// Package drivers owns persistence and business logic for drivers
// (racers). Each driver has a unique 3-letter nickname (A-Z,
// uppercase, exactly 3 chars), a name, an optional avatar URL and an
// optional clan reference.
package drivers

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

	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgxpool"
)

// Errors returned by the service.
var (
	ErrNotFound      = errors.New("driver not found")
	ErrInvalidInput  = errors.New("invalid input")
	ErrAlreadyExists = errors.New("driver already exists")
)

// nicknameRE enforces exactly 3 uppercase ASCII letters.
var nicknameRE = regexp.MustCompile(`^[A-Z]{3}$`)

// IsValidNickname reports whether s is a valid driver nickname.
func IsValidNickname(s string) bool { return nicknameRE.MatchString(s) }

// Driver is the canonical in-memory representation.
type Driver struct {
	ID        string
	Nickname  string
	Name      string
	AvatarURL string
	ClanID    string
	CreatedMs int64
	UpdatedMs int64
}

// PgStore is the Postgres-backed half of the package.
type PgStore struct {
	pool *pgxpool.Pool
}

// NewPgStore wraps an open pgxpool.
func NewPgStore(pool *pgxpool.Pool) *PgStore {
	return &PgStore{pool: pool}
}

// Exec exposes raw SQL for the seeder.
func (s *PgStore) Exec(ctx context.Context, sql string) (int64, error) {
	tag, err := s.pool.Exec(ctx, sql)
	if err != nil {
		return 0, err
	}
	return tag.RowsAffected(), nil
}

// Create inserts a driver.
func (s *PgStore) Create(ctx context.Context, d Driver) error {
	now := time.Now().UnixMilli()
	if d.CreatedMs == 0 {
		d.CreatedMs = now
	}
	d.UpdatedMs = now
	_, err := s.pool.Exec(ctx, `
		INSERT INTO drivers (id, nickname, name, avatar_url, clan_id, created_ms, updated_ms)
		VALUES ($1, $2, $3, $4, $5, $6, $7)`,
		d.ID, d.Nickname, d.Name, d.AvatarURL, nullableClan(d.ClanID), d.CreatedMs, d.UpdatedMs)
	if err != nil {
		return fmt.Errorf("insert driver: %w", err)
	}
	return nil
}

func nullableClan(id string) any {
	if id == "" {
		return nil
	}
	return id
}

// Get loads a driver by id.
func (s *PgStore) Get(ctx context.Context, id string) (Driver, error) {
	row := s.pool.QueryRow(ctx,
		`SELECT id, nickname, name, avatar_url, COALESCE(clan_id, ''), created_ms, updated_ms
		 FROM drivers WHERE id = $1`, id)
	var d Driver
	if err := row.Scan(&d.ID, &d.Nickname, &d.Name, &d.AvatarURL, &d.ClanID, &d.CreatedMs, &d.UpdatedMs); err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return Driver{}, ErrNotFound
		}
		return Driver{}, err
	}
	return d, nil
}

// GetByNickname loads a driver by their 3-letter nickname.
func (s *PgStore) GetByNickname(ctx context.Context, nick string) (Driver, error) {
	row := s.pool.QueryRow(ctx,
		`SELECT id, nickname, name, avatar_url, COALESCE(clan_id, ''), created_ms, updated_ms
		 FROM drivers WHERE nickname = $1`, nick)
	var d Driver
	if err := row.Scan(&d.ID, &d.Nickname, &d.Name, &d.AvatarURL, &d.ClanID, &d.CreatedMs, &d.UpdatedMs); err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return Driver{}, ErrNotFound
		}
		return Driver{}, err
	}
	return d, nil
}

// List returns all drivers, ordered by nickname.
func (s *PgStore) List(ctx context.Context, limit, offset int, clanID string) ([]Driver, error) {
	if limit <= 0 || limit > 200 {
		limit = 50
	}
	if offset < 0 {
		offset = 0
	}
	q := `SELECT id, nickname, name, avatar_url, COALESCE(clan_id, ''), created_ms, updated_ms
	      FROM drivers`
	args := []any{}
	if clanID != "" {
		q += ` WHERE clan_id = $1`
		args = append(args, clanID)
		args = append(args, limit, offset)
		q += ` ORDER BY nickname ASC LIMIT $2 OFFSET $3`
	} else {
		args = append(args, limit, offset)
		q += ` ORDER BY nickname ASC LIMIT $1 OFFSET $2`
	}
	rows, err := s.pool.Query(ctx, q, args...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	out := make([]Driver, 0)
	for rows.Next() {
		var d Driver
		if err := rows.Scan(&d.ID, &d.Nickname, &d.Name, &d.AvatarURL, &d.ClanID, &d.CreatedMs, &d.UpdatedMs); err != nil {
			return nil, err
		}
		out = append(out, d)
	}
	return out, rows.Err()
}

// Update applies a partial patch.
func (s *PgStore) Update(ctx context.Context, d Driver) error {
	d.UpdatedMs = time.Now().UnixMilli()
	tag, err := s.pool.Exec(ctx, `
		UPDATE drivers
		SET name = $2, avatar_url = $3, clan_id = $4, updated_ms = $5
		WHERE id = $1`,
		d.ID, d.Name, d.AvatarURL, nullableClan(d.ClanID), d.UpdatedMs)
	if err != nil {
		return err
	}
	if tag.RowsAffected() == 0 {
		return ErrNotFound
	}
	return nil
}

// Delete removes a driver by id.
func (s *PgStore) Delete(ctx context.Context, id string) error {
	tag, err := s.pool.Exec(ctx, `DELETE FROM drivers WHERE id = $1`, id)
	if err != nil {
		return err
	}
	if tag.RowsAffected() == 0 {
		return ErrNotFound
	}
	return nil
}

// Count returns the total number of drivers.
func (s *PgStore) Count(ctx context.Context) (int, error) {
	var n int
	row := s.pool.QueryRow(ctx, `SELECT COUNT(*) FROM drivers`)
	if err := row.Scan(&n); err != nil {
		return 0, err
	}
	return n, nil
}