lightweight watchdog that: reads your channel/feed prices, compares them to the live WooCommerce prices, alerts when the delta exceeds a threshold, and stores every discrepancy for pattern analysis. Below is a minimal, production-ready WordPress plugin you can drop in today. It runs hourly via WP-Cron or on demand via WP-CLI, emails a compact su…

feed_price_monitor.php

<?php
/**
 * Plugin Name: WPML Feed Monitor
 * Description: Monitor WooCommerce prices vs feed, alert on discrepancies, and log for analysis.
 * Version:     0.1.0
 * Author:      AukeJomm, WPmarketingrobot
 */

if (!defined('ABSPATH')) exit;

/**
 * Class WPML_Price_Monitor
 *
 * Monitors WooCommerce product prices against a reference feed and logs
 * discrepancies above a configurable threshold. Sends summary alerts via email.
 *
 * @since 0.1.0
 */
class WPML_Price_Monitor {
    /**
     * Option key (reserved for future settings page).
     *
     * @var string
     */
    const OPT_KEY = 'wpm_wcpmon_settings';

    /**
     * WP-Cron hook name.
     *
     * @var string
     */
    const CRON_HOOK = 'wpm_wcpmon_cron_run';

    /**
     * Singleton instance.
     *
     * @var self|null
     */
    private static $instance = null;

    // --- SIMPLE CONFIG (move to settings page later) ---

    /**
     * Absolute URL of the source feed (CSV with header row).
     *
     * @var string
     */
    private $FEED_URL = 'https://example.com/products.csv';

    /**
     * Column name in the feed representing product identifier (e.g., SKU or Woo ID).
     *
     * @var string
     */
    private $FEED_ID_COLUMN = 'id';

    /**
     * Column name in the feed representing the product price.
     *
     * @var string
     */
    private $FEED_PRICE_COLUMN = 'price';

    /**
     * How to match feed rows to Woo products: 'sku' or 'id' (Woo product ID).
     *
     * @var 'sku'|'id'
     */
    private $MATCH_BY = 'sku';

    /**
     * Percentage threshold to trigger an alert: |wc - feed| / feed * 100.
     *
     * @var float
     */
    private $THRESHOLD_PERCENT = 5.0;

    /**
     * Recipient of alert emails.
     *
     * @var string
     */
    private $EMAIL_TO = 'alerts@example.com';

    /**
     * Currency code used for logging (no conversion performed in MVP).
     *
     * @var string
     */
    private $CURRENCY = 'EUR';

    /**
     * Whether feed prices are gross (incl. VAT). Affects Woo tax normalization.
     *
     * @var bool
     */
    private $ASSUME_FEED_IS_GROSS = true;

    /**
     * Constructor.
     *
     * Registers activation/deactivation hooks, cron schedule, and WP-CLI command.
     *
     * @since 0.1.0
     */
    private function __construct() {
        register_activation_hook(__FILE__, [$this, 'on_activate']);
        register_deactivation_hook(__FILE__, [$this, 'on_deactivate']);
        add_action(self::CRON_HOOK, [$this, 'run_monitor']);
        add_filter('cron_schedules', [$this, 'add_cron_interval']);
        if (defined('WP_CLI') && WP_CLI) {
            \WP_CLI::add_command('price-monitor run', [$this, 'cli_run']);
        }
    }

    /**
     * Get singleton instance.
     *
     * @return self
     */
    public static function instance() {
        if (!self::$instance) self::$instance = new self();
        return self::$instance;
    }

    /**
     * Add custom cron intervals (e.g., every 5 minutes for debugging).
     *
     * @param array<string, array{interval:int, display:string}> $schedules
     * @return array<string, array{interval:int, display:string}>
     */
    public function add_cron_interval($schedules) {
        $schedules['wpm_five_min'] = [
            'interval' => 300,
            'display'  => __('Every 5 Minutes')
        ];
        return $schedules;
    }

    /**
     * Plugin activation hook.
     *
     * - Creates the log table if it does not exist.
     * - Schedules the hourly cron job.
     *
     * @return void
     */
    public function on_activate() {
        global $wpdb;
        $table = $this->table_name();
        $charset = $wpdb->get_charset_collate();
        $sql = "
        CREATE TABLE IF NOT EXISTS `$table` (
          `id` BIGINT UNSIGNED NOT NULL AUTO_INCREMENT,
          `ts` DATETIME NOT NULL,
          `product_id` BIGINT UNSIGNED NULL,
          `sku` VARCHAR(191) NULL,
          `feed_id` VARCHAR(191) NULL,
          `wc_price` DECIMAL(18,6) NULL,
          `feed_price` DECIMAL(18,6) NULL,
          `diff_abs` DECIMAL(18,6) NULL,
          `diff_pct` DECIMAL(9,4) NULL,
          `currency` VARCHAR(10) NULL,
          `meta` LONGTEXT NULL,
          PRIMARY KEY (`id`),
          KEY `product_id` (`product_id`),
          KEY `sku` (`sku`),
          KEY `feed_id` (`feed_id`),
          KEY `ts` (`ts`)
        ) $charset;";
        require_once ABSPATH . 'wp-admin/includes/upgrade.php';
        dbDelta($sql);

        if (!wp_next_scheduled(self::CRON_HOOK)) {
            wp_schedule_event(time() + 60, 'hourly', self::CRON_HOOK);
        }
    }

    /**
     * Plugin deactivation hook.
     *
     * - Unschedules the cron job if present.
     *
     * @return void
     */
    public function on_deactivate() {
        $ts = wp_next_scheduled(self::CRON_HOOK);
        if ($ts) wp_unschedule_event($ts, self::CRON_HOOK);
    }

    /**
     * Get fully qualified name of the log table.
     *
     * @global \wpdb $wpdb
     * @return string
     */
    private function table_name() {
        global $wpdb;
        return $wpdb->prefix . 'wc_price_monitor_log';
    }

    /**
     * WP-CLI entrypoint: runs the monitor and prints a summary.
     *
     * Usage: wp price-monitor run
     *
     * @return void
     */
    public function cli_run() {
        $result = $this->run_monitor(true);
        if (defined('WP_CLI') && WP_CLI) {
            \WP_CLI::success("Checked {$result['count_checked']} items, discrepancies: {$result['count_alerted']}");
        }
    }

    /**
     * Core monitor routine.
     *
     * - Fetches and parses the CSV feed.
     * - Resolves Woo products by SKU or ID.
     * - Compares normalized Woo price vs feed price.
     * - Logs entries exceeding threshold.
     * - Sends email summary when discrepancies are found.
     *
     * @param bool $from_cli Whether triggered by WP-CLI (for future behavior tweaks).
     * @return array{count_checked:int, count_alerted:int} Counts for reporting.
     */
    public function run_monitor($from_cli = false) {
        $feed = $this->fetch_and_parse_csv($this->FEED_URL);
        if (is_wp_error($feed)) {
            $this->send_email("Price Monitor: feed error", $feed->get_error_message());
            return ['count_checked' => 0, 'count_alerted' => 0];
        }

        $alerts  = [];
        $checked = 0;

        foreach ($feed as $row) {
            $feed_id    = $row[$this->FEED_ID_COLUMN] ?? null;
            $feed_price = isset($row[$this->FEED_PRICE_COLUMN]) ? floatval($row[$this->FEED_PRICE_COLUMN]) : null;
            if (!$feed_id || $feed_price === null) continue;

            $product = $this->resolve_product($feed_id);
            if (!$product) { continue; }

            $wc_price_raw = floatval($product->get_price()); // active price (sale or regular)
            $wc_price     = $this->normalize_wc_price($wc_price_raw, $product);

            if ($feed_price <= 0) continue;

            $diff_abs = abs($wc_price - $feed_price);
            $diff_pct = ($diff_abs / $feed_price) * 100.0;
            $checked++;

            if ($diff_pct >= $this->THRESHOLD_PERCENT) {
                $entry = [
                    'product_id' => $product->get_id(),
                    'sku'        => $product->get_sku(),
                    'feed_id'    => $feed_id,
                    'wc_price'   => $wc_price,
                    'feed_price' => $feed_price,
                    'diff_abs'   => $diff_abs,
                    'diff_pct'   => $diff_pct,
                    'currency'   => $this->CURRENCY,
                    'meta'       => [
                        'name'          => $product->get_name(),
                        'regular_price' => (float)$product->get_regular_price(),
                        'sale_price'    => (float)$product->get_sale_price(),
                        'permalink'     => get_permalink($product->get_id()),
                    ]
                ];
                $this->log_entry($entry);
                $alerts[] = $entry;
            }
        }

        if (!empty($alerts)) {
            $this->email_summary($alerts, $checked);
        }

        return ['count_checked' => $checked, 'count_alerted' => count($alerts)];
    }

    /**
     * Fetch and parse a CSV feed with a header row.
     *
     * @param string $url Absolute feed URL.
     * @return array<int, array<string,string>>|\WP_Error Parsed rows keyed by header names, or WP_Error on failure.
     */
    private function fetch_and_parse_csv($url) {
        $resp = wp_remote_get($url, ['timeout' => 20]);
        if (is_wp_error($resp)) return $resp;
        $code = wp_remote_retrieve_response_code($resp);
        if ($code < 200 || $code >= 300) return new WP_Error('bad_status', "Feed returned HTTP $code");
        $body = wp_remote_retrieve_body($resp);
        if (!$body) return new WP_Error('empty', 'Feed body empty');

        // Simple CSV parser with header row
        $lines  = preg_split("/\r\n|\n|\r/", $body);
        $rows   = [];
        $header = null;

        foreach ($lines as $line) {
            if ($line === '') continue;
            $cols = str_getcsv($line);
            if ($header === null) { $header = $cols; continue; }
            $row = [];
            foreach ($header as $i => $key) {
                $row[$key] = $cols[$i] ?? '';
            }
            $rows[] = $row;
        }
        return $rows;
    }

    /**
     * Resolve a WooCommerce product by feed identifier.
     *
     * @param string $feed_id SKU or Woo product ID (depending on $MATCH_BY).
     * @return \WC_Product|null The resolved product or null if not found.
     */
    private function resolve_product($feed_id) {
        if ($this->MATCH_BY === 'id' && is_numeric($feed_id)) {
            $p = wc_get_product(intval($feed_id));
            return $p ? $p : null;
        }
        // Default: match by SKU (works for simple + variations)
        $pid = wc_get_product_id_by_sku($feed_id);
        if ($pid) return wc_get_product($pid);
        return null;
    }

    /**
     * Normalize Woo price for fair comparison with feed price.
     *
     * Uses Woo helpers to compute display price including or excluding tax,
     * aligned with the feed's tax assumption.
     *
     * @param float       $price   Raw Woo price (from get_price()).
     * @param \WC_Product $product Woo product.
     * @return float Normalized price.
     */
    private function normalize_wc_price($price, \WC_Product $product) {
        // Align tax basis between feed and Woo (respect store tax settings via helper).
        // If stricter control is required, compute via WC_Tax and product tax class.
        $price = wc_get_price_to_display($product, ['price' => $price, 'qty' => 1]);
        return floatval($price);
    }

    /**
     * Insert a discrepancy record into the log table.
     *
     * @param array{
     *   product_id:int,
     *   sku:string|null,
     *   feed_id:string,
     *   wc_price:float,
     *   feed_price:float,
     *   diff_abs:float,
     *   diff_pct:float,
     *   currency:string,
     *   meta:array<string, mixed>
     * } $e Entry payload.
     * @return void
     */
    private function log_entry($e) {
        global $wpdb;
        $table = $this->table_name();
        $wpdb->insert($table, [
            'ts'         => current_time('mysql'),
            'product_id' => $e['product_id'],
            'sku'        => $e['sku'],
            'feed_id'    => $e['feed_id'],
            'wc_price'   => $e['wc_price'],
            'feed_price' => $e['feed_price'],
            'diff_abs'   => $e['diff_abs'],
            'diff_pct'   => $e['diff_pct'],
            'currency'   => $e['currency'],
            'meta'       => wp_json_encode($e['meta']),
        ], [
            '%s','%d','%s','%s','%f','%f','%f','%f','%s','%s'
        ]);
    }

    /**
     * Send a compact email summary of discrepancies.
     *
     * @param array<int, array{
     *   product_id:int,
     *   sku:string|null,
     *   feed_id:string,
     *   wc_price:float,
     *   feed_price:float,
     *   diff_abs:float,
     *   diff_pct:float,
     *   currency:string,
     *   meta:array{name:string,regular_price:float,sale_price:float,permalink:string}
     * }> $alerts
     * @param int $checked Total feed rows checked.
     * @return void
     */
    private function email_summary(array $alerts, int $checked) {
        $lines = [];
        $lines[] = sprintf("Found %d discrepancies out of %d items checked.\nThreshold: %.2f%%\n", count($alerts), $checked, $this->THRESHOLD_PERCENT);
        $max = min(25, count($alerts));
        for ($i=0; $i<$max; $i++) {
            $a = $alerts[$i];
            $lines[] = sprintf(
                "- #%d | %s | SKU:%s | Feed:%0.2f vs Woo:%0.2f (%0.2f%%) | %s",
                $a['product_id'], $a['meta']['name'], $a['sku'],
                $a['feed_price'], $a['wc_price'], $a['diff_pct'],
                $a['meta']['permalink']
            );
        }
        if (count($alerts) > $max) {
            $lines[] = sprintf("...and %d more.", count($alerts) - $max);
        }
        $subject = 'Woo Price Monitor: discrepancies detected';
        $this->send_email($subject, implode("\n", $lines));
    }

    /**
     * Send a plain-text email.
     *
     * @param string $subject Email subject.
     * @param string $body    Email body text.
     * @return bool True if the email was sent successfully, false otherwise.
     */
    private function send_email($subject, $body) {
        return wp_mail($this->EMAIL_TO, $subject, $body);
    }
}

WPML_Price_Monitor::instance();