package main

import (
	"context"
	"errors"
	"log"
	"net/http"
	"os"
	"os/signal"
	"strconv"
	"strings"
	"syscall"
	"time"

	"bookmarkmanager/backend/internal/api"
	"bookmarkmanager/backend/internal/httpmw"
	"bookmarkmanager/backend/internal/latest"
	"bookmarkmanager/backend/internal/store"
	"bookmarkmanager/backend/internal/token"
	"bookmarkmanager/backend/internal/userscript"
	"bookmarkmanager/backend/internal/web"
)

// Config holds all runtime settings, sourced from environment variables.
type Config struct {
	// TokenKey derives every Reader's userscript credential (internal/token).
	// Required: without it no install URL can ever be built.
	TokenKey       string
	AllowedOrigins []string
	// DatabaseURL is the Postgres connection URL; required, no default,
	// because a wrong guess would silently start on an empty database.
	DatabaseURL string
	Port        string
	// OwnerDiscordID identifies the seeded owner Reader (issue #22). Required:
	// bookmarks are scoped to a Reader, and a fresh deployment needs one
	// before anybody logs in. The owner is also the only Reader who can revoke
	// another Reader's sessions.
	OwnerDiscordID string
	// Discord is the OAuth application the browser UI signs in with.
	Discord web.DiscordConfig
	// UserscriptPath is the file served at /u/{token}/manga-bookmark.user.js.
	// Supplied by a bindmount so the script can be edited without a rebuild.
	UserscriptPath string
	// NovelUserscriptPath is the file served at
	// /u/{token}/novel-bookmark.user.js. Same bindmount, second script: the
	// two libraries are separate installs.
	NovelUserscriptPath string
	// LatestPoll configures the background latest-chapter fetcher.
	LatestPoll LatestPoll
	// Covers proxies kagane cover images for the web UI. Not from the
	// environment: it is the shared headless browser, wired in main once it
	// connects, and nil in every test router.
	Covers web.CoverFetcher
}

// LatestPoll configures the background latest-chapter poller.
//
// Sizing: batch x (cooldown / interval) is how many series hold a true cooldown
// cadence — 14 x (1h / 10m) = 84 with these defaults, which covers this
// deployment. Past that nothing breaks; the effective cadence stretches to
// N x interval / batch and the oldest-checked-first ordering keeps it uniform.
type LatestPoll struct {
	Enabled  bool
	Cooldown time.Duration
	Interval time.Duration
	Stagger  time.Duration
	Batch    int
}

const (
	defaultPollCooldown = time.Hour
	defaultPollInterval = 10 * time.Minute
	defaultPollStagger  = 20 * time.Second
	defaultPollBatch    = 14
	// minPollCooldown keeps a typo from turning a polite background check into
	// a hammer against sites that are already bot-scoring us.
	minPollCooldown = 15 * time.Minute
)

func envOr(key, def string) string {
	if v := os.Getenv(key); v != "" {
		return v
	}
	return def
}

// envBool reads a boolean env var. Anything unrecognised falls back to def.
func envBool(key string, def bool) bool {
	switch v := strings.ToLower(strings.TrimSpace(os.Getenv(key))); v {
	case "":
		return def
	case "0", "false", "no", "off":
		return false
	case "1", "true", "yes", "on":
		return true
	default:
		log.Printf("config: %s=%q is not a boolean, using %v", key, v, def)
		return def
	}
}

// envDuration reads a duration env var. An unparseable or non-positive value
// falls back to def and logs rather than failing startup: the poller is an
// enhancement, and a typo in one of its knobs must not stop bookmark sync.
func envDuration(key string, def time.Duration) time.Duration {
	raw := strings.TrimSpace(os.Getenv(key))
	if raw == "" {
		return def
	}
	d, err := time.ParseDuration(raw)
	if err != nil || d <= 0 {
		log.Printf("config: %s=%q is not a positive duration, using %s", key, raw, def)
		return def
	}
	return d
}

// envInt reads a positive integer env var, with the same fallback policy.
func envInt(key string, def int) int {
	raw := strings.TrimSpace(os.Getenv(key))
	if raw == "" {
		return def
	}
	n, err := strconv.Atoi(raw)
	if err != nil || n <= 0 {
		log.Printf("config: %s=%q is not a positive integer, using %d", key, raw, def)
		return def
	}
	return n
}

// loadLatestPoll reads the poller's settings, clamping anything that would make
// it antisocial.
func loadLatestPoll() LatestPoll {
	p := LatestPoll{
		Enabled:  envBool("LATEST_CHAPTER_POLL_ENABLED", true),
		Cooldown: envDuration("LATEST_CHAPTER_POLL_COOLDOWN", defaultPollCooldown),
		Interval: envDuration("LATEST_CHAPTER_POLL_INTERVAL", defaultPollInterval),
		Stagger:  envDuration("LATEST_CHAPTER_POLL_STAGGER", defaultPollStagger),
		Batch:    envInt("LATEST_CHAPTER_POLL_BATCH", defaultPollBatch),
	}
	if p.Cooldown < minPollCooldown {
		log.Printf("config: cooldown %s is below the %s floor, clamping", p.Cooldown, minPollCooldown)
		p.Cooldown = minPollCooldown
	}
	// batch x stagger has to fit inside one tick or a batch is still running
	// when the next one is due. Run() serialises them, so this degrades to a
	// slower cadence rather than to overlapping fetches — worth a warning, not
	// a failure.
	if span := time.Duration(p.Batch) * p.Stagger; span > p.Interval {
		log.Printf("config: batch(%d) x stagger(%s) = %s exceeds interval %s; batches will overrun their tick",
			p.Batch, p.Stagger, span, p.Interval)
	}
	return p
}

func loadConfig() Config {
	c := Config{
		TokenKey:            os.Getenv("TOKEN_KEY"),
		DatabaseURL:         os.Getenv("DATABASE_URL"),
		Port:                envOr("PORT", "8080"),
		OwnerDiscordID:      os.Getenv("OWNER_DISCORD_ID"),
		UserscriptPath:      envOr("USERSCRIPT_PATH", "/userscript/manga-bookmark.user.js"),
		NovelUserscriptPath: envOr("NOVEL_USERSCRIPT_PATH", "/userscript/novel-bookmark.user.js"),
		LatestPoll:          loadLatestPoll(),
	}
	c.Discord = web.DiscordConfig{
		ClientID:     os.Getenv("DISCORD_CLIENT_ID"),
		ClientSecret: os.Getenv("DISCORD_CLIENT_SECRET"),
		GuildID:      os.Getenv("DISCORD_GUILD_ID"),
		RequiredRole: os.Getenv("DISCORD_REQUIRED_ROLE"),
		APIBase:      envOr("DISCORD_API_BASE", "https://discord.com/api/v10"),
		RedirectURI:  os.Getenv("DISCORD_REDIRECT_URI"),
	}
	for _, o := range strings.Split(os.Getenv("ALLOWED_ORIGINS"), ",") {
		if o = strings.TrimSpace(o); o != "" {
			c.AllowedOrigins = append(c.AllowedOrigins, o)
		}
	}
	return c
}

// newRouter wires routes and middleware. CORS is the outermost layer so
// preflight OPTIONS short-circuits before auth; /bookmarks* is auth-protected,
// /healthz is public.
func newRouter(s *store.Store, cfg Config) http.Handler {
	mux := http.NewServeMux()
	mux.HandleFunc("GET /healthz", api.Healthz)

	// Outside httpmw.Auth (the updater sends no Authorization header) and
	// outside the web UI's Discord auth (the script must be installable
	// without a browser session). The path segment carries the credential
	// instead, and the script is rendered with the resolved Reader's
	// credential substituted in.
	mux.HandleFunc("GET /u/{token}/manga-bookmark.user.js",
		userscript.Handler(s, cfg.UserscriptPath))
	mux.HandleFunc("GET /u/{token}/novel-bookmark.user.js",
		userscript.Handler(s, cfg.NovelUserscriptPath))

	h := &api.Handler{Store: s}
	protected := http.NewServeMux()
	protected.HandleFunc("GET /bookmarks", h.List)
	protected.HandleFunc("PUT /bookmarks/{key}", h.Put)
	protected.HandleFunc("DELETE /bookmarks/{key}", h.Delete)

	auth := httpmw.Auth(s, protected)
	mux.Handle("/bookmarks", auth)
	mux.Handle("/bookmarks/", auth)

	// The browser UI is always registered; signing in is Discord OAuth, so
	// there is no password to forget and no gate to leave unset.
	wh, err := web.New(s, cfg.Discord, []byte(cfg.TokenKey),
		cfg.UserscriptPath, cfg.NovelUserscriptPath, cfg.Covers)
	if err != nil {
		log.Fatalf("web handler: %v", err)
	}
	wh.Register(mux)

	return httpmw.CORS(cfg.AllowedOrigins, httpmw.Gzip(guardEmptyUserscriptToken(mux)))
}

// guardEmptyUserscriptToken heads off ServeMux's own path-cleaning redirect:
// an empty {token} segment makes the request path "/u//manga-bookmark.user.js",
// and ServeMux 307s that to "/u/manga-bookmark.user.js" before pattern
// matching ever runs. The endpoint's contract is 404 for any wrong token,
// including this one, so catch it ahead of the mux.
func guardEmptyUserscriptToken(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if strings.HasPrefix(r.URL.Path, "/u//") {
			http.NotFound(w, r)
			return
		}
		next.ServeHTTP(w, r)
	})
}

func main() {
	cfg := loadConfig()
	if cfg.TokenKey == "" {
		log.Fatal("TOKEN_KEY is required")
	}
	if cfg.OwnerDiscordID == "" {
		log.Fatal("OWNER_DISCORD_ID is required")
	}
	if cfg.DatabaseURL == "" {
		log.Fatal("DATABASE_URL is required")
	}
	// The web UI signs in through Discord, so a deployment without the OAuth
	// application is misconfigured rather than passwordless.
	for key, v := range map[string]string{
		"DISCORD_CLIENT_ID":     cfg.Discord.ClientID,
		"DISCORD_CLIENT_SECRET": cfg.Discord.ClientSecret,
		"DISCORD_GUILD_ID":      cfg.Discord.GuildID,
		"DISCORD_REDIRECT_URI":  cfg.Discord.RedirectURI,
	} {
		if v == "" {
			log.Fatalf("%s is required", key)
		}
	}
	// The owner's userscript credential is derived from TOKEN_KEY at epoch 0
	// (internal/token); the readers row carries its SHA-256, not the
	// credential itself.
	owner := store.Owner{
		DiscordID: cfg.OwnerDiscordID,
		TokenHash: token.Hash(token.Token([]byte(cfg.TokenKey), cfg.OwnerDiscordID, 0)),
	}

	s, err := store.Open(cfg.DatabaseURL, owner)
	if err != nil {
		log.Fatalf("open store: %v", err)
	}
	defer s.Close()

	// The poller is off the request path entirely: if it cannot start, the
	// service still serves bookmarks and the userscript still captures latest
	// chapters on its own.
	//
	// One headless browser serves both consumers that need a Cloudflare
	// challenge cleared: the poller's kagane/novelfull fetches and the web
	// UI's kagane cover proxy. Optional — unset leaves both degraded to what
	// they were before the sidecar existed.
	var browser latest.Fetcher
	pollCtx, stopPoll := context.WithCancel(context.Background())
	defer stopPoll()
	if ws := strings.TrimSpace(os.Getenv("BROWSER_WS_URL")); ws != "" {
		bf, err := latest.NewBrowserFetcher(ws)
		if err != nil {
			log.Printf("browser fetcher disabled: %v", err)
		} else {
			browser = bf
			cfg.Covers = bf
			context.AfterFunc(pollCtx, bf.Close)
			log.Printf("browser fetcher at %s", ws)
		}
	}
	startLatestPoller(pollCtx, s, cfg.LatestPoll, browser)

	srv := &http.Server{
		Addr:              ":" + cfg.Port,
		Handler:           newRouter(s, cfg),
		ReadHeaderTimeout: 10 * time.Second,
	}

	go func() {
		// The connection URL carries a password, so it stays out of the log.
		log.Printf("listening on :%s (origins=%v)", cfg.Port, cfg.AllowedOrigins)
		if err := srv.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
			log.Fatalf("serve: %v", err)
		}
	}()

	stop := make(chan os.Signal, 1)
	signal.Notify(stop, syscall.SIGINT, syscall.SIGTERM)
	<-stop

	log.Println("shutting down")
	// Stop polling before draining requests, so an in-flight series fetch does
	// not hold the process open past the shutdown deadline.
	stopPoll()
	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()
	if err := srv.Shutdown(ctx); err != nil {
		log.Printf("shutdown: %v", err)
	}
}

// startLatestPoller launches the background poller unless it is disabled or its
// HTTP client cannot be built. Any problem here is logged and skipped: this
// feature going missing degrades the service to userscript-only latest-chapter
// tracking, which is exactly how it behaved before.
func startLatestPoller(ctx context.Context, s *store.Store, cfg LatestPoll, browser latest.Fetcher) {
	if !cfg.Enabled {
		log.Println("latest-chapter poller: disabled by config")
		return
	}
	f, err := latest.NewTLSFetcher()
	if err != nil {
		log.Printf("latest-chapter poller: disabled, cannot build client: %v", err)
		return
	}
	// Nil browser: sites behind a JavaScript challenge are simply not polled,
	// and their latest_chapter comes from the userscript alone — which is how
	// the service behaved before the sidecar existed.
	p := &latest.Poller{
		Store:        s,
		Fetch:        f,
		BrowserFetch: browser,
		Now:          time.Now,
		Cooldown:     cfg.Cooldown,
		Interval:     cfg.Interval,
		Stagger:      cfg.Stagger,
		Batch:        cfg.Batch,
	}

	go p.Run(ctx)
}