feat: add structured file-based logging with admin log viewer

- New WooList_Logger class writes to wp-content/uploads/woolist-logs/woolist.log
  - INFO level: subscription events, test connection results (always recorded)
  - ERROR level: API failures, config problems (always recorded + php error_log fallback)
  - DEBUG level: full request URLs (password redacted), raw responses, step-by-step
    flow (only when "Enable debug logging" is checked in settings)
  - Auto-rotates at 1 MB; log directory protected by .htaccess
- API class: logs every request URL (redacted) and raw response body at DEBUG,
  errors at ERROR; subscribe_email_to_list logs each step (lookup/create/add)
- Hooks class: logs hook fire, skip reasons, and sync intent at DEBUG/INFO/ERROR
- Shortcode class: logs AJAX submissions, coupon generation, and failures
- Admin: new Logging section with "Enable debug logging" checkbox;
  log viewer textarea (last 300 lines, dark theme) + Clear Log button
  both visible at bottom of WooCommerce → Settings → phpList tab

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

woolist-phplist/includes/class-woolist-admin.php

@@ -23,6 +23,9 @@ class WooList_Admin {
 		// Test connection admin-post handler.
 		add_action( 'admin_post_woolist_test_connection', [ $this, 'handle_test_connection' ] );
 
+		// Clear log admin-post handler.
+		add_action( 'admin_post_woolist_clear_log', [ $this, 'handle_clear_log' ] );
+
 		// Enqueue admin JS/CSS only on the WC settings page.
 		add_action( 'admin_enqueue_scripts', [ $this, 'enqueue_admin_assets' ] );
 	}
@@ -44,6 +47,7 @@ class WooList_Admin {
 	public function render_settings(): void {
 		woocommerce_admin_fields( $this->get_settings() );
 		$this->render_test_connection_button();
+		$this->render_log_viewer();
 	}
 
 	/**
@@ -79,6 +83,48 @@ class WooList_Admin {
 			. '</a></p>';
 	}
 
+	/**
+	 * Render the log viewer panel below all settings.
+	 */
+	private function render_log_viewer(): void {
+		$log_content = WooList_Logger::read_recent( 300 );
+		$log_path    = WooList_Logger::get_log_path();
+		$clear_url   = wp_nonce_url(
+			admin_url( 'admin-post.php?action=woolist_clear_log' ),
+			'woolist_clear_log'
+		);
+
+		$notice = get_transient( 'woolist_clear_log_notice_' . get_current_user_id() );
+		if ( $notice ) {
+			delete_transient( 'woolist_clear_log_notice_' . get_current_user_id() );
+			echo '<div class="notice notice-success inline"><p>' . esc_html( $notice ) . '</p></div>';
+		}
+
+		echo '<hr style="margin:2em 0;">';
+		echo '<h2>' . esc_html__( 'Activity Log', 'woolist-phplist' ) . '</h2>';
+		echo '<p style="color:#646970;">';
+		echo esc_html__( 'Log file: ', 'woolist-phplist' );
+		echo '<code>' . esc_html( $log_path ) . '</code>';
+		echo '</p>';
+
+		if ( $log_content === '' ) {
+			echo '<p><em>' . esc_html__( 'Log is empty.', 'woolist-phplist' ) . '</em></p>';
+		} else {
+			echo '<div style="position:relative;">';
+			echo '<textarea readonly rows="20" style="width:100%;font-family:monospace;font-size:12px;background:#1e1e1e;color:#d4d4d4;padding:12px;border:1px solid #ccc;border-radius:4px;resize:vertical;white-space:pre;">'
+				. esc_textarea( $log_content )
+				. '</textarea>';
+			echo '</div>';
+		}
+
+		echo '<p>';
+		echo '<a href="' . esc_url( $clear_url ) . '" class="button button-secondary" '
+			. 'onclick="return confirm(\'' . esc_js( __( 'Clear the entire log file?', 'woolist-phplist' ) ) . '\')">'
+			. esc_html__( 'Clear Log', 'woolist-phplist' )
+			. '</a>';
+		echo '</p>';
+	}
+
 	/**
 	 * Handle the "Test Connection" form action.
 	 */
@@ -89,10 +135,13 @@ class WooList_Admin {
 			wp_die( esc_html__( 'You do not have permission to perform this action.', 'woolist-phplist' ) );
 		}
 
+		WooList_Logger::info( 'Test Connection triggered by user ID ' . get_current_user_id() );
+
 		$result  = $this->api->lists_get();
 		$user_id = get_current_user_id();
 
 		if ( is_wp_error( $result ) ) {
+			WooList_Logger::error( 'Test Connection failed: ' . $result->get_error_message() );
 			set_transient(
 				'woolist_test_connection_notice_' . $user_id,
 				[
@@ -103,6 +152,7 @@ class WooList_Admin {
 			);
 		} else {
 			$count = is_array( $result ) ? count( $result ) : '?';
+			WooList_Logger::info( 'Test Connection succeeded, found ' . $count . ' list(s).' );
 			set_transient(
 				'woolist_test_connection_notice_' . $user_id,
 				[
@@ -121,6 +171,29 @@ class WooList_Admin {
 		exit;
 	}
 
+	/**
+	 * Handle the "Clear Log" admin-post action.
+	 */
+	public function handle_clear_log(): void {
+		check_admin_referer( 'woolist_clear_log' );
+
+		if ( ! current_user_can( 'manage_woocommerce' ) ) {
+			wp_die( esc_html__( 'You do not have permission to perform this action.', 'woolist-phplist' ) );
+		}
+
+		WooList_Logger::clear();
+		WooList_Logger::info( 'Log cleared by user ID ' . get_current_user_id() );
+
+		set_transient(
+			'woolist_clear_log_notice_' . get_current_user_id(),
+			__( 'Log file cleared.', 'woolist-phplist' ),
+			60
+		);
+
+		wp_safe_redirect( admin_url( 'admin.php?page=wc-settings&tab=woolist' ) );
+		exit;
+	}
+
 	/**
 	 * Enqueue admin-side assets on WC Settings → phpList tab.
 	 */
@@ -129,7 +202,6 @@ class WooList_Admin {
 		if ( ! $screen || strpos( $screen->id, 'woocommerce' ) === false ) {
 			return;
 		}
-		// No custom admin JS/CSS needed yet; WC handles the settings form.
 	}
 
 	/**
@@ -336,6 +408,25 @@ class WooList_Admin {
 				'type' => 'sectionend',
 				'id'   => 'woolist_section_newsletter',
 			],
+
+			// ── Section 6: Logging ───────────────────────────────────────────
+			[
+				'title' => __( 'Logging', 'woolist-phplist' ),
+				'type'  => 'title',
+				'desc'  => __( 'Control what gets recorded in the activity log shown below.', 'woolist-phplist' ),
+				'id'    => 'woolist_section_logging',
+			],
+			[
+				'title'   => __( 'Enable debug logging', 'woolist-phplist' ),
+				'desc'    => __( 'Log full API request URLs (password redacted) and raw responses. Disable on production once everything works.', 'woolist-phplist' ),
+				'id'      => 'woolist_enable_debug_log',
+				'type'    => 'checkbox',
+				'default' => 'no',
+			],
+			[
+				'type' => 'sectionend',
+				'id'   => 'woolist_section_logging',
+			],
 		];
 	}
 }

woolist-phplist/includes/class-woolist-api.php

@@ -12,7 +12,7 @@ class WooList_API {
 	/**
 	 * Retrieve a saved plugin option.
 	 *
-	 * @param string $key Option key (without prefix).
+	 * @param string $key Option key (without woolist_ prefix).
 	 * @param mixed  $default Default value.
 	 * @return mixed
 	 */
@@ -63,38 +63,45 @@ class WooList_API {
 		$url = $this->build_url( $cmd, $extra );
 
 		if ( is_wp_error( $url ) ) {
+			WooList_Logger::error( 'Cannot build URL for cmd=' . $cmd . ': ' . $url->get_error_message() );
 			return $url;
 		}
 
+		WooList_Logger::debug( '→ API request  cmd=' . $cmd . '  url=' . WooList_Logger::redact_url( $url ) );
+
 		$response = wp_remote_post( $url, [ 'timeout' => 15 ] );
 
 		if ( is_wp_error( $response ) ) {
-			error_log( '[WooList] API request failed for cmd=' . $cmd . ': ' . $response->get_error_message() );
+			WooList_Logger::error( 'HTTP request failed  cmd=' . $cmd . '  error=' . $response->get_error_message() );
 			return $response;
 		}
 
 		$code = wp_remote_retrieve_response_code( $response );
 		$body = wp_remote_retrieve_body( $response );
 
+		// Log the raw response at debug level (truncated to 2 KB to avoid huge entries).
+		WooList_Logger::debug( '← API response  cmd=' . $cmd . '  http=' . $code . '  body=' . substr( $body, 0, 2048 ) );
+
 		if ( $code < 200 || $code >= 300 ) {
-			error_log( '[WooList] API returned HTTP ' . $code . ' for cmd=' . $cmd );
+			WooList_Logger::error( 'API returned HTTP ' . $code . '  cmd=' . $cmd );
 			return new WP_Error( 'woolist_http_error', 'HTTP error ' . $code );
 		}
 
 		$data = json_decode( $body, true );
 
 		if ( json_last_error() !== JSON_ERROR_NONE ) {
-			error_log( '[WooList] API returned invalid JSON for cmd=' . $cmd . ': ' . $body );
+			WooList_Logger::error( 'Invalid JSON response  cmd=' . $cmd . '  body=' . substr( $body, 0, 500 ) );
 			return new WP_Error( 'woolist_json_error', 'Invalid JSON response from phpList.' );
 		}
 
 		// phpList REST API signals errors via a "status" field.
 		if ( isset( $data['status'] ) && strtolower( $data['status'] ) === 'error' ) {
 			$message = $data['errormessage'] ?? $data['message'] ?? 'Unknown API error';
-			error_log( '[WooList] API error for cmd=' . $cmd . ': ' . $message );
+			WooList_Logger::error( 'API error  cmd=' . $cmd . '  message=' . $message );
 			return new WP_Error( 'woolist_api_error', $message );
 		}
 
+		WooList_Logger::debug( 'API call succeeded  cmd=' . $cmd );
 		return $data;
 	}
 
@@ -118,9 +125,9 @@ class WooList_API {
 		return $this->call(
 			'subscriberAdd',
 			[
-				'email'      => rawurlencode( $email ),
+				'email'     => rawurlencode( $email ),
-				'confirmed'  => 1,
+				'confirmed' => 1,
-				'htmlemail'  => 1,
+				'htmlemail' => 1,
 			]
 		);
 	}
@@ -152,35 +159,45 @@ class WooList_API {
 	 * @return array{success: bool, subscriber_id: int|null}
 	 */
 	public function subscribe_email_to_list( string $email, int $list_id ): array {
-		// Try to find existing subscriber.
+		WooList_Logger::debug( 'subscribe_email_to_list  email=' . $email . '  list_id=' . $list_id );
+
+		// Step 1: look up existing subscriber.
 		$subscriber_id = null;
 		$existing      = $this->subscriber_get_by_email( $email );
 
 		if ( ! is_wp_error( $existing ) && ! empty( $existing['id'] ) ) {
 			$subscriber_id = (int) $existing['id'];
+			WooList_Logger::debug( 'Found existing subscriber  id=' . $subscriber_id . '  email=' . $email );
 		} else {
-			// Create new subscriber.
+			// Step 2: create a new subscriber.
+			WooList_Logger::debug( 'Subscriber not found, creating new  email=' . $email );
 			$added = $this->subscriber_add( $email );
+
 			if ( is_wp_error( $added ) ) {
-				error_log( '[WooList] Could not add subscriber ' . $email . ': ' . $added->get_error_message() );
+				WooList_Logger::error( 'Could not create subscriber  email=' . $email . '  error=' . $added->get_error_message() );
 				return [ 'success' => false, 'subscriber_id' => null ];
 			}
+
 			$subscriber_id = isset( $added['id'] ) ? (int) $added['id'] : null;
+
+			if ( $subscriber_id ) {
+				WooList_Logger::info( 'Created new subscriber  id=' . $subscriber_id . '  email=' . $email );
+			} else {
+				WooList_Logger::error( 'API returned no subscriber ID after add  email=' . $email . '  response=' . wp_json_encode( $added ) );
+				return [ 'success' => false, 'subscriber_id' => null ];
+			}
 		}
 
-		if ( ! $subscriber_id ) {
+		// Step 3: add subscriber to the list.
-			error_log( '[WooList] Could not determine subscriber ID for ' . $email );
+		WooList_Logger::debug( 'Adding subscriber ' . $subscriber_id . ' to list ' . $list_id );
-			return [ 'success' => false, 'subscriber_id' => null ];
-		}
-
-		// Add subscriber to the list.
 		$result = $this->list_subscriber_add( $list_id, $subscriber_id );
 
 		if ( is_wp_error( $result ) ) {
-			error_log( '[WooList] Could not add subscriber ' . $subscriber_id . ' to list ' . $list_id . ': ' . $result->get_error_message() );
+			WooList_Logger::error( 'Could not add subscriber to list  subscriber_id=' . $subscriber_id . '  list_id=' . $list_id . '  error=' . $result->get_error_message() );
 			return [ 'success' => false, 'subscriber_id' => $subscriber_id ];
 		}
 
+		WooList_Logger::info( 'Subscribed  email=' . $email . '  subscriber_id=' . $subscriber_id . '  list_id=' . $list_id );
 		return [ 'success' => true, 'subscriber_id' => $subscriber_id ];
 	}
 

woolist-phplist/includes/class-woolist-hooks.php

@@ -26,26 +26,32 @@ class WooList_Hooks {
 	 * @param int $order_id WooCommerce order ID.
 	 */
 	public function on_order_completed( int $order_id ): void {
+		WooList_Logger::debug( 'Hook fired: order_completed  order_id=' . $order_id );
+
 		if ( get_option( 'woolist_sync_completed' ) !== 'yes' ) {
+			WooList_Logger::debug( 'Completed order sync disabled, skipping.' );
 			return;
 		}
 
 		$list_id = (int) get_option( 'woolist_completed_list_id', 0 );
 		if ( $list_id < 1 ) {
-			error_log( '[WooList] Completed order sync enabled but no list ID configured.' );
+			WooList_Logger::error( 'Completed order sync enabled but no list ID configured  order_id=' . $order_id );
 			return;
 		}
 
 		$order = wc_get_order( $order_id );
 		if ( ! $order ) {
+			WooList_Logger::error( 'Could not load order  order_id=' . $order_id );
 			return;
 		}
 
 		$email = $order->get_billing_email();
 		if ( ! is_email( $email ) ) {
+			WooList_Logger::error( 'Order has no valid billing email  order_id=' . $order_id );
 			return;
 		}
 
+		WooList_Logger::info( 'Syncing completed order  order_id=' . $order_id . '  email=' . $email . '  list_id=' . $list_id );
 		$this->api->subscribe_email_to_list( $email, $list_id );
 	}
 
@@ -55,26 +61,32 @@ class WooList_Hooks {
 	 * @param int $order_id WooCommerce order ID.
 	 */
 	public function on_order_cancelled( int $order_id ): void {
+		WooList_Logger::debug( 'Hook fired: order_cancelled  order_id=' . $order_id );
+
 		if ( get_option( 'woolist_sync_cancelled' ) !== 'yes' ) {
+			WooList_Logger::debug( 'Cancelled order sync disabled, skipping.' );
 			return;
 		}
 
 		$list_id = (int) get_option( 'woolist_cancelled_list_id', 0 );
 		if ( $list_id < 1 ) {
-			error_log( '[WooList] Cancelled order sync enabled but no list ID configured.' );
+			WooList_Logger::error( 'Cancelled order sync enabled but no list ID configured  order_id=' . $order_id );
 			return;
 		}
 
 		$order = wc_get_order( $order_id );
 		if ( ! $order ) {
+			WooList_Logger::error( 'Could not load order  order_id=' . $order_id );
 			return;
 		}
 
 		$email = $order->get_billing_email();
 		if ( ! is_email( $email ) ) {
+			WooList_Logger::error( 'Order has no valid billing email  order_id=' . $order_id );
 			return;
 		}
 
+		WooList_Logger::info( 'Syncing cancelled order  order_id=' . $order_id . '  email=' . $email . '  list_id=' . $list_id );
 		$this->api->subscribe_email_to_list( $email, $list_id );
 	}
 
@@ -84,21 +96,26 @@ class WooList_Hooks {
 	 * @param int $user_id Newly registered user ID.
 	 */
 	public function on_user_register( int $user_id ): void {
+		WooList_Logger::debug( 'Hook fired: user_register  user_id=' . $user_id );
+
 		if ( get_option( 'woolist_sync_signup' ) !== 'yes' ) {
+			WooList_Logger::debug( 'Account signup sync disabled, skipping.' );
 			return;
 		}
 
 		$list_id = (int) get_option( 'woolist_signup_list_id', 0 );
 		if ( $list_id < 1 ) {
-			error_log( '[WooList] Account signup sync enabled but no list ID configured.' );
+			WooList_Logger::error( 'Account signup sync enabled but no list ID configured  user_id=' . $user_id );
 			return;
 		}
 
 		$user = get_userdata( $user_id );
 		if ( ! $user || ! is_email( $user->user_email ) ) {
+			WooList_Logger::error( 'Could not load user or invalid email  user_id=' . $user_id );
 			return;
 		}
 
+		WooList_Logger::info( 'Syncing new account  user_id=' . $user_id . '  email=' . $user->user_email . '  list_id=' . $list_id );
 		$this->api->subscribe_email_to_list( $user->user_email, $list_id );
 	}
 }

woolist-phplist/includes/class-woolist-logger.php

@@ -0,0 +1,141 @@
+<?php
+/**
+ * Simple file-based logger for WooList.
+ *
+ * Writes to wp-content/uploads/woolist-logs/woolist.log.
+ * The directory is protected from direct HTTP access via .htaccess.
+ *
+ * Levels:
+ *   INFO  — always written (subscription events, connection test results)
+ *   ERROR — always written (API failures, config problems)
+ *   DEBUG — written only when "Enable debug logging" is on (full request/response)
+ *
+ * @package WooList
+ */
+
+defined( 'ABSPATH' ) || exit;
+
+class WooList_Logger {
+
+	/** Absolute path to the log file. */
+	private static string $log_file = '';
+
+	/** Whether verbose debug lines are recorded. */
+	private static bool $debug_enabled = false;
+
+	/** Maximum log file size in bytes before rotation (1 MB). */
+	private const MAX_SIZE = 1048576;
+
+	/**
+	 * Initialise the logger: create the log directory and read the debug setting.
+	 * Must be called after WordPress options are available.
+	 */
+	public static function init(): void {
+		$upload     = wp_upload_dir();
+		$log_dir    = $upload['basedir'] . '/woolist-logs';
+
+		if ( ! is_dir( $log_dir ) ) {
+			wp_mkdir_p( $log_dir );
+		}
+
+		// Block direct HTTP access and directory listing.
+		$htaccess = $log_dir . '/.htaccess';
+		if ( ! file_exists( $htaccess ) ) {
+			file_put_contents( $htaccess, "Require all denied\ndeny from all\n" );
+		}
+		$index = $log_dir . '/index.php';
+		if ( ! file_exists( $index ) ) {
+			file_put_contents( $index, "<?php // Silence is golden.\n" );
+		}
+
+		self::$log_file      = $log_dir . '/woolist.log';
+		self::$debug_enabled = ( get_option( 'woolist_enable_debug_log' ) === 'yes' );
+	}
+
+	// ── Public logging methods ───────────────────────────────────────────────
+
+	/** Always logged. Use for normal subscription / connection events. */
+	public static function info( string $message ): void {
+		self::write( 'INFO', $message );
+	}
+
+	/** Always logged. Also echoes to php error_log as a fallback. */
+	public static function error( string $message ): void {
+		self::write( 'ERROR', $message );
+		error_log( '[WooList ERROR] ' . $message );
+	}
+
+	/**
+	 * Logged only when debug mode is enabled.
+	 * Use for full request URLs, raw response bodies, step-by-step flow.
+	 */
+	public static function debug( string $message ): void {
+		if ( self::$debug_enabled ) {
+			self::write( 'DEBUG', $message );
+		}
+	}
+
+	// ── Utility ─────────────────────────────────────────────────────────────
+
+	/**
+	 * Strip the password parameter from a phpList URL before logging it.
+	 *
+	 * @param string $url Full API URL.
+	 * @return string URL with password value replaced by ***.
+	 */
+	public static function redact_url( string $url ): string {
+		return preg_replace( '/(\bpassword=)[^&]+/', '$1***', $url );
+	}
+
+	/**
+	 * Return the last $lines lines of the log as a string.
+	 *
+	 * @param int $lines Number of lines to return.
+	 * @return string Log tail, or an empty string when the log doesn't exist yet.
+	 */
+	public static function read_recent( int $lines = 300 ): string {
+		if ( empty( self::$log_file ) || ! file_exists( self::$log_file ) ) {
+			return '';
+		}
+
+		$content = file_get_contents( self::$log_file );
+		if ( $content === false || $content === '' ) {
+			return '';
+		}
+
+		$all    = explode( "\n", rtrim( $content ) );
+		$recent = array_slice( $all, -$lines );
+		return implode( "\n", $recent );
+	}
+
+	/** Truncate the log file without deleting it. */
+	public static function clear(): void {
+		if ( ! empty( self::$log_file ) ) {
+			file_put_contents( self::$log_file, '' );
+		}
+	}
+
+	public static function get_log_path(): string {
+		return self::$log_file;
+	}
+
+	public static function is_debug_enabled(): bool {
+		return self::$debug_enabled;
+	}
+
+	// ── Internal ─────────────────────────────────────────────────────────────
+
+	private static function write( string $level, string $message ): void {
+		if ( empty( self::$log_file ) ) {
+			return;
+		}
+
+		// Rotate if the file exceeds MAX_SIZE.
+		if ( file_exists( self::$log_file ) && filesize( self::$log_file ) >= self::MAX_SIZE ) {
+			rename( self::$log_file, self::$log_file . '.old' );
+		}
+
+		$line = '[' . gmdate( 'Y-m-d H:i:s' ) . ' UTC] [' . $level . '] ' . $message . "\n";
+		file_put_contents( self::$log_file, $line, FILE_APPEND | LOCK_EX );
+	}
+}

woolist-phplist/includes/class-woolist-shortcode.php

@@ -101,24 +101,30 @@ class WooList_Shortcode {
 	public function handle_ajax(): void {
 		// 1. Verify nonce.
 		if ( ! check_ajax_referer( 'woolist_newsletter_nonce', 'nonce', false ) ) {
+			WooList_Logger::error( 'Newsletter AJAX: nonce verification failed' );
 			wp_send_json_error( [ 'message' => __( 'Security check failed. Please refresh and try again.', 'woolist-phplist' ) ], 403 );
 		}
 
 		// 2. Validate email.
 		$email = isset( $_POST['woolist_email'] ) ? sanitize_email( wp_unslash( $_POST['woolist_email'] ) ) : '';
 		if ( ! is_email( $email ) ) {
+			WooList_Logger::debug( 'Newsletter AJAX: invalid email submitted' );
 			wp_send_json_error( [ 'message' => __( 'Please enter a valid email address.', 'woolist-phplist' ) ], 400 );
 		}
 
+		WooList_Logger::debug( 'Newsletter AJAX: submission received  email=' . $email );
+
 		// 3. Get list ID.
 		$list_id = (int) get_option( 'woolist_newsletter_list_id', 0 );
 		if ( $list_id < 1 ) {
+			WooList_Logger::error( 'Newsletter AJAX: no list ID configured' );
 			wp_send_json_error( [ 'message' => __( 'Newsletter is not configured. Please contact the site administrator.', 'woolist-phplist' ) ], 500 );
 		}
 
 		// 4. Subscribe email to phpList.
 		$result = $this->api->subscribe_email_to_list( $email, $list_id );
 		if ( ! $result['success'] ) {
+			WooList_Logger::error( 'Newsletter AJAX: subscription failed  email=' . $email );
 			wp_send_json_error( [ 'message' => __( 'Could not subscribe your email. Please try again later.', 'woolist-phplist' ) ], 500 );
 		}
 
@@ -131,14 +137,18 @@ class WooList_Shortcode {
 
 			if ( $coupon_mode === 'fixed' ) {
 				$coupon_code = sanitize_text_field( get_option( 'woolist_coupon_fixed_code', '' ) );
+				WooList_Logger::debug( 'Newsletter AJAX: using fixed coupon  code=' . $coupon_code );
 			} else {
 				$coupon_code = $this->generate_coupon( $email );
+				WooList_Logger::info( 'Newsletter AJAX: generated coupon  code=' . $coupon_code . '  email=' . $email );
 			}
 		}
 
 		// Replace {coupon} placeholder in the thank-you message.
 		$thankyou_msg = str_replace( '{coupon}', esc_html( $coupon_code ), $thankyou_msg );
 
+		WooList_Logger::info( 'Newsletter AJAX: success  email=' . $email );
+
 		wp_send_json_success(
 			[
 				'message' => wp_kses_post( $thankyou_msg ),
@@ -155,13 +165,15 @@ class WooList_Shortcode {
 	 */
 	private function generate_coupon( string $email ): string {
 		if ( ! class_exists( 'WC_Coupon' ) ) {
-			error_log( '[WooList] WC_Coupon class not available; cannot generate coupon.' );
+			WooList_Logger::error( 'WC_Coupon class not available; cannot generate coupon.' );
 			return '';
 		}
 
-		$discount_pct  = (int) get_option( 'woolist_coupon_discount_pct', 10 );
+		$discount_pct = (int) get_option( 'woolist_coupon_discount_pct', 10 );
-		$expiry_days   = (int) get_option( 'woolist_coupon_expiry_days', 30 );
+		$expiry_days  = (int) get_option( 'woolist_coupon_expiry_days', 30 );
-		$coupon_code   = 'WOOLIST-' . strtoupper( substr( md5( $email . time() ), 0, 8 ) );
+		$coupon_code  = 'WOOLIST-' . strtoupper( substr( md5( $email . time() ), 0, 8 ) );
+
+		WooList_Logger::debug( 'Generating coupon  code=' . $coupon_code . '  discount=' . $discount_pct . '%  expiry_days=' . $expiry_days );
 
 		$expiry_date = '';
 		if ( $expiry_days > 0 ) {
@@ -180,11 +192,10 @@ class WooList_Shortcode {
 		);
 
 		if ( is_wp_error( $post_id ) ) {
-			error_log( '[WooList] Failed to create coupon post: ' . $post_id->get_error_message() );
+			WooList_Logger::error( 'Failed to create coupon post  error=' . $post_id->get_error_message() );
 			return '';
 		}
 
-		// Set coupon meta via WC functions.
 		update_post_meta( $post_id, 'discount_type', 'percent' );
 		update_post_meta( $post_id, 'coupon_amount', (string) $discount_pct );
 		update_post_meta( $post_id, 'usage_limit', '1' );
@@ -196,6 +207,7 @@ class WooList_Shortcode {
 			update_post_meta( $post_id, 'date_expires', strtotime( $expiry_date ) );
 		}
 
+		WooList_Logger::debug( 'Coupon created  post_id=' . $post_id . '  code=' . $coupon_code . '  expires=' . ( $expiry_date ?: 'never' ) );
 		return $coupon_code;
 	}
 }

woolist-phplist/woolist-phplist.php

@@ -42,6 +42,9 @@ function woolist_check_woocommerce() {
 function woolist_init() {
 	load_plugin_textdomain( 'woolist-phplist', false, dirname( plugin_basename( __FILE__ ) ) . '/languages' );
 
+	require_once WOOLIST_PATH . 'includes/class-woolist-logger.php';
+	WooList_Logger::init();
+
 	if ( ! woolist_check_woocommerce() ) {
 		return;
 	}