package processor

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"regexp"
	"strings"

	"github.com/google/uuid"

	"apskel-pos-be/internal/constants"
	"apskel-pos-be/internal/entities"
	"apskel-pos-be/internal/models"
	"apskel-pos-be/internal/repository"
)

// ErrEnakGameRejected wraps every reason an EnakGame request is refused: a field out
// of bounds, a slug in use, an archived game, a retired configuration. The message
// says which.
var ErrEnakGameRejected = errors.New("enakgame request refused")

const (
	enakGameDefaultSessionTTL = 600
	enakGameMaxSessionTTL     = 24 * 60 * 60
	enakGamePageLimit         = 20
	enakGameMaxPageLimit      = 100
)

var enakGameSlugPattern = regexp.MustCompile(`^[a-z0-9]+(-[a-z0-9]+)*$`)

func enakGameRejected(format string, args ...any) error {
	return fmt.Errorf("%w: %s", ErrEnakGameRejected, fmt.Sprintf(format, args...))
}

// EnakGameAdminProcessor manages an organization's EnakGame games and their reward
// configurations (docs/rfc-enakgame.md §5.1, §5.2, §11). Every change is written to
// audit_logs in the same transaction (§13).
type EnakGameAdminProcessor struct {
	games repository.EnakGameRepository
	audit *AuditLogger
	tx    TxRunner
}

func NewEnakGameAdminProcessor(games repository.EnakGameRepository, audit *AuditLogger, tx TxRunner) *EnakGameAdminProcessor {
	return &EnakGameAdminProcessor{games: games, audit: audit, tx: tx}
}

func (p *EnakGameAdminProcessor) record(ctx context.Context, organizationID, actor uuid.UUID, entityType string, entityID uuid.UUID, action string, before, after any, reason *string) error {
	return p.audit.Record(ctx, AuditEntry{
		OrganizationID: organizationID,
		ActorType:      constants.AuditActorUser,
		ActorID:        &actor,
		EntityType:     entityType,
		EntityID:       entityID,
		Action:         action,
		Before:         before,
		After:          after,
		Reason:         reason,
		Source:         constants.AuditSourceAdminAPI,
	})
}

// EnakGameInputFrom is a game's current values as an input, for a change that only
// sends the fields it changes.
func EnakGameInputFrom(game *models.EnakGame) models.EnakGameInput {
	return models.EnakGameInput{
		Name: game.Name, Type: game.Type, Slug: game.Slug, Description: game.Description,
		ThumbnailURL: game.ThumbnailURL, GameURL: game.GameURL, Version: game.Version, Status: game.Status,
		EntryCost: game.EntryCost, SessionTTLSeconds: game.SessionTTLSeconds, ResultRules: game.ResultRules,
	}
}

func (p *EnakGameAdminProcessor) CreateGame(ctx context.Context, organizationID, actor uuid.UUID, in models.EnakGameInput) (*models.EnakGame, error) {
	if in.Type == "" {
		in.Type = string(entities.GameTypeMinigame)
	}
	if in.Status == "" {
		in.Status = constants.GameStatusDraft
	}
	if in.SessionTTLSeconds == 0 {
		in.SessionTTLSeconds = enakGameDefaultSessionTTL
	}
	if err := validateEnakGameInput(&in); err != nil {
		return nil, err
	}
	switch in.Status {
	case constants.GameStatusDraft, constants.GameStatusActive, constants.GameStatusInactive:
	default:
		return nil, enakGameRejected("a new game must be DRAFT, ACTIVE or INACTIVE")
	}

	game := &entities.Game{OrganizationID: &organizationID, Status: in.Status}
	applyEnakGameInput(game, in)
	err := p.tx.WithTransaction(ctx, func(ctx context.Context) error {
		if err := p.games.CreateGame(ctx, game); err != nil {
			return err
		}
		return p.record(ctx, organizationID, actor, constants.AuditEntityGame, game.ID, "CREATED", nil, enakGameModel(game), nil)
	})
	if err != nil {
		return nil, enakGameError(err)
	}
	return enakGameModel(game), nil
}

func (p *EnakGameAdminProcessor) GetGame(ctx context.Context, organizationID, id uuid.UUID) (*models.EnakGame, error) {
	game, err := p.games.GetGame(ctx, organizationID, id)
	if err != nil {
		return nil, err
	}
	return enakGameModel(game), nil
}

func (p *EnakGameAdminProcessor) ListGames(ctx context.Context, organizationID uuid.UUID, q models.EnakGameListQuery) (*models.PaginatedResponse[models.EnakGame], error) {
	page, limit := enakGamePage(q.Page, q.Limit)
	statuses := []string{constants.GameStatusDraft, constants.GameStatusActive, constants.GameStatusInactive}
	if q.Status != "" {
		status := strings.ToUpper(strings.TrimSpace(q.Status))
		if !isEnakGameStatus(status) {
			return nil, enakGameRejected("unknown status %q", q.Status)
		}
		statuses = []string{status}
	}
	games, total, err := p.games.ListGames(ctx, repository.EnakGameFilter{
		OrganizationID: organizationID, Statuses: statuses, Search: strings.TrimSpace(q.Search),
		Offset: (page - 1) * limit, Limit: limit,
	})
	if err != nil {
		return nil, err
	}
	items := make([]models.EnakGame, 0, len(games))
	for i := range games {
		items = append(items, *enakGameModel(&games[i]))
	}
	return &models.PaginatedResponse[models.EnakGame]{Data: items, Pagination: enakGamePagination(page, limit, total)}, nil
}

// UpdateGame changes everything but the status, which has its own endpoint. An
// archived game never changes.
func (p *EnakGameAdminProcessor) UpdateGame(ctx context.Context, organizationID, actor, id uuid.UUID, in models.EnakGameInput) (*models.EnakGame, error) {
	if err := validateEnakGameInput(&in); err != nil {
		return nil, err
	}
	var after *models.EnakGame
	err := p.tx.WithTransaction(ctx, func(ctx context.Context) error {
		game, err := p.games.LockGame(ctx, organizationID, id)
		if err != nil {
			return err
		}
		if game.Status == constants.GameStatusArchived {
			return enakGameRejected("an archived game cannot change")
		}
		before := enakGameModel(game)
		applyEnakGameInput(game, in)
		if err := p.games.UpdateGame(ctx, game); err != nil {
			return err
		}
		after = enakGameModel(game)
		return p.record(ctx, organizationID, actor, constants.AuditEntityGame, id, "UPDATED", before, after, nil)
	})
	if err != nil {
		return nil, enakGameError(err)
	}
	return p.GetGame(ctx, organizationID, after.ID)
}

// SetGameStatus moves a game between DRAFT, ACTIVE and INACTIVE, or archives it for
// good. Sessions still open on a game leaving ACTIVE are refunded by the session job
// (§7.3), not here.
func (p *EnakGameAdminProcessor) SetGameStatus(ctx context.Context, organizationID, actor, id uuid.UUID, in models.EnakGameStatusInput) (*models.EnakGame, error) {
	status := strings.ToUpper(strings.TrimSpace(in.Status))
	if !isEnakGameStatus(status) {
		return nil, enakGameRejected("status must be DRAFT, ACTIVE, INACTIVE or ARCHIVED")
	}
	if err := validateReason(in.Reason); err != nil {
		return nil, err
	}
	err := p.tx.WithTransaction(ctx, func(ctx context.Context) error {
		game, err := p.games.LockGame(ctx, organizationID, id)
		if err != nil {
			return err
		}
		if game.Status == status {
			return nil
		}
		if game.Status == constants.GameStatusArchived {
			return enakGameRejected("an archived game cannot change")
		}
		if err := p.games.SetGameStatus(ctx, organizationID, id, status); err != nil {
			return err
		}
		return p.record(ctx, organizationID, actor, constants.AuditEntityGame, id, "STATUS_CHANGED",
			map[string]string{"status": game.Status}, map[string]string{"status": status}, in.Reason)
	})
	if err != nil {
		return nil, enakGameError(err)
	}
	return p.GetGame(ctx, organizationID, id)
}

// CreateRewardConfig stores a new DRAFT version of a game's reward configuration. A
// configuration is never edited (D7): a change is a new version, activated on its
// own.
func (p *EnakGameAdminProcessor) CreateRewardConfig(ctx context.Context, organizationID, actor, gameID uuid.UUID, in models.GameRewardConfigInput) (*models.GameRewardConfig, error) {
	rewardType := strings.ToUpper(strings.TrimSpace(in.RewardType))
	calculator, err := RewardCalculatorFor(rewardType)
	if err != nil {
		return nil, enakGameRejected("%v", err)
	}
	if len(in.Rules) == 0 {
		return nil, enakGameRejected("rules are required")
	}
	if err := calculator.Validate(in.Rules); err != nil {
		return nil, enakGameRejected("%v", err)
	}
	if in.MaxReward < 0 {
		return nil, enakGameRejected("max_reward must be 0 or more")
	}
	if err := validateReason(in.Reason); err != nil {
		return nil, err
	}
	var rules bytes.Buffer
	if err := json.Compact(&rules, in.Rules); err != nil {
		return nil, enakGameRejected("rules: %v", err)
	}

	config := &entities.GameRewardConfig{
		OrganizationID: organizationID, GameID: gameID, RewardType: rewardType,
		Rules: entities.JSONDocument(rules.Bytes()), MaxReward: in.MaxReward,
		Status: constants.GameRewardConfigStatusDraft, EffectiveAt: in.EffectiveAt, CreatedBy: actor, Reason: in.Reason,
	}
	err = p.tx.WithTransaction(ctx, func(ctx context.Context) error {
		// The game lock also orders versions of the same game one after the other.
		game, err := p.games.LockGame(ctx, organizationID, gameID)
		if err != nil {
			return err
		}
		if game.Status == constants.GameStatusArchived {
			return enakGameRejected("an archived game cannot change")
		}
		if err := p.games.CreateRewardConfig(ctx, config); err != nil {
			return err
		}
		return p.record(ctx, organizationID, actor, constants.AuditEntityGameRewardConfig, config.ID, "CREATED",
			nil, rewardConfigModel(config), in.Reason)
	})
	if err != nil {
		return nil, enakGameError(err)
	}
	return rewardConfigModel(config), nil
}

// ActivateRewardConfig makes a DRAFT version the game's active configuration and
// retires the one active before, in one transaction. Activating the active version
// again changes nothing. A retired version stays retired: going back means a new
// version with the old rules.
func (p *EnakGameAdminProcessor) ActivateRewardConfig(ctx context.Context, organizationID, actor, id uuid.UUID, in models.GameRewardConfigActivateInput) (*models.GameRewardConfig, error) {
	if err := validateReason(in.Reason); err != nil {
		return nil, err
	}
	var activated *entities.GameRewardConfig
	err := p.tx.WithTransaction(ctx, func(ctx context.Context) error {
		config, err := p.games.GetRewardConfig(ctx, organizationID, id)
		if err != nil {
			return err
		}
		// Activations of the same game wait for each other here, so exactly one
		// version ends up active.
		game, err := p.games.LockGame(ctx, organizationID, config.GameID)
		if err != nil {
			return err
		}
		if game.Status == constants.GameStatusArchived {
			return enakGameRejected("an archived game cannot change")
		}
		if config, err = p.games.GetRewardConfig(ctx, organizationID, id); err != nil {
			return err
		}
		activated = config
		switch config.Status {
		case constants.GameRewardConfigStatusActive:
			return nil
		case constants.GameRewardConfigStatusRetired:
			return enakGameRejected("version %d is retired; create a new version instead", config.Version)
		}

		current, err := p.games.GetActiveRewardConfig(ctx, organizationID, config.GameID)
		if err != nil && !errors.Is(err, repository.ErrGameRewardConfigNotFound) {
			return err
		}
		if current != nil {
			if _, err := p.moveRewardConfig(ctx, organizationID, actor, current, constants.GameRewardConfigStatusRetired, "RETIRED", in.Reason); err != nil {
				return err
			}
		}
		activated, err = p.moveRewardConfig(ctx, organizationID, actor, config, constants.GameRewardConfigStatusActive, "ACTIVATED", in.Reason)
		return err
	})
	if err != nil {
		return nil, enakGameError(err)
	}
	return rewardConfigModel(activated), nil
}

func (p *EnakGameAdminProcessor) moveRewardConfig(ctx context.Context, organizationID, actor uuid.UUID, config *entities.GameRewardConfig, to, action string, reason *string) (*entities.GameRewardConfig, error) {
	moved, err := p.games.SetRewardConfigStatus(ctx, organizationID, config.ID, config.Status, to)
	if err != nil {
		return nil, err
	}
	if !moved {
		return nil, enakGameRejected("version %d changed meanwhile; try again", config.Version)
	}
	before := config.Status
	next := *config
	next.Status = to
	err = p.record(ctx, organizationID, actor, constants.AuditEntityGameRewardConfig, config.ID, action,
		map[string]string{"status": before}, map[string]string{"status": to}, reason)
	return &next, err
}

// ListRewardConfigs returns every version of a game's configuration, newest first.
func (p *EnakGameAdminProcessor) ListRewardConfigs(ctx context.Context, organizationID, gameID uuid.UUID) ([]models.GameRewardConfig, error) {
	if _, err := p.games.GetGame(ctx, organizationID, gameID); err != nil {
		return nil, err
	}
	configs, err := p.games.ListRewardConfigs(ctx, organizationID, gameID)
	if err != nil {
		return nil, err
	}
	out := make([]models.GameRewardConfig, 0, len(configs))
	for i := range configs {
		out = append(out, *rewardConfigModel(&configs[i]))
	}
	return out, nil
}

// enakGameError turns a slug collision into a refusal; anything else passes as is.
func enakGameError(err error) error {
	if errors.Is(err, repository.ErrEnakGameSlugTaken) {
		return enakGameRejected("another game already uses this slug")
	}
	return err
}

func isEnakGameStatus(s string) bool {
	switch s {
	case constants.GameStatusDraft, constants.GameStatusActive, constants.GameStatusInactive, constants.GameStatusArchived:
		return true
	}
	return false
}

func validateReason(reason *string) error {
	if reason != nil && len(*reason) > 255 {
		return enakGameRejected("reason must be at most 255 characters")
	}
	return nil
}

func validateEnakGameInput(in *models.EnakGameInput) error {
	in.Name = strings.TrimSpace(in.Name)
	in.Slug = strings.TrimSpace(in.Slug)
	in.Type = strings.ToUpper(strings.TrimSpace(in.Type))
	in.Status = strings.ToUpper(strings.TrimSpace(in.Status))
	switch {
	case in.Name == "" || len(in.Name) > 255:
		return enakGameRejected("name is required, at most 255 characters")
	case in.Type != string(entities.GameTypeSpin) && in.Type != string(entities.GameTypeRaffle) && in.Type != string(entities.GameTypeMinigame):
		return enakGameRejected("type must be SPIN, RAFFLE or MINIGAME")
	case len(in.Slug) > 100 || !enakGameSlugPattern.MatchString(in.Slug):
		return enakGameRejected("slug must be lowercase letters, digits and single dashes, at most 100 characters")
	case in.EntryCost < 1:
		// PRD §10.1: no game is free.
		return enakGameRejected("entry_cost must be at least 1")
	case in.SessionTTLSeconds < 1 || in.SessionTTLSeconds > enakGameMaxSessionTTL:
		return enakGameRejected("session_ttl_seconds must be between 1 and %d", enakGameMaxSessionTTL)
	}
	for field, value := range map[string]*string{"thumbnail_url": in.ThumbnailURL, "game_url": in.GameURL} {
		if value != nil && len(*value) > 500 {
			return enakGameRejected("%s must be at most 500 characters", field)
		}
	}
	if in.Version != nil && len(*in.Version) > 50 {
		return enakGameRejected("version must be at most 50 characters")
	}
	return validateResultRules(in.ResultRules)
}

func validateResultRules(r entities.GameResultRules) error {
	switch {
	case r.MaxScore != nil && *r.MaxScore < 0:
		return enakGameRejected("result_rules.max_score must be 0 or more")
	case r.MinDurationSeconds != nil && *r.MinDurationSeconds < 0:
		return enakGameRejected("result_rules.min_duration_seconds must be 0 or more")
	case r.MaxScorePerSecond != nil && !(*r.MaxScorePerSecond > 0):
		return enakGameRejected("result_rules.max_score_per_second must be more than 0")
	case r.DailyRewardLimit != nil && *r.DailyRewardLimit < 0:
		return enakGameRejected("result_rules.daily_reward_limit must be 0 or more")
	}
	seen := map[string]bool{}
	for _, outcome := range r.Outcomes {
		if strings.TrimSpace(outcome) == "" {
			return enakGameRejected("result_rules.outcomes cannot hold an empty outcome")
		}
		if seen[outcome] {
			return enakGameRejected("result_rules.outcomes lists %q twice", outcome)
		}
		seen[outcome] = true
	}
	return nil
}

func applyEnakGameInput(game *entities.Game, in models.EnakGameInput) {
	slug := in.Slug
	game.Name = in.Name
	game.Type = entities.GameType(in.Type)
	game.Slug = &slug
	game.Description = in.Description
	game.ThumbnailURL = in.ThumbnailURL
	game.GameURL = in.GameURL
	game.Version = in.Version
	game.EntryCost = in.EntryCost
	game.SessionTTLSeconds = in.SessionTTLSeconds
	game.ResultRules = in.ResultRules
}

func enakGameModel(g *entities.Game) *models.EnakGame {
	m := &models.EnakGame{
		ID: g.ID, Name: g.Name, Type: string(g.Type), Description: g.Description, ThumbnailURL: g.ThumbnailURL,
		GameURL: g.GameURL, Version: g.Version, Status: g.Status, EntryCost: g.EntryCost,
		SessionTTLSeconds: g.SessionTTLSeconds, ResultRules: g.ResultRules, CreatedAt: g.CreatedAt, UpdatedAt: g.UpdatedAt,
	}
	if g.Slug != nil {
		m.Slug = *g.Slug
	}
	return m
}

func rewardConfigModel(c *entities.GameRewardConfig) *models.GameRewardConfig {
	return &models.GameRewardConfig{
		ID: c.ID, GameID: c.GameID, Version: c.Version, RewardType: c.RewardType, Rules: json.RawMessage(c.Rules),
		MaxReward: c.MaxReward, Status: c.Status, EffectiveAt: c.EffectiveAt, CreatedBy: c.CreatedBy,
		Reason: c.Reason, BaseConfigID: c.BaseConfigID, Multiplier: c.Multiplier, BudgetID: c.BudgetID, CreatedAt: c.CreatedAt,
	}
}

func enakGamePage(page, limit int) (int, int) {
	if page < 1 {
		page = 1
	}
	if limit < 1 || limit > enakGameMaxPageLimit {
		limit = enakGamePageLimit
	}
	return page, limit
}

func enakGamePagination(page, limit int, total int64) models.Pagination {
	return models.Pagination{Page: page, Limit: limit, Total: total, TotalPages: int((total + int64(limit) - 1) / int64(limit))}
}