notification_service.php

<?php
/**
 * Discord Notifications. An extension for the phpBB Forum Software package.
 *
 * @copyright (c) 2018, Tyler Olsen, https://github.com/rootslinux
 * @license GNU General Public License, version 2 (GPL-2.0)
 */

namespace mober\discordnotifications;

/**
 * Contains the core logic for formatting and sending notification message to Discord.
 * This includes common utilities, such as verifying notification configuration settings
 * and a few DB queries.
 */
class notification_service
{
	// Maximum number of characters allowed by Discord in a message description.
	// Reference: https://discordapp.com/developers/docs/resources/channel#embed-limits
	const MAX_MESSAGE_SIZE = 2048;

	// Maximum number of characters (not bytes) allowed by Discord in a message footer.
	const MAX_FOOTER_SIZE = 2048;

	// The notification color (gray) to use as a default if a missing or invalid color value is received.
	const DEFAULT_COLOR = 11777212;

	const ELLIPSIS = '…';

	/** @var \phpbb\config\config */
	protected $config;

	/** @var \phpbb\db\driver\driver_interface */
	protected $db;

	/** @var \phpbb\log\log $log */
	protected $log;

	/**
	 * Constructor
	 *
	 * @param \phpbb\config\config              $config
	 * @param \phpbb\db\driver\driver_interface $db
	 */
	public function __construct(\phpbb\config\config $config, \phpbb\db\driver\driver_interface $db, \phpbb\log\log $log)
	{
		$this->config = $config;
		$this->db = $db;
		$this->log = $log;
	}

	/**
	 * Check whether notifications are enabled for a certain type
	 *
	 * @param string $notification_type The name of the notification type to check
	 * @return bool if the global notification setting is disabled or this notification type is disabled
	 */
	public function is_notification_type_enabled($notification_type)
	{
		return $this->config['discord_notifications_enabled'] == 1 && $this->config[$notification_type] == 1;
	}

	/**
	 * Check whether notifications that occur on a specific forum should be generated
	 *
	 * @param int $forum_id The ID of the forum to check
	 * @return string|false
	 */
	public function get_forum_notification_url($forum_id)
	{
		global $table_prefix;

		if (!is_numeric($forum_id))
		{
			return false;
		}

		if ($this->config['discord_notifications_enabled'] == 0)
		{
			return false;
		}

		// Query the forum table where forum notification settings are stored
		$sql = "SELECT discord_notifications FROM " . FORUMS_TABLE . " WHERE forum_id = " . (int) $forum_id;
		$result = $this->db->sql_query($sql);
		$data = $this->db->sql_fetchrow($result);
		$this->db->sql_freeresult($result);

		if ($data['discord_notifications'])
		{
			$sql = "SELECT url FROM {$table_prefix}discord_webhooks WHERE alias = '" . $this->db->sql_escape($data['discord_notifications']) . "'";
			$result = $this->db->sql_query($sql);
			$data2 = $this->db->sql_fetchrow($result);
			$this->db->sql_freeresult($result);

			return $data2['url'];
		}

		return false;
	}

	/**
	 * Retrieve the value for the ACP settings configuration related to post preview length
	 *
	 * @return int The number of characters to display in the post preview. A zero value indicates that no preview
	 *             should be displayed
	 */
	public function get_post_preview_length()
	{
		return $this->config['discord_notifications_post_preview_length'];
	}

	/**
	 * Retrieves the name of a forum from the database when given an ID
	 *
	 * @param int $forum_id The ID of the forum to query
	 * @return string|false The name of the forum, or false if not found
	 */
	public function query_forum_name($forum_id)
	{
		if (!is_numeric($forum_id))
		{
			return null;
		}

		$sql = "SELECT forum_name from " . FORUMS_TABLE . " WHERE forum_id = " . (int) $forum_id;
		$result = $this->db->sql_query($sql);
		$data = $this->db->sql_fetchfield('forum_name');
		$this->db->sql_freeresult($result);
		return $data;
	}

	/**
	 * Retrieves the subject of a post from the database when given an ID
	 *
	 * @param int $post_id The ID of the post to query
	 * @return null|string The subject of the post, or NULL if not found
	 */
	public function query_post_subject($post_id)
	{
		if (!is_numeric($post_id))
		{
			return null;
		}

		$sql = "SELECT post_subject from " . POSTS_TABLE . " WHERE post_id = " . (int) $post_id;
		$result = $this->db->sql_query($sql);
		$data = $this->db->sql_fetchrow($result);
		$subject = $data['post_subject'];
		$this->db->sql_freeresult($result);
		return $subject;
	}

	/**
	 * Retrieves the title of a topic from the database when given an ID
	 *
	 * @param int $topic_id The ID of the topic to query
	 * @return string|false The name of the topic, or false if not found
	 */
	public function query_topic_title($topic_id)
	{
		if (!is_numeric($topic_id))
		{
			return null;
		}

		$sql = "SELECT topic_title from " . TOPICS_TABLE . " WHERE topic_id = " . (int) $topic_id;
		$result = $this->db->sql_query($sql);
		$data = $this->db->sql_fetchfield('topic_title');
		$this->db->sql_freeresult($result);
		return $data;
	}

	/**
	 * Runs a query to fetch useful data about a specific forum topic. The return data includes information on the
	 * first poster, number of posts, which forum contains the topic, and more.
	 *
	 * @param int $topic_id The ID of the topic to query
	 * @return array containing data about the topic and the forum it is contained in
	 */
	public function query_topic_details($topic_id)
	{
		if (!is_numeric($topic_id))
		{
			return [];
		}

		$sql = "SELECT
				f.forum_id, f.forum_name,
				t.topic_id, t.topic_title, t.topic_poster, t.topic_first_post_id, t.topic_first_poster_name, t.topic_posts_approved, t.topic_visibility
				FROM " . FORUMS_TABLE . " f, " . TOPICS_TABLE . " t
				WHERE t.forum_id = f.forum_id and t.topic_id = " . (int) $topic_id;
		$result = $this->db->sql_query($sql);
		$data = $this->db->sql_fetchrow($result);
		$this->db->sql_freeresult($result);

		return $data;
	}

	/**
	 * Retrieves the name of a user from the database when given an ID
	 *
	 * @param int $user_id The ID of the user to query
	 * @return string|false The name of the user, or false if not found
	 */
	public function query_user_name($user_id)
	{
		if (!is_numeric($user_id))
		{
			return false;
		}

		$sql = "SELECT username from " . USERS_TABLE . " WHERE user_id = " . (int) $user_id;
		$result = $this->db->sql_query($sql);
		$data = $this->db->sql_fetchfield('username');
		$this->db->sql_freeresult($result);
		return $data;
	}

	/**
	 * Sends a notification message to Discord. This function checks the master switch configuration for the extension,
	 * but does no further checks. The caller is responsible for performing full validation of the notification prior
	 * to calling this function.
	 *
	 * @param string      $color   The color to use in the notification (decimal value of a hexadecimal RGB code)
	 * @param string      $message The message text to send.
	 * @param null|string $webhook_url
	 * @param null|string $footer  Text to place in the footer of the message. Optional.
	 */
	public function send_discord_notification($color, $message, $webhook_url = null, $title = null, $preview = null, $footer = null)
	{
		global $table_prefix;

		if ($this->config['discord_notifications_enabled'] == 0 || !isset($message))
		{
			return;
		}

		// Note that the value stored in the config table will always be a valid URL when discord_notifications_enabled is set
		if (is_null($webhook_url))
		{
			$default = $this->config['discord_notification_default_webhook'];
			if ($default)
			{
				$sql = "SELECT url FROM {$table_prefix}discord_webhooks WHERE alias = '" . $this->db->sql_escape($default) . "'";
				$result = $this->db->sql_query($sql);
				$data   = $this->db->sql_fetchrow($result);
				$this->db->sql_freeresult($result);
				$webhook_url = $data['url'];
			}
		}
		$this->execute_discord_webhook($webhook_url, $color, $message, $title, $preview, $footer);
	}

	/**
	 * Sends a message to Discord, disregarding any configurations that are currently set. This method is primarily
	 * used by users to test their notifications from the ACP.
	 *
	 * @param string $discord_webhook_url The URL of the Discord webhook to transmit the message to. If this is an
	 *                                    invalid URL, no message will be sent.
	 * @param string $message             The message text to send. Must be a non-empty string.
	 * @return bool indicating whether the message transmission resulted in success or failure.
	 */
	public function force_send_discord_notification($discord_webhook_url, $message)
	{
		if (!filter_var($discord_webhook_url, FILTER_VALIDATE_URL) || !is_string($message) || $message == '')
		{
			return false;
		}

		return $this->execute_discord_webhook($discord_webhook_url, self::DEFAULT_COLOR, $message);
	}

	/**
	 * Helper function that performs the message transmission. This method checks the inputs to prevent any problematic
	 * characters in strings. Note that this function checks that the message and footer do not exceed the maximum
	 * allowable limits by the Discord API, but it does -not- check configuration settings such as the
	 * post_preview_length. The code invoking this method is responsible for checking those settings.
	 *
	 * @param string      $discord_webhook_url The URL of the Discord webhook to transmit the message to.
	 * @param string      $color               Color to set for the message. Should be a positive non-zero integer
	 *                                         representing a hex color code.
	 * @param string      $message             The message text to send. Must be a non-empty string.
	 * @param string      $title               Title of the preview (for example "Preview" or "Reason"). Optional.
	 * @param string      $preview             Content of the preview. Optional.
	 * @param string      $footer              The text to place in the footer. Optional.
	 * @return bool indicating whether the message transmission resulted in success or failure.
	 * @see https://discordapp.com/developers/docs/resources/webhook#execute-webhook
	 * @see https://discord.com/developers/docs/resources/channel#embed-object
	 */
	private function execute_discord_webhook($discord_webhook_url, $color, $message, $title = null, $preview = null, $footer = null)
	{
		if (!isset($discord_webhook_url) || $discord_webhook_url === '')
		{
			return false;
		}
		if (!is_integer($color) || $color < 0)
		{
			// Use the default color if we did not receive a valid color value
			$color = self::DEFAULT_COLOR;
		}
		if (!is_string($message) || $message == '')
		{
			return false;
		}
		if (isset($footer) && (!is_string($footer) || $footer == ''))
		{
			return false;
		}

		// Clean up the message and footer text before sending by trimming whitespace from the front and end of the message and footer strings.
		$message = trim($message);
		if (isset($footer))
		{
			$footer = trim($footer);
		}

		// Abort if we find that either of our text fields are now empty strings
		if ($message === '')
		{
			return false;
		}
		if (isset($footer) && $footer === '')
		{
			return false;
		}

		// Verify that the message and footer size is within the allowable limit and truncate if necessary. We add "..." as the last three characters
		// when we require truncation.
		if (mb_strlen($message) > self::MAX_MESSAGE_SIZE)
		{
			$message = mb_substr($message, 0, self::MAX_MESSAGE_SIZE - 1) . self::ELLIPSIS;
		}
		if (isset($footer) && mb_strlen($footer) > self::MAX_FOOTER_SIZE)
		{
			$footer = mb_substr($footer, 0, self::MAX_FOOTER_SIZE - 1) . self::ELLIPSIS;
		}

		// Place the message inside the JSON structure that Discord expects to receive at the REST endpoint.

		$embed = [
			'timestamp'		=> date('c', time()),
			'color'			=> $color,
			'description'	=> $message,
		];

		if (isset($footer))
		{
			$embed['footer'] = [
				'text' => $footer,
			];
		}

		if (isset($title) && isset($preview))
		{
			$title = trim($title);
			$preview = trim($preview);
			if ($title !== '' && $preview !== '')
			{
				$embed['fields'] = [
					[
						'name'		=> $title,
						'value'		=> $preview,
						'inline'	=> false,
					],
				];
			}
		}

		$payload = [
			'embeds' => [$embed],
		];

		$json = \json_encode($payload, JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE);
		if ($json === false)
		{
			$this->log->add('admin', ANONYMOUS, '127.0.0.1', 'ACP_DISCORD_NOTIFICATIONS_JSON_ERROR', time(), [json_last_error_msg()]);
			return false;
		}

		// Use the CURL library to transmit the message via a POST operation to the webhook URL.
		$h = curl_init();
		curl_setopt($h, CURLOPT_HTTPHEADER, ['Content-type: application/json']);
		curl_setopt($h, CURLOPT_URL, $discord_webhook_url);
		curl_setopt($h, CURLOPT_POST, 1);
		curl_setopt($h, CURLOPT_POSTFIELDS, $json);
		curl_setopt($h, CURLOPT_RETURNTRANSFER, 1);
		curl_setopt($h, CURLOPT_CONNECTTIMEOUT, (int) $this->config['discord_notifications_connect_timeout']);
		curl_setopt($h, CURLOPT_TIMEOUT, (int) $this->config['discord_notifications_exec_timeout']);
		$response = curl_exec($h);
		$error = curl_errno($h);
		$status = curl_getinfo($h, CURLINFO_HTTP_CODE);
		curl_close($h);

		// TODO: Retry?
		if ($error == 0)
		{
			if ($status < 200 || $status > 299)
			{
				$this->log->add('admin', ANONYMOUS, '127.0.0.1', 'ACP_DISCORD_NOTIFICATIONS_WEBHOOK_ERROR', time(), [$status]);
				return false;
			}
		}
		else
		{
			$this->log->add('admin', ANONYMOUS, '127.0.0.1', 'ACP_DISCORD_NOTIFICATIONS_CURL_ERROR', time(), [$error]);
			return false;
		}

		return true;
	}
}