package repository

import (
	"context"
	"errors"
	"fmt"
	"time"

	"github.com/google/uuid"
	"gorm.io/gorm"
	"gorm.io/gorm/clause"

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

var (
	// ErrEnakGameNotFound means no game with that id in the organization, or, for a
	// write, none that may still change: an archived game never does.
	ErrEnakGameNotFound = errors.New("enakgame: game not found")
	// ErrGameRewardConfigNotFound means no reward configuration with that id in the
	// organization, or no active one for the game.
	ErrGameRewardConfigNotFound = errors.New("enakgame: reward config not found")
	// ErrEnakGameSlugTaken means another game of the organization has the slug.
	ErrEnakGameSlugTaken = errors.New("enakgame: slug already used")
)

// EnakGameFilter selects an organization's games.
type EnakGameFilter struct {
	OrganizationID uuid.UUID
	// Empty for every status.
	Statuses []string
	// Matched against the name, case-insensitively.
	Search string
	Offset int
	Limit  int
}

// EnakGameRepository stores EnakGame games and their reward configurations
// (docs/rfc-enakgame.md §5.1, §5.2). Every read and write is scoped to an
// organization (D8), so the old games, which have none, never show up.
type EnakGameRepository interface {
	CreateGame(ctx context.Context, game *entities.Game) error
	GetGame(ctx context.Context, organizationID, id uuid.UUID) (*entities.Game, error)
	// LockGame is GetGame with the row locked until the transaction ends.
	LockGame(ctx context.Context, organizationID, id uuid.UUID) (*entities.Game, error)
	// ListGames returns a page of games, newest first, and the total.
	ListGames(ctx context.Context, filter EnakGameFilter) ([]entities.Game, int64, error)
	// UpdateGame stores the game's editable columns, everything but its organization
	// and status.
	UpdateGame(ctx context.Context, game *entities.Game) error
	SetGameStatus(ctx context.Context, organizationID, id uuid.UUID, status string) error

	// CreateRewardConfig stores a configuration as the game's next version and sets
	// config.Version.
	CreateRewardConfig(ctx context.Context, config *entities.GameRewardConfig) error
	GetRewardConfig(ctx context.Context, organizationID, id uuid.UUID) (*entities.GameRewardConfig, error)
	GetActiveRewardConfig(ctx context.Context, organizationID, gameID uuid.UUID) (*entities.GameRewardConfig, error)
	// ListRewardConfigs returns every version of a game's configuration, newest first.
	ListRewardConfigs(ctx context.Context, organizationID, gameID uuid.UUID) ([]entities.GameRewardConfig, error)
	// SetRewardConfigStatus moves a configuration from one status to another, the only
	// change a configuration allows (D7). It reports false when the configuration was
	// not in from.
	SetRewardConfigStatus(ctx context.Context, organizationID, id uuid.UUID, from, to string) (bool, error)

	// ListActiveRewardConfigs returns the active configuration of every game of the
	// organization that is not archived, by game name.
	ListActiveRewardConfigs(ctx context.Context, organizationID uuid.UUID) ([]ActiveRewardConfig, error)
	// LastBudgetControllerChange is when the organization last accepted a Budget
	// Controller recommendation, or nil when it never did.
	LastBudgetControllerChange(ctx context.Context, organizationID uuid.UUID) (*time.Time, error)
}

// ActiveRewardConfig is a game's active configuration with the game's name.
type ActiveRewardConfig struct {
	entities.GameRewardConfig `gorm:"embedded"`
	GameName                  string
}

type enakGameRepository struct {
	db *gorm.DB
}

func NewEnakGameRepository(db *gorm.DB) EnakGameRepository {
	return &enakGameRepository{db: db}
}

func (r *enakGameRepository) CreateGame(ctx context.Context, game *entities.Game) error {
	if err := DBFromContext(ctx, r.db).WithContext(ctx).Omit(clause.Associations).Create(game).Error; err != nil {
		if isUniqueViolation(err, "uq_games_org_slug") {
			return ErrEnakGameSlugTaken
		}
		return fmt.Errorf("failed to create game: %w", err)
	}
	return nil
}

func (r *enakGameRepository) getGame(ctx context.Context, organizationID, id uuid.UUID, lock bool) (*entities.Game, error) {
	q := DBFromContext(ctx, r.db).WithContext(ctx).Where("organization_id = ? AND id = ?", organizationID, id)
	if lock {
		q = q.Clauses(clause.Locking{Strength: "UPDATE"})
	}
	var game entities.Game
	if err := q.First(&game).Error; err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, ErrEnakGameNotFound
		}
		return nil, fmt.Errorf("failed to read game: %w", err)
	}
	return &game, nil
}

func (r *enakGameRepository) GetGame(ctx context.Context, organizationID, id uuid.UUID) (*entities.Game, error) {
	return r.getGame(ctx, organizationID, id, false)
}

func (r *enakGameRepository) LockGame(ctx context.Context, organizationID, id uuid.UUID) (*entities.Game, error) {
	return r.getGame(ctx, organizationID, id, true)
}

func (r *enakGameRepository) ListGames(ctx context.Context, filter EnakGameFilter) ([]entities.Game, int64, error) {
	q := DBFromContext(ctx, r.db).WithContext(ctx).Model(&entities.Game{}).Where("organization_id = ?", filter.OrganizationID)
	if len(filter.Statuses) > 0 {
		q = q.Where("status IN ?", filter.Statuses)
	}
	if filter.Search != "" {
		q = q.Where("name ILIKE ?", "%"+filter.Search+"%")
	}
	var total int64
	if err := q.Count(&total).Error; err != nil {
		return nil, 0, fmt.Errorf("failed to count games: %w", err)
	}
	var games []entities.Game
	if err := q.Order("created_at DESC, id").Offset(filter.Offset).Limit(filter.Limit).Find(&games).Error; err != nil {
		return nil, 0, fmt.Errorf("failed to list games: %w", err)
	}
	return games, total, nil
}

func (r *enakGameRepository) UpdateGame(ctx context.Context, game *entities.Game) error {
	if game.OrganizationID == nil {
		return ErrEnakGameNotFound
	}
	result := DBFromContext(ctx, r.db).WithContext(ctx).Exec(`
		UPDATE games SET name = ?, type = ?, slug = ?, description = ?, thumbnail_url = ?, game_url = ?,
			version = ?, entry_cost = ?, session_ttl_seconds = ?, result_rules = ?, updated_at = NOW()
		WHERE organization_id = ? AND id = ? AND status <> ?`,
		game.Name, game.Type, game.Slug, game.Description, game.ThumbnailURL, game.GameURL,
		game.Version, game.EntryCost, game.SessionTTLSeconds, game.ResultRules,
		*game.OrganizationID, game.ID, constants.GameStatusArchived)
	if result.Error != nil {
		if isUniqueViolation(result.Error, "uq_games_org_slug") {
			return ErrEnakGameSlugTaken
		}
		return fmt.Errorf("failed to update game: %w", result.Error)
	}
	if result.RowsAffected == 0 {
		return ErrEnakGameNotFound
	}
	return nil
}

func (r *enakGameRepository) SetGameStatus(ctx context.Context, organizationID, id uuid.UUID, status string) error {
	result := DBFromContext(ctx, r.db).WithContext(ctx).Exec(`
		UPDATE games SET status = ?, updated_at = NOW()
		WHERE organization_id = ? AND id = ? AND status <> ?`,
		status, organizationID, id, constants.GameStatusArchived)
	if result.Error != nil {
		return fmt.Errorf("failed to change game status: %w", result.Error)
	}
	if result.RowsAffected == 0 {
		return ErrEnakGameNotFound
	}
	return nil
}

func (r *enakGameRepository) CreateRewardConfig(ctx context.Context, config *entities.GameRewardConfig) error {
	if config.ID == uuid.Nil {
		config.ID = uuid.New()
	}
	if config.Status == "" {
		config.Status = constants.GameRewardConfigStatusDraft
	}
	// The version is computed in the insert. Two inserts at once may compute the same
	// one, and the unique (game_id, version) refuses the second.
	var rows []struct {
		Version   int
		CreatedAt time.Time
	}
	err := DBFromContext(ctx, r.db).WithContext(ctx).Raw(`
		INSERT INTO game_reward_configs (id, organization_id, game_id, version, reward_type, rules,
			max_reward, status, effective_at, created_by, reason, base_config_id, multiplier, budget_id)
		SELECT ?, g.organization_id, g.id,
			COALESCE((SELECT MAX(version) FROM game_reward_configs WHERE game_id = g.id), 0) + 1,
			?, ?::jsonb, ?, ?, ?, ?, ?, ?, ?, ?
		FROM games g WHERE g.organization_id = ? AND g.id = ?
		RETURNING version, created_at`,
		config.ID, config.RewardType, config.Rules, config.MaxReward, config.Status, config.EffectiveAt,
		config.CreatedBy, config.Reason, config.BaseConfigID, config.Multiplier, config.BudgetID,
		config.OrganizationID, config.GameID).Scan(&rows).Error
	if err != nil {
		return fmt.Errorf("failed to create reward config: %w", err)
	}
	if len(rows) == 0 {
		return ErrEnakGameNotFound
	}
	config.Version, config.CreatedAt = rows[0].Version, rows[0].CreatedAt
	return nil
}

func (r *enakGameRepository) firstRewardConfig(q *gorm.DB) (*entities.GameRewardConfig, error) {
	var config entities.GameRewardConfig
	if err := q.First(&config).Error; err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, ErrGameRewardConfigNotFound
		}
		return nil, fmt.Errorf("failed to read reward config: %w", err)
	}
	return &config, nil
}

func (r *enakGameRepository) GetRewardConfig(ctx context.Context, organizationID, id uuid.UUID) (*entities.GameRewardConfig, error) {
	return r.firstRewardConfig(DBFromContext(ctx, r.db).WithContext(ctx).
		Where("organization_id = ? AND id = ?", organizationID, id))
}

func (r *enakGameRepository) GetActiveRewardConfig(ctx context.Context, organizationID, gameID uuid.UUID) (*entities.GameRewardConfig, error) {
	return r.firstRewardConfig(DBFromContext(ctx, r.db).WithContext(ctx).
		Where("organization_id = ? AND game_id = ? AND status = ?", organizationID, gameID, constants.GameRewardConfigStatusActive))
}

func (r *enakGameRepository) ListRewardConfigs(ctx context.Context, organizationID, gameID uuid.UUID) ([]entities.GameRewardConfig, error) {
	var configs []entities.GameRewardConfig
	err := DBFromContext(ctx, r.db).WithContext(ctx).
		Where("organization_id = ? AND game_id = ?", organizationID, gameID).
		Order("version DESC").Find(&configs).Error
	if err != nil {
		return nil, fmt.Errorf("failed to list reward configs: %w", err)
	}
	return configs, nil
}

func (r *enakGameRepository) SetRewardConfigStatus(ctx context.Context, organizationID, id uuid.UUID, from, to string) (bool, error) {
	result := DBFromContext(ctx, r.db).WithContext(ctx).Exec(`
		UPDATE game_reward_configs SET status = ? WHERE organization_id = ? AND id = ? AND status = ?`,
		to, organizationID, id, from)
	if result.Error != nil {
		return false, fmt.Errorf("failed to change reward config status: %w", result.Error)
	}
	return result.RowsAffected == 1, nil
}

func (r *enakGameRepository) ListActiveRewardConfigs(ctx context.Context, organizationID uuid.UUID) ([]ActiveRewardConfig, error) {
	var configs []ActiveRewardConfig
	err := DBFromContext(ctx, r.db).WithContext(ctx).Raw(`
		SELECT c.*, g.name AS game_name
		FROM game_reward_configs c
		JOIN games g ON g.id = c.game_id
		WHERE c.organization_id = ? AND c.status = ? AND g.status <> ?
		ORDER BY g.name, g.id`,
		organizationID, constants.GameRewardConfigStatusActive, constants.GameStatusArchived).Scan(&configs).Error
	if err != nil {
		return nil, fmt.Errorf("failed to list active reward configs: %w", err)
	}
	return configs, nil
}

func (r *enakGameRepository) LastBudgetControllerChange(ctx context.Context, organizationID uuid.UUID) (*time.Time, error) {
	// effective_at, set by the Budget Controller from its clock, not created_at from
	// the database's.
	var last []time.Time
	err := DBFromContext(ctx, r.db).WithContext(ctx).Raw(`
		SELECT effective_at FROM game_reward_configs
		WHERE organization_id = ? AND budget_id IS NOT NULL
		ORDER BY effective_at DESC LIMIT 1`, organizationID).Scan(&last).Error
	if err != nil {
		return nil, fmt.Errorf("failed to read the last Budget Controller change: %w", err)
	}
	if len(last) == 0 {
		return nil, nil
	}
	return &last[0], nil
}