package leaderboard

import (
	"context"
	"encoding/json"
	"strconv"
	"strings"
	"time"

	domain "knowfoolery/backend/services/leaderboard-service/internal/domain/leaderboard"
	sharedsecurity "knowfoolery/backend/shared/infra/security"
)

// StateStore defines cache operations used by leaderboard service.
type StateStore interface {
	Get(ctx context.Context, key string) (string, bool)
	Set(ctx context.Context, key, value string, ttl time.Duration) error
	Delete(ctx context.Context, keys ...string) error
}

// Config controls leaderboard behavior.
type Config struct {
	TopLimit             int
	PlayerHistoryDefault int
	PlayerHistoryMax     int
	CacheTTL             time.Duration
	UpdateRequireAuth    bool
}

// Service orchestrates leaderboard use-cases.
type Service struct {
	repo  domain.Repository
	state StateStore
	cfg   Config
}

// NewService creates a leaderboard service.
func NewService(repo domain.Repository, state StateStore, cfg Config) *Service {
	if cfg.TopLimit <= 0 {
		cfg.TopLimit = 10
	}
	if cfg.PlayerHistoryDefault <= 0 {
		cfg.PlayerHistoryDefault = 20
	}
	if cfg.PlayerHistoryMax <= 0 {
		cfg.PlayerHistoryMax = 100
	}
	if cfg.CacheTTL <= 0 {
		cfg.CacheTTL = 60 * time.Second
	}
	return &Service{repo: repo, state: state, cfg: cfg}
}

// UpdateScore ingests a final session result.
func (s *Service) UpdateScore(ctx context.Context, in UpdateScoreInput) (*domain.LeaderboardEntry, error) {
	entry, err := s.validateUpdateInput(in)
	if err != nil {
		return nil, err
	}

	ingested, _, err := s.repo.IngestEntry(ctx, entry)
	if err != nil {
		return nil, err
	}

	_ = s.state.Delete(
		ctx,
		"lb:top10:v1",
		"lb:stats:global:v1",
		"lb:rank:"+ingested.PlayerID,
	)
	return ingested, nil
}

// GetTop10 returns top leaderboard entries.
func (s *Service) GetTop10(ctx context.Context, in GetTopInput) (*Top10Result, error) {
	filter := domain.TopFilter{
		CompletionType: strings.TrimSpace(in.CompletionType),
		Window:         normalizeWindow(in.Window),
	}
	cacheKey := "lb:top10:v1:" + filter.CompletionType + ":" + string(filter.Window)
	if payload, ok := s.state.Get(ctx, cacheKey); ok {
		var result Top10Result
		if err := json.Unmarshal([]byte(payload), &result); err == nil {
			return &result, nil
		}
	}

	items, err := s.repo.ListTop(ctx, filter, s.cfg.TopLimit)
	if err != nil {
		return nil, err
	}
	result := &Top10Result{Items: make([]RankedEntry, 0, len(items))}
	for i, item := range items {
		result.Items = append(result.Items, RankedEntry{
			Rank:  i + 1,
			Entry: *item,
		})
	}

	if payload, err := json.Marshal(result); err == nil {
		_ = s.state.Set(ctx, cacheKey, string(payload), s.cfg.CacheTTL)
	}
	return result, nil
}

// GetPlayerRanking returns player rank, stats, and paginated history.
func (s *Service) GetPlayerRanking(ctx context.Context, in GetPlayerRankingInput) (*PlayerRankingResult, error) {
	playerID := strings.TrimSpace(in.PlayerID)
	if playerID == "" {
		return nil, domain.ErrInvalidInput
	}
	p := in.Pagination
	if p.Page <= 0 {
		p.Page = 1
	}
	if p.PageSize <= 0 {
		p.PageSize = s.cfg.PlayerHistoryDefault
	}
	if p.PageSize > s.cfg.PlayerHistoryMax {
		p.PageSize = s.cfg.PlayerHistoryMax
	}

	player, err := s.repo.GetPlayerStats(ctx, playerID)
	if err != nil {
		return nil, err
	}

	var rank int64
	rankKey := "lb:rank:" + playerID
	if cached, ok := s.state.Get(ctx, rankKey); ok {
		if parsed, parseErr := strconv.ParseInt(cached, 10, 64); parseErr == nil {
			rank = parsed
		}
	}
	if rank == 0 {
		rank, err = s.repo.GetPlayerRank(ctx, playerID)
		if err != nil {
			return nil, err
		}
		_ = s.state.Set(ctx, rankKey, strconv.FormatInt(rank, 10), s.cfg.CacheTTL)
	}

	historyItems, total, err := s.repo.ListPlayerHistory(ctx, playerID, p)
	if err != nil {
		return nil, err
	}
	history := make([]domain.LeaderboardEntry, 0, len(historyItems))
	for _, item := range historyItems {
		history = append(history, *item)
	}

	return &PlayerRankingResult{
		Player:     *player,
		Rank:       rank,
		History:    history,
		Pagination: p,
		Total:      total,
	}, nil
}

// GetGlobalStats returns aggregate leaderboard statistics.
func (s *Service) GetGlobalStats(ctx context.Context, in GetStatsInput) (*domain.GlobalStats, error) {
	filter := domain.TopFilter{
		CompletionType: strings.TrimSpace(in.CompletionType),
		Window:         normalizeWindow(in.Window),
	}
	cacheKey := "lb:stats:global:v1:" + filter.CompletionType + ":" + string(filter.Window)
	if payload, ok := s.state.Get(ctx, cacheKey); ok {
		var result domain.GlobalStats
		if err := json.Unmarshal([]byte(payload), &result); err == nil {
			return &result, nil
		}
	}

	stats, err := s.repo.GetGlobalStats(ctx, filter)
	if err != nil {
		return nil, err
	}
	if payload, err := json.Marshal(stats); err == nil {
		_ = s.state.Set(ctx, cacheKey, string(payload), s.cfg.CacheTTL)
	}
	return stats, nil
}

func (s *Service) validateUpdateInput(in UpdateScoreInput) (*domain.LeaderboardEntry, error) {
	sessionID := strings.TrimSpace(in.SessionID)
	playerID := strings.TrimSpace(in.PlayerID)
	if sessionID == "" || playerID == "" {
		return nil, domain.ErrInvalidInput
	}
	if in.TotalScore < 0 || in.QuestionsAsked < 0 || in.QuestionsCorrect < 0 || in.DurationSeconds < 0 {
		return nil, domain.ErrInvalidInput
	}
	if in.QuestionsCorrect > in.QuestionsAsked {
		return nil, domain.ErrInvalidInput
	}
	completionType := strings.TrimSpace(in.CompletionType)
	if completionType == "" {
		return nil, domain.ErrInvalidInput
	}
	if completionType != string(domain.CompletionCompleted) &&
		completionType != string(domain.CompletionTimedOut) &&
		completionType != string(domain.CompletionAbandoned) {
		return nil, domain.ErrInvalidInput
	}

	completedAt := in.CompletedAt.UTC()
	if completedAt.IsZero() {
		completedAt = time.Now().UTC()
	}
	rate := 0.0
	if in.QuestionsAsked > 0 {
		rate = float64(in.QuestionsCorrect) * 100.0 / float64(in.QuestionsAsked)
	}
	playerName := sharedsecurity.SanitizePlayerName(in.PlayerName)
	if playerName == "" {
		playerName = "Player"
	}

	return &domain.LeaderboardEntry{
		SessionID:        sessionID,
		PlayerID:         playerID,
		PlayerName:       playerName,
		Score:            in.TotalScore,
		QuestionsAsked:   in.QuestionsAsked,
		QuestionsCorrect: in.QuestionsCorrect,
		HintsUsed:        in.HintsUsed,
		DurationSeconds:  in.DurationSeconds,
		SuccessRate:      rate,
		CompletionType:   domain.CompletionType(completionType),
		CompletedAt:      completedAt,
	}, nil
}

func normalizeWindow(w domain.Window) domain.Window {
	switch w {
	case domain.Window24h, domain.Window7d, domain.Window30d, domain.WindowAll:
		return w
	default:
		return domain.WindowAll
	}
}