verdande/internal/httpapi/server.go

// Package httpapi wires verdande's HTTP surface: the REST API under /api/v1, the
// WebSocket endpoint, and the static PWA that the same binary serves.
package httpapi

import (
	"encoding/json"
	"errors"
	"io/fs"
	"log/slog"
	"net/http"
	"os"
	"path"
	"strings"
	"sync"
	"time"

	"github.com/go-chi/chi/v5"
	"github.com/go-chi/chi/v5/middleware"

	"github.com/kristianwind/verdande/internal/auth"
	"github.com/kristianwind/verdande/internal/config"
	"github.com/kristianwind/verdande/internal/mail"
	"github.com/kristianwind/verdande/internal/mcp"
	"github.com/kristianwind/verdande/internal/realtime"
	"github.com/kristianwind/verdande/internal/store"
	"github.com/kristianwind/verdande/internal/update"
)

// Version is stamped by main at build time, and is what the update check compares
// against. A package-level variable rather than a config field because it is a
// property of the binary, not of how it was configured.
var Version = "dev"

type Server struct {
	cfg     *config.Config
	db      *store.DB
	log     *slog.Logger
	web     fs.FS
	mail    *mail.Sender
	hub     *realtime.Hub
	mcp     *mcp.Server
	updates *update.Checker

	// syncing serialises reads of one mailbox against itself. Two runs at once —
	// somebody pressing "Fetch now" while the ten-minute sweep is in the middle of
	// the same mailbox — both start from the marker as it was, both fetch the same
	// messages, and both make tasks out of them. That is how forty copies of one
	// mail arrived in a single second.
	//
	// A map of mutexes rather than one lock: two people's mailboxes have nothing to
	// say to each other, and a single lock would make one slow host everybody's
	// problem. Never cleaned out, because the key is a mailbox id and there are as
	// many of those as there are mailboxes.
	syncing sync.Map

	// Nil when the base URL is not something an authenticator will accept — a bare
	// hostname with no scheme, say. The endpoints answer 503 rather than the
	// process refusing to start: passkeys are one way in among three, and an
	// instance should not be unreachable because one of them cannot be offered.
	passkeys *auth.WebAuthn

	// Password guessing is the attack this application is actually exposed to, so
	// the endpoints that check a secret are limited separately and more tightly
	// than the rest of the API.
	loginLimiter *limiter
	resetLimiter *limiter
	// Second factors are counted against the *account*, not the address. An
	// address bucket is defeated by anybody with more than one address, which is
	// the ordinary case — and a six-digit code is only safe while guesses are
	// scarce, so the scarcity has to be counted against the thing being attacked.
	totpLimiter *limiter

	// Computed once from the built index.html; see csp.go.
	csp string

	router chi.Router
}

// New builds the router. `web` is the built SvelteKit app, embedded into the binary
// at build time; a nil value serves an explanatory placeholder instead so that a
// backend-only build still runs and reports its health.
func New(cfg *config.Config, db *store.DB, log *slog.Logger, web fs.FS) *Server {
	s := &Server{
		cfg: cfg, db: db, log: log, web: web,
		mail:         mail.New(cfg.SMTP, cfg.BaseURL, log),
		hub:          realtime.NewHub(log),
		loginLimiter: newLimiter(10, 15*time.Minute),
		resetLimiter: newLimiter(5, time.Hour),
		// Tighter than the password bucket, and for a whole hour. Somebody typing
		// their own code gets it right on the first or second try; ten in an hour is
		// generous for a person and hopeless for a search through a million.
		totpLimiter: newLimiter(10, time.Hour),
	}
	s.csp = contentSecurityPolicy(scriptHashes(web))
	if w, err := auth.NewWebAuthn(cfg.BaseURL, "verdande"); err == nil {
		s.passkeys = w
	} else {
		log.Warn("passkeys are unavailable", "err", err, "base_url", cfg.BaseURL)
	}
	s.mcp = s.buildMCP()
	s.updates = update.New(Version, cfg.UpdateCheck)

	r := chi.NewRouter()
	r.Use(middleware.RequestID)
	r.Use(middleware.RealIP)
	r.Use(requestLogger(log))
	r.Use(middleware.Recoverer)
	r.Use(middleware.Timeout(30 * time.Second))
	r.Use(s.securityHeaders)

	// Unauthenticated, and deliberately outside /api/v1: the Rune healthcheck and
	// Docker both need this to answer before anyone has logged in.
	r.Get("/healthz", s.handleHealth)

	// The calendar feed is outside /api/v1 and outside the session: a calendar
	// client cannot log in, so the token in the path is the whole credential.
	r.Get("/ics/{token}", s.handleICSFeed)

	// CalDAV, outside /api/v1 because clients do well-known-path discovery
	// against the root and authenticate with Basic rather than a session.
	r.Get("/.well-known/caldav", s.wellKnownCalDAV)

	// Inbound mail. Delivered by the mail server rather than by a browser, and
	// authenticated by the token in the recipient address.
	r.Post("/inbound/mail", s.handleInboundMail)

	// MCP with the token in the query string, for clients that cannot send a
	// header. Claude's custom-connector dialog takes a URL and nothing else, so
	// /api/v1/mcp — which wants Authorization: Bearer — cannot be configured from
	// it at all. Same reasoning as the calendar feed above: a client that cannot
	// be told to send a header means the token in the URL is the credential.
	//
	// Outside /api/v1 deliberately, because it must not be reachable with a
	// session cookie. A cookie-authenticated POST with no CSRF check is a
	// cross-site request waiting to happen; handleMCPWithKey accepts the key and
	// nothing else.
	r.Post("/mcp", s.handleMCPWithKey)

	// Google sends the browser here after consent. Outside /api/v1 because it is a
	// top-level navigation rather than a fetch, but still behind the session — the
	// tokens it exchanges belong to whoever is signed in.
	r.Group(func(r chi.Router) {
		r.Use(s.requireAuth)
		r.Get("/oauth/gmail/callback", s.handleGmailCallback)
		// The calendar comes back on a URI of its own rather than sharing Gmail's.
		// One callback deciding from stored state which of the two flows had
		// returned would put the choice of *which token store to write* behind a
		// lookup — and when that goes wrong it goes wrong by overwriting a working
		// Gmail connection with calendar tokens.
		r.Get("/oauth/calendar/callback", s.handleCalendarCallback)
	})
	r.Route("/caldav", s.caldavRoutes)

	r.Route("/api/v1", func(r chi.Router) {
		r.Use(s.requireCSRF)

		r.Get("/ping", func(w http.ResponseWriter, r *http.Request) {
			writeJSON(w, http.StatusOK, map[string]string{"status": "ok"})
		})

		// The beacon's receiving end, and the number it produces. Both without a
		// session, because the caller is a stranger's installation — that is the
		// whole feature. Rate limited like the login routes: it is the one endpoint
		// anybody on the internet can write to, and a row per request is a row per
		// request whether or not the request is honest.
		//
		// Refused with a 404 unless this instance has been told it is the collector,
		// so an ordinary installation is not a spam sink that answers 200 to
		// anything.
		r.Method(http.MethodPost, "/beacon",
			s.rateLimit(s.loginLimiter, http.HandlerFunc(s.handleBeaconPing)))
		r.Get("/beacon/count", s.handleBeaconCount)

		// Reachable without being signed in — these are how you become signed in.
		r.Route("/auth", func(r chi.Router) {
			r.Get("/setup", s.handleSetupState)
			r.Method(http.MethodPost, "/setup",
				s.rateLimit(s.loginLimiter, http.HandlerFunc(s.handleBootstrap)))
			r.Method(http.MethodPost, "/login",
				s.rateLimit(s.loginLimiter, http.HandlerFunc(s.handleLogin)))
			r.Method(http.MethodPost, "/signup",
				s.rateLimit(s.loginLimiter, http.HandlerFunc(s.handleSignup)))
			r.Method(http.MethodPost, "/password/forgot",
				s.rateLimit(s.resetLimiter, http.HandlerFunc(s.handleForgotPassword)))
			r.Method(http.MethodPost, "/password/reset",
				s.rateLimit(s.resetLimiter, http.HandlerFunc(s.handleResetPassword)))

			// Signing in with a passkey. Rate-limited like the password path: a
			// signature cannot be guessed, but the endpoint can still be used to
			// hammer the database.
			r.Method(http.MethodPost, "/passkey/login/begin",
				s.rateLimit(s.loginLimiter, http.HandlerFunc(s.handleBeginPasskeyLogin)))
			r.Method(http.MethodPost, "/passkey/login/finish",
				s.rateLimit(s.loginLimiter, http.HandlerFunc(s.handleFinishPasskeyLogin)))

			// The second step of a login: a session that has passed the password
			// but not yet the code, and can reach nothing else.
			r.Group(func(r chi.Router) {
				r.Use(s.requirePendingSession)
				r.Method(http.MethodPost, "/login/totp",
					s.rateLimit(s.loginLimiter, http.HandlerFunc(s.handleLoginTOTP)))
			})

			r.Group(func(r chi.Router) {
				r.Use(s.requireAuth)
				r.Get("/me", s.handleMe)
				r.Patch("/me", s.handleUpdateProfile)
				r.Put("/sidebar-sections", s.handleSetSidebarSections)
				r.Put("/nav-order", s.handleSetNavOrder)
				r.Post("/logout", s.handleLogout)
				r.Post("/password/change", s.handleChangePassword)
				r.Get("/recovery-codes", s.handleRecoveryCodesCount)

				// Behind requireSession, like the API tokens and for the same
				// reason: a leaked token must not be able to end the sessions of
				// the person it was stolen from, or list their devices.
				r.Group(func(r chi.Router) {
					r.Use(s.requireSession)
					r.Get("/sessions", s.handleListSessions)
					r.Delete("/sessions/{sessionID}", s.handleDeleteSession)

					// Turning the second factor on, and the codes that get you back
					// in. Sessions only, and setup asks for the password.
					//
					// These sat outside this group, which meant the door opened with
					// a token and closed only with a password: `disable` has always
					// asked for the password, `setup` asked for nothing. A stolen
					// token could therefore fetch the secret, load it into its own
					// authenticator, confirm it, and keep the only copy of the
					// recovery codes. The owner's next login would stop at a code
					// they do not have, and they could not turn it off without
					// logging in first. A theft becomes a tenancy — the same
					// sentence written next door about passkeys, and the same rule.
					r.Post("/totp/setup", s.handleTOTPSetup)
					r.Post("/totp/confirm", s.handleTOTPConfirm)
					r.Post("/totp/disable", s.handleTOTPDisable)
					r.Post("/recovery-codes", s.handleRecoveryCodesRegenerate)

					// Registering a key, and the list of them. Sessions only, for
					// the same reason: a leaked token must not be able to add its
					// own way in — that would turn a theft into a tenancy.
					r.Get("/passkeys", s.handleListPasskeys)
					r.Post("/passkeys/register/begin", s.handleBeginPasskeyRegistration)
					r.Post("/passkeys/register/finish", s.handleFinishPasskeyRegistration)
					r.Patch("/passkeys/{passkeyID}", s.handleRenamePasskey)
					r.Delete("/passkeys/{passkeyID}", s.handleDeletePasskey)
				})
			})
		})

		// Everything past this point needs a complete login.
		r.Group(func(r chi.Router) {
			r.Use(s.requireAuth)

			r.Get("/ws", s.handleWebSocket)

			// The MCP endpoint. Reachable with a personal API token, so a connector
			// sees exactly what its owner sees.
			r.Post("/mcp", s.handleMCP)

			r.Get("/today", s.handleToday)
			r.Get("/filters/preview", s.handlePreviewFilter)

			r.Route("/filters", func(r chi.Router) {
				r.Get("/", s.handleListFilters)
				r.Post("/", s.handleCreateFilter)
				r.Get("/{filterID}/tasks", s.handleRunFilter)
				r.Patch("/{filterID}", s.handleUpdateFilter)
				r.Delete("/{filterID}", s.handleDeleteFilter)
			})

			r.Get("/feed", s.handleGetFeed)

			r.Route("/notifications", func(r chi.Router) {
				r.Get("/", s.handleListNotifications)
				r.Post("/read", s.handleMarkNotificationsRead)
				r.Post("/{notificationID}/read", s.handleMarkNotificationsRead)
			})

			r.Route("/push", func(r chi.Router) {
				r.Get("/key", s.handlePushKey)
				r.Post("/subscribe", s.handleSubscribePush)
				r.Post("/unsubscribe", s.handleUnsubscribePush)
			})

			r.Route("/attachments/{attachmentID}", func(r chi.Router) {
				r.Get("/", s.handleDownloadAttachment)
				r.Delete("/", s.handleDeleteAttachment)
			})

			r.Route("/comments/{commentID}", func(r chi.Router) {
				r.Patch("/", s.handleUpdateComment)
				r.Delete("/", s.handleDeleteComment)
			})
			r.Post("/feed/rotate", s.handleRotateFeed)

			r.Get("/mail-address", s.handleGetMailAddress)
			r.Post("/mail-address/rotate", s.handleRotateMailAddress)

			// Personal API tokens. Behind requireSession rather than the ambient
			// auth: a token must not be able to mint or revoke another.
			r.Route("/tokens", func(r chi.Router) {
				r.Use(s.requireSession)
				r.Get("/", s.handleListAPITokens)
				r.Post("/", s.handleCreateAPIToken)
				r.Delete("/{tokenID}", s.handleDeleteAPIToken)
			})

			r.Route("/ai", func(r chi.Router) {
				r.Get("/settings", s.handleGetAISettings)
				r.Put("/settings", s.handleSetAISettings)
				r.Post("/summary", s.handleAISummary)
				r.Post("/tasks/{taskID}/split", s.handleAISplit)
			})

			r.Get("/version", s.handleVersion)

			// Mailboxes read over IMAP — iCloud, Fastmail, any ordinary host. Each
			// belongs to the person who connected it, so there is no admin gate
			// here and no shared registration: the credential is theirs.
			// Notes. Listing and searching are the same endpoint because they answer
			// the same question with different words; the backwards one — what has
			// been written about this task — hangs off the thing being asked about.
			r.Route("/notes", func(r chi.Router) {
				r.Get("/", s.handleListNotes)
				r.Post("/", s.handleCreateNote)
				r.Post("/import", s.handleImportNotes)
				r.Get("/linking/{kind}/{targetID}", s.handleNotesLinking)
				r.Get("/{noteID}", s.handleGetNote)
				r.Patch("/{noteID}", s.handleUpdateNote)
				r.Delete("/{noteID}", s.handleDeleteNote)
				// A picture pasted or dropped into a note. The import could bring
				// files in and nothing else could, which made the most ordinary act
				// in a notes app — paste a screenshot — do nothing at all.
				r.Post("/{noteID}/attachments", s.handleUploadNoteAttachment)
				// Mange på én gang. Efter en import af tolv hundrede noter er det at
				// vælge halvtreds det almindelige tilfælde, ikke det yderste.
				r.Post("/bulk", s.handleNoteBulk)
			})

			r.Route("/mailboxes", func(r chi.Router) {
				r.Get("/", s.handleListMailboxes)
				r.Post("/", s.handleAddMailbox)
				r.Delete("/{mailboxID}", s.handleDeleteMailbox)
				r.Post("/{mailboxID}/sync", s.handleSyncMailbox)
			})

			r.Route("/gmail", func(r chi.Router) {
				r.Get("/", s.handleGetGmail)
				r.Put("/", s.handleSetGmail)
				r.Delete("/", s.handleDisconnectGmail)
				r.Post("/authorize", s.handleGmailAuthorize)
				r.Post("/sync", s.handleGmailSyncNow)

				// The OAuth client itself is the instance's registration with
				// Google, not anybody's mailbox — so unlike everything above it, it
				// is administrators only, and behind a session as well: a leaked
				// token must not be able to read or replace this instance's
				// identity to Google.
				r.Group(func(r chi.Router) {
					r.Use(s.requireSession, s.requireAdmin)
					r.Get("/client", s.handleGetGmailClient)
					r.Put("/client", s.handleSetGmailClient)
				})
			})

			// A calendar read from somewhere else, laid under verdande's own dated
			// tasks. Read-only, so there is no write here to gate: the events are a
			// copy of somebody else's calendar, and the only thing a person decides
			// is which of them to look at.
			r.Route("/calendar", func(r chi.Router) {
				r.Get("/", s.handleGetCalendar)
				r.Put("/calendars", s.handleSetCalendars)
				r.Delete("/", s.handleDisconnectCalendar)
				r.Post("/authorize", s.handleCalendarAuthorize)
				r.Post("/sync", s.handleCalendarSyncNow)
				r.Get("/events", s.handleCalendarEvents)
			})

			r.Route("/import", func(r chi.Router) {
				r.Post("/todoist", s.handleImportTodoist)
				r.Post("/csv", s.handleImportCSV)
			})

			r.Get("/export/account", s.handleExportAccount)
			r.Get("/export/notes.zip", s.handleExportNotes)
			r.Get("/export/projects/{projectID}.csv", s.handleExportProject)
			r.Get("/export/projects/{projectID}.ics", s.handleExportProjectICS)

			r.Route("/templates", func(r chi.Router) {
				r.Get("/", s.handleListTemplates)
				r.Post("/", s.handleSaveTemplate)
				r.Post("/{templateID}/use", s.handleUseTemplate)
				r.Delete("/{templateID}", s.handleDeleteTemplate)
			})

			r.Delete("/reminders/{reminderID}", s.handleDeleteReminder)

			r.Route("/labels", func(r chi.Router) {
				r.Get("/", s.handleListLabels)
				r.Post("/", s.handleCreateLabel)
				r.Patch("/{labelID}", s.handleUpdateLabel)
				r.Delete("/{labelID}", s.handleDeleteLabel)
			})
			r.Get("/upcoming", s.handleUpcoming)
			r.Get("/delegated", s.handleDelegated)
			r.Get("/people", s.handlePeople)
			r.Get("/search", s.handleSearch)

			r.Route("/projects", func(r chi.Router) {
				r.Get("/", s.handleListProjects)
				r.Post("/", s.handleCreateProject)
				// Above /{projectID}, or chi reads "reorder" as an id.
				r.Post("/reorder", s.handleReorderProjects)

				r.Route("/{projectID}", func(r chi.Router) {
					// Read access is the floor for the whole subtree; the writes
					// below tighten it to editor or owner individually.
					r.Use(s.requireProject(store.RoleViewer))

					r.Get("/", s.handleGetProject)
					r.Get("/sections", s.handleListSections)
					r.Get("/members", s.handleListMembers)
					r.Get("/activity", s.handleActivity)

					r.Group(func(r chi.Router) {
						r.Use(s.requireProject(store.RoleEditor))
						r.Post("/sections", s.handleCreateSection)
					})

					r.Group(func(r chi.Router) {
						r.Use(s.requireProject(store.RoleOwner))
						r.Patch("/", s.handleUpdateProject)
						r.Delete("/", s.handleDeleteProject)
						r.Post("/invites", s.handleInvite)
						r.Patch("/members/{userID}", s.handleSetMemberRole)
						r.Delete("/members/{userID}", s.handleRemoveMember)
					})
				})
			})

			// The instance's membership. Administrators only, and behind
			// requireSession as well as requireAdmin: an API token belongs to a
			// person, and a leaked one must not be able to mint an account or
			// delete somebody else's.
			r.Group(func(r chi.Router) {
				r.Use(s.requireSession, s.requireAdmin)
				r.Get("/errors", s.handleListErrors)
				// Restarting this instance from its own interface. The panel does
				// the work — a container cannot replace its own image — and pulls
				// `:latest` on the way, which is what makes a restart an update.
				r.Get("/panel", s.handlePanelStatus)
				r.Post("/panel/restart", s.handleRestartFromPanel)
				// Who this instance reports to, and whether it does. An
				// administrator's decision, not a person's: there is one
				// installation and it either phones home or it does not.
				r.Get("/beacon/settings", s.handleBeaconStatus)
				r.Put("/beacon/settings", s.handleSetBeacon)
				// A backup file is a complete copy of the database, so this whole
				// group is sessions-only as well as administrators-only: a leaked
				// token must not be able to download everybody's data.
				r.Get("/backups", s.handleListBackups)
				r.Post("/backups", s.handleRunBackup)
				r.Get("/backups/{backupID}", s.handleDownloadBackup)
				// The instance-wide history. Above the per-project one in every
				// sense: it crosses projects the caller is not a member of, which
				// is the whole reason it is here and not there.
				r.Get("/activity", s.handleAuditLog)
				r.Get("/activity/events", s.handleAuditEvents)
				r.Get("/users", s.handleListUsers)
				r.Post("/users", s.handleCreateUser)
				r.Patch("/users/{userID}", s.handleUpdateUser)
				r.Delete("/users/{userID}", s.handleDeleteUser)
				r.Delete("/invites/{inviteID}", s.handleDeleteInvite)
			})

			// Groups are a person's own headings over their projects, so there is
			// no project permission to check — every query here is scoped to the
			// caller.
			r.Route("/project-groups", func(r chi.Router) {
				r.Get("/", s.handleListProjectGroups)
				r.Post("/", s.handleCreateProjectGroup)
				// Above /{groupID}, or chi reads "reorder" as an id.
				r.Post("/reorder", s.handleReorderProjectGroups)
				r.Get("/{groupID}", s.handleGetProjectGroup)
				r.Patch("/{groupID}", s.handleUpdateProjectGroup)
				r.Delete("/{groupID}", s.handleDeleteProjectGroup)
				r.Post("/{groupID}/attachments", s.handleUploadGroupAttachment)
			})

			// The trash is outside the block above: a deleted project is invisible
			// to the permission check by design, so these handlers resolve
			// ownership themselves.
			r.Get("/trash/projects", s.handleListTrashedProjects)
			r.Post("/trash/projects/{projectID}/restore", s.handleRestoreProject)

			r.Route("/sections/{sectionID}", func(r chi.Router) {
				r.Patch("/", s.handleUpdateSection)
				r.Delete("/", s.handleDeleteSection)
			})

			r.Route("/tasks", func(r chi.Router) {
				r.Get("/", s.handleListTasks)
				r.Post("/", s.handleCreateTask)
				r.Post("/quick-add", s.handleQuickAdd)
				r.Get("/quick-add/preview", s.handleQuickAddPreview)

				r.Route("/{taskID}", func(r chi.Router) {
					r.Get("/", s.handleGetTask)
					r.Patch("/", s.handleUpdateTask)
					r.Delete("/", s.handleDeleteTask)
					r.Get("/comments", s.handleListComments)
					r.Post("/comments", s.handleCreateComment)
					r.Post("/attachments", s.handleUploadAttachment)
					r.Get("/reminders", s.handleListReminders)
					r.Post("/reminders", s.handleCreateReminder)
					r.Post("/complete", s.handleCompleteTask)
					r.Post("/reopen", s.handleReopenTask)
					r.Post("/move", s.handleMoveTask)
				})
			})
		})
	})

	r.NotFound(s.serveWeb)

	s.router = r
	return s
}

func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) { s.router.ServeHTTP(w, r) }

// Mail and Hub are exposed so the background jobs can deliver through the same
// sender and the same live connections the request path uses — a reminder should
// arrive in an open tab exactly as a colleague's edit does.
func (s *Server) Mail() *mail.Sender { return s.mail }
func (s *Server) Hub() *realtime.Hub { return s.hub }

// handleHealth reports whether verdande can actually serve requests, which means
// reaching the database — a process that is up but cannot read its own data is not
// healthy, and answering 200 for it would keep a broken container in rotation.
func (s *Server) handleHealth(w http.ResponseWriter, r *http.Request) {
	ctx, cancel := contextWithTimeout(r, 2*time.Second)
	defer cancel()

	var one int
	if err := s.db.QueryRowContext(ctx, `SELECT 1`).Scan(&one); err != nil {
		s.log.Error("health check failed", "err", err)
		writeJSON(w, http.StatusServiceUnavailable, map[string]string{
			"status": "unhealthy",
			"error":  "database unreachable",
		})
		return
	}
	// The version travels with the health check because this is the one endpoint
	// that answers without a session. "Which version is actually running?" is
	// otherwise a question you cannot ask from outside — and after a deploy it is
	// the first question there is.
	writeJSON(w, http.StatusOK, map[string]string{"status": "ok", "version": Version})
}

// serveWeb serves the PWA, falling back to index.html so that client-side routes
// survive a page reload. A request under /api that reaches here is a genuine 404 and
// must say so in JSON rather than being handed the HTML shell — a client parsing
// "<!doctype html>" as a JSON error message is a confusing way to learn about a typo.
func (s *Server) serveWeb(w http.ResponseWriter, r *http.Request) {
	if strings.HasPrefix(r.URL.Path, "/api/") {
		writeJSON(w, http.StatusNotFound, map[string]string{"error": "not found"})
		return
	}

	// /.well-known/ is reserved by RFC 8615 and is never a route in the app.
	// Handing back the shell there does not merely waste a response: it tells
	// whoever asked that the thing they were looking for exists.
	//
	// That is not hypothetical. Claude probes
	// /.well-known/oauth-authorization-server before connecting to an MCP server,
	// read 200 and a page of HTML as "there is an authorization server here", and
	// then failed trying to register with it — reporting a broken sign-in service
	// on a server that has none and needs none. A 404 means "no OAuth here", the
	// client stops asking, and the key in the URL is used as intended.
	if strings.HasPrefix(r.URL.Path, "/.well-known/") {
		writeJSON(w, http.StatusNotFound, map[string]string{"error": "not found"})
		return
	}
	if s.web == nil {
		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
		w.WriteHeader(http.StatusOK)
		w.Write([]byte("verdande — API is running. The web interface was not built into this binary.\n"))
		return
	}

	name := strings.TrimPrefix(path.Clean(r.URL.Path), "/")
	if name == "" || name == "." {
		name = "index.html"
	}

	f, err := s.web.Open(name)
	if errors.Is(err, fs.ErrNotExist) {
		// A client-side route: hand back the shell and let the app route it.
		name = "index.html"
		f, err = s.web.Open(name)
	}
	if err != nil {
		writeJSON(w, http.StatusNotFound, map[string]string{"error": "not found"})
		return
	}
	defer f.Close()

	info, err := f.Stat()
	if err != nil || info.IsDir() {
		writeJSON(w, http.StatusNotFound, map[string]string{"error": "not found"})
		return
	}
	seeker, ok := f.(interface {
		Read([]byte) (int, error)
		Seek(int64, int) (int64, error)
	})
	if !ok {
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": "cannot serve asset"})
		return
	}

	// Hashed build assets are immutable; the shell must never be cached, or a
	// deploy leaves people on the previous version until they hard-reload.
	if strings.HasPrefix(name, "_app/immutable/") {
		w.Header().Set("Cache-Control", "public, max-age=31536000, immutable")
	} else {
		w.Header().Set("Cache-Control", "no-cache")
	}
	http.ServeContent(w, r, name, info.ModTime(), seeker)
}

// securityHeaders sets the headers that are the same on every response.
func (s *Server) securityHeaders(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		h := w.Header()
		h.Set("X-Content-Type-Options", "nosniff")
		h.Set("X-Frame-Options", "DENY")
		h.Set("Referrer-Policy", "same-origin")
		h.Set("Content-Security-Policy", s.csp)
		next.ServeHTTP(w, r)
	})
}

func requestLogger(log *slog.Logger) func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			start := time.Now()
			ww := middleware.NewWrapResponseWriter(w, r.ProtoMajor)
			next.ServeHTTP(ww, r)

			level := slog.LevelInfo
			if ww.Status() >= 500 {
				level = slog.LevelError
			}
			// The health check runs every few seconds forever; logging it at info
			// buries everything else.
			if r.URL.Path == "/healthz" && ww.Status() < 400 {
				level = slog.LevelDebug
			}
			log.Log(r.Context(), level, "request",
				"method", r.Method,
				"path", r.URL.Path,
				"status", ww.Status(),
				"bytes", ww.BytesWritten(),
				"duration", time.Since(start).Round(time.Millisecond).String(),
				// RealIP has already resolved this through the proxy headers, so
				// behind a Cloudflare Tunnel it is the caller and not the tunnel.
				// The panel's log watchers roll failed logins up per address.
				"remote", r.RemoteAddr,
				"request_id", middleware.GetReqID(r.Context()),
			)
		})
	}
}

func writeJSON(w http.ResponseWriter, status int, v any) {
	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	w.WriteHeader(status)
	if err := json.NewEncoder(w).Encode(v); err != nil {
		// The status line is already sent, so there is nothing to report to the
		// client; this only ever means a dropped connection.
		slog.Debug("write json response", "err", err)
	}
}

// NewLogger returns the process logger. Text in development because a person is
// reading it; JSON in production because the panel and log tooling are.
func NewLogger(dev bool) *slog.Logger {
	if dev {
		return slog.New(slog.NewTextHandler(os.Stdout, &slog.HandlerOptions{Level: slog.LevelDebug}))
	}
	return slog.New(slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{Level: slog.LevelInfo}))
}