package main

import (
	"context"
	"crypto/rand"
	"encoding/base64"
	"encoding/json"
	"errors"
	"hash/fnv"
	"log"
	"math"
	"net/http"
	"os"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/coreos/go-oidc/v3/oidc"
	"github.com/gorilla/websocket"
	"github.com/jackc/pgx/v5/pgxpool"
)

const (
	worldSize          = 3600.0
	spawnX             = 1200.0
	spawnY             = 1550.0
	playerMaxHull      = 100
	playerMaxSpeed     = 180.0
	playerReverseSpeed = -55.0
	playerAcceleration = 92.0
	playerBrake        = 118.0
	playerTurnRate     = 76.0
	playerCoastDrag    = 0.992
	broadsideReload    = 850 * time.Millisecond
	shotSpeed          = 520.0
	shotLifetime       = 900 * time.Millisecond
	shotDamage         = 16
	shipHitRadius      = 44.0
	respawnDelay       = 2200 * time.Millisecond
	simTick            = time.Second / 30
	snapshotTick       = 50 * time.Millisecond
)

type config struct {
	Port           string
	DatabaseURL    string
	Issuer         string
	ClientID       string
	AllowedOrigins map[string]bool
	WorldSeed      string
}

type claims struct {
	Subject           string      `json:"sub"`
	PreferredUsername string      `json:"preferred_username"`
	Name              string      `json:"name"`
	AuthorizedParty   string      `json:"azp"`
	Audience          interface{} `json:"aud"`
}

type contextKey string

const claimsKey contextKey = "claims"

type ticket struct {
	Subject string
	Name    string
	Expires time.Time
}

type ticketStore struct {
	mu    sync.Mutex
	items map[string]ticket
}

func newTicketStore() *ticketStore { return &ticketStore{items: map[string]ticket{}} }

func (s *ticketStore) issue(subject, name string) (string, error) {
	buf := make([]byte, 24)
	if _, err := rand.Read(buf); err != nil {
		return "", err
	}
	value := base64.RawURLEncoding.EncodeToString(buf)
	s.mu.Lock()
	s.items[value] = ticket{Subject: subject, Name: name, Expires: time.Now().Add(30 * time.Second)}
	s.mu.Unlock()
	return value, nil
}

func (s *ticketStore) consume(value string) (ticket, bool) {
	s.mu.Lock()
	defer s.mu.Unlock()
	item, ok := s.items[value]
	delete(s.items, value)
	if !ok || time.Now().After(item.Expires) {
		return ticket{}, false
	}
	return item, true
}

func (s *ticketStore) prune() {
	s.mu.Lock()
	defer s.mu.Unlock()
	now := time.Now()
	for key, item := range s.items {
		if now.After(item.Expires) {
			delete(s.items, key)
		}
	}
}

type playerState struct {
	ID         string  `json:"id"`
	Name       string  `json:"name"`
	X          float64 `json:"x"`
	Y          float64 `json:"y"`
	Angle      float64 `json:"angle"`
	Speed      float64 `json:"speed"`
	Hull       int     `json:"hull"`
	MaxHull    int     `json:"maxHull"`
	Alive      bool    `json:"alive"`
	Online     bool    `json:"online"`
	Kills      int     `json:"kills"`
	Deaths     int     `json:"deaths"`
	InputSeq   int64   `json:"inputSeq"`
	RespawnAt  int64   `json:"respawnAt,omitempty"`
	LastKiller string  `json:"lastKiller,omitempty"`
}

type inputState struct {
	Throttle float64
	Steer    float64
	Stop     bool
	Docked   bool
	Seq      int64
}

type projectileState struct {
	ID      string  `json:"id"`
	OwnerID string  `json:"ownerId"`
	X       float64 `json:"x"`
	Y       float64 `json:"y"`
	VX      float64 `json:"vx"`
	VY      float64 `json:"vy"`
	Damage  int     `json:"damage"`
	bornAt  time.Time
}

type clientMessage struct {
	Type     string  `json:"type"`
	Seq      int64   `json:"seq"`
	Throttle float64 `json:"throttle"`
	Steer    float64 `json:"steer"`
	Stop     bool    `json:"stop"`
	Docked   bool    `json:"docked"`
	Side     string  `json:"side"`
}

type serverMessage struct {
	Type        string            `json:"type"`
	PlayerID    string            `json:"playerId,omitempty"`
	WorldSeed   string            `json:"worldSeed,omitempty"`
	Players     []playerState     `json:"players,omitempty"`
	Projectiles []projectileState `json:"projectiles,omitempty"`
	ServerTime  int64             `json:"serverTime,omitempty"`
}

type client struct {
	conn     *websocket.Conn
	writeMu  sync.Mutex
	state    playerState
	input    inputState
	lastFire map[string]time.Time
}

func (c *client) writeJSON(v any) error {
	c.writeMu.Lock()
	defer c.writeMu.Unlock()
	_ = c.conn.SetWriteDeadline(time.Now().Add(2 * time.Second))
	return c.conn.WriteJSON(v)
}

type hub struct {
	mu             sync.RWMutex
	clients        map[string]*client
	projectiles    map[string]projectileState
	nextProjectile uint64
	worldSeed      string
}

func newHub(seed string) *hub {
	return &hub{
		clients:     map[string]*client{},
		projectiles: map[string]projectileState{},
		worldSeed:   seed,
	}
}

func newPlayerState(id, name string, kills, deaths int) playerState {
	x, y := spawnFor(id)
	return playerState{
		ID: id, Name: name, X: x, Y: y, Angle: 0, Speed: 0,
		Hull: playerMaxHull, MaxHull: playerMaxHull, Alive: true, Online: true,
		Kills: kills, Deaths: deaths,
	}
}

func spawnFor(id string) (float64, float64) {
	h := fnv.New32a()
	_, _ = h.Write([]byte(id))
	v := h.Sum32()
	dx := float64(int(v%241) - 120)
	dy := float64(int((v/241)%181) - 90)
	return clampFloat(spawnX+dx, 90, worldSize-90), clampFloat(spawnY+dy, 90, worldSize-90)
}

func (h *hub) add(c *client) {
	h.mu.Lock()
	if previous := h.clients[c.state.ID]; previous != nil && previous != c {
		_ = previous.conn.Close()
	}
	h.clients[c.state.ID] = c
	h.mu.Unlock()
}

func (h *hub) remove(id string, c *client) {
	h.mu.Lock()
	if h.clients[id] == c {
		delete(h.clients, id)
	}
	h.mu.Unlock()
}

func (h *hub) count() int {
	h.mu.RLock()
	defer h.mu.RUnlock()
	return len(h.clients)
}

func (h *hub) updateInput(id string, msg clientMessage) {
	h.mu.Lock()
	defer h.mu.Unlock()
	c := h.clients[id]
	if c == nil || msg.Seq <= c.input.Seq {
		return
	}
	c.input = inputState{
		Throttle: clampFloat(msg.Throttle, -1, 1),
		Steer:    clampFloat(msg.Steer, -1, 1),
		Stop:     msg.Stop,
		Docked:   msg.Docked,
		Seq:      msg.Seq,
	}
}

func (h *hub) fire(id, side string, now time.Time) bool {
	h.mu.Lock()
	defer h.mu.Unlock()
	c := h.clients[id]
	if c == nil || !c.state.Alive || (side != "port" && side != "starboard") {
		return false
	}
	if c.lastFire == nil {
		c.lastFire = map[string]time.Time{}
	}
	if last := c.lastFire[side]; !last.IsZero() && now.Sub(last) < broadsideReload {
		return false
	}
	c.lastFire[side] = now

	sideSign := 1.0
	if side == "port" {
		sideSign = -1
	}
	base := headingRadians(c.state.Angle) + sideSign*math.Pi/2
	shipVX := math.Cos(headingRadians(c.state.Angle)) * c.state.Speed
	shipVY := math.Sin(headingRadians(c.state.Angle)) * c.state.Speed

	for _, offset := range []float64{-7, 0, 7} {
		angle := base + offset*math.Pi/180
		h.nextProjectile++
		projectileID := id + ":" + strconv.FormatUint(h.nextProjectile, 10)
		h.projectiles[projectileID] = projectileState{
			ID: projectileID, OwnerID: id,
			X:      c.state.X + math.Cos(base)*34,
			Y:      c.state.Y + math.Sin(base)*34,
			VX:     math.Cos(angle)*shotSpeed + shipVX*0.25,
			VY:     math.Sin(angle)*shotSpeed + shipVY*0.25,
			Damage: shotDamage,
			bornAt: now,
		}
	}
	return true
}

func (h *hub) step(now time.Time, dt float64) {
	h.mu.Lock()
	defer h.mu.Unlock()

	for _, c := range h.clients {
		stepPlayer(&c.state, c.input, now, dt)
	}

	for id, shot := range h.projectiles {
		if now.Sub(shot.bornAt) >= shotLifetime {
			delete(h.projectiles, id)
			continue
		}
		shot.X += shot.VX * dt
		shot.Y += shot.VY * dt
		if shot.X < -80 || shot.X > worldSize+80 || shot.Y < -80 || shot.Y > worldSize+80 {
			delete(h.projectiles, id)
			continue
		}

		hit := false
		for _, target := range h.clients {
			if target.state.ID == shot.OwnerID || !target.state.Alive {
				continue
			}
			dx := target.state.X - shot.X
			dy := target.state.Y - shot.Y
			if dx*dx+dy*dy > shipHitRadius*shipHitRadius {
				continue
			}
			target.state.Hull = clampInt(target.state.Hull-shot.Damage, 0, target.state.MaxHull)
			if target.state.Hull <= 0 {
				target.state.Alive = false
				target.state.Speed = 0
				target.state.Deaths++
				target.state.RespawnAt = now.Add(respawnDelay).UnixMilli()
				if owner := h.clients[shot.OwnerID]; owner != nil {
					owner.state.Kills++
					target.state.LastKiller = owner.state.Name
				}
			}
			delete(h.projectiles, id)
			hit = true
			break
		}
		if hit {
			continue
		}
		h.projectiles[id] = shot
	}
}

func stepPlayer(state *playerState, input inputState, now time.Time, dt float64) {
	state.InputSeq = input.Seq
	if !state.Alive {
		if state.RespawnAt > 0 && now.UnixMilli() >= state.RespawnAt {
			x, y := spawnFor(state.ID)
			state.X = x
			state.Y = y
			state.Angle = 0
			state.Speed = 0
			state.Hull = state.MaxHull
			state.Alive = true
			state.RespawnAt = 0
			state.LastKiller = ""
		}
		return
	}
	if input.Docked {
		state.Speed = 0
		return
	}

	if input.Throttle > 0 {
		state.Speed += playerAcceleration * input.Throttle * dt
	} else if input.Throttle < 0 {
		state.Speed += playerBrake * input.Throttle * dt
	} else if !input.Stop {
		state.Speed *= math.Pow(playerCoastDrag, dt*60)
	}
	if input.Stop {
		state.Speed *= math.Pow(0.025, dt)
	}
	state.Speed = clampFloat(state.Speed, playerReverseSpeed, playerMaxSpeed)

	turnStrength := clampFloat(math.Abs(state.Speed)/100, 0.28, 1)
	directionSign := 1.0
	if state.Speed < 0 {
		directionSign = -1
	}
	state.Angle = normalizeAngle(state.Angle + playerTurnRate*turnStrength*directionSign*input.Steer*dt)

	heading := headingRadians(state.Angle)
	state.X = clampFloat(state.X+math.Cos(heading)*state.Speed*dt, 0, worldSize)
	state.Y = clampFloat(state.Y+math.Sin(heading)*state.Speed*dt, 0, worldSize)
}

func headingRadians(angle float64) float64 { return (angle - 90) * math.Pi / 180 }

func (h *hub) snapshot() ([]*client, []playerState, []projectileState) {
	h.mu.RLock()
	defer h.mu.RUnlock()
	clients := make([]*client, 0, len(h.clients))
	players := make([]playerState, 0, len(h.clients))
	projectiles := make([]projectileState, 0, len(h.projectiles))
	for _, c := range h.clients {
		clients = append(clients, c)
		players = append(players, c.state)
	}
	for _, shot := range h.projectiles {
		projectiles = append(projectiles, shot)
	}
	return clients, players, projectiles
}

func (h *hub) run(ctx context.Context) {
	simTicker := time.NewTicker(simTick)
	snapshotTicker := time.NewTicker(snapshotTick)
	defer simTicker.Stop()
	defer snapshotTicker.Stop()
	lastSim := time.Now()

	for {
		select {
		case <-ctx.Done():
			return
		case now := <-simTicker.C:
			dt := now.Sub(lastSim).Seconds()
			if dt <= 0 || dt > 0.1 {
				dt = simTick.Seconds()
			}
			lastSim = now
			h.step(now, dt)
		case now := <-snapshotTicker.C:
			clients, players, projectiles := h.snapshot()
			msg := serverMessage{
				Type: "snapshot", Players: players, Projectiles: projectiles,
				ServerTime: now.UnixMilli(),
			}
			for _, c := range clients {
				if err := c.writeJSON(msg); err != nil {
					_ = c.conn.Close()
				}
			}
		}
	}
}

func clampFloat(v, min, max float64) float64 {
	if math.IsNaN(v) || math.IsInf(v, 0) {
		return min
	}
	if v < min {
		return min
	}
	if v > max {
		return max
	}
	return v
}

func clampInt(v, min, max int) int {
	if v < min {
		return min
	}
	if v > max {
		return max
	}
	return v
}

func normalizeAngle(v float64) float64 {
	if math.IsNaN(v) || math.IsInf(v, 0) {
		return 0
	}
	v = math.Mod(v, 360)
	if v < 0 {
		v += 360
	}
	return v
}

func loadConfig() (config, error) {
	origins := map[string]bool{}
	for _, origin := range strings.Split(env("ALLOWED_ORIGINS", "https://airship.arrowstack.dev"), ",") {
		origin = strings.TrimSpace(origin)
		if origin != "" {
			origins[origin] = true
		}
	}
	cfg := config{
		Port: env("PORT", "8080"), DatabaseURL: os.Getenv("DATABASE_URL"),
		Issuer: os.Getenv("KEYCLOAK_ISSUER"), ClientID: os.Getenv("KEYCLOAK_CLIENT_ID"),
		AllowedOrigins: origins, WorldSeed: env("WORLD_SEED", "SKYWARD-001"),
	}
	if cfg.DatabaseURL == "" || cfg.Issuer == "" || cfg.ClientID == "" {
		return cfg, errors.New("DATABASE_URL, KEYCLOAK_ISSUER and KEYCLOAK_CLIENT_ID are required")
	}
	return cfg, nil
}

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

func migrate(ctx context.Context, db *pgxpool.Pool) error {
	_, err := db.Exec(ctx, `
		CREATE TABLE IF NOT EXISTS player_profiles (
			keycloak_sub TEXT PRIMARY KEY,
			display_name TEXT NOT NULL,
			credits INTEGER NOT NULL DEFAULT 650,
			scrap INTEGER NOT NULL DEFAULT 0,
			progression JSONB NOT NULL DEFAULT '{}'::jsonb,
			pvp_kills INTEGER NOT NULL DEFAULT 0,
			pvp_deaths INTEGER NOT NULL DEFAULT 0,
			created_at TIMESTAMPTZ NOT NULL DEFAULT now(),
			updated_at TIMESTAMPTZ NOT NULL DEFAULT now(),
			last_seen_at TIMESTAMPTZ NOT NULL DEFAULT now()
		);
		ALTER TABLE player_profiles ADD COLUMN IF NOT EXISTS pvp_kills INTEGER NOT NULL DEFAULT 0;
		ALTER TABLE player_profiles ADD COLUMN IF NOT EXISTS pvp_deaths INTEGER NOT NULL DEFAULT 0
	`)
	return err
}

func ensurePlayer(ctx context.Context, db *pgxpool.Pool, sub, name string) error {
	_, err := db.Exec(ctx, `
		INSERT INTO player_profiles (keycloak_sub, display_name)
		VALUES ($1, $2)
		ON CONFLICT (keycloak_sub) DO UPDATE SET
			display_name = EXCLUDED.display_name,
			updated_at = now(),
			last_seen_at = now()
	`, sub, name)
	return err
}

func loadPvPStats(ctx context.Context, db *pgxpool.Pool, sub string) (int, int, error) {
	var kills, deaths int
	err := db.QueryRow(ctx, `SELECT pvp_kills, pvp_deaths FROM player_profiles WHERE keycloak_sub = $1`, sub).Scan(&kills, &deaths)
	return kills, deaths, err
}

func savePvPStats(ctx context.Context, db *pgxpool.Pool, state playerState) error {
	_, err := db.Exec(ctx, `
		UPDATE player_profiles SET
			pvp_kills = $2,
			pvp_deaths = $3,
			updated_at = now(),
			last_seen_at = now()
		WHERE keycloak_sub = $1
	`, state.ID, state.Kills, state.Deaths)
	return err
}

type app struct {
	cfg      config
	db       *pgxpool.Pool
	verifier *oidc.IDTokenVerifier
	tickets  *ticketStore
	hub      *hub
	upgrader websocket.Upgrader
}

func (a *app) authenticate(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		auth := r.Header.Get("Authorization")
		if !strings.HasPrefix(auth, "Bearer ") {
			http.Error(w, "unauthorized", http.StatusUnauthorized)
			return
		}
		raw := strings.TrimSpace(strings.TrimPrefix(auth, "Bearer "))
		token, err := a.verifier.Verify(r.Context(), raw)
		if err != nil {
			http.Error(w, "invalid token", http.StatusUnauthorized)
			return
		}
		var c claims
		if err := token.Claims(&c); err != nil || c.Subject == "" {
			http.Error(w, "invalid claims", http.StatusUnauthorized)
			return
		}
		if !audienceMatches(c, a.cfg.ClientID) {
			http.Error(w, "wrong client", http.StatusForbidden)
			return
		}
		if c.PreferredUsername == "" {
			c.PreferredUsername = c.Name
		}
		if c.PreferredUsername == "" {
			c.PreferredUsername = "Captain"
		}
		if err := ensurePlayer(r.Context(), a.db, c.Subject, c.PreferredUsername); err != nil {
			http.Error(w, "database unavailable", http.StatusServiceUnavailable)
			return
		}
		next.ServeHTTP(w, r.WithContext(context.WithValue(r.Context(), claimsKey, c)))
	})
}

func audienceMatches(c claims, clientID string) bool {
	if c.AuthorizedParty == clientID {
		return true
	}
	switch aud := c.Audience.(type) {
	case string:
		return aud == clientID
	case []interface{}:
		for _, item := range aud {
			if s, ok := item.(string); ok && s == clientID {
				return true
			}
		}
	}
	return false
}

func (a *app) cors(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		origin := r.Header.Get("Origin")
		if origin != "" && a.cfg.AllowedOrigins[origin] {
			w.Header().Set("Access-Control-Allow-Origin", origin)
			w.Header().Set("Vary", "Origin")
			w.Header().Set("Access-Control-Allow-Headers", "Authorization, Content-Type")
			w.Header().Set("Access-Control-Allow-Methods", "GET, POST, OPTIONS")
		}
		if r.Method == http.MethodOptions {
			w.WriteHeader(http.StatusNoContent)
			return
		}
		next.ServeHTTP(w, r)
	})
}

func jsonResponse(w http.ResponseWriter, status int, value any) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(value)
}

func (a *app) health(w http.ResponseWriter, r *http.Request) {
	ctx, cancel := context.WithTimeout(r.Context(), time.Second)
	defer cancel()
	if err := a.db.Ping(ctx); err != nil {
		jsonResponse(w, 503, map[string]any{"ok": false, "database": false})
		return
	}
	jsonResponse(w, 200, map[string]any{
		"ok": true, "database": true, "players": a.hub.count(),
		"worldSeed": a.cfg.WorldSeed, "authority": "movement+pvp",
	})
}

func (a *app) me(w http.ResponseWriter, r *http.Request) {
	c := r.Context().Value(claimsKey).(claims)
	jsonResponse(w, 200, map[string]any{"id": c.Subject, "name": c.PreferredUsername, "worldSeed": a.cfg.WorldSeed})
}

func (a *app) wsTicket(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}
	c := r.Context().Value(claimsKey).(claims)
	value, err := a.tickets.issue(c.Subject, c.PreferredUsername)
	if err != nil {
		http.Error(w, "ticket unavailable", http.StatusInternalServerError)
		return
	}
	jsonResponse(w, 201, map[string]any{"ticket": value, "expiresIn": 30})
}

func (a *app) ws(w http.ResponseWriter, r *http.Request) {
	value := r.URL.Query().Get("ticket")
	t, ok := a.tickets.consume(value)
	if !ok {
		http.Error(w, "invalid websocket ticket", http.StatusUnauthorized)
		return
	}
	conn, err := a.upgrader.Upgrade(w, r, nil)
	if err != nil {
		return
	}

	kills, deaths, err := loadPvPStats(r.Context(), a.db, t.Subject)
	if err != nil {
		kills, deaths = 0, 0
	}
	c := &client{
		conn:     conn,
		state:    newPlayerState(t.Subject, t.Name, kills, deaths),
		lastFire: map[string]time.Time{},
	}
	a.hub.add(c)
	defer func() {
		a.hub.remove(t.Subject, c)
		_ = conn.Close()
		ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
		defer cancel()
		_ = ensurePlayer(ctx, a.db, t.Subject, t.Name)
		_ = savePvPStats(ctx, a.db, c.state)
	}()

	_ = c.writeJSON(serverMessage{
		Type: "welcome", PlayerID: t.Subject, WorldSeed: a.cfg.WorldSeed,
		ServerTime: time.Now().UnixMilli(),
	})
	conn.SetReadLimit(4096)
	for {
		_ = conn.SetReadDeadline(time.Now().Add(45 * time.Second))
		var msg clientMessage
		if err := conn.ReadJSON(&msg); err != nil {
			return
		}
		switch msg.Type {
		case "input":
			a.hub.updateInput(t.Subject, msg)
		case "fire":
			a.hub.fire(t.Subject, strings.ToLower(msg.Side), time.Now())
		}
	}
}

func main() {
	cfg, err := loadConfig()
	if err != nil {
		log.Fatal(err)
	}
	ctx := context.Background()
	db, err := pgxpool.New(ctx, cfg.DatabaseURL)
	if err != nil {
		log.Fatal(err)
	}
	defer db.Close()
	if err := db.Ping(ctx); err != nil {
		log.Fatalf("database ping: %v", err)
	}
	if err := migrate(ctx, db); err != nil {
		log.Fatalf("migration: %v", err)
	}
	provider, err := oidc.NewProvider(ctx, cfg.Issuer)
	if err != nil {
		log.Fatalf("oidc provider: %v", err)
	}
	verifier := provider.Verifier(&oidc.Config{SkipClientIDCheck: true})
	application := &app{
		cfg: cfg, db: db, verifier: verifier,
		tickets: newTicketStore(), hub: newHub(cfg.WorldSeed),
	}
	application.upgrader = websocket.Upgrader{CheckOrigin: func(r *http.Request) bool {
		origin := r.Header.Get("Origin")
		return origin == "" || cfg.AllowedOrigins[origin]
	}}
	go application.hub.run(ctx)
	go func() {
		ticker := time.NewTicker(15 * time.Second)
		defer ticker.Stop()
		for range ticker.C {
			application.tickets.prune()
		}
	}()

	mux := http.NewServeMux()
	mux.HandleFunc("/health", application.health)
	mux.Handle("/api/me", application.cors(application.authenticate(http.HandlerFunc(application.me))))
	mux.Handle("/api/ws-ticket", application.cors(application.authenticate(http.HandlerFunc(application.wsTicket))))
	mux.HandleFunc("/ws", application.ws)
	server := &http.Server{
		Addr: ":" + cfg.Port, Handler: mux,
		ReadHeaderTimeout: 5 * time.Second, IdleTimeout: 60 * time.Second,
	}
	log.Printf("airship game server listening on :%s world=%s authority=movement+pvp", cfg.Port, cfg.WorldSeed)
	log.Fatal(server.ListenAndServe())
}