package main

import (
	"context"
	"database/sql"
	"flag"
	"fmt"
	"net/http"
	"os"
	"os/signal"
	"strconv"
	"syscall"
	"time"

	"github.com/cosmic-clash/cosmic-clash/server/api"
	"github.com/cosmic-clash/cosmic-clash/server/domain"
	"github.com/cosmic-clash/cosmic-clash/server/migrations"
	"github.com/cosmic-clash/cosmic-clash/server/observability"
	"github.com/cosmic-clash/cosmic-clash/server/steam"
	"github.com/cosmic-clash/cosmic-clash/server/store"
	_ "github.com/jackc/pgx/v5/stdlib"
	"github.com/redis/go-redis/v9"
)

func main() {
	listen := flag.String("listen", ":8080", "HTTP listen address")
	role := flag.String("role", "api", "control-plane role; currently api")
	dsn := flag.String("dsn", os.Getenv("COSMIC_CLASH_POSTGRES_DSN"), "PostgreSQL connection string")
	migrationDir := flag.String("migrations", "migrations", "directory containing numbered SQL migrations")
	redisAddr := flag.String("redis-addr", os.Getenv("COSMIC_CLASH_REDIS_ADDR"), "optional Redis address for the candidate projection")
	redisPrefix := flag.String("redis-prefix", envOrDefault("COSMIC_CLASH_REDIS_PREFIX", "cosmic-clash"), "Redis key prefix")
	redisTTL := flag.Duration("redis-ttl", 60*time.Second, "TTL for transient candidate projection entries")
	workloadSecret := flag.String("workload-secret", os.Getenv("COSMIC_CLASH_WORKLOAD_SECRET"), "HMAC secret for control-plane-issued workload tokens (see workload/signed_token.go); server registration/result submission return 503 until this is set")
	degraded := flag.Bool("degraded", false, "start with new login, queue, and proposal mutations rejected; SIGUSR1 enables and SIGUSR2 disables this mode")
	rateLimit := flag.Int("rate-limit", 120, "maximum requests per per-credential/IP fixed window")
	rateWindow := flag.Duration("rate-limit-window", time.Minute, "fixed window for the per-replica request limiter")
	rateMaxKeys := flag.Int("rate-limit-max-keys", 10000, "maximum credential/IP keys retained by the per-replica request limiter")
	trustedProxyCIDRs := flag.String("trusted-proxy-cidrs", os.Getenv("COSMIC_CLASH_TRUSTED_PROXY_CIDRS"), "comma-separated immediate proxy CIDRs allowed to supply X-Forwarded-For")
	steamPublisherKey := flag.String("steam-publisher-key", os.Getenv("COSMIC_CLASH_STEAM_PUBLISHER_KEY"), "Steamworks publisher Web API key. Required for player sign-in; POST /v1/session/steam returns 503 until it and --steam-app-id are set. Never expose this to clients")
	steamAppID := flag.Uint64("steam-app-id", 0, "Steamworks App ID this build authenticates tickets for; may also be set via COSMIC_CLASH_STEAM_APP_ID")
	steamRejectBanned := flag.Bool("steam-reject-banned", true, "refuse sign-in for VAC- or publisher-banned accounts")
	minProtocolVersion := flag.Int("min-protocol-version", 0, "reject queue_create below this protocol_version with 426 Upgrade Required instead of queueing a client the matcher can never pair with anyone; zero disables the floor")
	flag.Parse()
	if *role != "api" {
		fatalf("unsupported role %q (only api is implemented)", *role)
	}
	if *dsn == "" {
		fatalf("--dsn or COSMIC_CLASH_POSTGRES_DSN is required")
	}
	if *redisTTL <= 0 {
		fatalf("--redis-ttl must be positive")
	}
	if *minProtocolVersion < 0 {
		fatalf("--min-protocol-version must be non-negative")
	}
	rateLimiter, err := api.NewRateLimiter(*rateLimit, *rateWindow, *rateMaxKeys)
	if err != nil {
		fatalf("invalid request limiter configuration: %v", err)
	}
	clientIPs, err := api.NewClientIPResolver(*trustedProxyCIDRs)
	if err != nil {
		fatalf("invalid trusted proxy configuration: %v", err)
	}
	db, err := sql.Open("pgx", *dsn)
	if err != nil {
		fatalf("open PostgreSQL: %v", err)
	}
	defer db.Close()
	startupCtx, startupCancel := context.WithTimeout(context.Background(), 30*time.Second)
	defer startupCancel()
	if err := db.PingContext(startupCtx); err != nil {
		fatalf("ping PostgreSQL: %v", err)
	}
	if err := migrations.Apply(startupCtx, db, *migrationDir); err != nil {
		fatalf("apply migrations: %v", err)
	}
	var candidateIndex api.CandidateIndex
	var redisClient *redis.Client
	if *redisAddr != "" {
		redisClient = redis.NewClient(&redis.Options{Addr: *redisAddr})
		defer redisClient.Close()
		candidateIndex = store.RedisCandidateIndex{Client: redisClient, Prefix: *redisPrefix, TTL: *redisTTL}
	}
	if *workloadSecret == "" {
		fmt.Fprintln(os.Stderr, "control-plane: warning: --workload-secret / COSMIC_CLASH_WORKLOAD_SECRET is unset; server registration and result submission will return 503")
	}
	if *steamAppID == 0 {
		if value := os.Getenv("COSMIC_CLASH_STEAM_APP_ID"); value != "" {
			parsed, parseErr := strconv.ParseUint(value, 10, 64)
			if parseErr != nil {
				fatalf("COSMIC_CLASH_STEAM_APP_ID must be a positive integer")
			}
			*steamAppID = parsed
		}
	}
	service := newAPIService(db, *workloadSecret, candidateIndex)
	// Tier thresholds live in the database so they can be retuned with a
	// rolling restart rather than a rebuilt image. A malformed durable policy
	// stops startup instead of silently mis-tiering every player; an empty
	// table is a supported state and falls back to the compiled launch policy.
	tierPolicy, err := store.LoadTierPolicy(startupCtx, db)
	if err != nil {
		fatalf("load tier policy: %v", err)
	}
	service.TierPolicy = tierPolicy
	// Player sign-in is configuration-gated rather than always-on: without a
	// publisher key there is no safe way to verify a ticket, and silently
	// accepting one would be worse than refusing to authenticate at all. The
	// endpoint keeps returning 503 until both values are supplied.
	if *steamPublisherKey != "" && *steamAppID != 0 {
		service.SteamLogin = api.SteamLogin{
			DB: db,
			Verifier: steam.WebAPIVerifier{
				PublisherKey: *steamPublisherKey,
				AppID:        *steamAppID,
				RejectBanned: *steamRejectBanned,
			},
		}
	} else {
		fmt.Fprintln(os.Stderr, "control-plane: warning: --steam-publisher-key and --steam-app-id are unset; player sign-in will return 503")
	}
	service.RateLimiter = rateLimiter
	service.ClientIPs = clientIPs
	service.MinProtocolVersion = *minProtocolVersion
	admission := api.NewAdmissionGate(*degraded)
	service.Admission = admission
	server := &http.Server{Addr: *listen, Handler: service.Handler(), ReadHeaderTimeout: 5 * time.Second}
	serveErr := make(chan error, 1)
	go func() { serveErr <- server.ListenAndServe() }()
	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
	defer stop()
	operatorSignals := make(chan os.Signal, 2)
	signal.Notify(operatorSignals, syscall.SIGUSR1, syscall.SIGUSR2)
	defer signal.Stop(operatorSignals)
	go func() {
		for sig := range operatorSignals {
			switch sig {
			case syscall.SIGUSR1:
				admission.SetDegraded(true)
				fmt.Fprintln(os.Stderr, "control-plane: degraded admission enabled")
			case syscall.SIGUSR2:
				admission.SetDegraded(false)
				fmt.Fprintln(os.Stderr, "control-plane: degraded admission disabled")
			}
		}
	}()
	// Fan committed outbox events out to every replica. Subscribers live in
	// each process's in-memory hub, but any replica may drain a given outbox
	// row, so without this a client connected elsewhere never sees the event
	// and delivery degrades as replicas are added.
	service.EventFanout = func(event api.ControlPlaneEvent) error {
		payload, err := api.EncodeFannedOutEvent(event)
		if err != nil {
			return err
		}
		return store.NotifyControlPlaneEvent(ctx, db, payload)
	}
	go store.ListenControlPlaneEvents(ctx, *dsn, func(payload []byte) {
		event, err := api.DecodeFannedOutEvent(payload)
		if err != nil {
			return
		}
		// Publishing to a player with no local subscriber is a no-op, so every
		// replica can handle every notification.
		_ = service.PublishControlPlaneEvent(event)
	}, func(err error) {
		fmt.Fprintf(os.Stderr, "control-plane: event fan-out listener: %v\n", err)
	})
	go api.RunProposalOutboxDispatcher(ctx, db, service)
	go api.RunResultOutboxDispatcher(ctx, db, service)
	go api.RunStateOutboxDispatcher(ctx, db, service)
	select {
	case err := <-serveErr:
		if err != nil && err != http.ErrServerClosed {
			fatalf("serve API: %v", err)
		}
	case <-ctx.Done():
		shutdownCtx, shutdownCancel := context.WithTimeout(context.Background(), 10*time.Second)
		defer shutdownCancel()
		if err := server.Shutdown(shutdownCtx); err != nil {
			fatalf("shutdown API: %v", err)
		}
	}
}

func newAPIHandler(db *sql.DB, workloadSecret string, indexes ...api.CandidateIndex) http.Handler {
	return newAPIService(db, workloadSecret, indexes...).Handler()
}

func newAPIService(db *sql.DB, workloadSecret string, indexes ...api.CandidateIndex) *api.Service {
	var candidateIndex api.CandidateIndex
	if len(indexes) > 0 {
		candidateIndex = indexes[0]
	}
	return &api.Service{
		SessionBackend:        store.PostgresSessions{DB: db},
		SessionIssuer:         store.PostgresSessions{DB: db},
		QueueBackend:          store.PostgresQueue{DB: db},
		ProposalBackend:       api.ProposalProviderFromStore(db),
		ProposalPromoter:      api.ProposalPromoterFromStore(db),
		ServerRegistrar:       api.ServerRegistrarFromStore(db),
		ServerShutdowner:      api.ServerShutdownerFromStore(db),
		ServerConnections:     api.ServerConnectionsFromStore(db),
		ResultSubmitter:       store.PostgresResults{DB: db},
		RankedProfileProvider: store.PostgresRankedProfiles{DB: db},
		TierPolicy:            domain.DefaultTierPolicy(),
		Assignment:            api.AssignmentProviderFromStore(db),
		Roster: func(ctx context.Context, binding domain.WorkloadBinding, now time.Time) ([][]byte, error) {
			return store.GetAssignmentRoster(ctx, db, binding.MatchID, binding.ServerID, now)
		},
		CandidateIndex: candidateIndex,
		ProbeRecorder:  store.PostgresQueue{DB: db},
		// Regional latency placement. Without both of these the probe endpoint
		// is unreachable, queue_tickets.predicted_rtt stays empty, and
		// domain.validCandidate rejects every client-created ticket -- so the
		// matcher can never form a match from real traffic.
		ProbeChallenger: func(ctx context.Context, playerID, region string, now time.Time) ([]byte, error) {
			return store.IssueProbeChallenge(ctx, db, playerID, region, now)
		},
		Probe: func(ctx context.Context, playerID, region string, opaqueLocation, nonce []byte, receivedAt time.Time) (domain.ProbeEvidence, []byte, error) {
			return store.ProbeEvidenceFromChallenge(ctx, db, playerID, region, opaqueLocation, nonce, receivedAt)
		},
		// Repairs the transient index after a probe changes the durable RTT;
		// the candidate inserted at enqueue time has an empty map.
		CandidateRefresh: func(ctx context.Context, playerID string, now time.Time) (domain.Candidate, bool, error) {
			return store.FindQueuedCandidateByPlayer(ctx, db, playerID, now)
		},
		WorkloadVerify: api.WorkloadVerifierFromSignedToken([]byte(workloadSecret), db),
		ReadinessCheck: db.PingContext,
		Now:            func() time.Time { return time.Now().UTC() },
		Log:            logEvent,
		Metrics:        observability.NewMetrics(),
	}
}

// logEvent writes one credential-safe structured event per line to stderr.
// Best-effort: a logging failure must never fail or block the request it
// describes, so encode errors are swallowed rather than surfaced.
func logEvent(event observability.Event) {
	payload, err := observability.Encode(event)
	if err != nil {
		return
	}
	fmt.Fprintln(os.Stderr, string(payload))
}

func envOrDefault(name, fallback string) string {
	if value := os.Getenv(name); value != "" {
		return value
	}
	return fallback
}

func fatalf(format string, args ...any) {
	fmt.Fprintf(os.Stderr, "control-plane: "+format+"\n", args...)
	os.Exit(1)
}