<?php
/**
 * Queued notifications.
 *
 * @package ReplyPing
 */

namespace PlugWren\ReplyPing;

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

/**
 * Notifier.
 */
final class Notifier {

	const HOOK       = 'replyping_send_notifications';
	const BATCH_SIZE = 50;
	const MAILED_KEY = '_replyping_mailed';

	/**
	 * Register hooks.
	 */
	public function __construct() {
		add_action( 'comment_post', array( $this, 'on_comment_post' ), 20, 2 );
		add_action( 'transition_comment_status', array( $this, 'on_transition' ), 10, 3 );
		add_action( self::HOOK, array( $this, 'process' ), 10, 2 );
	}

	/**
	 * New comment saved.
	 *
	 * @param int        $comment_id Comment ID.
	 * @param int|string $approved   Approval.
	 */
	public function on_comment_post( $comment_id, $approved ) {
		if ( '1' === (string) $approved ) {
			$this->queue( (int) $comment_id );
		}
	}

	/**
	 * Comment status changed.
	 *
	 * @param string      $new_status New status.
	 * @param string      $old_status Old status.
	 * @param \WP_Comment $comment    Comment.
	 */
	public function on_transition( $new_status, $old_status, $comment ) {
		if ( 'approved' === $new_status && 'approved' !== $old_status && $comment instanceof \WP_Comment ) {
			$this->queue( (int) $comment->comment_ID );
		}
	}

	/**
	 * Queue a comment once (atomic via unique meta).
	 *
	 * @param int $comment_id Comment ID.
	 */
	private function queue( $comment_id ) {
		if ( ! $comment_id || ! add_comment_meta( $comment_id, '_replyping_queued', 1, true ) ) {
			return;
		}
		wp_schedule_single_event( time() + 10, self::HOOK, array( $comment_id, 0 ) );
	}

	/**
	 * Short hash of an email for the mailed-record.
	 *
	 * @param string $email Email.
	 * @return string
	 */
	private function email_hash( $email ) {
		return substr( hash( 'sha256', strtolower( $email ) ), 0, 20 );
	}

	/**
	 * Cron: send one batch.
	 *
	 * @param int $comment_id Comment ID.
	 * @param int $last_id    Last subscription ID handled (cursor).
	 */
	public function process( $comment_id, $last_id = 0 ) {
		$comment_id = absint( $comment_id );
		$last_id    = absint( $last_id );
		$comment    = get_comment( $comment_id );
		if ( ! $comment || '1' !== (string) $comment->comment_approved ) {
			return;
		}
		if ( ! in_array( $comment->comment_type, array( '', 'comment' ), true ) ) {
			return;
		}
		$post = get_post( (int) $comment->comment_post_ID );
		if ( ! $post || 'publish' !== $post->post_status || '' !== $post->post_password ) {
			return;
		}

		$rows     = Db::get_recipients( (int) $post->ID, (int) $comment->comment_parent, $last_id, self::BATCH_SIZE + 1 );
		$has_more = count( $rows ) > self::BATCH_SIZE;
		$rows     = array_slice( $rows, 0, self::BATCH_SIZE );
		$cursor   = $last_id;
		if ( $rows ) {
			$tail   = end( $rows );
			$cursor = (int) $tail->id;
		}

		$mailed = get_comment_meta( $comment_id, self::MAILED_KEY, true );
		$mailed = is_array( $mailed ) ? $mailed : array();
		$author = strtolower( trim( $comment->comment_author_email ) );
		$list   = array();
		foreach ( $rows as $sub ) {
			$email = strtolower( $sub->email );
			$hash  = $this->email_hash( $email );
			if ( $email === $author || isset( $mailed[ $hash ] ) ) {
				continue;
			}
			$mailed[ $hash ] = 1;
			$list[]          = $sub;
		}

		$list = array_values( (array) apply_filters( 'replyping_notification_recipients', $list, $comment, $post ) );

		// Record before sending so a crash cannot cause duplicates on retry.
		update_comment_meta( $comment_id, self::MAILED_KEY, $mailed );

		foreach ( $list as $sub ) {
			Mailer::send_notification( $sub, $comment, $post );
		}

		if ( $has_more ) {
			wp_schedule_single_event( time() + 30, self::HOOK, array( $comment_id, $cursor ) );
		}
	}
}