package snake

import (
	"context"
	"crypto/rand"
	"encoding/hex"
	"sync"

	"github.com/ryanhamamura/c4/db/repository"
)

type SnakeStore struct {
	games      map[string]*SnakeGameInstance
	gamesMu    sync.RWMutex
	queries    *repository.Queries
	notifyFunc func(gameID string)
}

func NewSnakeStore(queries *repository.Queries) *SnakeStore {
	return &SnakeStore{
		games:   make(map[string]*SnakeGameInstance),
		queries: queries,
	}
}

func (ss *SnakeStore) SetNotifyFunc(f func(gameID string)) {
	ss.notifyFunc = f
}

func (ss *SnakeStore) makeNotify(gameID string) func() {
	return func() {
		if ss.notifyFunc != nil {
			ss.notifyFunc(gameID)
		}
	}
}

func (ss *SnakeStore) Create(width, height int, mode GameMode, speed int) *SnakeGameInstance {
	if speed <= 0 {
		speed = DefaultSpeed
	}
	id := generateID(4)
	sg := &SnakeGame{
		ID: id,
		State: &GameState{
			Width:  width,
			Height: height,
		},
		Players: make([]*Player, 8),
		Status:  StatusWaitingForPlayers,
		Mode:    mode,
		Speed:   speed,
	}
	si := &SnakeGameInstance{
		game:    sg,
		notify:  ss.makeNotify(id),
		queries: ss.queries,
		store:   ss,
	}

	ss.gamesMu.Lock()
	ss.games[id] = si
	ss.gamesMu.Unlock()

	if ss.queries != nil {
		ss.saveSnakeGame(sg) //nolint:errcheck
	}

	return si
}

func (ss *SnakeStore) Get(id string) (*SnakeGameInstance, bool) {
	ss.gamesMu.RLock()
	si, ok := ss.games[id]
	ss.gamesMu.RUnlock()

	if ok {
		return si, true
	}

	if ss.queries == nil {
		return nil, false
	}

	sg, err := ss.loadSnakeGame(id)
	if err != nil || sg == nil {
		return nil, false
	}

	players, _ := ss.loadSnakePlayers(id)
	if sg.Players == nil {
		sg.Players = make([]*Player, 8)
	}
	for _, p := range players {
		if p.Slot >= 0 && p.Slot < 8 {
			sg.Players[p.Slot] = p
		}
	}

	si = &SnakeGameInstance{
		game:    sg,
		notify:  ss.makeNotify(id),
		queries: ss.queries,
		store:   ss,
	}

	ss.gamesMu.Lock()
	ss.games[id] = si
	ss.gamesMu.Unlock()

	return si, true
}

func (ss *SnakeStore) Delete(id string) error {
	ss.gamesMu.Lock()
	si, ok := ss.games[id]
	delete(ss.games, id)
	ss.gamesMu.Unlock()

	if ok && si != nil {
		si.Stop()
	}

	if ss.queries != nil {
		return ss.queries.DeleteSnakeGame(context.Background(), id)
	}
	return nil
}

// ActiveGames returns metadata of multiplayer games that can be joined.
// Single player games are excluded. Copies game data to avoid holding nested locks.
func (ss *SnakeStore) ActiveGames() []*SnakeGame {
	ss.gamesMu.RLock()
	instances := make([]*SnakeGameInstance, 0, len(ss.games))
	for _, si := range ss.games {
		instances = append(instances, si)
	}
	ss.gamesMu.RUnlock()

	var games []*SnakeGame
	for _, si := range instances {
		si.gameMu.RLock()
		g := si.game
		if g.Mode == ModeMultiplayer && (g.Status == StatusWaitingForPlayers || g.Status == StatusCountdown) {
			games = append(games, g)
		}
		si.gameMu.RUnlock()
	}
	return games
}

type SnakeGameInstance struct {
	game            *SnakeGame
	gameMu          sync.RWMutex
	pendingDirQueue [8][]Direction // queued directions per slot (max 3)
	notify          func()
	queries         *repository.Queries
	store           *SnakeStore
	stopCh          chan struct{}
	loopOnce        sync.Once
}

func (si *SnakeGameInstance) ID() string {
	si.gameMu.RLock()
	defer si.gameMu.RUnlock()
	return si.game.ID
}

// GetGame returns a snapshot of the game state safe for concurrent read.
func (si *SnakeGameInstance) GetGame() *SnakeGame {
	si.gameMu.RLock()
	defer si.gameMu.RUnlock()
	return si.game.snapshot()
}

func (si *SnakeGameInstance) GetPlayerSlot(pid PlayerID) int {
	si.gameMu.RLock()
	defer si.gameMu.RUnlock()
	for i, p := range si.game.Players {
		if p != nil && p.ID == pid {
			return i
		}
	}
	return -1
}

func (si *SnakeGameInstance) Join(player *Player) bool {
	si.gameMu.Lock()
	defer si.gameMu.Unlock()

	if si.game.Status == StatusInProgress || si.game.Status == StatusFinished {
		return false
	}

	slot := -1
	for i, p := range si.game.Players {
		if p == nil {
			slot = i
			break
		}
	}
	if slot == -1 {
		return false
	}

	player.Slot = slot
	si.game.Players[slot] = player

	if si.queries != nil {
		si.saveSnakePlayer(si.game.ID, player) //nolint:errcheck
		si.saveSnakeGame(si.game)              //nolint:errcheck
	}

	si.notify()

	// Single player starts countdown immediately when 1 player joins
	if si.game.Mode == ModeSinglePlayer && si.game.PlayerCount() >= 1 {
		si.startOrResetCountdownLocked()
	} else if si.game.Mode == ModeMultiplayer && si.game.PlayerCount() >= 2 {
		si.startOrResetCountdownLocked()
	}

	return true
}

// SetDirection queues a direction change for the given slot.
// Validates against the last queued direction (or current snake dir) to prevent 180° turns.
func (si *SnakeGameInstance) SetDirection(slot int, dir Direction) {
	if slot < 0 || slot >= 8 {
		return
	}
	si.gameMu.Lock()
	defer si.gameMu.Unlock()

	if si.game.State == nil || slot >= len(si.game.State.Snakes) {
		return
	}
	s := si.game.State.Snakes[slot]
	if s == nil || !s.Alive {
		return
	}

	// Validate against last queued direction, or current snake direction if queue empty
	refDir := s.Dir
	if len(si.pendingDirQueue[slot]) > 0 {
		refDir = si.pendingDirQueue[slot][len(si.pendingDirQueue[slot])-1]
	}
	if !ValidateDirection(refDir, dir) {
		return
	}

	// Cap queue at 3 to prevent unbounded growth
	if len(si.pendingDirQueue[slot]) >= 3 {
		return
	}
	si.pendingDirQueue[slot] = append(si.pendingDirQueue[slot], dir)
}

func (si *SnakeGameInstance) Stop() {
	if si.stopCh != nil {
		select {
		case <-si.stopCh:
		default:
			close(si.stopCh)
		}
	}
}

func (si *SnakeGameInstance) CreateRematch() *SnakeGameInstance {
	si.gameMu.Lock()

	if !si.game.IsFinished() || si.game.RematchGameID != nil {
		si.gameMu.Unlock()
		return nil
	}

	// Capture state needed, then release lock before calling store.Create
	// (which acquires gamesMu) to avoid lock ordering deadlock.
	width := si.game.State.Width
	height := si.game.State.Height
	mode := si.game.Mode
	speed := si.game.Speed
	si.gameMu.Unlock()

	newSI := si.store.Create(width, height, mode, speed)
	newID := newSI.ID()

	si.gameMu.Lock()
	// Re-check after reacquiring lock
	if si.game.RematchGameID != nil {
		si.gameMu.Unlock()
		return newSI
	}
	si.game.RematchGameID = &newID

	if si.queries != nil {
		si.saveSnakeGame(si.game) //nolint:errcheck
	}
	si.gameMu.Unlock()

	si.notify()
	return newSI
}

func generateID(size int) string {
	b := make([]byte, size)
	_, _ = rand.Read(b)
	return hex.EncodeToString(b)
}