allow", "GET, HEAD")
				http.Error(w, "Zip archives are read-only", http.StatusMethodNotAllowed)
				return
			}
			if r.Method != http.MethodGet && r.Method != http.MethodHead {
				w.Header().Set("Allow", "GET, HEAD")
				http.Error(w, "Method Not Allowed", http.StatusMethodNotAllowed)
				return
			}
			chain, err := zddc.EffectivePolicy(cfg.Root, filepath.Dir(zipAbs))
			if err != nil {
				slog.Warn("ACL policy error on zip parent", "path", filepath.Dir(zipAbs), "err", err)
			}
			if allowed, _ := policy.AllowFromChain(r.Context(), handler.DeciderFromContext(r), chain, email, urlPath); !allowed {
				http.Error(w, "Forbidden", http.StatusForbidden)
				return
			}
			handler.ServeZip(cfg, w, r, zipAbs, member)
			return
		}
	}

	// File API — authenticated CRUD over the served tree. Catches PUT,
	// DELETE, and POST on any non-reserved path. Read methods (GET/HEAD)
	// fall through to the static / apps / directory pipeline below.
	// Forms and .profile/.archive POSTs are already routed above this
	// point so they take precedence.
	if handler.IsWriteMethod(r.Method) {
		handler.ServeFileAPI(cfg, w, r)
		return
	}

	// Apps resolution for the root landing path: GET / or /index.html with
	// no real index.html on disk → serve via apps.Serve("landing"). The
	// other four apps are caught by the "stat fails → app HTML?" branch
	// below, which only triggers when no concrete file is at the URL path.
	//
	// The landing page is intentionally public (no ACL gate). It's a
	// project picker — the per-project ACL filtering done by
	// fs.ListDirectory still hides projects an anonymous (or unauthorized)
	// caller can't reach. See also handler.ServeDirectory's matching
	// root-path bypass.
	if appsSrv != nil && (urlPath == "/" || urlPath == "/index.html") {
		realIndex := filepath.Join(cfg.Root, "index.html")
		if _, err := os.Stat(realIndex); os.IsNotExist(err) {
			chain, _ := zddc.EffectivePolicy(cfg.Root, cfg.Root)
			if apps.AppAvailableAt(cfg.Root, cfg.Root, "landing") {
				appsSrv.Serve(w, r, "landing", chain, cfg.Root)
				return
			}
		}
	}

	// Resolve the physical path
	cleanPath := filepath.FromSlash(strings.TrimPrefix(urlPath, "/"))
	absPath := filepath.Join(cfg.Root, cleanPath)

	// Guard against path traversal
	if !strings.HasPrefix(absPath, cfg.Root+string(filepath.Separator)) && absPath != cfg.Root {
		http.Error(w, "Not Found", http.StatusNotFound)
		return
	}

	// Check filesystem
	info, err := os.Stat(absPath)
	if err != nil {
		if os.IsNotExist(err) {
			// Default MDL spec fallback: archive/<party>/mdl.table.yaml
			// and archive/<party>/mdl.form.yaml are served from embedded
			// bytes when no operator file exists on disk. The table app
			// fetches these client-side; the fallback lets a fresh
			// project work out of the box.
			if r.Method == http.MethodGet || r.Method == http.MethodHead {
				if bytes, ok := handler.IsDefaultMdlSpec(cfg.Root, urlPath); ok {
					chain, _ := zddc.EffectivePolicy(cfg.Root, filepath.Dir(absPath))
					if allowed, _ := policy.AllowFromChain(r.Context(), handler.DeciderFromContext(r), chain, email, urlPath); !allowed {
						http.Error(w, "Forbidden", http.StatusForbidden)
						return
					}
					w.Header().Set("Content-Type", "application/yaml; charset=utf-8")
					w.Header().Set("Cache-Control", "no-store")
					w.Header().Set("X-ZDDC-Source", "default-mdl-spec")
					if r.Method == http.MethodHead {
						return
					}
					_, _ = w.Write(bytes)
					return
				}
			}
			// File doesn't exist at this path. If the URL matches one of
			// the canonical app HTML names AND the request directory is
			// one where that app is available (working/staging/incoming
			// for classifier, staging for transmittal, anywhere for
			// archive + browse, root only for landing), resolve via the
			// apps subsystem.
			if appsSrv != nil {
				if app, requestDirRel := apps.MatchAppHTML(urlPath); app != "" {
					requestDir := filepath.Join(cfg.Root, filepath.FromSlash(requestDirRel))
					if apps.AppAvailableAt(cfg.Root, requestDir, app) {
						chain, _ := zddc.EffectivePolicy(cfg.Root, requestDir)
						if allowed, _ := policy.AllowFromChain(r.Context(), handler.DeciderFromContext(r), chain, email, urlPath); !allowed {
							http.Error(w, "Forbidden", http.StatusForbidden)
							return
						}
						appsSrv.Serve(w, r, app, chain, requestDir)
						return
					}
				}
			}
			// Reviewing aggregator. <project>/reviewing/[<tracking>/] is
			// a virtual view. The shape rule mirrors the other canonical
			// folders (slash → browse, no-slash → default tool):
			//   - JSON request, any depth → aggregator listing (handler.ServeReviewing)
			//   - HTML, no slash → browse (default tool, via DefaultAppAt;
			//                        browse hosts the markdown editor plugin)
			//   - HTML, with slash → browse.html (via ServeDirectory).
			//                        browse fetches JSON which routes back
			//                        through here to ServeReviewing.
			// Depth-3 no-slash (reviewing/<tracking>) 302s to the slash form.
			// Depth-2 no-slash (reviewing) falls through to the canonical-
			// folder block below where DefaultAppAt routes to browse.
			if r.Method == http.MethodGet || r.Method == http.MethodHead {
				if proj, tracking, sidePath, ok := handler.IsReviewingPath(urlPath); ok {
					if !strings.HasSuffix(urlPath, "/") {
						if tracking != "" {
							http.Redirect(w, r, urlPath+"/", http.StatusFound)
							return
						}
						// Depth-2 no-slash falls through to canonical-folder block.
					} else if strings.Contains(r.Header.Get("Accept"), "application/json") {
						chain, _ := zddc.EffectivePolicy(cfg.Root, filepath.Join(cfg.Root, proj))
						if allowed, _ := policy.AllowFromChain(r.Context(), handler.DeciderFromContext(r), chain, email, urlPath); !allowed {
							http.Error(w, "Forbidden", http.StatusForbidden)
							return
						}
						handler.ServeReviewing(cfg, w, r, proj, tracking, sidePath)
						return
					}
					// HTML trailing-slash falls through to canonical-folder
					// block → ServeDirectory → embedded browse.html.
				}
			}
			// Cascade-declared paths: the .zddc cascade (embedded
			// defaults + on-disk overrides) declares this URL even
			// if the on-disk directory doesn't exist yet. Land on a
			// usable view rather than 404, via the same slash/no-slash
			// routing convention used for real directories:
			//   - slash    → ServeDirectory (DirTool; browse by default)
			//   - no-slash → default_tool ("specialized app") if any,
			//                else a 302 to the slash form.
			//
			// Guard: only directory-shaped URLs qualify. The bare "*"
			// project glob matches *any* first-level segment — including
			// "foo.html", "foo.txt", etc. — so without the extension
			// check a non-existent top-level file would 302-to-slash
			// instead of 404. A trailing slash, or no file extension on
			// the last segment, means "asking for a directory".
			if (r.Method == http.MethodGet || r.Method == http.MethodHead) &&
				(strings.HasSuffix(urlPath, "/") || filepath.Ext(urlPath) == "") &&
				zddc.IsDeclaredPath(cfg.Root, absPath) {
				if r.URL.Query().Has("zip") {
					// Subtree download of a cascade-declared dir that
					// doesn't exist on disk yet → an empty zip.
					handler.ServeSubtreeZip(cfg, w, r, absPath)
					return
				}
				if strings.HasSuffix(urlPath, "/") {
					handler.ServeDirectory(cfg, appsSrv, w, r)
					return
				}
				if serveSpecializedNoSlash(cfg, appsSrv, w, r, absPath, urlPath, email) {
					return
				}
				http.Redirect(w, r, urlPath+"/", http.StatusFound)
				return
			}
			http.Error(w, "Not Found", http.StatusNotFound)
		} else {
			http.Error(w, "Internal Server Error", http.StatusInternalServerError)
		}
		return
	}

	if info.IsDir() {
		// ACL check — bypassed at the root path so the landing page (the
		// project picker) is reachable by anyone, including anonymous.
		// Per-project filtering happens inside ServeDirectory →
		// fs.ListDirectory, which hides directories the caller can't
		// reach. Subdirectory requests still hit this gate.
		isRoot := urlPath == "/"
		if !isRoot {
			chain, _ := zddc.EffectivePolicy(cfg.Root, absPath)
			if allowed, _ := policy.AllowFromChain(r.Context(), handler.DeciderFromContext(r), chain, email, urlPath); !allowed {
				http.Error(w, "Forbidden", http.StatusForbidden)
				return
			}
		}
		// Subtree download: GET /dir/?zip=1 streams an application/zip of
		// every readable file under this directory, ACL-filtered. Checked
		// before the slash/no-slash routing so it works on both /dir and
		// /dir/. Writes (PUT/DELETE/POST) never reach here — they're
		// intercepted by the file API earlier — so this is GET/HEAD only.
		if r.URL.Query().Has("zip") {
			handler.ServeSubtreeZip(cfg, w, r, absPath)
			return
		}
		// Slash/no-slash routing convention: trailing slash → the
		// directory view (handler.ServeDirectory → DirTool, which
		// resolves to browse by default; JSON requests always get the
		// raw listing regardless). No trailing slash → the directory's
		// default_tool ("specialized app") — browse under working/+
		// reviewing/ (hosts the markdown editor), transmittal under
		// staging/, archive under archive/, tables under
		// archive/<party>/mdl/ — if one is declared; otherwise
		// (after the project-root landing case below) a 302 to the
		// slash form.
		if !strings.HasSuffix(urlPath, "/") && (r.Method == http.MethodGet || r.Method == http.MethodHead) && !isRoot {
			if serveSpecializedNoSlash(cfg, appsSrv, w, r, absPath, urlPath, email) {
				return
			}
		}
		// Project root (depth-1 dir, no trailing slash) serves the
		// landing tool, which detects mode='project' from
		// location.pathname and renders the lifecycle-stage cards +
		// MDL section. Same single-file SPA as the deployment-root
		// project picker — one tool, two URL shapes. With trailing
		// slash, the project falls through to the regular browse
		// listing.
		if !strings.HasSuffix(urlPath, "/") &&
			(r.Method == http.MethodGet || r.Method == http.MethodHead) &&
			handler.IsProjectRootURL(urlPath) {
			if appsSrv != nil {
				chain, _ := zddc.EffectivePolicy(cfg.Root, absPath)
				appsSrv.Serve(w, r, "landing", chain, absPath)
				return
			}
		}
		if !strings.HasSuffix(urlPath, "/") {
			http.Redirect(w, r, urlPath+"/", http.StatusFound)
			return
		}
		handler.ServeDirectory(cfg, appsSrv, w, r)
		return
	}

	// Regular file: ACL on parent directory
	chain, _ := zddc.EffectivePolicy(cfg.Root, filepath.Dir(absPath))
	if allowed, _ := policy.AllowFromChain(r.Context(), handler.DeciderFromContext(r), chain, email, urlPath); !allowed {
		http.Error(w, "Forbidden", http.StatusForbidden)
		return
	}

	// MD→{docx,html,pdf} on-demand conversion. The endpoint reuses the
	// source file's read policy (already gated above), so no separate
	// ACL verb. Only .md sources are convertible; everything else falls
	// through to the regular file serve.
	if fmt := r.URL.Query().Get("convert"); fmt != "" &&
		strings.HasSuffix(strings.ToLower(absPath), ".md") {
		handler.ServeConverted(cfg, w, r, absPath, fmt, chain)
		return
	}

	handler.ServeFile(w, r, absPath)
}

// runPeriodicRescan calls idx.Rebuild on `interval` until ctx is cancelled.
// Each tick walks fsRoot from scratch and atomically replaces the live index;
// concurrent reads are safe via the index's RWMutex. Errors are logged but do
// not stop the loop — a transient walk failure shouldn't disable rescans.
func runPeriodicRescan(ctx context.Context, fsRoot string, idx *archive.Index, interval time.Duration) {
	ticker := time.NewTicker(interval)
	defer ticker.Stop()
	slog.Info("archive periodic rescan started", "interval", interval)
	for {
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
			dur, projects, tracking, err := idx.Rebuild(fsRoot)
			if err != nil {
				slog.Warn("archive rescan failed", "err", err, "duration", dur)
				continue
			}
			slog.Debug("archive rescan ok", "duration", dur, "projects", projects, "tracking", tracking)
		}
	}
}

// setupLogger installs a slog default that fans every record out to stderr
// (the existing TextHandler — user-visible logging is unchanged) AND to an
// in-memory ring buffer that backs the /.profile/logs endpoint. Returns
// the ring so handlers can read it.
func setupLogger(level string) *handler.LogRing {
	var l slog.Level
	switch strings.ToLower(level) {
	case "debug":
		l = slog.LevelDebug
	case "warn":
		l = slog.LevelWarn
	case "error":
		l = slog.LevelError
	default:
		l = slog.LevelInfo
	}
	ring := handler.NewLogRing(500)
	text := slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: l})
	rh := handler.NewRingHandler(ring, l)
	slog.SetDefault(slog.New(handler.NewMultiHandler(text, rh)))
	return ring
}