// Command tmplatformd is the TextMachine control plane: HTTP for the frontend, Postgres for the
// read model, and (from P-1 onward) a worker that supervises tmctl processes. It contains no
// translation logic: the engine is spawned, never linked (D39.81).
package main

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

	"textmachine/platform/internal/auth"
	"textmachine/platform/internal/config"
	"textmachine/platform/internal/httpapi"
	"textmachine/platform/internal/login"
	"textmachine/platform/internal/pgstore"
	"textmachine/platform/internal/reqid"
)

// sessionSweep is how often expired sessions are deleted. The table is small and the work is a
// single DELETE, so the interval is about not accumulating rows, not about load.
const sessionSweep = time.Hour

func main() {
	// Structured logs on stderr, like the engine's: stdout stays free for anything machine-read.
	// The handler is wrapped so every *Context call carries its request id without saying so.
	log := slog.New(reqid.WithContext(slog.NewJSONHandler(os.Stderr, &slog.HandlerOptions{Level: slog.LevelInfo})))
	if err := run(log); err != nil {
		log.Error("fatal", "err", err)
		os.Exit(1)
	}
}

func run(log *slog.Logger) error {
	cfg, err := config.Load()
	if err != nil {
		return err
	}

	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
	defer stop()

	var db *pgstore.Store
	if cfg.DSN == "" {
		// Deliberate: the process still serves liveness so a supervisor can start it before the
		// database exists. /readyz is the honest signal, and it says no.
		log.Warn("no TM_PLATFORM_DSN: starting without a database, /readyz will report not ready")
	} else {
		if cfg.Migrate {
			if err := pgstore.Migrate(ctx, cfg.DSN); err != nil {
				return err
			}
			log.Info("migrations applied")
		}
		if db, err = pgstore.Open(ctx, cfg.DSN); err != nil {
			return err
		}
		defer db.Close()
	}

	cookies := auth.Cookies{Insecure: cfg.InsecureCookies}
	if cfg.InsecureCookies {
		log.Warn("TM_PLATFORM_INSECURE_COOKIES: serving the session cookie without Secure, under a dev name — never in production")
	}
	authn := &auth.Authenticator{
		IdleTTL: cfg.SessionIdleTTL,
		Cookies: cookies,
		Log:     log,
		Deny:    httpapi.ProblemHandler(http.StatusUnauthorized, "Session missing or invalid"),
	}
	deps := httpapi.Deps{Log: log, Auth: authn, TrustedOrigins: cfg.TrustedOrigins, HSTS: !cfg.InsecureCookies}
	if db != nil {
		deps.DB = db
		authn.Sessions = db
		go sweepSessions(ctx, db, log)
	}

	switch {
	case !cfg.LoginEnabled():
		log.Warn("no TM_PLATFORM_OIDC_ISSUER: sign-in is not mounted")
	case db == nil:
		// A login writes rows. Mounting it without a database would answer every attempt with a 503
		// from deep inside the flow instead of saying so once, here.
		return errors.New("sign-in is configured but TM_PLATFORM_DSN is not: a login needs the database")
	default:
		lg, err := login.New(login.Config{
			Provider:            cfg.OIDCProvider,
			Issuer:              cfg.OIDCIssuer,
			ClientID:            cfg.OIDCClientID,
			ClientSecret:        cfg.OIDCClientSecret,
			RedirectURL:         cfg.OIDCRedirectURL,
			AfterLogin:          cfg.AfterLogin,
			SessionIdleTTL:      cfg.SessionIdleTTL,
			SessionMaxAge:       cfg.SessionMaxAge,
			SignupGrantMicroUSD: cfg.SignupGrantMicroUSD,
		}, db, cookies, log)
		if err != nil {
			return err
		}
		lg.SetFail(httpapi.WriteProblem)
		deps.Login = lg
		go sweepLogins(ctx, db, log)
	}

	handler, err := httpapi.New(deps)
	if err != nil {
		return err
	}

	// A second signal must kill rather than wait: once the drain starts, the handler is
	// unregistered and the next SIGTERM goes back to being fatal.
	go func() {
		<-ctx.Done()
		stop()
	}()

	srv := httpapi.NewServer(cfg.Addr, handler, log)
	ln, err := srv.Listen(ctx)
	if err != nil {
		return err
	}
	log.Info("listening", "addr", ln.Addr().String())
	return srv.Run(ctx, ln)
}

// sweepSessions deletes rows past their absolute expiry (PD-7). A failed sweep is logged and
// retried on the next tick: it is housekeeping, and it must never take the service down.
func sweepSessions(ctx context.Context, db *pgstore.Store, log *slog.Logger) {
	t := time.NewTicker(sessionSweep)
	defer t.Stop()
	for {
		select {
		case <-ctx.Done():
			return
		case <-t.C:
			c, cancel := context.WithTimeout(ctx, 30*time.Second)
			n, err := db.SweepSessions(c, time.Now())
			cancel()
			switch {
			case err != nil:
				log.Error("session sweep failed", "err", err)
			case n > 0:
				log.Info("session sweep", "deleted", n)
			}
		}
	}
}

// loginJournalRetention is how long a sign-in stays in the journal. Long enough to answer "was
// that me last month", short enough that an unauthenticated endpoint cannot grow the table without
// end.
const loginJournalRetention = 180 * 24 * time.Hour

// sweepLogins deletes abandoned authorization requests and journal entries past retention.
func sweepLogins(ctx context.Context, db *pgstore.Store, log *slog.Logger) {
	t := time.NewTicker(15 * time.Minute)
	defer t.Stop()
	for {
		select {
		case <-ctx.Done():
			return
		case <-t.C:
			c, cancel := context.WithTimeout(ctx, time.Minute)
			states, err := db.DeleteExpiredLoginStates(c, time.Now())
			if err != nil {
				log.Error("login state sweep failed", "err", err)
			}
			events, err := db.DeleteOldLoginEvents(c, time.Now().Add(-loginJournalRetention))
			cancel()
			if err != nil {
				log.Error("login journal sweep failed", "err", err)
			}
			if states > 0 || events > 0 {
				log.Info("login sweep", "states", states, "events", events)
			}
		}
	}
}