<?php
namespace StoreSuit;

defined( 'ABSPATH' ) || exit;
// phpcs:disable WordPress.Security.EscapeOutput.ExceptionNotEscaped -- Messages are returned as JSON by Admin::ajax() and the stock alert REST route and shown with textContent; HTML output escapes them where printed.

/**
 * "Email me when it is back" requests. A shopper asks for one email about one
 * out-of-stock product or option; StoreSuit keeps the request, sends it once
 * through the WooCommerce mailer when the product is back in stock, and keeps
 * the waiting demand visible to purchasing. Off by default; nothing is shown
 * on the storefront until the store owner turns it on.
 */
final class StockAlerts {
    public const SCHEMA = 'storesuit_stock_alerts_schema';
    public const EMAIL_ID = 'storesuit_stock_alert';
    private const SETTINGS = 'storesuit_stock_alerts';
    private const HOOK = 'storesuit_stock_alert_send';
    private const CLEANUP = 'storesuit_stock_alert_cleanup';
    private const BATCH = 50;

    public static function table(): string { global $wpdb; return $wpdb->prefix . 'storesuit_stock_alerts'; }

    public static function install(): void {
        // 2: the cancel key is indexed (Denetim R0-8): the public cancel route looked it up among every waiting request.
        if ( get_option( self::SCHEMA ) === '2' ) { return; }
        global $wpdb;
        require_once ABSPATH . 'wp-admin/includes/upgrade.php';
        $table = self::table(); $charset = $wpdb->get_charset_collate();
        dbDelta( "CREATE TABLE $table (
            id bigint(20) unsigned NOT NULL AUTO_INCREMENT,
            product_id bigint(20) unsigned NOT NULL,
            email varchar(190) NOT NULL,
            email_hash char(64) NOT NULL,
            customer_id bigint(20) unsigned NOT NULL DEFAULT 0,
            status varchar(12) NOT NULL DEFAULT 'waiting',
            token char(32) NOT NULL,
            created datetime NOT NULL,
            notified datetime NULL,
            PRIMARY KEY  (id),
            UNIQUE KEY product_email (product_id,email_hash),
            KEY status_product (status,product_id),
            KEY email_hash (email_hash),
            KEY token (token)
        ) $charset;" );
        update_option( self::SCHEMA, '2', false );
    }

    public static function hooks(): void {
        add_filter( 'woocommerce_get_stock_html', array( __CLASS__, 'form' ), 20, 2 );
        add_action( 'wp_enqueue_scripts', array( __CLASS__, 'assets' ) );
        add_action( 'rest_api_init', array( __CLASS__, 'routes' ) );
        add_action( 'woocommerce_product_set_stock_status', array( __CLASS__, 'restocked' ), 10, 2 );
        add_action( 'woocommerce_variation_set_stock_status', array( __CLASS__, 'restocked' ), 10, 2 );
        add_action( 'transition_post_status', array( __CLASS__, 'republished' ), 10, 3 );
        add_action( self::HOOK, array( __CLASS__, 'send_batch' ) );
        add_action( self::CLEANUP, array( __CLASS__, 'cleanup' ) );
        add_filter( 'woocommerce_email_classes', static function ( $emails ) {
            require_once __DIR__ . '/StockAlertEmail.php';
            $emails['StoreSuit_Stock_Alert'] = new StockAlertEmail();
            return $emails;
        } );
        add_filter( 'wp_privacy_personal_data_exporters', static function ( $exporters ) { $exporters['storesuit-stock-alerts'] = array( 'exporter_friendly_name'=>I18n::t( 'Back-in-stock requests' ), 'callback'=>array( __CLASS__, 'export' ) ); return $exporters; } );
        add_filter( 'wp_privacy_personal_data_erasers', static function ( $erasers ) { $erasers['storesuit-stock-alerts'] = array( 'eraser_friendly_name'=>I18n::t( 'Back-in-stock requests' ), 'callback'=>array( __CLASS__, 'erase' ) ); return $erasers; } );
        add_action( 'init', static function () { if ( ! wp_next_scheduled( self::CLEANUP ) ) { wp_schedule_event( time() + HOUR_IN_SECONDS, 'daily', self::CLEANUP ); } }, 99 );
    }

    /* ---------- Settings ---------- */

    public static function settings(): array {
        $saved = get_option( self::SETTINGS, array() ); $saved = is_array( $saved ) ? $saved : array();
        return array( 'enabled'=>! empty( $saved['enabled'] ), 'auto_send'=>! array_key_exists( 'auto_send', $saved ) || ! empty( $saved['auto_send'] ) );
    }

    /* ---------- Storefront ---------- */

    /** On sale in the store: published, and for a variation its product too (a variation keeps "publish" when its product goes back to draft). */
    private static function published( \WC_Product $product ): bool {
        return $product->get_status() === 'publish' && ( ! $product->is_type( 'variation' ) || get_post_status( $product->get_parent_id() ) === 'publish' );
    }

    private static function eligible( $product ): bool {
        // A variation of a product taken off sale takes no new request (Codex SA-02).
        return $product instanceof \WC_Product && ! $product->is_type( array( 'variable', 'grouped', 'external' ) ) && ! $product->is_in_stock() && self::published( $product );
    }

    /**
     * Not a <form>: WooCommerce prints option and grouped stock text inside its own cart form, where a nested
     * form is dropped by the browser and its button would submit the cart. Fields carry no name for the same reason.
     */
    public static function form( $html, $product ) {
        if ( ! self::settings()['enabled'] || ! self::eligible( $product ) || is_admin() ) { return $html; }
        self::front_assets();
        $user = wp_get_current_user(); $email = $user && $user->exists() ? $user->user_email : '';
        $id = (string) $product->get_id();
        return $html . '<div class="storesuit-stock-alert" role="group" aria-labelledby="storesuit-stock-alert-' . esc_attr( $id ) . '" data-product="' . esc_attr( $id ) . '">'
            . '<p class="storesuit-stock-alert__title" id="storesuit-stock-alert-' . esc_attr( $id ) . '">' . esc_html( (string) apply_filters( 'storesuit_stock_alert_title', I18n::t( 'Email me when this is back in stock' ), $product ) ) . '</p>'
            . '<label class="storesuit-stock-alert__field"><span>' . esc_html( I18n::t( 'Email address' ) ) . '</span><input type="email" data-field="email" aria-required="true" autocomplete="email" value="' . esc_attr( $email ) . '"></label>'
            . '<label class="storesuit-stock-alert__consent"><input type="checkbox" data-field="consent" value="1"> ' . esc_html( I18n::t( 'Send me one email when this product is back in stock. My address is used only for this.' ) ) . '</label>'
            . '<input type="text" data-field="website" value="" tabindex="-1" autocomplete="off" aria-hidden="true" class="storesuit-stock-alert__hp" style="position:absolute;left:-9999px;width:1px;height:1px;overflow:hidden">'
            . '<button type="button" class="button wp-element-button storesuit-stock-alert__send">' . esc_html( I18n::t( 'Notify me' ) ) . '</button>'
            . '<p class="storesuit-stock-alert__status" role="status" aria-live="polite"></p></div>';
    }

    public static function assets(): void {
        if ( self::settings()['enabled'] && function_exists( 'is_product' ) && is_product() ) { self::front_assets(); } // Options loaded later by AJAX need the script too.
    }

    private static function front_assets(): void {
        if ( wp_script_is( 'storesuit-stock-alerts', 'enqueued' ) ) { return; }
        wp_enqueue_script( 'storesuit-stock-alerts', plugins_url( 'assets/stock-alerts.js', STORESUIT_FILE ), array(), (string) filemtime( STORESUIT_DIR . 'assets/stock-alerts.js' ), true );
        wp_localize_script( 'storesuit-stock-alerts', 'StoreSuitStockAlerts', array(
            'url'      => esc_url_raw( rest_url( 'storesuit/v1/stock-alerts' ) ),
            'sending'  => I18n::t( 'Saving…' ),
            'done'     => I18n::t( 'Done. We will email you once when it is back in stock.' ),
            'cancel'   => I18n::t( 'Cancel this request' ),
            'cancelled'=> I18n::t( 'Your request was cancelled.' ),
            'failed'   => I18n::t( 'This could not be saved. Check the address and try again.' ),
            'consent'  => I18n::t( 'Tick the box to confirm the email.' ),
            'email'    => I18n::t( 'Enter a valid email address.' ),
        ) );
        wp_register_style( 'storesuit-stock-alerts', false, array(), STORESUIT_VERSION );
        wp_enqueue_style( 'storesuit-stock-alerts' );
        wp_add_inline_style( 'storesuit-stock-alerts', '.storesuit-stock-alert{display:grid;gap:.6em;margin:1em 0;text-align:start;padding:1em;border:1px solid currentColor;border-color:color-mix(in srgb,currentColor 20%,transparent);border-radius:4px}.storesuit-stock-alert__title{margin:0;font-weight:600}.storesuit-stock-alert__field{display:grid;gap:.25em}:where(.storesuit-stock-alert__field) input{box-sizing:border-box;width:100%;max-width:28em;padding:.5em .6em;font:inherit}.storesuit-stock-alert .button{justify-self:start}.storesuit-stock-alert-row td{padding-top:0}.storesuit-stock-alert__consent{display:flex;gap:.5em;align-items:flex-start;font-size:.9em}.storesuit-stock-alert__hp{position:absolute!important;left:-9999px!important;width:1px;height:1px;opacity:0}.storesuit-stock-alert__status:empty{display:none}' );
    }

    /**
     * The storefront's two routes are public on purpose (permission_callback __return_true): a shopper who is not signed in
     * asks for one e-mail, or cancels that request with the key only its own answer carried. The consent box, a hidden field
     * for bots, an hourly limit per visitor network (an IPv6 /64), a daily limit per inbox and the product's own checks guard
     * them; nothing private is answered.
     * Every parameter is sanitized by WordPress before the callback runs, and validated there.
     */
    public static function routes(): void {
        register_rest_route( 'storesuit/v1', '/stock-alerts', array(
            'methods'=>'POST', 'callback'=>array( __CLASS__, 'rest_subscribe' ), 'permission_callback'=>'__return_true',
            'args'=>array(
                'product'=>array( 'description'=>'The out-of-stock product or variation.', 'sanitize_callback'=>'absint' ),
                'email'=>array( 'description'=>'The shopper\'s email address.', 'sanitize_callback'=>'sanitize_email' ),
                'consent'=>array( 'description'=>'The ticked consent box.', 'sanitize_callback'=>'rest_sanitize_boolean' ),
                // Anything other than text (an array, say) counts as filled in, as before: only a bot sends it.
                'website'=>array( 'description'=>'A hidden field that only bots fill in.', 'sanitize_callback'=>static fn( $value ) => is_scalar( $value ) ? sanitize_text_field( (string) $value ) : 'filled' ),
            ),
        ) );
        register_rest_route( 'storesuit/v1', '/stock-alerts/cancel', array(
            'methods'=>'POST', 'callback'=>array( __CLASS__, 'rest_cancel' ), 'permission_callback'=>'__return_true',
            'args'=>array( 'token'=>array( 'description'=>'The cancel key of the shopper\'s own request.', 'sanitize_callback'=>'sanitize_key' ) ),
        ) );
    }

    public static function rest_subscribe( \WP_REST_Request $request ) {
        try { return rest_ensure_response( self::subscribe( (array) $request->get_json_params() + (array) $request->get_body_params(), Store::visitor_ip() ) ); }
        catch ( \Throwable $e ) { return new \WP_Error( 'storesuit_stock_alert', $e->getMessage(), array( 'status'=>400 ) ); }
    }

    public static function rest_cancel( \WP_REST_Request $request ) {
        $token = sanitize_key( (string) ( $request->get_param( 'token' ) ?? '' ) );
        return rest_ensure_response( array( 'cancelled'=>self::cancel( $token ) ) );
    }

    /** One waiting request per product and address; repeats return the same request. */
    public static function subscribe( array $data, string $ip ): array {
        if ( ! self::settings()['enabled'] ) { throw new \RuntimeException( I18n::t( 'Back-in-stock emails are not available.' ) ); }
        if ( trim( (string) ( $data['website'] ?? '' ) ) !== '' ) { return array( 'ok'=>true, 'token'=>'' ); } // Bots filling the hidden field get no record.
        if ( empty( $data['consent'] ) ) { throw new \InvalidArgumentException( I18n::t( 'Tick the box to confirm the email.' ) ); }
        $email = sanitize_email( (string) ( $data['email'] ?? '' ) );
        if ( ! is_email( $email ) || strlen( $email ) > 190 ) { throw new \InvalidArgumentException( I18n::t( 'Enter a valid email address.' ) ); }
        $product = wc_get_product( absint( $data['product'] ?? 0 ) );
        if ( ! self::eligible( $product ) ) { throw new \InvalidArgumentException( I18n::t( 'This product is available now; no request is needed.' ) ); }
        // 10 an hour from one visitor network: an IPv4 address, or a whole IPv6 /64 (one connection's addresses), counted in
        // one atomic statement (security review S09).
        $network = Store::network( $ip );
        if ( ! Store::throttle( 'stock-alert-network', $network !== '' ? $network : 'unknown', 10, HOUR_IN_SECONDS ) ) { throw new \RuntimeException( I18n::t( 'Too many requests. Please try again later.' ) ); }
        global $wpdb; $table = self::table(); $hash = hash( 'sha256', strtolower( $email ) );
        $row = $wpdb->get_row( $wpdb->prepare( 'SELECT id,status,token FROM %i WHERE product_id=%d AND email_hash=%s', $table, $product->get_id(), $hash ), ARRAY_A );
        // A repeat gets no cancel key: whoever knows an address must not be able to cancel that shopper's request. The same
        // inbox under another spelling (a +tag, Gmail's dots) is a repeat too: one email per inbox and product.
        if ( ( $row && $row['status'] === 'waiting' ) || self::waiting_mailbox( $product->get_id(), $email ) ) { return array( 'ok'=>true, 'token'=>'' ); }
        // At most 5 new or renewed requests a day for one inbox, whatever its spelling: nobody can sign someone else up for
        // every product, or again after each restock.
        if ( ! Store::throttle( 'stock-alert-mailbox', Store::mailbox( $email ), 5, DAY_IN_SECONDS ) ) { throw new \RuntimeException( I18n::t( 'Too many requests. Please try again later.' ) ); }
        $token = bin2hex( random_bytes( 16 ) ); $now = current_time( 'mysql', true );
        if ( $row ) { $wpdb->update( $table, array( 'status'=>'waiting', 'token'=>$token, 'created'=>$now, 'notified'=>null, 'email'=>$email ), array( 'id'=>$row['id'] ) ); }
        else { $wpdb->insert( $table, array( 'product_id'=>$product->get_id(), 'email'=>$email, 'email_hash'=>$hash, 'customer_id'=>get_current_user_id(), 'status'=>'waiting', 'token'=>$token, 'created'=>$now ) ); }
        return array( 'ok'=>true, 'token'=>$token );
    }

    /** Whether a waiting request for this product already goes to the same inbox as $email under another spelling. */
    private static function waiting_mailbox( int $product_id, string $email ): bool {
        global $wpdb;
        $mailbox = Store::mailbox( $email ); $domain = (string) substr( (string) strrchr( $mailbox, '@' ), 1 );
        if ( $domain === '' ) { return false; }
        $other = $domain === 'gmail.com' ? 'googlemail.com' : $domain;
        $emails = (array) $wpdb->get_col( $wpdb->prepare( "SELECT email FROM %i WHERE product_id=%d AND status='waiting' AND ( email LIKE %s OR email LIKE %s ) LIMIT 500", self::table(), $product_id, '%@' . $wpdb->esc_like( $domain ), '%@' . $wpdb->esc_like( $other ) ) );
        foreach ( $emails as $address ) { if ( Store::mailbox( (string) $address ) === $mailbox ) { return true; } }
        return false;
    }

    public static function cancel( string $token ): bool {
        if ( ! preg_match( '/^[a-f0-9]{32}$/', $token ) ) { return false; }
        global $wpdb;
        return (bool) $wpdb->update( self::table(), array( 'status'=>'cancelled' ), array( 'token'=>$token, 'status'=>'waiting' ) );
    }

    /* ---------- Sending ---------- */

    public static function restocked( $product_id, $status ): void {
        $settings = self::settings();
        if ( ! $settings['enabled'] || ! $settings['auto_send'] || $status !== 'instock' ) { return; }
        self::queue( (int) $product_id );
        // Variations that use their parent's stock are switched by WooCommerce without an event of their own.
        global $wpdb;
        foreach ( (array) $wpdb->get_col( $wpdb->prepare( "SELECT DISTINCT a.product_id FROM %i a JOIN %i p ON p.ID=a.product_id WHERE a.status='waiting' AND p.post_parent=%d AND p.post_type='product_variation'", self::table(), $wpdb->posts, (int) $product_id ) ) as $child ) { self::queue( (int) $child ); }
    }

    /**
     * A product put back on sale (published again): its waiting requests for items already in stock are queued, as when the
     * stock comes back. While it was off sale nothing was sent (Codex SA-02), and nothing else would queue them later
     * (review of 0.57). For a variable product: its variations with waiting requests.
     */
    public static function republished( $new, $old, $post ): void {
        if ( $new !== 'publish' || $old === 'publish' || ! $post instanceof \WP_Post || ! in_array( $post->post_type, array( 'product', 'product_variation' ), true ) ) { return; }
        $settings = self::settings();
        if ( ! $settings['enabled'] || ! $settings['auto_send'] ) { return; }
        global $wpdb;
        $ids = (array) $wpdb->get_col( $wpdb->prepare( "SELECT DISTINCT a.product_id FROM %i a JOIN %i p ON p.ID=a.product_id WHERE a.status='waiting' AND ( p.ID=%d OR ( p.post_parent=%d AND p.post_type='product_variation' ) )", self::table(), $wpdb->posts, (int) $post->ID, (int) $post->ID ) );
        foreach ( $ids as $id ) { $product = wc_get_product( (int) $id ); if ( $product && $product->is_in_stock() ) { self::queue( (int) $id ); } }
    }

    /** A follow-up batch is not unique: the job that schedules it is still running and would count as its duplicate. */
    private static function queue( int $product_id, bool $follow_up = false ): void {
        if ( $follow_up && function_exists( 'as_schedule_single_action' ) ) { as_schedule_single_action( time() + 30, self::HOOK, array( $product_id ), 'storesuit-stock-alert-' . $product_id ); }
        elseif ( function_exists( 'as_enqueue_async_action' ) ) { as_enqueue_async_action( self::HOOK, array( $product_id ), 'storesuit-stock-alert-' . $product_id, true ); }
        else { wp_schedule_single_event( time() + ( $follow_up ? 30 : 1 ), self::HOOK, array( $product_id ) ); }
    }

    /**
     * Sends up to one batch; each request is marked before it is mailed so a retry never emails twice. Whether requests
     * are on is checked when the job runs, not when it was queued: a job left over from before the owner turned them
     * off sends nothing, and its waiting requests stay as they are.
     */
    public static function send_batch( int $product_id ): int {
        if ( ! self::settings()['enabled'] ) { return 0; }
        $product = wc_get_product( $product_id );
        // Checked when the job runs: a product taken off sale meanwhile (for a variation, its product) sends nothing, and the
        // waiting requests stay as they are (Codex SA-02).
        if ( ! $product || ! $product->is_in_stock() || ! self::published( $product ) ) { return 0; }
        global $wpdb; $table = self::table();
        $rows = $wpdb->get_results( $wpdb->prepare( "SELECT id,email,token FROM %i WHERE product_id=%d AND status='waiting' ORDER BY id ASC LIMIT %d", $table, $product_id, self::BATCH ), ARRAY_A );
        $mailer = WC()->mailer(); $emails = $mailer->get_emails(); $email = $emails['StoreSuit_Stock_Alert'] ?? null;
        $sent = 0;
        foreach ( $rows as $row ) {
            $claimed = $wpdb->update( $table, array( 'status'=>'sending' ), array( 'id'=>$row['id'], 'status'=>'waiting' ) );
            if ( ! $claimed ) { continue; }
            $ok = $email && $email->is_enabled() ? $email->trigger( $row['email'], $product ) : false;
            $wpdb->update( $table, array( 'status'=>$ok ? 'sent' : 'waiting', 'notified'=>$ok ? current_time( 'mysql', true ) : null ), array( 'id'=>$row['id'] ) );
            if ( $ok ) { ++$sent; }
        }
        if ( count( $rows ) === self::BATCH && $sent ) { self::queue( $product_id, true ); }
        return $sent;
    }

    /* ---------- Merchant view ---------- */

    public static function read(): array {
        Store::require_cap( 'manage_woocommerce' );
        global $wpdb; $table = self::table();
        $top = $wpdb->get_results( $wpdb->prepare( "SELECT product_id, COUNT(*) AS waiting, MIN(created) AS since FROM %i WHERE status='waiting' GROUP BY product_id ORDER BY waiting DESC, since ASC LIMIT 30", $table ), ARRAY_A );
        $rows = array();
        foreach ( $top as $row ) {
            $product = wc_get_product( (int) $row['product_id'] );
            if ( ! $product ) { continue; }
            $rows[] = array( 'id'=>$product->get_id(), 'parent'=>$product->get_parent_id() ?: $product->get_id(), 'name'=>$product->get_name(), 'sku'=>$product->get_sku(), 'waiting'=>(int) $row['waiting'], 'since'=>wp_date( get_option( 'date_format' ), strtotime( $row['since'] . ' UTC' ) ), 'in_stock'=>$product->is_in_stock() );
        }
        $email = WC()->mailer()->get_emails()['StoreSuit_Stock_Alert'] ?? null;
        return array(
            'settings' => self::settings(),
            'waiting'  => (int) $wpdb->get_var( $wpdb->prepare( "SELECT COUNT(*) FROM %i WHERE status='waiting'", $table ) ),
            'sent'     => (int) $wpdb->get_var( $wpdb->prepare( "SELECT COUNT(*) FROM %i WHERE status='sent' AND notified>=%s", $table, gmdate( 'Y-m-d H:i:s', time() - 30 * DAY_IN_SECONDS ) ) ),
            'rows'     => $rows,
            'email_enabled' => $email ? $email->is_enabled() : false,
            'email_settings' => admin_url( 'admin.php?page=wc-settings&tab=email&section=' . strtolower( 'StoreSuit_Stock_Alert' ) ),
        );
    }

    public static function save( array $data ): array {
        Store::require_cap( 'manage_woocommerce' );
        $current = self::settings(); $enabled = ! empty( $data['enabled'] ) && $data['enabled'] !== '0';
        if ( $enabled !== $current['enabled'] && empty( $data['confirmed'] ) ) { throw new \InvalidArgumentException( I18n::t( 'Confirm this change before saving.' ) ); }
        update_option( self::SETTINGS, array( 'enabled'=>$enabled, 'auto_send'=>! isset( $data['auto_send'] ) ? $current['auto_send'] : ( ! empty( $data['auto_send'] ) && $data['auto_send'] !== '0' ) ), false );
        // Off: the emails already queued are cancelled and the waiting requests are kept. Turning requests on again
        // queues nothing, so no old request is emailed silently: waiting shoppers are emailed after a product comes
        // back in stock from then on, or when the owner sends by hand.
        if ( ! $enabled ) { self::unschedule(); }
        if ( $enabled !== $current['enabled'] ) { Store::audit( 'settings', 0, $enabled ? 'stock_alerts_enabled' : 'stock_alerts_disabled', array() ); }
        return self::read();
    }

    private static function unschedule(): void {
        if ( function_exists( 'as_unschedule_all_actions' ) ) { as_unschedule_all_actions( self::HOOK ); }
        wp_unschedule_hook( self::HOOK );
    }

    /** Adds how many shoppers wait for each product to purchase-suggestion rows (one query per page). */
    public static function with_waiting( array $rows ): array {
        $ids = array_filter( array_map( static fn( $row ) => (int) ( $row['product_id'] ?? 0 ), $rows ) );
        if ( ! $ids || ! get_option( self::SCHEMA ) ) { return $rows; }
        global $wpdb;
        $counts = $wpdb->get_results( $wpdb->prepare( "SELECT product_id, COUNT(*) AS waiting FROM %i WHERE status='waiting' AND product_id IN (" . implode( ',', array_fill( 0, count( $ids ), '%d' ) ) . ') GROUP BY product_id', array_merge( array( self::table() ), $ids ) ), OBJECT_K );
        foreach ( $rows as &$row ) { $row['waiting'] = isset( $counts[ (int) ( $row['product_id'] ?? 0 ) ] ) ? (int) $counts[ (int) $row['product_id'] ]->waiting : 0; }
        return $rows;
    }

    /** Manual send for a product that is in stock again (for stores that turn off automatic sending). */
    public static function send_now( int $product_id ): array {
        Store::require_cap( 'manage_woocommerce' );
        if ( ! self::settings()['enabled'] ) { throw new \RuntimeException( I18n::t( 'Back-in-stock requests are off.' ) ); }
        $product = wc_get_product( $product_id );
        if ( ! $product || ! $product->is_in_stock() ) { throw new \InvalidArgumentException( I18n::t( 'Emails go out only when the product is in stock.' ) ); }
        self::queue( $product_id );
        Store::audit( 'product', $product_id, 'stock_alerts_sent', array() );
        return self::read();
    }

    /* ---------- Privacy and retention ---------- */

    public static function export( string $email, int $page = 1 ): array {
        global $wpdb; $data = array();
        foreach ( (array) $wpdb->get_results( $wpdb->prepare( 'SELECT id,product_id,status,created FROM %i WHERE email_hash=%s', self::table(), hash( 'sha256', strtolower( $email ) ) ), ARRAY_A ) as $row ) {
            $product = wc_get_product( (int) $row['product_id'] );
            $data[] = array( 'group_id'=>'storesuit-stock-alerts', 'group_label'=>I18n::t( 'Back-in-stock requests' ), 'item_id'=>'stock-alert-' . $row['id'], 'data'=>array(
                array( 'name'=>I18n::t( 'Product' ), 'value'=>$product ? $product->get_name() : '#' . $row['product_id'] ),
                array( 'name'=>I18n::t( 'Status' ), 'value'=>array( 'waiting'=>I18n::t( 'Waiting' ), 'sending'=>I18n::t( 'Sending' ), 'sent'=>I18n::t( 'Sent' ), 'cancelled'=>I18n::t( 'Cancelled' ) )[ $row['status'] ] ?? $row['status'] ),
                array( 'name'=>I18n::t( 'Requested' ), 'value'=>$row['created'] ),
            ) );
        }
        return array( 'data'=>$data, 'done'=>true );
    }

    public static function erase( string $email, int $page = 1 ): array {
        global $wpdb;
        $removed = (int) $wpdb->delete( self::table(), array( 'email_hash'=>hash( 'sha256', strtolower( $email ) ) ) );
        return array( 'items_removed'=>$removed > 0, 'items_retained'=>false, 'messages'=>array(), 'done'=>true );
    }

    public static function cleanup(): void {
        global $wpdb; $table = self::table();
        // A request stuck in 'sending' (the process stopped mid-mail) is never retried, so it cannot be emailed twice; it just ages out.
        $wpdb->query( $wpdb->prepare( "DELETE FROM %i WHERE status IN ('sent','cancelled','sending') AND created<%s", $table, gmdate( 'Y-m-d H:i:s', time() - 90 * DAY_IN_SECONDS ) ) );
        $wpdb->query( $wpdb->prepare( "DELETE FROM %i WHERE status='waiting' AND created<%s", $table, gmdate( 'Y-m-d H:i:s', time() - 365 * DAY_IN_SECONDS ) ) );
    }
}