package api

// Accounts and their sessions. Every person has their own login, and the console's look
// (theme, accents, dashboard layout) follows the account rather than the machine. Anyone
// signed in may add or remove accounts — a household console, not a tenancy — but removing
// one, or resetting another's password, asks for the caller's own password first, so a
// picked-up unlocked phone is not enough.

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

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

// actor is who a request is from: a signed-in account (with its session), or a token.
type actor struct {
	User    string // account name, "" for a token
	Session string // session ID, "" for a token
	token   string // the raw cookie token, so a handler can spare the current session
	Token   string // token name, "" for a session
	// Guest marks a temporary look-around login, and Expires is when it stops working. What
	// a guest may reach is decided in the middleware, not here; see internal/api/guests.go.
	Guest   bool
	Expires time.Time
}

type ctxKey int

const actorKey ctxKey = 1

func withActor(r *http.Request, a actor) *http.Request {
	return r.WithContext(context.WithValue(r.Context(), actorKey, a))
}

func actorOf(r *http.Request) actor {
	a, _ := r.Context().Value(actorKey).(actor)
	return a
}

// who names the caller for a log line: "core@10.0.0.5" for a person, "token:hub:core@…" for a hub.
func (a actor) String() string {
	switch {
	case a.User != "" && a.Guest:
		return "guest:" + a.User
	case a.User != "":
		return a.User
	case a.Token != "":
		return "token:" + a.Token
	}
	return ""
}

// ---- users ----

func (s *Server) listUsers(w http.ResponseWriter, r *http.Request) {
	me := actorOf(r).User
	counts := s.sessions.Count()
	var out []map[string]any
	s.cfg.View(func(c *config.Config) {
		for _, u := range c.Accounts() { // guest logins are listed on their own, see listGuests
			var seen any
			if !u.LastSeen.IsZero() {
				seen = u.LastSeen
			}
			out = append(out, map[string]any{"name": u.Name, "created": u.Created, "last_seen": seen, "sessions": counts[u.Name], "self": u.Name == me})
		}
	})
	if out == nil {
		out = []map[string]any{}
	}
	jsonOK(w, 200, out)
}

func (s *Server) addUser(w http.ResponseWriter, r *http.Request) {
	var body struct{ Name, Password string }
	if err := json.NewDecoder(io.LimitReader(r.Body, 4096)).Decode(&body); err != nil {
		jsonErr(w, 400, "bad request")
		return
	}
	name := strings.TrimSpace(body.Name)
	if !auth.UserNameRe.MatchString(name) {
		jsonErr(w, 400, "a user name is 1–32 lower-case letters, digits, . _ or -, starting with a letter or digit")
		return
	}
	if strings.HasPrefix(name, guestPrefix) {
		jsonErr(w, 400, "names starting with "+guestPrefix+" belong to guest logins")
		return
	}
	if len(body.Password) < auth.MinPasswordLen {
		jsonErr(w, 400, "password must be at least 12 characters")
		return
	}
	h, err := auth.HashPassword(body.Password)
	if err != nil {
		jsonErr(w, 500, err.Error())
		return
	}
	clash := false
	if err := s.cfg.Update(func(c *config.Config) {
		if _, ok := c.User(name); ok {
			clash = true
			return
		}
		c.Users = append(c.Users, config.User{Name: name, Hash: h, Created: time.Now()})
	}); err != nil {
		jsonErr(w, 500, err.Error())
		return
	}
	if clash {
		jsonErr(w, 409, "a user with that name exists")
		return
	}
	log.Printf("user %q added (by %s)", name, clientIP(r))
	jsonOK(w, 200, map[string]any{"name": name})
}

// confirmSelf checks the caller's own password, the gate on anything done to another account.
func (s *Server) confirmSelf(w http.ResponseWriter, r *http.Request, current string) bool {
	me := actorOf(r).User
	if me == "" {
		jsonErr(w, 403, "only a signed-in user may do that")
		return false
	}
	var users []config.User
	s.cfg.View(func(c *config.Config) { users = append(users, c.Users...) })
	if !auth.CheckUser(users, me, current) {
		jsonErr(w, 403, "your password is wrong")
		return false
	}
	return true
}

func (s *Server) removeUser(w http.ResponseWriter, r *http.Request) {
	name := r.PathValue("name")
	var body struct{ Current string }
	_ = json.NewDecoder(io.LimitReader(r.Body, 4096)).Decode(&body)
	if name == actorOf(r).User {
		jsonErr(w, 400, "you can't remove the account you are signed in as")
		return
	}
	if !s.confirmSelf(w, r, body.Current) {
		return
	}
	found, last := false, false
	if err := s.cfg.Update(func(c *config.Config) {
		if len(c.Accounts()) <= 1 { // guest logins don't keep the last real account alive
			last = true
			return
		}
		kept := c.Users[:0]
		for _, u := range c.Users {
			if u.Name == name {
				found = true
				continue
			}
			kept = append(kept, u)
		}
		c.Users = kept
	}); err != nil {
		jsonErr(w, 500, err.Error())
		return
	}
	if last {
		jsonErr(w, 400, "the last account can't be removed")
		return
	}
	if !found {
		jsonErr(w, 404, "no such user")
		return
	}
	s.sessions.RevokeUser(name)
	_ = s.store.Update(func(st *store.State) { delete(st.Users, name) })
	log.Printf("user %q removed (by %s)", name, clientIP(r))
	w.WriteHeader(204)
}

// resetPassword sets another user's password, on the caller's own password.
func (s *Server) resetPassword(w http.ResponseWriter, r *http.Request) {
	name := r.PathValue("name")
	var body struct{ Current, Password string }
	if err := json.NewDecoder(io.LimitReader(r.Body, 4096)).Decode(&body); err != nil {
		jsonErr(w, 400, "bad request")
		return
	}
	if !s.confirmSelf(w, r, body.Current) {
		return
	}
	if len(body.Password) < auth.MinPasswordLen {
		jsonErr(w, 400, "password must be at least 12 characters")
		return
	}
	if !s.setPassword(w, name, body.Password) {
		return
	}
	if name != actorOf(r).User { // whoever held the old password is signed out
		s.sessions.RevokeUser(name)
	}
	log.Printf("password of %q reset (by %s)", name, clientIP(r))
	w.WriteHeader(204)
}

func (s *Server) setPassword(w http.ResponseWriter, name, pw string) bool {
	h, err := auth.HashPassword(pw)
	if err != nil {
		jsonErr(w, 500, err.Error())
		return false
	}
	found := false
	if err := s.cfg.Update(func(c *config.Config) {
		for i := range c.Users {
			if c.Users[i].Name == name {
				c.Users[i].Hash = h
				found = true
			}
		}
	}); err != nil {
		jsonErr(w, 500, err.Error())
		return false
	}
	if !found {
		jsonErr(w, 404, "no such user")
		return false
	}
	return true
}

// ---- sessions: where the caller's account is signed in ----

func (s *Server) listSessions(w http.ResponseWriter, r *http.Request) {
	a := actorOf(r)
	if a.User == "" {
		jsonOK(w, 200, []any{})
		return
	}
	var out []map[string]any
	for _, ses := range s.sessions.List(a.User) {
		out = append(out, map[string]any{"id": ses.ID, "created": ses.Created, "last_seen": ses.LastSeen, "expires": ses.Expires, "ip": ses.IP, "agent": ses.Agent, "current": ses.ID == a.Session})
	}
	if out == nil {
		out = []map[string]any{}
	}
	jsonOK(w, 200, out)
}

func (s *Server) revokeSession(w http.ResponseWriter, r *http.Request) {
	a := actorOf(r)
	id := r.PathValue("id")
	if a.User == "" || !s.sessions.Revoke(a.User, id) {
		jsonErr(w, 404, "no such session")
		return
	}
	log.Printf("session %s of %q revoked (by %s)", id, a.User, clientIP(r))
	if id == a.Session {
		s.setCookie(w, r, "", -1)
	}
	w.WriteHeader(204)
}

// revokeIdleSessions drops the caller's sessions that have not been used for ?hours (24 by
// default): the scripts and headless browsers that signed in once and never came back,
// without touching the phone that was used this morning.
func (s *Server) revokeIdleSessions(w http.ResponseWriter, r *http.Request) {
	a := actorOf(r)
	if a.User == "" {
		jsonErr(w, 403, "only a signed-in user may do that")
		return
	}
	hours := 24
	if h := r.URL.Query().Get("hours"); h != "" {
		n, err := strconv.Atoi(h)
		if err != nil || n < 1 || n > 24*365 {
			jsonErr(w, 400, "hours is a whole number from 1 to 8760")
			return
		}
		hours = n
	}
	n := s.sessions.RevokeIdle(a.User, a.token, time.Duration(hours)*time.Hour)
	log.Printf("%d idle session(s) of %q revoked (idle > %dh, by %s)", n, a.User, hours, clientIP(r))
	jsonOK(w, 200, map[string]int{"revoked": n})
}

func (s *Server) revokeOtherSessions(w http.ResponseWriter, r *http.Request) {
	a := actorOf(r)
	if a.User == "" {
		jsonErr(w, 403, "only a signed-in user may do that")
		return
	}
	n := s.sessions.RevokeOthers(a.User, a.token)
	log.Printf("%d other session(s) of %q revoked (by %s)", n, a.User, clientIP(r))
	jsonOK(w, 200, map[string]int{"revoked": n})
}