<?php
/**
 * Class for creating a backup codes provider.
 *
 * @since 0.1-dev
 *
 * @package Two_Factor
 */
class Two_Factor_Backup_Codes extends Two_Factor_Provider {

	/**
	 * The user meta backup codes key.
	 * @type string
	 */
	const BACKUP_CODES_META_KEY = '_two_factor_backup_codes';

	/**
	 * The number backup codes.
	 * @type int
	 */
	const NUMBER_OF_CODES = 10;

	/**
	 * Ensures only one instance of this class exists in memory at any one time.
	 *
	 * @since 0.1-dev
	 */
	static function get_instance() {
		static $instance;
		$class = __CLASS__;
		if ( ! is_a( $instance, $class ) ) {
			$instance = new $class;
		}
		return $instance;
	}

	/**
	 * Class constructor.
	 *
	 * @since 0.1-dev
	 */
	protected function __construct() {
		add_action( 'two-factor-user-options-' . __CLASS__, array( $this, 'user_options' ) );
		add_action( 'two-factor-admin-options-' . __CLASS__, array( $this, 'description' ) );
		add_action( 'admin_notices', array( $this, 'admin_notices' ) );
		add_action( 'wp_ajax_two_factor_backup_codes_generate', array( $this, 'ajax_generate_json' ) );

		return parent::__construct();
	}

	/**
	 * Displays an admin notice when backup codes have run out.
	 *
	 * @since 0.1-dev
	 */
	public function admin_notices() {
		$user = wp_get_current_user();

		// Return if the provider is not enabled.
		if ( ! in_array( __CLASS__, Two_Factor_Core::get_enabled_providers_for_user( $user->ID ) ) ) {
			return;
		}

		// Return if we are not out of codes.
		if ( $this->is_available_for_user( $user ) ) {
			return;
		}
		?>
		<div class="error">
			<p>
				<span><?php printf( // WPCS: XSS OK.
					__( 'Two-Factor: You are out of backup codes and need to <a href="%s">regenerate!</a>', 'it-l10n-ithemes-security-pro' ),
					esc_url( get_edit_user_link( $user->ID ) . '#two-factor-backup-codes' )
				); ?><span>
			</p>
		</div>
		<?php
	}

	/**
	 * Returns the name of the provider.
	 *
	 * @since 0.1-dev
	 */
	public function get_label() {
		return _x( 'Backup Verification Codes', 'Provider Label', 'it-l10n-ithemes-security-pro' );
	}

	/**
	 * Whether this Two-Factor provider is configured and codes are available for the user specified.
	 *
	 * @since 0.1-dev
	 *
	 * @param WP_User $user WP_User object of the logged-in user.
	 * @return boolean
	 */
	public function is_available_for_user( $user ) {
		// Does this user have available codes?
		if ( 0 < self::codes_remaining_for_user( $user ) ) {
			return true;
		}
		return false;
	}

	/**
	 * Inserts markup at the end of the user profile field for this provider.
	 *
	 * @since 0.1-dev
	 *
	 * @param WP_User $user WP_User object of the logged-in user.
	 */
	public function user_options( $user ) {
		$ajax_nonce = wp_create_nonce( 'two-factor-backup-codes-generate-json-' . $user->ID );
		$count = self::codes_remaining_for_user( $user );
		?>
		<p></p>
		<p id="two-factor-backup-codes">
			<button type="button" class="button button-two-factor-backup-codes-generate button-secondary hide-if-no-js">
				<?php esc_html_e( 'Generate Verification Codes', 'it-l10n-ithemes-security-pro' ); ?>
			</button>
			<span class="two-factor-backup-codes-count"><?php echo esc_html( sprintf( _n( '%s unused code remaining.', '%s unused codes remaining.', $count ), $count ) ); ?></span>
		</p>
		<div class="two-factor-backup-codes-wrapper" style="display:none;">
			<ol class="two-factor-backup-codes-unused-codes"></ol>
			<p class="description"><?php esc_html_e( 'Write these down!  Once you navigate away from this page, you will not be able to view these codes again.', 'it-l10n-ithemes-security-pro' ); ?></p>
		</div>
		<script type="text/javascript">
			jQuery( document ).ready( function( $ ) {
				$( '.button-two-factor-backup-codes-generate' ).click( function() {
					$.ajax( {
						method: 'POST',
						url: ajaxurl,
						data: {
							action: 'two_factor_backup_codes_generate',
							user_id: '<?php echo esc_js( $user->ID ); ?>',
							nonce: '<?php echo esc_js( $ajax_nonce ); ?>'
						},
						dataType: 'JSON',
						success: function( response ) {
							$( '.two-factor-backup-codes-wrapper' ).show();
							$( '.two-factor-backup-codes-unused-codes' ).html( '' );

							// Append the codes.
							$.each( response.data.codes, function( key, val ) {
								$( '.two-factor-backup-codes-unused-codes' ).append( '<li>' + val + '</li>' );
							} );

							// Update counter.
							$( '.two-factor-backup-codes-count' ).html( response.data.i18n );
						}
					} );
				} );
			} );
		</script>
		<?php
	}

	/**
	 * Generates backup codes & updates the user meta.
	 *
	 * @since 0.1-dev
	 *
	 * @param WP_User $user WP_User object of the logged-in user.
	 * @param array   $args Optional arguments for assinging new codes.
	 */
	public function generate_codes( $user, $args = '' ) {
		$codes = array();
		$codes_hashed = array();

		// Check for arguments.
		if ( isset( $args['number'] ) ) {
			$num_codes = (int) $args['number'];
		} else {
			$num_codes = self::NUMBER_OF_CODES;
		}

		// Append or replace (default).
		if ( isset( $args['method'] ) && 'append' === $args['method'] ) {
			$codes_hashed = (array) get_user_meta( $user->ID, self::BACKUP_CODES_META_KEY, true );
		}

		for ( $i = 0; $i < $num_codes; $i++ ) {
			$code = $this->get_code();
			$codes_hashed[] = wp_hash_password( $code );
			$codes[] = $code;
			unset( $code );
		}

		update_user_meta( $user->ID, self::BACKUP_CODES_META_KEY, $codes_hashed );

		// Unhashed.
		return $codes;
	}

	/**
	 * Generates a JSON object of backup codes.
	 *
	 * @since 0.1-dev
	 */
	public function ajax_generate_json() {
		$user = get_user_by( 'id', sanitize_text_field( $_POST['user_id'] ) );
		check_ajax_referer( 'two-factor-backup-codes-generate-json-' . $user->ID, 'nonce' );

		// Setup the return data.
		$codes = $this->generate_codes( $user );
		$count = self::codes_remaining_for_user( $user );
		$i18n = esc_html( sprintf( _n( '%s unused code remaining.', '%s unused codes remaining.', $count ), $count ) );

		// Send the response.
		wp_send_json_success( array( 'codes' => $codes, 'i18n' => $i18n ) );
	}

	/**
	 * Returns the number of unused codes for the specified user
	 *
	 * @param WP_User $user WP_User object of the logged-in user.
	 * @return int $int  The number of unused codes remaining
	 */
	public static function codes_remaining_for_user( $user ) {
		$backup_codes = get_user_meta( $user->ID, self::BACKUP_CODES_META_KEY, true );
		if ( is_array( $backup_codes ) && ! empty( $backup_codes ) ) {
			return count( $backup_codes );
		}
		return 0;
	}

	/**
	 * Prints the form that prompts the user to authenticate.
	 *
	 * @since 0.1-dev
	 *
	 * @param WP_User $user WP_User object of the logged-in user.
	 */
	public function authentication_page( $user ) {
		require_once( ABSPATH .  '/wp-admin/includes/template.php' );
		?>
		<p style="padding-bottom:1em;"><?php esc_html_e( 'Enter a backup verification code.', 'it-l10n-ithemes-security-pro' ); ?></p><br/>
		<p>
			<label for="authcode"><?php esc_html_e( 'Verification Code:', 'it-l10n-ithemes-security-pro' ); ?></label>
			<input type="tel" name="two-factor-backup-code" id="authcode" class="input" value="" size="20" pattern="[0-9]*" />
		</p>
		<script type="text/javascript">
			setTimeout( function(){
				var d;
				try{
					d = document.getElementById('authcode');
					d.value = '';
					d.focus();
				} catch(e){}
			}, 200);
		</script>
		<?php
		submit_button( __( 'Submit', 'it-l10n-ithemes-security-pro' ) );
	}

	/**
	 * Validates the users input token.
	 *
	 * In this class we just return true.
	 *
	 * @since 0.1-dev
	 *
	 * @param WP_User $user WP_User object of the logged-in user.
	 * @return boolean
	 */
	public function validate_authentication( $user ) {
		return $this->validate_code( $user, $_POST['two-factor-backup-code'] );
	}

	/**
	 * Validates a backup code.
	 *
	 * Backup Codes are single use and are deleted upon a successful validation.
	 *
	 * @since 0.1-dev
	 *
	 * @param WP_User $user WP_User object of the logged-in user.
	 * @param int     $code The backup code.
	 * @return boolean
	 */
	public function validate_code( $user, $code ) {
		$backup_codes = get_user_meta( $user->ID, self::BACKUP_CODES_META_KEY, true );

		foreach ( $backup_codes as $code_index => $code_hashed ) {
			if ( wp_check_password( $code, $code_hashed, $user->ID ) ) {
				$this->delete_code( $user, $code_hashed );
				return true;
			}
		}
		return false;
	}

	/**
	 * Deletes a backup code.
	 *
	 * @since 0.1-dev
	 *
	 * @param WP_User $user WP_User object of the logged-in user.
	 * @param string  $code_hashed The hashed the backup code.
	 */
	public function delete_code( $user, $code_hashed ) {
		$backup_codes = get_user_meta( $user->ID, self::BACKUP_CODES_META_KEY, true );

		// Delete the current code from the list since it's been used.
		$backup_codes = array_flip( $backup_codes );
		unset( $backup_codes[ $code_hashed ] );
		$backup_codes = array_values( array_flip( $backup_codes ) );

		// Update the backup code master list.
		update_user_meta( $user->ID, self::BACKUP_CODES_META_KEY, $backup_codes );
	}

	public function description() {
		echo '<p class="description">' . __( 'The backup verification codes provider generates a set of codes that can be used to provide the additional authentication required to access the site. Since each code expires after it is used, the codes are meant to be kept in a secure location and used in the event that access to the primary two-factor provider is lost.', 'it-l10n-ithemes-security-pro' ) . '</p>';
	}
}
