<?php
namespace AccessNow\SimpleLMS;

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

class Notifications {

	public static function init() {
		add_action( 'accessnow_slms_enrolled', array( __CLASS__, 'on_enrolled' ), 20, 4 );
		add_action( 'accessnow_slms_course_completed', array( __CLASS__, 'on_course_completed' ), 20, 4 );
		add_action( 'accessnow_slms_quiz_submitted', array( __CLASS__, 'on_quiz_submitted' ), 20, 3 );
		add_action( 'accessnow_slms_quiz_regraded', array( __CLASS__, 'on_quiz_regraded' ), 20, 3 );
	}

	/**
	 * Self-enrolment emails (to the student and, if enabled, to the site admin).
	 *
	 * Enrolments made by an administrator send nothing.
	 *
	 * @param int $user_id       User ID.
	 * @param int $course_id     Course ID.
	 * @param int $enrollment_id Enrolment ID.
	 * @param int $enrolled_by   0 for self-enrolment.
	 */
	public static function on_enrolled( $user_id, $course_id, $enrollment_id, $enrolled_by ) {
		if ( $enrolled_by ) {
			return;
		}
		if ( Settings::get( 'email_enrollment' ) ) {
			self::send_enrollment_email( $user_id, $course_id );
		}
		if ( Settings::get( 'email_admin_enrollment' ) ) {
			self::notify_admin_enrollment( $user_id, $course_id );
		}
	}

	/**
	 * Completion email, the first time an enrolment is completed.
	 *
	 * @param int  $user_id          User ID.
	 * @param int  $course_id        Course ID.
	 * @param int  $enrollment_id    Enrolment ID.
	 * @param bool        $first_completion False when a reopened enrolment is completed again.
	 * @param object|null $certificate      The certificate issued for it.
	 */
	public static function on_course_completed( $user_id, $course_id, $enrollment_id, $first_completion, $certificate = null ) {
		if ( $first_completion && Settings::get( 'email_completion' ) ) {
			self::send_completion_email( $user_id, $course_id, $certificate );
		}
	}

	/**
	 * Quiz result email, sent only when the student passes (an email after every attempt is noise).
	 *
	 * @param int   $user_id User ID.
	 * @param int   $quiz_id Quiz ID.
	 * @param array $result  Graded result.
	 */
	/**
	 * The pass email, when an attempt is marked or regraded as a pass after it was submitted.
	 *
	 * @param int    $attempt_id Attempt ID.
	 * @param object $old        Attempt row before the change.
	 * @param array  $result     New result (passed, pending, percentage).
	 */
	public static function on_quiz_regraded( $attempt_id, $old, $result ) {
		if ( empty( $old->passed ) ) {
			self::on_quiz_submitted( (int) $old->user_id, (int) $old->quiz_id, $result );
		}
	}

	public static function on_quiz_submitted( $user_id, $quiz_id, $result ) {
		if ( ! empty( $result['passed'] ) && Settings::get( 'email_quiz_result', 1 ) ) {
			self::send_quiz_result_email( $user_id, $quiz_id, $result );
		}
	}

	/**
	 * Send one of the plugin's emails through accessnow_slms_email_{$type}. Public, so an add-on's
	 * emails go through the same filter (with its own type).
	 *
	 * @param string $type    'enrollment', 'completion', 'quiz_result' or 'admin_enrollment'.
	 * @param array  $email   to, subject, message, headers.
	 * @param array  $context IDs the email is about (user_id, course_id, quiz_id, result).
	 * @return bool Whether it was sent.
	 */
	public static function send( $type, array $email, array $context ) {
		$email = wp_parse_args( $email, array( 'headers' => array() ) );

		/**
		 * Filters one of the plugin's emails before it is sent. Return false to not send it.
		 *
		 * The dynamic part is the email type: accessnow_slms_email_enrollment,
		 * accessnow_slms_email_completion, accessnow_slms_email_quiz_result and
		 * accessnow_slms_email_admin_enrollment.
		 *
		 * @since 1.0.0
		 *
		 * @param array|false $email   {
		 *     @type string|string[] $to      Recipient(s).
		 *     @type string          $subject Subject.
		 *     @type string          $message Plain-text body.
		 *     @type string|string[] $headers Extra headers.
		 * }
		 * @param array       $context user_id, and course_id or quiz_id (plus result for quiz_result).
		 */
		$email = apply_filters( "accessnow_slms_email_{$type}", $email, $context );
		if ( ! is_array( $email ) || empty( $email['to'] ) ) {
			return false;
		}
		return wp_mail( $email['to'], (string) $email['subject'], (string) $email['message'], $email['headers'] );
	}

	public static function send_enrollment_email( $user_id, $course_id ) {
		$user   = get_userdata( $user_id );
		$course = get_post( $course_id );
		if ( ! $user || ! $course ) {
			return;
		}

		/* translators: %s: course title. */
		$subject = sprintf( __( 'You have been enrolled in: %s', 'accessnow-lms' ), $course->post_title );
		$message = sprintf(
			/* translators: 1: student name, 2: course title, 3: course URL. */
			__( "Hi %1\$s,\n\nYou have been enrolled in the course \"%2\$s\".\n\nVisit the course: %3\$s\n\nHappy learning!", 'accessnow-lms' ),
			$user->display_name,
			$course->post_title,
			get_permalink( $course_id )
		);

		self::send(
			'enrollment',
			array(
				'to'      => $user->user_email,
				'subject' => $subject,
				'message' => $message,
			),
			array(
				'user_id'   => (int) $user_id,
				'course_id' => (int) $course_id,
			)
		);
	}

	/**
	 * Congratulate a student on completing a course, linking to their certificate when there is one.
	 *
	 * @param int         $user_id     User ID.
	 * @param int         $course_id   Course ID.
	 * @param object|null $certificate Certificate row; looked up from the student's latest one if omitted.
	 */
	public static function send_completion_email( $user_id, $course_id, $certificate = null ) {
		$user   = get_userdata( $user_id );
		$course = get_post( $course_id );
		if ( ! $user || ! $course ) {
			return;
		}

		if ( ! $certificate ) {
			foreach ( Certificates::get_user_certificates( $user_id ) as $candidate ) {
				if ( (int) $candidate->course_id === (int) $course_id ) {
					$certificate = $candidate; // Newest first.
					break;
				}
			}
		}
		$link = $certificate ? Certificates::get_certificate_url( $certificate->certificate_code ) : get_permalink( $course_id );

		/* translators: %s: course title. */
		$subject = sprintf( __( 'Congratulations! You completed: %s', 'accessnow-lms' ), $course->post_title );
		$message = sprintf(
			/* translators: 1: student name, 2: course title, 3: certificate URL. */
			__( "Hi %1\$s,\n\nCongratulations on completing the course \"%2\$s\"!\n\nView your certificate: %3\$s\n\nKeep learning!", 'accessnow-lms' ),
			$user->display_name,
			$course->post_title,
			$link
		);

		self::send(
			'completion',
			array(
				'to'      => $user->user_email,
				'subject' => $subject,
				'message' => $message,
			),
			array(
				'user_id'   => (int) $user_id,
				'course_id' => (int) $course_id,
			)
		);
	}

	public static function send_quiz_result_email( $user_id, $quiz_id, $grade_result ) {
		$user = get_userdata( $user_id );
		$quiz = get_post( $quiz_id );
		if ( ! $user || ! $quiz ) {
			return;
		}

		$status = $grade_result['passed'] ? __( 'Passed', 'accessnow-lms' ) : __( 'Failed', 'accessnow-lms' );
		/* translators: 1: quiz title, 2: Passed or Failed. */
		$subject = sprintf( __( 'Quiz Result: %1$s - %2$s', 'accessnow-lms' ), $quiz->post_title, $status );
		$message = sprintf(
			/* translators: 1: student name, 2: quiz title, 3: score percentage, 4: Passed or Failed. */
			__( "Hi %1\$s,\n\nYou completed the quiz \"%2\$s\".\n\nScore: %3\$s%%\nStatus: %4\$s\n\nKeep going!", 'accessnow-lms' ),
			$user->display_name,
			$quiz->post_title,
			$grade_result['percentage'],
			$status
		);

		self::send(
			'quiz_result',
			array(
				'to'      => $user->user_email,
				'subject' => $subject,
				'message' => $message,
			),
			array(
				'user_id' => (int) $user_id,
				'quiz_id' => (int) $quiz_id,
				'result'  => $grade_result,
			)
		);
	}

	public static function notify_admin_enrollment( $user_id, $course_id ) {
		$user   = get_userdata( $user_id );
		$course = get_post( $course_id );
		if ( ! $user || ! $course ) {
			return;
		}

		$admin_email = get_option( 'admin_email' );
		/* translators: 1: student name, 2: course title. */
		$subject = sprintf( __( 'New enrollment: %1$s in %2$s', 'accessnow-lms' ), $user->display_name, $course->post_title );
		$message = sprintf(
			/* translators: 1: student name, 2: course title. */
			__( '%1$s has enrolled in the course "%2$s".', 'accessnow-lms' ),
			$user->display_name,
			$course->post_title
		);

		self::send(
			'admin_enrollment',
			array(
				'to'      => $admin_email,
				'subject' => $subject,
				'message' => $message,
			),
			array(
				'user_id'   => (int) $user_id,
				'course_id' => (int) $course_id,
			)
		);
	}
}