package support

import (
	"context"
	"errors"
	"fmt"

	"github.com/google/uuid"
	"github.com/jackc/pgx/v5"
)

// ListNotifications returns in-app support notifications for a user (newest first).
func (s *Service) ListNotifications(ctx context.Context, userID uuid.UUID, unreadOnly bool, limit, offset int) ([]Notification, int64, error) {
	where := `n.user_id = $1`
	args := []any{userID}
	if unreadOnly {
		where += ` AND n.read_at IS NULL`
	}
	var total int64
	if err := s.Pool.QueryRow(ctx, `SELECT count(*) FROM support_notifications n WHERE `+where, args...).Scan(&total); err != nil {
		return nil, 0, err
	}
	args = append(args, limit, offset)
	q := fmt.Sprintf(`
		SELECT n.id, n.user_id, n.ticket_id, n.message_id, n.kind, n.read_at, n.created_at, COALESCE(t.subject, '')
		FROM support_notifications n
		LEFT JOIN support_tickets t ON t.id = n.ticket_id
		WHERE %s
		ORDER BY n.created_at DESC
		LIMIT $%d OFFSET $%d`, where, len(args)-1, len(args))
	rows, err := s.Pool.Query(ctx, q, args...)
	if err != nil {
		return nil, 0, err
	}
	defer rows.Close()
	out := make([]Notification, 0)
	for rows.Next() {
		var n Notification
		if err := rows.Scan(&n.ID, &n.UserID, &n.TicketID, &n.MessageID, &n.Kind, &n.ReadAt, &n.CreatedAt, &n.Subject); err != nil {
			return nil, 0, err
		}
		out = append(out, n)
	}
	return out, total, rows.Err()
}

// UnreadNotificationCount returns unread support notification count for the bell badge.
func (s *Service) UnreadNotificationCount(ctx context.Context, userID uuid.UUID) (int64, error) {
	var n int64
	err := s.Pool.QueryRow(ctx, `
		SELECT count(*) FROM support_notifications
		WHERE user_id = $1 AND read_at IS NULL`, userID).Scan(&n)
	return n, err
}

// MarkNotificationRead marks one notification owned by the user as read.
func (s *Service) MarkNotificationRead(ctx context.Context, userID, notificationID uuid.UUID) error {
	tag, err := s.Pool.Exec(ctx, `
		UPDATE support_notifications SET read_at = now()
		WHERE id = $1 AND user_id = $2 AND read_at IS NULL`, notificationID, userID)
	if err != nil {
		return err
	}
	if tag.RowsAffected() == 0 {
		var exists bool
		err = s.Pool.QueryRow(ctx, `
			SELECT EXISTS(SELECT 1 FROM support_notifications WHERE id = $1 AND user_id = $2)`,
			notificationID, userID).Scan(&exists)
		if err != nil {
			return err
		}
		if !exists {
			return ErrNotificationGone
		}
	}
	return nil
}

// MarkAllNotificationsRead marks all unread notifications for the user as read.
func (s *Service) MarkAllNotificationsRead(ctx context.Context, userID uuid.UUID) (int64, error) {
	tag, err := s.Pool.Exec(ctx, `
		UPDATE support_notifications SET read_at = now()
		WHERE user_id = $1 AND read_at IS NULL`, userID)
	if err != nil {
		return 0, err
	}
	return tag.RowsAffected(), nil
}

// ErrIsNoRows exposes pgx.ErrNoRows for tests without importing pgx elsewhere.
func ErrIsNoRows(err error) bool {
	return errors.Is(err, pgx.ErrNoRows)
}