// fleet-manager — server-side control plane for the diskless kiosk fleet.
//
// Two planes with DISTINCT trust models:
//
//   - ADMIN plane: HTTPS (server-auth TLS) + browser identity via WebAuthn/passkey
//     (YubiKey) → server-side session. Serves the JSON API + the SPA to admins.
//     (manager→broker is separately mTLS; that's service-to-service.)
//   - AGENT plane: gRPC + mTLS verified by the FLEET CA — the host's reused TPM
//     identity cert. Bidi stream: health/metrics up, desired-state down.
//
// A `register-admin` subcommand mints a one-time passkey-enrolment link.
package main

import (
	"crypto/tls"
	"fmt"
	"log"
	"net/http"
	"os"
	"strconv"
	"sync"
	"time"

	"github.com/go-webauthn/webauthn/webauthn"
)

type config struct {
	adminAddr     string
	adminInsecure bool
	adminCert     string
	adminKey      string

	agentAddr     string
	agentCert     string
	agentKey      string
	agentClientCA string // FLEET CA (verifies host TPM identity certs)

	// enrol-broker admin plane (the authorise pillar drives it over mTLS).
	brokerAdminURL   string
	brokerClientCert string
	brokerClientKey  string
	brokerCA         string

	// InfluxDB (the manager is the only reader/writer; token is server-side only).
	influx influxConfig

	// Admin browser auth = WebAuthn/passkey (replaces browser mTLS). Origin-bound.
	rpID          string
	rpOrigin      string
	rpDisplayName string
	enrollKeyFile string
	credStorePath string
	sessionTTL    time.Duration

	inventoryPath string
	seed          bool
	hostnqnBase   string
}

func loadConfig() config {
	return config{
		adminAddr:     env("FLEET_MGR_ADMIN_ADDR", "127.0.0.1:9500"),
		adminInsecure: env("FLEET_MGR_ADMIN_INSECURE", "") == "true",
		adminCert:     env("FLEET_MGR_ADMIN_CERT", ""),
		adminKey:      env("FLEET_MGR_ADMIN_KEY", ""),

		agentAddr:     env("FLEET_MGR_AGENT_ADDR", "127.0.0.1:9600"),
		agentCert:     env("FLEET_MGR_AGENT_CERT", ""),
		agentKey:      env("FLEET_MGR_AGENT_KEY", ""),
		agentClientCA: env("FLEET_MGR_AGENT_CLIENT_CA", ""),

		brokerAdminURL:   env("FLEET_MGR_BROKER_URL", ""),
		brokerClientCert: env("FLEET_MGR_BROKER_CLIENT_CERT", ""),
		brokerClientKey:  env("FLEET_MGR_BROKER_CLIENT_KEY", ""),
		brokerCA:         env("FLEET_MGR_BROKER_CA", ""),

		influx: influxConfig{
			url:    env("FLEET_MGR_INFLUX_URL", ""),
			token:  env("FLEET_MGR_INFLUX_TOKEN", ""),
			org:    env("FLEET_MGR_INFLUX_ORG", "fleet"),
			bucket: env("FLEET_MGR_INFLUX_BUCKET", "fleet_health"),
		},

		rpID:          env("FLEET_MGR_RP_ID", ""),
		rpOrigin:      env("FLEET_MGR_RP_ORIGIN", ""),
		rpDisplayName: env("FLEET_MGR_RP_NAME", "Fleet Command"),
		enrollKeyFile: env("FLEET_MGR_ENROLL_KEY_FILE", ""),
		credStorePath: env("FLEET_MGR_ADMIN_STORE", "/var/lib/fleet-manager/admins.json"),
		sessionTTL:    time.Duration(envInt("FLEET_MGR_SESSION_TTL_MIN", 720)) * time.Minute,

		inventoryPath: env("FLEET_MGR_INVENTORY", "/var/lib/fleet-manager/inventory.json"),
		seed:          env("FLEET_MGR_SEED", "") == "true",
		hostnqnBase:   env("HOSTNQN_BASE", "nqn.2026-06.org.example.fleet:host-"),
	}
}

// server bundles the shared dependencies the handlers close over.
type server struct {
	cfg    config
	store  Store
	hub    *agentHub     // live agent streams; nil if the agent plane isn't configured
	broker *brokerClient // enrol-broker admin client; nil if authorise isn't configured
	influx *influxSink   // metrics gateway; nil if InfluxDB isn't configured

	// Admin passkey auth (nil in insecure dev mode).
	wa         *webauthn.WebAuthn
	creds      *credStore
	sessions   *sessionStore
	ceremonies *ceremonyStore
	enrollKey  []byte
}

func main() {
	// Subcommand: `fleet-manager register-admin <name>` mints a passkey-enrolment
	// link (no server needed) — the bootstrap for the WebAuthn admin plane.
	if len(os.Args) > 1 && os.Args[1] == "register-admin" {
		os.Exit(runRegisterAdmin(os.Args[2:]))
	}

	log.SetFlags(log.LstdFlags | log.LUTC)
	cfg := loadConfig()

	store, err := newJSONStore(cfg.inventoryPath)
	if err != nil {
		log.Fatalf("inventory: %v", err)
	}
	if cfg.seed {
		if n := seedHosts(store, cfg.hostnqnBase); n > 0 {
			log.Printf("seeded %d demo host(s) (FLEET_MGR_SEED=true — dev only)", n)
		}
	}

	s := &server{cfg: cfg, store: store}

	// Authorise pillar: the enrol-broker admin client (nil = disabled, so the
	// manager runs standalone before a broker is wired).
	broker, err := newBrokerClient(cfg)
	if err != nil {
		log.Fatalf("broker client: %v", err)
	}
	s.broker = broker
	if broker == nil {
		log.Printf("authorise pillar DISABLED (set FLEET_MGR_BROKER_URL + client cert/key + CA to enable)")
	}

	// Metrics gateway: the manager is the only reader/writer of InfluxDB. nil (a
	// no-op MetricsSink) when unconfigured, so the manager runs without metrics.
	var sink MetricsSink
	if cfg.influx.url != "" && cfg.influx.token != "" {
		s.influx = newInfluxSink(cfg.influx)
		defer s.influx.Close()
		sink = s.influx
		log.Printf("InfluxDB metrics gateway -> %s (org=%s bucket=%s)", cfg.influx.url, cfg.influx.org, cfg.influx.bucket)
	} else {
		log.Printf("InfluxDB DISABLED (set FLEET_MGR_INFLUX_URL + _TOKEN to enable metrics)")
	}

	// Agent plane (gRPC/mTLS, fleet CA). Started only when configured; the admin
	// plane can run standalone (e.g. before any host is enrolled). The hub is the
	// live-stream registry the lifecycle API pushes desired-state through, and it
	// writes each snapshot to the metrics sink.
	if cfg.agentCert != "" && cfg.agentKey != "" && cfg.agentClientCA != "" {
		s.hub = newAgentHub(store, sink)
		go func() {
			if err := serveAgent(cfg, s.hub); err != nil {
				log.Fatalf("agent plane: %v", err)
			}
		}()
	} else {
		log.Printf("agent plane DISABLED (set FLEET_MGR_AGENT_CERT/_KEY/_CLIENT_CA to enable)")
	}

	// Admin browser auth = WebAuthn/passkey (secure mode only). Sets up the RP,
	// the credential store, the shared enrol key, sessions + ceremonies. The admin
	// TLS below is server-auth only — browser identity comes from the passkey.
	if !cfg.adminInsecure {
		wa, err := newWebAuthn(cfg)
		if err != nil {
			log.Fatalf("webauthn: %v", err)
		}
		creds, err := newCredStore(cfg.credStorePath)
		if err != nil {
			log.Fatalf("admin store: %v", err)
		}
		key, err := loadEnrollKey(cfg.enrollKeyFile)
		if err != nil {
			log.Fatalf("enrol key: %v", err)
		}
		s.wa, s.creds, s.enrollKey = wa, creds, key
		s.sessions = newSessionStore(cfg.sessionTTL)
		s.ceremonies = newCeremonyStore()
		if creds.count() == 0 {
			log.Printf("NOTE: no admins enrolled yet — run `fleet-manager register-admin <name>` and open the link to add a passkey")
		}
	}

	// HTTP handler: public liveness + WebAuthn ceremonies at the root; the admin
	// API under /api/ gated by the passkey session (requireSession). The SPA (ckpt
	// 6) will be served at / from an embedded FS.
	root := http.NewServeMux()
	s.authRoutes(root)
	apiMux := http.NewServeMux()
	s.apiRoutes(apiMux)
	root.Handle("/api/", s.requireSession(apiMux))
	// SPA at the root (catch-all; the more specific /api, /auth, /healthz win).
	// Embedded only in `-tags embedspa` builds; a stub otherwise (see spa_*.go).
	root.Handle("/", s.spaHandler())

	srv := &http.Server{
		Addr:              cfg.adminAddr,
		Handler:           root,
		ReadHeaderTimeout: 5 * time.Second,
		ReadTimeout:       15 * time.Second,
		WriteTimeout:      30 * time.Second,
		IdleTimeout:       60 * time.Second,
	}

	if cfg.adminInsecure {
		log.Printf("WARNING: admin plane INSECURE (plaintext, NO passkey auth) on %s — dev/lab only", cfg.adminAddr)
		log.Fatal(srv.ListenAndServe())
	}

	tlsCfg, err := adminTLS(cfg)
	if err != nil {
		log.Fatalf("admin TLS: %v", err)
	}
	srv.TLSConfig = tlsCfg
	log.Printf("fleet-manager admin (HTTPS + passkey) listening on %s (rp=%s)", cfg.adminAddr, cfg.rpID)
	log.Fatal(srv.ListenAndServeTLS("", "")) // certs are in TLSConfig
}

// adminTLS builds the admin plane's SERVER-AUTH TLS. Browser identity is a passkey
// (WebAuthn), not a client cert, so there is no ClientCAs/ClientAuth here — just
// our server cert. (manager→broker mTLS is separate; see broker.go.)
//
// The cert is served via a hot-reloading GetCertificate so an out-of-band renewal
// is picked up WITHOUT a restart. The intended deployment is a publicly-trusted
// cert obtained by an external ACME client via Let's Encrypt DNS-01 (the UI is on
// the mgmt network, not internet-reachable, so HTTP-01/TLS-ALPN-01 can't validate;
// DNS-01 proves control via a TXT record and supports wildcards). The ACME client
// (lego/certbot + a DNS provider) writes cert+key to FLEET_MGR_ADMIN_CERT/_KEY on
// a shared volume; this reloader notices the mtime bump and swaps the cert live.
func adminTLS(cfg config) (*tls.Config, error) {
	if cfg.adminCert == "" || cfg.adminKey == "" {
		return nil, errString("FLEET_MGR_ADMIN_CERT and FLEET_MGR_ADMIN_KEY are required (or set FLEET_MGR_ADMIN_INSECURE=true for dev)")
	}
	rl := &certReloader{certFile: cfg.adminCert, keyFile: cfg.adminKey}
	if _, err := rl.GetCertificate(nil); err != nil { // fail fast on a bad/missing cert
		return nil, err
	}
	return &tls.Config{
		MinVersion:     tls.VersionTLS12,
		GetCertificate: rl.GetCertificate,
	}, nil
}

// certReloader serves the admin server cert, reloading from disk when the file's
// mtime advances (an ACME renewal), so Let's Encrypt DNS-01 rotations apply live.
type certReloader struct {
	certFile, keyFile string
	mu                sync.Mutex
	cached            *tls.Certificate
	mtime             time.Time
}

func (c *certReloader) GetCertificate(*tls.ClientHelloInfo) (*tls.Certificate, error) {
	c.mu.Lock()
	defer c.mu.Unlock()
	fi, statErr := os.Stat(c.certFile)
	if statErr == nil && (c.cached == nil || fi.ModTime().After(c.mtime)) {
		cert, err := tls.LoadX509KeyPair(c.certFile, c.keyFile)
		if err != nil {
			if c.cached != nil {
				return c.cached, nil // serve the last good cert through a transient mid-rotation error
			}
			return nil, err
		}
		c.cached, c.mtime = &cert, fi.ModTime()
	}
	if c.cached == nil {
		return nil, fmt.Errorf("admin cert unavailable: %v", statErr)
	}
	return c.cached, nil
}

// ---- tiny helpers ---------------------------------------------------------

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

func envInt(k string, def int) int {
	if v := os.Getenv(k); v != "" {
		if n, err := strconv.Atoi(v); err == nil {
			return n
		}
	}
	return def
}

type errString string

func (e errString) Error() string { return string(e) }