package bossraid

import (
	"context"
	"crypto/rand"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"log"
	"time"

	"github.com/redis/go-redis/v9"
	"github.com/tolelom/tolchain/core"
)

const (
	// defaultMaxPlayers is the maximum number of players allowed in a boss raid room.
	defaultMaxPlayers = 3
	// entryTokenTTL is the TTL for boss raid entry tokens in Redis.
	entryTokenTTL = 5 * time.Minute
	// entryTokenPrefix is the Redis key prefix for entry token → {username, sessionName}.
	entryTokenPrefix = "bossraid:entry:"
	// pendingEntryPrefix is the Redis key prefix for username → {sessionName, entryToken}.
	pendingEntryPrefix = "bossraid:pending:"
)

// entryTokenData is stored in Redis for each entry token.
type entryTokenData struct {
	Username    string `json:"username"`
	SessionName string `json:"sessionName"`
}

type Service struct {
	repo        *Repository
	rdb         *redis.Client
	rewardGrant func(username string, tokenAmount uint64, assets []core.MintAssetPayload) (txID string, err error)
	expGrant    func(username string, exp int) error
}

func NewService(repo *Repository, rdb *redis.Client) *Service {
	return &Service{repo: repo, rdb: rdb}
}

// SetRewardGranter sets the callback for granting rewards via blockchain.
// The callback returns the blockchain transaction ID and an error.
func (s *Service) SetRewardGranter(fn func(username string, tokenAmount uint64, assets []core.MintAssetPayload) (txID string, err error)) {
	s.rewardGrant = fn
}

// SetExpGranter sets the callback for granting experience to players.
func (s *Service) SetExpGranter(fn func(username string, exp int) error) {
	s.expGrant = fn
}

// RequestEntry creates a new boss room for a party.
// Allocates an idle room slot from a registered dedicated server.
// Returns the room with assigned session name.
func (s *Service) RequestEntry(usernames []string, bossID int) (*BossRoom, error) {
	// 좀비 슬롯 정리 — idle 슬롯 검색 전에 stale 인스턴스를 리셋
	s.CheckStaleSlots()

	if len(usernames) == 0 {
		return nil, fmt.Errorf("플레이어 목록이 비어있습니다")
	}
	if len(usernames) > 3 {
		return nil, fmt.Errorf("최대 3명까지 입장할 수 있습니다")
	}

	// 중복 플레이어 검증
	seen := make(map[string]bool, len(usernames))
	for _, u := range usernames {
		if seen[u] {
			return nil, fmt.Errorf("중복된 플레이어가 있습니다: %s", u)
		}
		seen[u] = true
	}

	playersJSON, err := json.Marshal(usernames)
	if err != nil {
		return nil, fmt.Errorf("플레이어 목록 직렬화 실패: %w", err)
	}

	var room *BossRoom

	// Wrap slot allocation + active-room check + creation in a transaction.
	err = s.repo.Transaction(func(txRepo *Repository) error {
		// Find an idle room slot from a live dedicated server instance
		staleThreshold := time.Now().Add(-30 * time.Second)
		slot, err := txRepo.FindIdleRoomSlot(staleThreshold)
		if err != nil {
			return fmt.Errorf("현재 이용 가능한 보스 레이드 방이 없습니다")
		}

		for _, username := range usernames {
			count, err := txRepo.CountActiveByUsername(username)
			if err != nil {
				return fmt.Errorf("플레이어 상태 확인 실패: %w", err)
			}
			if count > 0 {
				return fmt.Errorf("플레이어 %s가 이미 보스 레이드 중입니다", username)
			}
		}

		room = &BossRoom{
			SessionName: slot.SessionName,
			BossID:      bossID,
			Status:      StatusWaiting,
			MaxPlayers:  defaultMaxPlayers,
			Players:     string(playersJSON),
		}
		if err := txRepo.Create(room); err != nil {
			return fmt.Errorf("방 생성 실패: %w", err)
		}

		// Mark slot as waiting and link to the boss room
		slot.Status = SlotWaiting
		slot.BossRoomID = &room.ID
		if err := txRepo.UpdateRoomSlot(slot); err != nil {
			return fmt.Errorf("슬롯 상태 업데이트 실패: %w", err)
		}
		return nil
	})
	if err != nil {
		return nil, err
	}

	return room, nil
}

// StartRaid marks a room as in_progress and updates the slot status.
// Uses optimistic locking (WHERE status = 'waiting') to prevent concurrent state transitions.
func (s *Service) StartRaid(sessionName string) (*BossRoom, error) {
	now := time.Now()
	err := s.repo.TransitionRoomStatus(sessionName, StatusWaiting, StatusInProgress, map[string]interface{}{
		"started_at": now,
	})
	if err == ErrStatusConflict {
		return nil, fmt.Errorf("시작할 수 없는 상태입니다 (이미 변경됨)")
	}
	if err != nil {
		return nil, fmt.Errorf("상태 업데이트 실패: %w", err)
	}

	// Update slot status to in_progress (non-fatal if fails)
	s.repo.TransitionSlotStatus(sessionName, SlotWaiting, SlotInProgress)

	room, err := s.repo.FindBySessionName(sessionName)
	if err != nil {
		return nil, fmt.Errorf("방을 찾을 수 없습니다: %w", err)
	}
	return room, nil
}

// PlayerReward describes the reward for a single player.
type PlayerReward struct {
	Username    string                  `json:"username"`
	TokenAmount uint64                  `json:"tokenAmount"`
	Assets      []core.MintAssetPayload `json:"assets"`
	Experience  int                     `json:"experience"` // 경험치 보상
}

// RewardResult holds the result of granting a reward to one player.
type RewardResult struct {
	Username string `json:"username"`
	Success  bool   `json:"success"`
	Error    string `json:"error,omitempty"`
}

// CompleteRaid marks a room as completed and grants rewards via blockchain.
// Uses optimistic locking (WHERE status = 'in_progress') to prevent double-completion.
func (s *Service) CompleteRaid(sessionName string, rewards []PlayerReward) (*BossRoom, []RewardResult, error) {
	var resultRewards []RewardResult

	// Validate reward recipients are room players before transitioning
	room, err := s.repo.FindBySessionName(sessionName)
	if err != nil {
		return nil, nil, fmt.Errorf("방을 찾을 수 없습니다: %w", err)
	}

	var players []string
	if err := json.Unmarshal([]byte(room.Players), &players); err != nil {
		return nil, nil, fmt.Errorf("플레이어 목록 파싱 실패: %w", err)
	}
	playerSet := make(map[string]bool, len(players))
	for _, p := range players {
		playerSet[p] = true
	}
	for _, r := range rewards {
		if !playerSet[r.Username] {
			return nil, nil, fmt.Errorf("보상 대상 %s가 방의 플레이어가 아닙니다", r.Username)
		}
	}

	// Atomically transition status: in_progress → completed
	now := time.Now()
	err = s.repo.TransitionRoomStatus(sessionName, StatusInProgress, StatusCompleted, map[string]interface{}{
		"completed_at": now,
	})
	if err == ErrStatusConflict {
		return nil, nil, fmt.Errorf("완료할 수 없는 상태입니다 (이미 변경됨)")
	}
	if err != nil {
		return nil, nil, fmt.Errorf("상태 업데이트 실패: %w", err)
	}

	// Re-fetch the updated room
	resultRoom, err := s.repo.FindBySessionName(sessionName)
	if err != nil {
		return nil, nil, fmt.Errorf("방을 찾을 수 없습니다: %w", err)
	}

	// Grant rewards outside the transaction to avoid holding the lock during RPC calls.
	// Each reward is attempted up to 3 times with exponential backoff before being
	// recorded as a RewardFailure for background retry.
	resultRewards = make([]RewardResult, 0, len(rewards))
	hasRewardFailure := false
	if s.rewardGrant != nil {
		for _, r := range rewards {
			lastTxID, grantErr := s.grantWithRetry(r.Username, r.TokenAmount, r.Assets)
			result := RewardResult{Username: r.Username, Success: grantErr == nil}
			if grantErr != nil {
				result.Error = grantErr.Error()
				log.Printf("보상 지급 실패 (재시도 소진): %s: %v", r.Username, grantErr)
				hasRewardFailure = true
				// 실패한 보상을 DB에 기록하여 백그라운드 재시도 가능하게 함
				s.saveRewardFailure(sessionName, r, grantErr, lastTxID)
			}
			resultRewards = append(resultRewards, result)
		}
	}

	// Grant experience to players (with retry)
	if s.expGrant != nil {
		for _, r := range rewards {
			if r.Experience > 0 {
				expErr := s.grantExpWithRetry(r.Username, r.Experience)
				if expErr != nil {
					log.Printf("경험치 지급 실패 (재시도 소진): %s: %v", r.Username, expErr)
					hasRewardFailure = true
					// 경험치 실패도 RewardFailure에 기록 (토큰/에셋 없이 경험치만)
					s.saveRewardFailure(sessionName, PlayerReward{
						Username:   r.Username,
						Experience: r.Experience,
					}, expErr, "")
				}
			}
		}
	}

	// 보상 실패(블록체인 또는 경험치)가 있으면 상태를 reward_failed로 업데이트
	if hasRewardFailure {
		if err := s.repo.TransitionRoomStatus(sessionName, StatusCompleted, StatusRewardFailed, nil); err != nil {
			log.Printf("보상 실패 상태 업데이트 실패: %s: %v", sessionName, err)
		}
	}

	// BossRoom 삭제 후 슬롯 리셋 — 다음 파티가 즉시 슬롯 재사용 가능
	if err := s.repo.DeleteRoomBySessionName(sessionName); err != nil {
		log.Printf("BossRoom 삭제 실패 (complete): %s: %v", sessionName, err)
	}
	if err := s.repo.ResetRoomSlot(sessionName); err != nil {
		log.Printf("슬롯 리셋 실패 (complete): %s: %v", sessionName, err)
	}

	return resultRoom, resultRewards, nil
}

// FailRaid marks a room as failed and resets the slot.
// Uses optimistic locking (WHERE status IN ('waiting','in_progress')) to prevent concurrent state transitions.
func (s *Service) FailRaid(sessionName string) (*BossRoom, error) {
	now := time.Now()
	err := s.repo.TransitionRoomStatusMulti(sessionName,
		[]RoomStatus{StatusWaiting, StatusInProgress},
		StatusFailed,
		map[string]interface{}{"completed_at": now},
	)
	if err == ErrStatusConflict {
		return nil, fmt.Errorf("실패 처리할 수 없는 상태입니다 (이미 변경됨)")
	}
	if err != nil {
		return nil, fmt.Errorf("상태 업데이트 실패: %w", err)
	}

	// 응답용 room 조회 (삭제 전에 수행)
	room, err := s.repo.FindBySessionName(sessionName)
	if err != nil {
		return nil, fmt.Errorf("방을 찾을 수 없습니다: %w", err)
	}

	// BossRoom 삭제 후 슬롯 리셋 — 다음 파티가 즉시 슬롯 재사용 가능
	if err := s.repo.DeleteRoomBySessionName(sessionName); err != nil {
		log.Printf("BossRoom 삭제 실패 (fail): %s: %v", sessionName, err)
	}
	if err := s.repo.ResetRoomSlot(sessionName); err != nil {
		log.Printf("슬롯 리셋 실패 (fail): %s: %v", sessionName, err)
	}

	return room, nil
}

// GetRoom returns a room by session name.
func (s *Service) GetRoom(sessionName string) (*BossRoom, error) {
	return s.repo.FindBySessionName(sessionName)
}

// generateToken creates a cryptographically random hex token.
func generateToken() (string, error) {
	b := make([]byte, 32)
	if _, err := rand.Read(b); err != nil {
		return "", err
	}
	return hex.EncodeToString(b), nil
}

// GenerateEntryTokens creates entry tokens for all players in a room
// and stores them in Redis. Returns a map of username → entryToken.
func (s *Service) GenerateEntryTokens(sessionName string, usernames []string) (map[string]string, error) {
	ctx := context.Background()
	tokens := make(map[string]string, len(usernames))

	for _, username := range usernames {
		token, err := generateToken()
		if err != nil {
			return nil, fmt.Errorf("토큰 생성 실패: %w", err)
		}
		tokens[username] = token

		// Store entry token → {username, sessionName}
		data, _ := json.Marshal(entryTokenData{
			Username:    username,
			SessionName: sessionName,
		})
		entryKey := entryTokenPrefix + token
		if err := s.rdb.Set(ctx, entryKey, string(data), entryTokenTTL).Err(); err != nil {
			return nil, fmt.Errorf("Redis 저장 실패: %w", err)
		}

		// Store pending entry: username → {sessionName, entryToken}
		pendingData, _ := json.Marshal(map[string]string{
			"sessionName": sessionName,
			"entryToken":  token,
		})
		pendingKey := pendingEntryPrefix + username
		if err := s.rdb.Set(ctx, pendingKey, string(pendingData), entryTokenTTL).Err(); err != nil {
			return nil, fmt.Errorf("Redis 저장 실패: %w", err)
		}
	}

	return tokens, nil
}

// ValidateEntryToken validates and consumes a one-time entry token.
// Returns the username and sessionName if valid.
func (s *Service) ValidateEntryToken(token string) (username, sessionName string, err error) {
	ctx := context.Background()
	key := entryTokenPrefix + token

	val, err := s.rdb.GetDel(ctx, key).Result()
	if err == redis.Nil {
		return "", "", fmt.Errorf("유효하지 않거나 만료된 입장 토큰입니다")
	}
	if err != nil {
		return "", "", fmt.Errorf("토큰 검증 실패: %w", err)
	}

	var data entryTokenData
	if err := json.Unmarshal([]byte(val), &data); err != nil {
		return "", "", fmt.Errorf("토큰 데이터 파싱 실패: %w", err)
	}

	return data.Username, data.SessionName, nil
}

// GetMyEntryToken returns the pending entry token for a username.
func (s *Service) GetMyEntryToken(username string) (sessionName, entryToken string, err error) {
	ctx := context.Background()
	key := pendingEntryPrefix + username

	val, err := s.rdb.Get(ctx, key).Result()
	if err == redis.Nil {
		return "", "", fmt.Errorf("대기 중인 입장 토큰이 없습니다")
	}
	if err != nil {
		return "", "", fmt.Errorf("토큰 조회 실패: %w", err)
	}

	var data map[string]string
	if err := json.Unmarshal([]byte(val), &data); err != nil {
		return "", "", fmt.Errorf("토큰 데이터 파싱 실패: %w", err)
	}

	return data["sessionName"], data["entryToken"], nil
}

// RequestEntryWithTokens creates a boss room and generates entry tokens for all players.
// Returns the room and a map of username → entryToken.
func (s *Service) RequestEntryWithTokens(usernames []string, bossID int) (*BossRoom, map[string]string, error) {
	room, err := s.RequestEntry(usernames, bossID)
	if err != nil {
		return nil, nil, err
	}

	tokens, err := s.GenerateEntryTokens(room.SessionName, usernames)
	if err != nil {
		return nil, nil, fmt.Errorf("입장 토큰 생성 실패: %w", err)
	}

	return room, tokens, nil
}

// --- Dedicated Server Management ---

const staleTimeout = 30 * time.Second

// RegisterServer registers a dedicated server instance (container).
// Creates the server group + slots if needed, then assigns a slot to this instance.
// Returns the assigned sessionName.
func (s *Service) RegisterServer(serverName, instanceID string, maxRooms int) (string, error) {
	if serverName == "" || instanceID == "" {
		return "", fmt.Errorf("serverName과 instanceId는 필수입니다")
	}
	if maxRooms <= 0 {
		maxRooms = 10
	}

	// Ensure server group exists
	server := &DedicatedServer{
		ServerName: serverName,
		MaxRooms:   maxRooms,
	}
	if err := s.repo.UpsertDedicatedServer(server); err != nil {
		return "", fmt.Errorf("서버 그룹 등록 실패: %w", err)
	}

	// Re-fetch to get the ID
	server, err := s.repo.FindDedicatedServerByName(serverName)
	if err != nil {
		return "", fmt.Errorf("서버 조회 실패: %w", err)
	}

	// Ensure all room slots exist
	if err := s.repo.EnsureRoomSlots(server.ID, serverName, maxRooms); err != nil {
		return "", fmt.Errorf("슬롯 생성 실패: %w", err)
	}

	// Assign a slot to this instance
	staleThreshold := time.Now().Add(-staleTimeout)
	slot, err := s.repo.AssignSlotToInstance(server.ID, instanceID, staleThreshold)
	if err != nil {
		return "", fmt.Errorf("슬롯 배정 실패: %w", err)
	}

	return slot.SessionName, nil
}

// Heartbeat updates the heartbeat for a container instance.
func (s *Service) Heartbeat(instanceID string) error {
	return s.repo.UpdateHeartbeat(instanceID)
}

// CheckStaleSlots resets slots whose instances have gone silent.
func (s *Service) CheckStaleSlots() {
	threshold := time.Now().Add(-staleTimeout)
	count, err := s.repo.ResetStaleSlots(threshold)
	if err != nil {
		log.Printf("스태일 슬롯 체크 실패: %v", err)
		return
	}
	if count > 0 {
		log.Printf("스태일 슬롯 %d개 리셋", count)
	}
}

// ResetRoom resets a room slot back to idle and cleans up any lingering BossRoom records.
// Called by the dedicated server after a raid ends and the runner is recycled.
func (s *Service) ResetRoom(sessionName string) error {
	// 완료/실패되지 않은 BossRoom 레코드 정리 (waiting/in_progress 상태)
	if err := s.repo.DeleteRoomBySessionName(sessionName); err != nil {
		log.Printf("BossRoom 레코드 정리 실패: %s: %v", sessionName, err)
	}
	return s.repo.ResetRoomSlot(sessionName)
}

// GetServerStatus returns a server group and its room slots.
func (s *Service) GetServerStatus(serverName string) (*DedicatedServer, []RoomSlot, error) {
	server, err := s.repo.FindDedicatedServerByName(serverName)
	if err != nil {
		return nil, nil, fmt.Errorf("서버를 찾을 수 없습니다: %w", err)
	}
	slots, err := s.repo.GetRoomSlotsByServer(server.ID)
	if err != nil {
		return nil, nil, fmt.Errorf("슬롯 조회 실패: %w", err)
	}
	return server, slots, nil
}

// --- Reward retry helpers ---

const immediateRetries = 3

// grantWithRetry attempts the reward grant up to 3 times with backoff (1s, 2s).
// Returns the last attempted transaction ID (may be empty) and the error.
func (s *Service) grantWithRetry(username string, tokenAmount uint64, assets []core.MintAssetPayload) (string, error) {
	delays := []time.Duration{1 * time.Second, 2 * time.Second}
	var lastErr error
	var lastTxID string
	for attempt := 0; attempt < immediateRetries; attempt++ {
		txID, err := s.rewardGrant(username, tokenAmount, assets)
		if txID != "" {
			lastTxID = txID
		}
		if err == nil {
			return txID, nil
		}
		lastErr = err
		if attempt < len(delays) {
			log.Printf("보상 지급 재시도 (%d/%d): %s: %v", attempt+1, immediateRetries, username, lastErr)
			time.Sleep(delays[attempt])
		}
	}
	return lastTxID, lastErr
}

// grantExpWithRetry attempts the experience grant up to 3 times with backoff (1s, 2s).
func (s *Service) grantExpWithRetry(username string, exp int) error {
	delays := []time.Duration{1 * time.Second, 2 * time.Second}
	var lastErr error
	for attempt := 0; attempt < immediateRetries; attempt++ {
		lastErr = s.expGrant(username, exp)
		if lastErr == nil {
			return nil
		}
		if attempt < len(delays) {
			log.Printf("경험치 지급 재시도 (%d/%d): %s: %v", attempt+1, immediateRetries, username, lastErr)
			time.Sleep(delays[attempt])
		}
	}
	return lastErr
}

// saveRewardFailure records a failed reward in the DB for background retry.
func (s *Service) saveRewardFailure(sessionName string, r PlayerReward, grantErr error, lastTxID string) {
	assets := "[]"
	if len(r.Assets) > 0 {
		if data, err := json.Marshal(r.Assets); err == nil {
			assets = string(data)
		}
	}
	rf := &RewardFailure{
		SessionName: sessionName,
		Username:    r.Username,
		TokenAmount: r.TokenAmount,
		Assets:      assets,
		Experience:  r.Experience,
		Error:       grantErr.Error(),
		LastTxID:    lastTxID,
	}
	if err := s.repo.SaveRewardFailure(rf); err != nil {
		log.Printf("보상 실패 기록 저장 실패: %s/%s: %v", sessionName, r.Username, err)
	}
}