// Package blind provides blind structure management: CRUD operations,
// the structure wizard algorithm, and built-in template definitions.
package blind

import (
	"context"
	"database/sql"
	"fmt"
	"time"
)

// BlindStructure represents a reusable blind level progression.
type BlindStructure struct {
	ID              int64       `json:"id"`
	Name            string      `json:"name"`
	IsBuiltin       bool        `json:"is_builtin"`
	GameTypeDefault string      `json:"game_type_default"`
	Notes           string      `json:"notes"`
	Levels          []BlindLevel `json:"levels,omitempty"`
	CreatedAt       time.Time   `json:"created_at"`
	UpdatedAt       time.Time   `json:"updated_at"`
}

// BlindLevel represents a single level in a blind structure.
type BlindLevel struct {
	ID                      int64  `json:"id,omitempty"`
	StructureID             int64  `json:"structure_id,omitempty"`
	Position                int    `json:"position"`
	LevelType               string `json:"level_type"`
	GameType                string `json:"game_type"`
	SmallBlind              int64  `json:"small_blind"`
	BigBlind                int64  `json:"big_blind"`
	Ante                    int64  `json:"ante"`
	BBAnte                  int64  `json:"bb_ante"`
	DurationSeconds         int    `json:"duration_seconds"`
	ChipUpDenominationValue *int64 `json:"chip_up_denomination_value,omitempty"`
	Notes                   string `json:"notes"`
}

// StructureService provides CRUD operations for blind structures.
type StructureService struct {
	db *sql.DB
}

// NewStructureService creates a new StructureService.
func NewStructureService(db *sql.DB) *StructureService {
	return &StructureService{db: db}
}

// validateLevels checks that levels meet all requirements.
func validateLevels(levels []BlindLevel) error {
	if len(levels) == 0 {
		return fmt.Errorf("at least one level is required")
	}

	hasRound := false
	for i, l := range levels {
		if l.Position != i {
			return fmt.Errorf("positions must be contiguous starting from 0, got %d at index %d", l.Position, i)
		}
		if l.DurationSeconds <= 0 {
			return fmt.Errorf("level %d: duration must be positive", i)
		}
		if l.LevelType == "round" {
			hasRound = true
			if l.SmallBlind >= l.BigBlind && l.BigBlind > 0 {
				return fmt.Errorf("level %d: small blind (%d) must be less than big blind (%d)", i, l.SmallBlind, l.BigBlind)
			}
		}
		if l.LevelType != "round" && l.LevelType != "break" {
			return fmt.Errorf("level %d: invalid level type %q (must be 'round' or 'break')", i, l.LevelType)
		}
	}

	if !hasRound {
		return fmt.Errorf("at least one round level is required")
	}

	return nil
}

// CreateStructure creates a new blind structure with levels.
func (s *StructureService) CreateStructure(ctx context.Context, name string, levels []BlindLevel) (*BlindStructure, error) {
	if name == "" {
		return nil, fmt.Errorf("structure name is required")
	}
	if err := validateLevels(levels); err != nil {
		return nil, err
	}

	tx, err := s.db.BeginTx(ctx, nil)
	if err != nil {
		return nil, fmt.Errorf("begin transaction: %w", err)
	}
	defer tx.Rollback()

	now := time.Now().Unix()
	gameTypeDefault := "nlhe"
	if len(levels) > 0 && levels[0].GameType != "" {
		gameTypeDefault = levels[0].GameType
	}

	res, err := tx.ExecContext(ctx,
		"INSERT INTO blind_structures (name, is_builtin, game_type_default, notes, created_at, updated_at) VALUES (?, 0, ?, '', ?, ?)",
		name, gameTypeDefault, now, now,
	)
	if err != nil {
		return nil, fmt.Errorf("insert structure: %w", err)
	}
	id, err := res.LastInsertId()
	if err != nil {
		return nil, fmt.Errorf("get structure id: %w", err)
	}

	if err := insertLevels(ctx, tx, id, levels); err != nil {
		return nil, err
	}

	if err := tx.Commit(); err != nil {
		return nil, fmt.Errorf("commit: %w", err)
	}

	return s.GetStructure(ctx, id)
}

// insertLevels inserts levels into the blind_levels table within a transaction.
func insertLevels(ctx context.Context, tx *sql.Tx, structureID int64, levels []BlindLevel) error {
	for i, l := range levels {
		gameType := l.GameType
		if gameType == "" {
			gameType = "nlhe"
		}
		levelType := l.LevelType
		if levelType == "" {
			levelType = "round"
		}

		_, err := tx.ExecContext(ctx,
			`INSERT INTO blind_levels (structure_id, position, level_type, game_type, small_blind, big_blind, ante, bb_ante, duration_seconds, chip_up_denomination_value, notes)
			 VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`,
			structureID, l.Position, levelType, gameType,
			l.SmallBlind, l.BigBlind, l.Ante, l.BBAnte,
			l.DurationSeconds, l.ChipUpDenominationValue, l.Notes,
		)
		if err != nil {
			return fmt.Errorf("insert level %d: %w", i, err)
		}
	}
	return nil
}

// GetStructure retrieves a blind structure by ID, including levels ordered by position.
func (s *StructureService) GetStructure(ctx context.Context, id int64) (*BlindStructure, error) {
	bs := &BlindStructure{}
	var isBuiltin int
	var createdAt, updatedAt int64

	err := s.db.QueryRowContext(ctx,
		"SELECT id, name, is_builtin, game_type_default, notes, created_at, updated_at FROM blind_structures WHERE id = ?", id,
	).Scan(&bs.ID, &bs.Name, &isBuiltin, &bs.GameTypeDefault, &bs.Notes, &createdAt, &updatedAt)
	if err == sql.ErrNoRows {
		return nil, fmt.Errorf("blind structure not found: %d", id)
	}
	if err != nil {
		return nil, fmt.Errorf("get structure: %w", err)
	}
	bs.IsBuiltin = isBuiltin != 0
	bs.CreatedAt = time.Unix(createdAt, 0)
	bs.UpdatedAt = time.Unix(updatedAt, 0)

	rows, err := s.db.QueryContext(ctx,
		`SELECT id, structure_id, position, level_type, game_type, small_blind, big_blind, ante, bb_ante, duration_seconds, chip_up_denomination_value, notes
		 FROM blind_levels WHERE structure_id = ? ORDER BY position`, id,
	)
	if err != nil {
		return nil, fmt.Errorf("get levels: %w", err)
	}
	defer rows.Close()

	for rows.Next() {
		var l BlindLevel
		if err := rows.Scan(&l.ID, &l.StructureID, &l.Position, &l.LevelType, &l.GameType,
			&l.SmallBlind, &l.BigBlind, &l.Ante, &l.BBAnte,
			&l.DurationSeconds, &l.ChipUpDenominationValue, &l.Notes); err != nil {
			return nil, fmt.Errorf("scan level: %w", err)
		}
		bs.Levels = append(bs.Levels, l)
	}
	return bs, rows.Err()
}

// ListStructures returns all blind structures (without levels).
func (s *StructureService) ListStructures(ctx context.Context) ([]BlindStructure, error) {
	rows, err := s.db.QueryContext(ctx,
		"SELECT id, name, is_builtin, game_type_default, notes, created_at, updated_at FROM blind_structures ORDER BY is_builtin DESC, name",
	)
	if err != nil {
		return nil, fmt.Errorf("list structures: %w", err)
	}
	defer rows.Close()

	var structs []BlindStructure
	for rows.Next() {
		var bs BlindStructure
		var isBuiltin int
		var createdAt, updatedAt int64
		if err := rows.Scan(&bs.ID, &bs.Name, &isBuiltin, &bs.GameTypeDefault, &bs.Notes, &createdAt, &updatedAt); err != nil {
			return nil, fmt.Errorf("scan structure: %w", err)
		}
		bs.IsBuiltin = isBuiltin != 0
		bs.CreatedAt = time.Unix(createdAt, 0)
		bs.UpdatedAt = time.Unix(updatedAt, 0)
		structs = append(structs, bs)
	}
	return structs, rows.Err()
}

// UpdateStructure updates a blind structure name and replaces its levels.
func (s *StructureService) UpdateStructure(ctx context.Context, id int64, name string, levels []BlindLevel) error {
	if name == "" {
		return fmt.Errorf("structure name is required")
	}
	if err := validateLevels(levels); err != nil {
		return err
	}

	tx, err := s.db.BeginTx(ctx, nil)
	if err != nil {
		return fmt.Errorf("begin transaction: %w", err)
	}
	defer tx.Rollback()

	now := time.Now().Unix()
	res, err := tx.ExecContext(ctx,
		"UPDATE blind_structures SET name = ?, updated_at = ? WHERE id = ?",
		name, now, id,
	)
	if err != nil {
		return fmt.Errorf("update structure: %w", err)
	}
	n, _ := res.RowsAffected()
	if n == 0 {
		return fmt.Errorf("blind structure not found: %d", id)
	}

	// Replace levels
	if _, err := tx.ExecContext(ctx, "DELETE FROM blind_levels WHERE structure_id = ?", id); err != nil {
		return fmt.Errorf("delete old levels: %w", err)
	}
	if err := insertLevels(ctx, tx, id, levels); err != nil {
		return err
	}

	return tx.Commit()
}

// DeleteStructure deletes a blind structure. Built-in structures cannot be deleted.
func (s *StructureService) DeleteStructure(ctx context.Context, id int64) error {
	var isBuiltin int
	err := s.db.QueryRowContext(ctx, "SELECT is_builtin FROM blind_structures WHERE id = ?", id).Scan(&isBuiltin)
	if err == sql.ErrNoRows {
		return fmt.Errorf("blind structure not found: %d", id)
	}
	if err != nil {
		return fmt.Errorf("check structure: %w", err)
	}
	if isBuiltin != 0 {
		return fmt.Errorf("cannot delete built-in blind structure")
	}

	// Check if referenced by active tournaments
	var refCount int
	err = s.db.QueryRowContext(ctx,
		"SELECT COUNT(*) FROM tournaments WHERE blind_structure_id = ? AND status NOT IN ('completed', 'cancelled')", id,
	).Scan(&refCount)
	if err != nil {
		return fmt.Errorf("check references: %w", err)
	}
	if refCount > 0 {
		return fmt.Errorf("blind structure is referenced by %d active tournament(s)", refCount)
	}

	res, err := s.db.ExecContext(ctx, "DELETE FROM blind_structures WHERE id = ?", id)
	if err != nil {
		return fmt.Errorf("delete structure: %w", err)
	}
	n, _ := res.RowsAffected()
	if n == 0 {
		return fmt.Errorf("blind structure not found: %d", id)
	}
	return nil
}

// DuplicateStructure creates an independent copy of a blind structure.
func (s *StructureService) DuplicateStructure(ctx context.Context, id int64, newName string) (*BlindStructure, error) {
	original, err := s.GetStructure(ctx, id)
	if err != nil {
		return nil, fmt.Errorf("get original: %w", err)
	}

	if newName == "" {
		newName = original.Name + " (Copy)"
	}

	return s.CreateStructure(ctx, newName, original.Levels)
}