<?php
/**
 * Verification service, separate from logging.
 *
 * @package Enrollment_Verifier_Logger
 */

defined( 'ABSPATH' ) || exit;

/**
 * Evaluates whether the resulting state looks consistent with the event.
 * It does not assume enrollment is correct or unenrollment is wrong.
 */
class EVLFL_Event_Verifier {

	/**
	 * Verify an event.
	 *
	 * @param array $event   Event incl. resolved origin.
	 * @param array $context Context snapshot.
	 * @param array $state   Snapshot at event time: expires_on (int|null), has_access (bool|null), now (int).
	 * @return array status, verification_reason, confidence.
	 */
	public function verify( array $event, array $context, array $state ) {
		$now        = isset( $state['now'] ) ? (int) $state['now'] : time();
		$expires_on = ( isset( $state['expires_on'] ) && (int) $state['expires_on'] > 0 ) ? (int) $state['expires_on'] : null;
		$has_access = array_key_exists( 'has_access', $state ) ? $state['has_access'] : null;

		$result = $this->unknown( __( 'Not enough information to verify this event safely.', 'accesstrace-for-learndash' ) );

		if ( EVLFL_Event::ACTION_ENROLLED === $event['action'] ) {
			if ( null !== $expires_on && $expires_on <= $now ) {
				$result = $this->result( 'invalid', __( 'Enrolled, but the recorded course access expiration is already in the past.', 'accesstrace-for-learndash' ), 'detected' );
			} elseif ( null !== $expires_on || true === $has_access ) {
				$result = $this->result( 'valid', __( 'Enrolled with course access that has not expired; no conflicting indicators were found.', 'accesstrace-for-learndash' ), 'detected' );
			} else {
				$result = $this->unknown( __( 'The resulting access state could not be confirmed at event time.', 'accesstrace-for-learndash' ) );
			}
		} elseif ( EVLFL_Event::ACTION_UNENROLLED === $event['action'] ) {
			$by_admin      = 'admin' === $event['actor_type'] && 'manual' === $event['event_trigger'];
			$expired_trig  = 'course_access_expired' === $event['event_trigger'];
			$future_expiry = null !== $expires_on && $expires_on > $now;

			if ( $future_expiry && ! $by_admin ) {
				$result = $this->result( 'invalid', __( 'Unenrolled although the course access expiration is still in the future, and no administrator action was detected.', 'accesstrace-for-learndash' ), 'inferred' );
			} elseif ( 'access_reset' === $event['event_trigger'] ) {
				$result = $this->result( 'valid', __( 'Access was removed and granted again within the same WooCommerce order request. This matches how LearnDash restarts expired access on a repeat purchase; the user ends up enrolled.', 'accesstrace-for-learndash' ), 'inferred' );
			} elseif ( $expired_trig ) {
				$result = $this->result( 'valid', __( 'LearnDash reported the course access as expired for this user and course.', 'accesstrace-for-learndash' ), 'confirmed' );
			} elseif ( null !== $expires_on ) {
				$result = $this->result( 'valid', __( 'Course access expiration had passed, which is consistent with the unenrollment.', 'accesstrace-for-learndash' ), 'inferred' );
			} elseif ( $by_admin ) {
				$result = $this->result( 'valid', __( 'Unenrolled by a deliberate administrator action; no conflicting access indicators were found.', 'accesstrace-for-learndash' ), 'detected' );
			} else {
				$result = $this->unknown( __( 'Unenrolled, but the cause could not be determined with the information available.', 'accesstrace-for-learndash' ) );
			}
		}

		$filtered = apply_filters( 'evlfl_verify_event', $result, $event, $context, $state );
		if ( is_array( $filtered ) && isset( $filtered['status'] ) && isset( EVLFL_Event::get_statuses()[ $filtered['status'] ] ) ) {
			$result = array(
				'status'              => $filtered['status'],
				'verification_reason' => isset( $filtered['verification_reason'] ) ? (string) $filtered['verification_reason'] : $result['verification_reason'],
				'confidence'          => isset( $filtered['confidence'] ) ? (string) $filtered['confidence'] : 'unknown',
			);
		}
		return $result;
	}

	/**
	 * Build a result.
	 *
	 * @param string $status     Status.
	 * @param string $reason     Reason.
	 * @param string $confidence Confidence.
	 * @return array
	 */
	private function result( $status, $reason, $confidence ) {
		return array(
			'status'              => $status,
			'verification_reason' => $reason,
			'confidence'          => $confidence,
		);
	}

	/**
	 * Unknown result.
	 *
	 * @param string $reason Reason.
	 * @return array
	 */
	private function unknown( $reason ) {
		return $this->result( 'unknown', $reason, 'unknown' );
	}
}