// Package web serves the public site, the staff panel and their JSON APIs.
package web

import (
	"context"
	"embed"
	"encoding/json"
	"errors"
	"io/fs"
	"log/slog"
	"net/http"
	"net/url"
	"strconv"
	"time"

	"git.zio.sh/cs2/simpleadmin-web/internal/live"
	"git.zio.sh/cs2/simpleadmin-web/internal/rcon"
	"git.zio.sh/cs2/simpleadmin-web/internal/saconfig"
	"git.zio.sh/cs2/simpleadmin-web/internal/store"
)

//go:embed assets
var assets embed.FS

type Config struct {
	BaseURL       string // e.g. https://bans.example.com, no trailing slash
	SessionSecret []byte
	SiteFile      string
	// ServerAddress is shown on the public page for "Join server".
	ServerAddress string
	// Limits used when SimpleAdmin's config file isn't available.
	MaxBanDuration  int
	MaxMuteDuration int
}

type Server struct {
	cfg    Config
	site   Site
	st     *store.Store
	rc     *rcon.Client
	poll   *live.Poller
	sacfg  *saconfig.File // nil when no config path is set
	staff  *staffCache
	http   *http.Client
	secure bool
}

func New(cfg Config, st *store.Store, rc *rcon.Client, poll *live.Poller, sacfg *saconfig.File) (*Server, error) {
	site, err := loadSite(cfg.SiteFile)
	if err != nil {
		return nil, err
	}
	u, err := url.Parse(cfg.BaseURL)
	if err != nil || u.Host == "" {
		return nil, errors.New("base URL must be absolute, like https://bans.example.com")
	}
	return &Server{
		cfg:    cfg,
		site:   site,
		st:     st,
		rc:     rc,
		poll:   poll,
		sacfg:  sacfg,
		staff:  &staffCache{st: st, ttl: 15 * time.Second},
		http:   &http.Client{Timeout: 10 * time.Second},
		secure: u.Scheme == "https",
	}, nil
}

func (s *Server) Handler() http.Handler {
	mux := http.NewServeMux()
	static, _ := fs.Sub(assets, "assets")
	files := http.FileServerFS(static)

	mux.HandleFunc("GET /{$}", func(w http.ResponseWriter, r *http.Request) {
		http.ServeFileFS(w, r, static, "public.html")
	})
	mux.HandleFunc("GET /admin", s.adminPage(static))
	mux.Handle("GET /static/", http.StripPrefix("/static/", files))

	mux.HandleFunc("GET /auth/login", s.login)
	mux.HandleFunc("GET /auth/callback", s.callback)
	mux.HandleFunc("POST /auth/logout", s.logout)

	mux.HandleFunc("GET /api/me", s.me)
	mux.HandleFunc("GET /api/public/server", s.publicServer)
	mux.HandleFunc("GET /api/public/bans", s.publicBans)
	mux.HandleFunc("GET /api/public/comms", s.publicComms)
	mux.HandleFunc("GET /api/public/staff", s.publicStaff)
	mux.HandleFunc("GET /api/public/players/{steamid}", s.publicPlayer)

	admin := func(pattern string, h adminHandler) { mux.HandleFunc(pattern, s.requireStaff(h)) }
	admin("GET /api/admin/overview", s.adminOverview)
	admin("GET /api/admin/players", s.adminPlayers)
	admin("GET /api/admin/players/{steamid}", s.adminPlayer)
	admin("GET /api/admin/bans", s.adminBans)
	admin("GET /api/admin/comms", s.adminComms)
	admin("GET /api/admin/staff", s.adminStaff)
	admin("GET /api/admin/settings", s.adminSettings)

	admin("POST /api/admin/penalties", s.addPenalty)
	admin("POST /api/admin/penalties/lift", s.liftPenalty)
	admin("POST /api/admin/kick", s.kick)
	admin("POST /api/admin/say", s.say)
	admin("POST /api/admin/map", s.changeMap)
	admin("POST /api/admin/restart", s.restartRound)
	admin("POST /api/admin/reload-admins", s.reloadAdmins)
	admin("POST /api/admin/groups", s.createGroup)
	admin("PUT /api/admin/groups/{id}", s.updateGroup)
	admin("DELETE /api/admin/groups/{id}", s.deleteGroup)
	admin("POST /api/admin/staff", s.addStaff)
	admin("PUT /api/admin/staff/{steamid}", s.setStaffRank)
	admin("DELETE /api/admin/staff/{steamid}", s.removeStaff)
	admin("POST /api/admin/settings/cvars", s.saveCvars)
	admin("POST /api/admin/settings/simpleadmin", s.saveSimpleAdmin)

	return s.headers(mux)
}

func (s *Server) headers(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("Referrer-Policy", "same-origin")
		h.Set("X-Frame-Options", "DENY")
		h.Set("Content-Security-Policy", "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline' https://fonts.googleapis.com; font-src https://fonts.gstatic.com; img-src 'self' data:; frame-ancestors 'none'")
		next.ServeHTTP(w, r)
	})
}

// ---------------------------------------------------------------- JSON helpers

type apiError struct {
	Error string `json:"error"`
}

func writeJSON(w http.ResponseWriter, status int, v any) {
	w.Header().Set("Content-Type", "application/json")
	w.Header().Set("Cache-Control", "no-store")
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(v)
}

func fail(w http.ResponseWriter, status int, msg string) {
	writeJSON(w, status, apiError{Error: msg})
}

// internal logs the real error and tells the browser something generic.
func internal(w http.ResponseWriter, r *http.Request, err error) {
	slog.Error("request failed", "path", r.URL.Path, "err", err)
	fail(w, http.StatusInternalServerError, "Something went wrong on the server. The error has been logged.")
}

func readJSON(r *http.Request, v any) error {
	dec := json.NewDecoder(http.MaxBytesReader(nil, r.Body, 64<<10))
	dec.DisallowUnknownFields()
	if err := dec.Decode(v); err != nil {
		return errors.New("the request wasn't valid JSON")
	}
	return nil
}

func page(r *http.Request) (limit, offset, num int) {
	num, _ = strconv.Atoi(r.URL.Query().Get("page"))
	if num < 1 {
		num = 1
	}
	return pageSize, (num - 1) * pageSize, num
}

const pageSize = 50

type list[T any] struct {
	Items    []T `json:"items"`
	Total    int `json:"total"`
	Page     int `json:"page"`
	PageSize int `json:"pageSize"`
}

func newList[T any](items []T, total, num int) list[T] {
	if items == nil {
		items = []T{}
	}
	return list[T]{Items: items, Total: total, Page: num, PageSize: pageSize}
}

func (s *Server) staffIdx(ctx context.Context) (*staffIndex, error) {
	return s.staff.get(ctx)
}