package auth

import (
	"context"
	"encoding/json"
	"errors"
	"strings"

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

	"galo/internal/models"
)

var ErrNotFound = errors.New("not found")

// ErrEmailTaken and ErrPhoneTaken are returned when a unique constraint on the
// corresponding identifier is violated, so callers can map a race to the same
// conflict code as the pre-flight existence check.
var (
	ErrEmailTaken = errors.New("email taken")
	ErrPhoneTaken = errors.New("phone taken")
)

type Store struct {
	pool *pgxpool.Pool
}

func NewStore(pool *pgxpool.Pool) *Store { return &Store{pool: pool} }

const userColumns = `id, COALESCE(email, ''), COALESCE(phone, ''), password_hash, name,
	COALESCE(avatar_url, ''), COALESCE(preferences, '{}'::jsonb)::text, created_at`

func (s *Store) CreateUser(ctx context.Context, u *models.User) error {
	_, err := s.pool.Exec(ctx,
		`INSERT INTO users (id, email, phone, password_hash, name, avatar_url)
		 VALUES ($1, $2, $3, $4, $5, $6)`,
		u.ID, nullIfEmpty(u.Email), nullIfEmpty(u.Phone), u.PasswordHash, u.Name, nullIfEmpty(u.AvatarURL),
	)
	return mapUniqueViolation(err)
}

func (s *Store) GetUserByEmail(ctx context.Context, email string) (*models.User, error) {
	return s.scanUser(s.pool.QueryRow(ctx,
		`SELECT `+userColumns+` FROM users WHERE lower(email) = lower($1)`, email))
}

func (s *Store) GetUserByPhone(ctx context.Context, phone string) (*models.User, error) {
	return s.scanUser(s.pool.QueryRow(ctx,
		`SELECT `+userColumns+` FROM users WHERE phone = $1`, phone))
}

func (s *Store) GetUserByID(ctx context.Context, id string) (*models.User, error) {
	return s.scanUser(s.pool.QueryRow(ctx,
		`SELECT `+userColumns+` FROM users WHERE id = $1`, id))
}

func (s *Store) scanUser(row pgx.Row) (*models.User, error) {
	var u models.User
	var prefs string
	if err := row.Scan(&u.ID, &u.Email, &u.Phone, &u.PasswordHash, &u.Name, &u.AvatarURL, &prefs, &u.CreatedAt); err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return nil, ErrNotFound
		}
		return nil, err
	}
	if prefs != "" && prefs != "null" {
		_ = json.Unmarshal([]byte(prefs), &u.Preferences)
	}
	return &u, nil
}

func (s *Store) UpdateName(ctx context.Context, userID, name string) error {
	tag, err := s.pool.Exec(ctx, `UPDATE users SET name = $2 WHERE id = $1`, userID, name)
	return requireRow(tag, err)
}

func (s *Store) UpdatePasswordHash(ctx context.Context, userID, hash string) error {
	tag, err := s.pool.Exec(ctx, `UPDATE users SET password_hash = $2 WHERE id = $1`, userID, hash)
	return requireRow(tag, err)
}

func (s *Store) AddIdentifier(ctx context.Context, userID, email, phone string) error {
	tag, err := s.pool.Exec(ctx,
		`UPDATE users
		    SET email = COALESCE(NULLIF($2, ''), email),
		        phone = COALESCE(NULLIF($3, ''), phone)
		  WHERE id = $1`,
		userID, email, phone)
	if err != nil {
		return mapUniqueViolation(err)
	}
	return requireRow(tag, nil)
}

func (s *Store) DeleteUser(ctx context.Context, userID string) error {
	tag, err := s.pool.Exec(ctx, `DELETE FROM users WHERE id = $1`, userID)
	return requireRow(tag, err)
}

func (s *Store) UpdatePreferences(ctx context.Context, userID string, raw []byte) error {
	tag, err := s.pool.Exec(ctx,
		`UPDATE users SET preferences = $2::jsonb WHERE id = $1`, userID, string(raw))
	return requireRow(tag, err)
}

func (s *Store) CreateRefreshToken(ctx context.Context, t *models.RefreshToken) error {
	_, err := s.pool.Exec(ctx,
		`INSERT INTO refresh_tokens (id, user_id, token_hash, expires_at)
		 VALUES ($1, $2, $3, $4)`,
		t.ID, t.UserID, t.TokenHash, t.ExpiresAt,
	)
	return err
}

func (s *Store) GetRefreshToken(ctx context.Context, hash string) (*models.RefreshToken, error) {
	var t models.RefreshToken
	err := s.pool.QueryRow(ctx,
		`SELECT id, user_id, token_hash, expires_at, revoked_at, created_at
		 FROM refresh_tokens WHERE token_hash = $1`, hash).
		Scan(&t.ID, &t.UserID, &t.TokenHash, &t.ExpiresAt, &t.RevokedAt, &t.CreatedAt)
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return nil, ErrNotFound
		}
		return nil, err
	}
	return &t, nil
}

func (s *Store) RevokeRefreshToken(ctx context.Context, id string) error {
	_, err := s.pool.Exec(ctx,
		`UPDATE refresh_tokens SET revoked_at = now() WHERE id = $1 AND revoked_at IS NULL`, id)
	return err
}

func (s *Store) RevokeAllUserTokens(ctx context.Context, userID string) error {
	_, err := s.pool.Exec(ctx,
		`UPDATE refresh_tokens SET revoked_at = now() WHERE user_id = $1 AND revoked_at IS NULL`, userID)
	return err
}

func nullIfEmpty(s string) *string {
	if s == "" {
		return nil
	}
	return &s
}

type commandTag interface {
	RowsAffected() int64
}

func requireRow(tag commandTag, err error) error {
	if err != nil {
		return err
	}
	if tag.RowsAffected() == 0 {
		return ErrNotFound
	}
	return nil
}

// mapUniqueViolation converts a PostgreSQL unique constraint violation into the
// domain sentinel so the service can return a conflict for the right field.
func mapUniqueViolation(err error) error {
	if err == nil {
		return nil
	}
	var pgErr *pgconn.PgError
	if errors.As(err, &pgErr) && pgErr.Code == "23505" {
		if strings.Contains(pgErr.ConstraintName, "phone") {
			return ErrPhoneTaken
		}
		return ErrEmailTaken
	}
	return err
}