package api

// Guest logins: a temporary account for showing somebody the console. It expires by itself
// (half an hour by default), it can be revoked in one tap, and it may only look — it cannot
// change a thing, on this machine or on any machine this hub manages.
//
// The gate is a list of what a guest may reach, and nothing else, so a route added later is
// shut to guests until somebody decides otherwise. It is applied to the *scoped* path, which
// is what makes it hold for managed machines too: the hub proxies to a node as itself, with a
// token that is full control of that node, so the node cannot tell a guest from its owner —
// the decision has to be made here, before the request leaves.

import (
	"encoding/json"
	"io"
	"log"
	"net/http"
	"net/url"
	"strings"
	"time"

	"hamlab/internal/auth"
	"hamlab/internal/config"
	"hamlab/internal/store"
)

const (
	guestPrefix     = "guest-"
	guestTTLDefault = 30 * time.Minute
	guestTTLMax     = 24 * time.Hour
	guestReapEvery  = time.Minute
)

// guestRoutes is every route a guest login may reach, by the pattern it is registered under
// in New. Reading only, with three exceptions that are the guest's own: signing out, and the
// theme and page order that follow the login.
//
// Deliberately not here, though they only read:
//   - terminals — attaching is a root-capable shell, and attaching is a GET
//   - files — reading a file is reading every file, including keys and this config
//   - a container's logs, inspect, events and health — env vars and logs are where secrets are
//   - stack files and .env — same
//   - cron/jobs, alerts — the jobs are commands; a channel URL is a key to his phone
//   - KVM — a screen and a keyboard on a machine, and its assets load with a GET
//   - updates — what is unpatched on his box is not a thing to show a visitor
var guestRoutes = map[string]bool{
	"GET /api/me":                    true,
	"POST /api/logout":               true,
	"GET /api/nodes":                 true, // the machine switcher: a guest may look at any of them
	"GET /api/prefs/ui":              true,
	"PUT /api/prefs/ui":              true, // the look is the login's own
	"GET /api/prefs/history":         true,
	"GET /api/prefs/sampler":         true,
	"GET /api/procs":                 true,
	"GET /api/hardware":              true,
	"GET /api/storage":               true,
	"GET /api/storage/smart/{dev}":   true,
	"GET /api/storage/zfs/snapshots": true,
	"GET /api/zfs":                   true,
	"GET /api/docker":                true, // containers, images, volumes, networks — the lists only
	"GET /api/docker/stacks":         true,
	"GET /api/services":              true,
	"GET /api/services/{unit}":       true,
	"GET /api/space":                 true,
	"GET /api/space/{disk}":          true,
	"GET /api/space/{disk}/tree":     true,
	"GET /api/space/{disk}/largest":  true,
	"GET /api/tasks":                 true,
	"GET /api/tasks/{id}":            true,
	// sensors: the read-only interface the dashboard and every graph are built on. A query
	// is a POST when the list of ids is too long for a URL, and still only a read.
	"GET /api/sensors":              true,
	"GET /api/sensors/query":        true,
	"POST /api/sensors/query":       true,
	"GET /api/sensors/stream":       true,
	"GET /api/sensors/history":      true,
	"GET /api/sensors/{id}":         true,
	"GET /api/sensors/{id}/history": true,
	"GET /api/fleet/sensors/query":  true,
	"POST /api/fleet/sensors/query": true,
}

// guestScope is the path whose permission decides this request. A hub route for a managed
// machine is the same route on that machine — /api/nodes/grid/procs is /api/procs — so it is
// judged by the same line of guestRoutes. A path with nothing after the machine name is the
// machine record itself (adding or removing one), which is no guest's business.
func guestScope(p string) string {
	rest, ok := strings.CutPrefix(p, "/api/nodes/")
	if !ok {
		return p
	}
	i := strings.IndexByte(rest, '/')
	if i < 0 {
		return ""
	}
	return "/api" + rest[i:]
}

// guestMay decides a request by asking the router which handler it would reach, so the
// answer can never drift from the route it is about. An unrouted path lands on the catch-all,
// which is not in the list, so it is refused.
func (s *Server) guestMay(r *http.Request) bool {
	probe := r
	if p := guestScope(r.URL.Path); p != r.URL.Path {
		if p == "" {
			return false
		}
		probe = &http.Request{Method: r.Method, URL: &url.URL{Path: p}, Host: r.Host}
	}
	_, pattern := s.mux.Handler(probe)
	return guestRoutes[pattern]
}

// ---- the accounts themselves ----

func (s *Server) listGuests(w http.ResponseWriter, r *http.Request) {
	now := time.Now()
	counts := s.sessions.Count()
	out := []map[string]any{}
	s.cfg.View(func(c *config.Config) {
		for _, u := range c.Users {
			if !u.Guest || u.Expired(now) {
				continue
			}
			out = append(out, map[string]any{
				"name": u.Name, "created": u.Created, "expires": u.Expires,
				"issued_by": u.IssuedBy, "sessions": counts[u.Name], "used": !u.LastSeen.IsZero(),
			})
		}
	})
	jsonOK(w, 200, out)
}

// addGuest makes a guest login and hands back its password — the only time it is ever
// readable, here as everywhere else a password is generated.
func (s *Server) addGuest(w http.ResponseWriter, r *http.Request) {
	me := actorOf(r)
	if me.Guest {
		jsonErr(w, 403, "a guest login can only look around")
		return
	}
	var body struct {
		Minutes int `json:"minutes"`
	}
	_ = json.NewDecoder(io.LimitReader(r.Body, 4096)).Decode(&body)
	ttl := guestTTLDefault
	if body.Minutes > 0 {
		ttl = time.Duration(body.Minutes) * time.Minute
	}
	if ttl > guestTTLMax {
		jsonErr(w, 400, "a guest login lasts at most 24 hours")
		return
	}
	pw, err := auth.GuestPassword()
	if err != nil {
		jsonErr(w, 500, err.Error())
		return
	}
	hash, err := auth.HashPassword(pw)
	if err != nil {
		jsonErr(w, 500, err.Error())
		return
	}
	var name string
	for try := 0; try < 8 && name == ""; try++ {
		suffix, err := auth.GuestSuffix()
		if err != nil {
			jsonErr(w, 500, err.Error())
			return
		}
		candidate := guestPrefix + suffix
		s.cfg.View(func(c *config.Config) {
			if _, taken := c.User(candidate); !taken {
				name = candidate
			}
		})
	}
	if name == "" {
		jsonErr(w, 500, "could not find a free guest name")
		return
	}
	now := time.Now()
	expires := now.Add(ttl)
	if err := s.cfg.Update(func(c *config.Config) {
		c.Users = append(c.Users, config.User{Name: name, Hash: hash, Created: now, Guest: true, Expires: expires, IssuedBy: me.User})
	}); err != nil {
		jsonErr(w, 500, err.Error())
		return
	}
	log.Printf("guest login %q issued until %s (by %s)", name, expires.Format(time.RFC3339), clientIP(r))
	jsonOK(w, 200, map[string]any{"name": name, "password": pw, "expires": expires, "minutes": int(ttl.Minutes())})
}

// revokeGuest ends a guest login now. No password: it only ever takes access away, and the
// whole point of the thing is that ending it is one tap.
func (s *Server) revokeGuest(w http.ResponseWriter, r *http.Request) {
	if actorOf(r).Guest {
		jsonErr(w, 403, "a guest login can only look around")
		return
	}
	name := r.PathValue("name")
	found := false
	if err := s.cfg.Update(func(c *config.Config) {
		kept := c.Users[:0]
		for _, u := range c.Users {
			if u.Name == name && u.Guest {
				found = true
				continue
			}
			kept = append(kept, u)
		}
		c.Users = kept
	}); err != nil {
		jsonErr(w, 500, err.Error())
		return
	}
	if !found {
		jsonErr(w, 404, "no such guest login")
		return
	}
	s.forgetGuest(name)
	log.Printf("guest login %q revoked (by %s)", name, clientIP(r))
	w.WriteHeader(204)
}

// forgetGuest signs a guest out everywhere and drops the look they left behind.
func (s *Server) forgetGuest(name string) {
	s.sessions.RevokeUser(name)
	_ = s.store.Update(func(st *store.State) { delete(st.Users, name) })
}

// watchGuests clears out guest logins whose time is up. Expiry is enforced on every request
// as well — this is what keeps the config file from collecting them, and what signs a guest
// out of a console they left open rather than waiting for their next click.
func (s *Server) watchGuests() {
	for {
		s.reapGuests()
		time.Sleep(guestReapEvery)
	}
}

func (s *Server) reapGuests() {
	now := time.Now()
	var gone []string
	var have bool
	s.cfg.View(func(c *config.Config) {
		for _, u := range c.Users {
			if u.Guest {
				have = true
				if u.Expired(now) {
					gone = append(gone, u.Name)
				}
			}
		}
	})
	if !have || len(gone) == 0 {
		return
	}
	expired := map[string]bool{}
	for _, n := range gone {
		expired[n] = true
	}
	if err := s.cfg.Update(func(c *config.Config) {
		kept := c.Users[:0]
		for _, u := range c.Users {
			if expired[u.Name] {
				continue
			}
			kept = append(kept, u)
		}
		c.Users = kept
	}); err != nil {
		log.Printf("guests: %v", err)
		return
	}
	for _, n := range gone {
		s.forgetGuest(n)
	}
	log.Printf("guest login(s) expired: %s", strings.Join(gone, ", "))
}