// fleet-manager — server-side control plane for the diskless kiosk fleet.
//
// Two planes, mirroring the enrol-broker's two-listener pattern but with distinct
// trust anchors (see docs/tpm-enrolment-design.md §5 "identity"):
//
//   - ADMIN plane (this checkpoint): HTTPS + mTLS verified by the DEDICATED admin
//     CA (admin-pki.sh) — NOT the fleet CA — so an enrolled host cert can never
//     reach approve/deny/lifecycle. Serves the JSON API and (later) the SPA to
//     admin browsers.
//   - AGENT plane (checkpoint 2): gRPC + mTLS verified by the FLEET CA — the
//     host's reused TPM identity cert. Bidi stream: health/metrics up,
//     desired-state down.
//
// Checkpoint 1 wires only the admin plane + inventory + a seed host.
package main

import (
	"crypto/tls"
	"crypto/x509"
	"log"
	"net/http"
	"os"
	"strconv"
	"time"
)

type config struct {
	adminAddr     string
	adminInsecure bool
	adminCert     string
	adminKey      string
	adminClientCA string // dedicated admin CA (verifies admin browser certs)
	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", ""),
		adminClientCA: env("FLEET_MGR_ADMIN_CLIENT_CA", ""),
		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
}

func main() {
	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}

	mux := http.NewServeMux()
	s.routes(mux)

	srv := &http.Server{
		Addr:              cfg.adminAddr,
		Handler:           mux,
		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 client-cert auth) on %s — dev/lab only", cfg.adminAddr)
		log.Printf("fleet-manager admin (insecure) listening on %s", 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 (mTLS) listening on %s", cfg.adminAddr)
	log.Fatal(srv.ListenAndServeTLS("", "")) // certs are in TLSConfig
}

// adminTLS builds the mTLS server config: our server cert + REQUIRE a client cert
// signed by the dedicated admin CA. Reusing the fleet CA here would let any host
// cert authenticate to the admin plane — privilege escalation — so it is a hard
// error to omit the admin client CA in secure mode.
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)")
	}
	if cfg.adminClientCA == "" {
		return nil, errString("FLEET_MGR_ADMIN_CLIENT_CA is required — the dedicated admin CA that verifies admin browser certs (must NOT be the fleet CA)")
	}
	cert, err := tls.LoadX509KeyPair(cfg.adminCert, cfg.adminKey)
	if err != nil {
		return nil, err
	}
	caPEM, err := os.ReadFile(cfg.adminClientCA)
	if err != nil {
		return nil, err
	}
	pool := x509.NewCertPool()
	if !pool.AppendCertsFromPEM(caPEM) {
		return nil, errString("no certificates parsed from FLEET_MGR_ADMIN_CLIENT_CA")
	}
	return &tls.Config{
		MinVersion:   tls.VersionTLS12,
		Certificates: []tls.Certificate{cert},
		ClientAuth:   tls.RequireAndVerifyClientCert,
		ClientCAs:    pool,
	}, 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) }