class AccessResult

abstract class AccessResult implements AccessResultInterface, RefinableCacheableDependencyInterface {
    use RefinableCacheableDependencyTrait;
    
    /**
     * Creates an AccessResultInterface object with isNeutral() === TRUE.
     *
     * @param string|null $reason
     *   (optional) The reason why access is neutral. Intended for developers,
     *   hence not translatable.
     *
     * @return \Drupal\Core\Access\AccessResultNeutral
     *   isNeutral() will be TRUE.
     */
    public static function neutral($reason = NULL) {
        assert(is_string($reason) || is_null($reason));
        return new AccessResultNeutral($reason);
    }
    
    /**
     * Creates an AccessResultInterface object with isAllowed() === TRUE.
     *
     * @return \Drupal\Core\Access\AccessResultAllowed
     *   isAllowed() will be TRUE.
     */
    public static function allowed() {
        return new AccessResultAllowed();
    }
    
    /**
     * Creates an AccessResultInterface object with isForbidden() === TRUE.
     *
     * @param string|null $reason
     *   (optional) The reason why access is forbidden. Intended for developers,
     *   hence not translatable.
     *
     * @return \Drupal\Core\Access\AccessResultForbidden
     *   isForbidden() will be TRUE.
     */
    public static function forbidden($reason = NULL) {
        assert(is_string($reason) || is_null($reason));
        return new AccessResultForbidden($reason);
    }
    
    /**
     * Creates an allowed or neutral access result.
     *
     * @param bool $condition
     *   The condition to evaluate.
     *
     * @return \Drupal\Core\Access\AccessResult
     *   If $condition is TRUE, isAllowed() will be TRUE, otherwise isNeutral()
     *   will be TRUE.
     */
    public static function allowedIf($condition) {
        return $condition ? static::allowed() : static::neutral();
    }
    
    /**
     * Creates a forbidden or neutral access result.
     *
     * @param bool $condition
     *   The condition to evaluate.
     * @param string|null $reason
     *   (optional) The reason why access is forbidden. Intended for developers,
     *   hence not translatable
     *
     * @return \Drupal\Core\Access\AccessResult
     *   If $condition is TRUE, isForbidden() will be TRUE, otherwise isNeutral()
     *   will be TRUE.
     */
    public static function forbiddenIf($condition, $reason = NULL) {
        return $condition ? static::forbidden($reason) : static::neutral();
    }
    
    /**
     * Creates an allowed access result if the permission is present, neutral otherwise.
     *
     * Checks the permission and adds a 'user.permissions' cache context.
     *
     * @param \Drupal\Core\Session\AccountInterface $account
     *   The account for which to check a permission.
     * @param string $permission
     *   The permission to check for.
     *
     * @return \Drupal\Core\Access\AccessResult
     *   If the account has the permission, isAllowed() will be TRUE, otherwise
     *   isNeutral() will be TRUE.
     */
    public static function allowedIfHasPermission(AccountInterface $account, $permission) {
        $access_result = static::allowedIf($account->hasPermission($permission))
            ->addCacheContexts([
            'user.permissions',
        ]);
        if ($access_result instanceof AccessResultReasonInterface) {
            $access_result->setReason("The '{$permission}' permission is required.");
        }
        return $access_result;
    }
    
    /**
     * Creates an allowed access result if the permissions are present, neutral otherwise.
     *
     * Checks the permission and adds a 'user.permissions' cache contexts.
     *
     * @param \Drupal\Core\Session\AccountInterface $account
     *   The account for which to check permissions.
     * @param array $permissions
     *   The permissions to check.
     * @param string $conjunction
     *   (optional) 'AND' if all permissions are required, 'OR' in case just one.
     *   Defaults to 'AND'
     *
     * @return \Drupal\Core\Access\AccessResult
     *   If the account has the permissions, isAllowed() will be TRUE, otherwise
     *   isNeutral() will be TRUE.
     */
    public static function allowedIfHasPermissions(AccountInterface $account, array $permissions, $conjunction = 'AND') {
        $access = FALSE;
        if ($conjunction == 'AND' && !empty($permissions)) {
            $access = TRUE;
            foreach ($permissions as $permission) {
                if (!$account->hasPermission($permission)) {
                    $access = FALSE;
                    break;
                }
            }
        }
        else {
            foreach ($permissions as $permission) {
                if ($account->hasPermission($permission)) {
                    $access = TRUE;
                    break;
                }
            }
        }
        $access_result = static::allowedIf($access)->addCacheContexts(empty($permissions) ? [] : [
            'user.permissions',
        ]);
        if ($access_result instanceof AccessResultReasonInterface) {
            if (count($permissions) === 1) {
                $access_result->setReason("The '{$permission}' permission is required.");
            }
            elseif (count($permissions) > 1) {
                $quote = function ($s) {
                    return "'{$s}'";
                };
                $access_result->setReason(sprintf("The following permissions are required: %s.", implode(" {$conjunction} ", array_map($quote, $permissions))));
            }
        }
        return $access_result;
    }
    
    /**
     * {@inheritdoc}
     *
     * @see \Drupal\Core\Access\AccessResultAllowed
     */
    public function isAllowed() {
        return FALSE;
    }
    
    /**
     * {@inheritdoc}
     *
     * @see \Drupal\Core\Access\AccessResultForbidden
     */
    public function isForbidden() {
        return FALSE;
    }
    
    /**
     * {@inheritdoc}
     *
     * @see \Drupal\Core\Access\AccessResultNeutral
     */
    public function isNeutral() {
        return FALSE;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getCacheContexts() {
        return $this->cacheContexts;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getCacheTags() {
        return $this->cacheTags;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getCacheMaxAge() {
        return $this->cacheMaxAge;
    }
    
    /**
     * Resets cache contexts (to the empty array).
     *
     * @return $this
     */
    public function resetCacheContexts() {
        $this->cacheContexts = [];
        return $this;
    }
    
    /**
     * Resets cache tags (to the empty array).
     *
     * @return $this
     */
    public function resetCacheTags() {
        $this->cacheTags = [];
        return $this;
    }
    
    /**
     * Sets the maximum age for which this access result may be cached.
     *
     * @param int $max_age
     *   The maximum time in seconds that this access result may be cached.
     *
     * @return $this
     */
    public function setCacheMaxAge($max_age) {
        $this->cacheMaxAge = $max_age;
        return $this;
    }
    
    /**
     * Convenience method, adds the "user.permissions" cache context.
     *
     * @return $this
     */
    public function cachePerPermissions() {
        $this->addCacheContexts([
            'user.permissions',
        ]);
        return $this;
    }
    
    /**
     * Convenience method, adds the "user" cache context.
     *
     * @return $this
     */
    public function cachePerUser() {
        $this->addCacheContexts([
            'user',
        ]);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function orIf(AccessResultInterface $other) {
        $merge_other = FALSE;
        // $other's cacheability metadata is merged if $merge_other gets set to TRUE
        // and this happens in three cases:
        // 1. $other's access result is the one that determines the combined access
        //    result.
        // 2. This access result is not cacheable and $other's access result is the
        //    same. i.e. attempt to return a cacheable access result.
        // 3. Neither access result is 'forbidden' and both are cacheable: inherit
        //    the other's cacheability metadata because it may turn into a
        //    'forbidden' for another value of the cache contexts in the
        //    cacheability metadata. In other words: this is necessary to respect
        //    the contagious nature of the 'forbidden' access result.
        //    e.g. we have two access results A and B. Neither is forbidden. A is
        //    globally cacheable (no cache contexts). B is cacheable per role. If we
        //    don't have merging case 3, then A->orIf(B) will be globally cacheable,
        //    which means that even if a user of a different role logs in, the
        //    cached access result will be used, even though for that other role, B
        //    is forbidden!
        if ($this->isForbidden() || $other->isForbidden()) {
            $result = static::forbidden();
            if (!$this->isForbidden() || $this->getCacheMaxAge() === 0 && $other->isForbidden()) {
                $merge_other = TRUE;
            }
            if ($this->isForbidden() && $this instanceof AccessResultReasonInterface && $this->getReason() !== '') {
                $result->setReason($this->getReason());
            }
            elseif ($other->isForbidden() && $other instanceof AccessResultReasonInterface && $other->getReason() !== '') {
                $result->setReason($other->getReason());
            }
        }
        elseif ($this->isAllowed() || $other->isAllowed()) {
            $result = static::allowed();
            if (!$this->isAllowed() || $this->getCacheMaxAge() === 0 && $other->isAllowed() || $this->getCacheMaxAge() !== 0 && $other instanceof CacheableDependencyInterface && $other->getCacheMaxAge() !== 0) {
                $merge_other = TRUE;
            }
        }
        else {
            $result = static::neutral();
            if ($this->getCacheMaxAge() === 0 || $other instanceof CacheableDependencyInterface && $other->getCacheMaxAge() !== 0) {
                $merge_other = TRUE;
            }
            if ($this instanceof AccessResultReasonInterface && $this->getReason() !== '') {
                $result->setReason($this->getReason());
            }
            elseif ($other instanceof AccessResultReasonInterface && $other->getReason() !== '') {
                $result->setReason($other->getReason());
            }
        }
        $result->inheritCacheability($this);
        if ($merge_other) {
            $result->inheritCacheability($other);
        }
        return $result;
    }
    
    /**
     * {@inheritdoc}
     */
    public function andIf(AccessResultInterface $other) {
        // The other access result's cacheability metadata is merged if $merge_other
        // gets set to TRUE. It gets set to TRUE in one case: if the other access
        // result is used.
        $merge_other = FALSE;
        if ($this->isForbidden() || $other->isForbidden()) {
            $result = static::forbidden();
            if (!$this->isForbidden()) {
                if ($other instanceof AccessResultReasonInterface) {
                    $result->setReason($other->getReason());
                }
                $merge_other = TRUE;
            }
            else {
                if ($this instanceof AccessResultReasonInterface) {
                    $result->setReason($this->getReason());
                }
            }
        }
        elseif ($this->isAllowed() && $other->isAllowed()) {
            $result = static::allowed();
            $merge_other = TRUE;
        }
        else {
            $result = static::neutral();
            if (!$this->isNeutral()) {
                $merge_other = TRUE;
                if ($other instanceof AccessResultReasonInterface) {
                    $result->setReason($other->getReason());
                }
            }
            else {
                if ($this instanceof AccessResultReasonInterface) {
                    $result->setReason($this->getReason());
                }
            }
        }
        $result->inheritCacheability($this);
        if ($merge_other) {
            $result->inheritCacheability($other);
            // If this access result is not cacheable, then an AND with another access
            // result must also not be cacheable, except if the other access result
            // has isForbidden() === TRUE. isForbidden() access results are contagious
            // in that they propagate regardless of the other value.
            if ($this->getCacheMaxAge() === 0 && !$result->isForbidden()) {
                $result->setCacheMaxAge(0);
            }
        }
        return $result;
    }
    
    /**
     * Inherits the cacheability of the other access result, if any.
     *
     * This method differs from addCacheableDependency() in how it handles
     * max-age, because it is designed to inherit the cacheability of the second
     * operand in the andIf() and orIf() operations. There, the situation
     * "allowed, max-age=0 OR allowed, max-age=1000" needs to yield max-age 1000
     * as the end result.
     *
     * @param \Drupal\Core\Access\AccessResultInterface $other
     *   The other access result, whose cacheability (if any) to inherit.
     *
     * @return $this
     */
    public function inheritCacheability(AccessResultInterface $other) {
        $this->addCacheableDependency($other);
        if ($other instanceof CacheableDependencyInterface) {
            if ($this->getCacheMaxAge() !== 0 && $other->getCacheMaxAge() !== 0) {
                $this->setCacheMaxAge(Cache::mergeMaxAges($this->getCacheMaxAge(), $other->getCacheMaxAge()));
            }
            else {
                $this->setCacheMaxAge($other->getCacheMaxAge());
            }
        }
        return $this;
    }

}