<?php

namespace Drupal\Core\Access;

use Drupal\Core\Cache\Cache;
use Drupal\Core\Cache\CacheableDependencyInterface;
use Drupal\Core\Cache\RefinableCacheableDependencyInterface;
use Drupal\Core\Cache\RefinableCacheableDependencyTrait;
use Drupal\Core\Session\AccountInterface;

/**
 * Value object for passing an access result with cacheability metadata.
 *
 * The access result itself — excluding the cacheability metadata — is
 * immutable. There are subclasses for each of the three possible access results
 * themselves:
 *
 * @see \Drupal\Core\Access\AccessResultAllowed
 * @see \Drupal\Core\Access\AccessResultForbidden
 * @see \Drupal\Core\Access\AccessResultNeutral
 *
 * When using ::orIf() and ::andIf(), cacheability metadata will be merged
 * accordingly as well.
 */
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->isNeutral() || ($this->getCacheMaxAge() === 0 && $other->isNeutral()) || ($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;
  }

}
