class ContextConfig

class ContextConfig {
    
    /**
     * The config array.
     *
     * @var array
     */
    protected $config = [
        'context_values' => [],
        'context_mapping' => [],
        'context_processors' => [],
        'provides_mapping' => [],
    ];
    
    /**
     * Creates a context config object.
     *
     * @param array $values
     *   (optional) Some initial values to set. In the same format as returned
     *   from static::toArray().
     *
     * @return $this
     */
    public static function create(array $values = []) {
        return new static($values);
    }
    
    /**
     * Constructs the object.
     *
     * @param array $values
     *   Some initial values to set. In the same format as returned from
     *   static::toArray().
     */
    protected function __construct(array $values) {
        $this->config = $values + $this->config;
    }
    
    /**
     * Maps the data specified by the selector to the given context.
     *
     * @param string $context_name
     *   The name of the context.
     * @param string $property_path
     *   A valid property path; e.g., "node.uid.target_id".
     *
     * @throws \Drupal\rules\Exception\LogicException
     *   Thrown if a context value and map are set for a given context at the same
     *   time.
     *
     * @return $this
     */
    public function map($context_name, $property_path) {
        if (isset($this->config['context_values'][$context_name])) {
            throw new LogicException("Cannot map a context value and pre-define it at the same time.");
        }
        $this->config['context_mapping'][$context_name] = $property_path;
        return $this;
    }
    
    /**
     * Sets a pre-defined value for the given context.
     *
     * @param string $context_name
     *   The name of the context.
     * @param mixed $value
     *   The value to set for the context. The value must be a valid value for the
     *   context's data type, unless a data processor takes care of processing it
     *   to a valid value.
     *
     * @throws \Drupal\rules\Exception\LogicException
     *   Thrown if a context value and map are set for a given context at the same
     *   time.
     *
     * @return $this
     */
    public function setValue($context_name, $value) {
        if (isset($this->config['context_mapping'][$context_name])) {
            throw new LogicException("Cannot map a context value and pre-define it at the same time.");
        }
        $this->config['context_values'][$context_name] = $value;
        return $this;
    }
    
    /**
     * Maps the name of a provided context.
     *
     * @param string $provided_context_name
     *   The name of the provided context.
     * @param string $context_name
     *   The context name under which the provided context should be registered.
     *
     * @return $this
     */
    public function provideAs($provided_context_name, $context_name) {
        $this->config['provides_mapping'][$provided_context_name] = $context_name;
        return $this;
    }
    
    /**
     * Sets an arbitrary configuration value under the given key.
     *
     * This may be used for setting any configuration options that are not making
     * use of the context system.
     *
     * @param string $key
     *   The config key to set.
     * @param mixed $value
     *   The value to set for the config key.
     *
     * @return $this
     */
    public function setConfigKey($key, $value) {
        $this->config[$key] = $value;
        return $this;
    }
    
    /**
     * Configures a data processor for the given context.
     *
     * @param string $context_name
     *   The name of the context.
     * @param string $plugin_id
     *   The id of the data processor plugin to use.
     * @param array $options
     *   (optional) An array of plugin configuration, as used by the plugin.
     *
     * @return $this
     */
    public function process($context_name, $plugin_id, array $options = []) {
        $this->config['context_processors'][$context_name][$plugin_id] = $options;
        return $this;
    }
    
    /**
     * Negates the result of the plugin (or not).
     *
     * Only applicable to condition plugins.
     *
     * @param bool $bool
     *   Whether to negate the result.
     *
     * @return $this
     */
    public function negateResult($bool = TRUE) {
        return $this->setConfigKey('negate', $bool);
    }
    
    /**
     * Exports the configuration to an array.
     *
     * @return array
     *   The config array, with the following keys set:
     *   - context_map: An array of data selectors, keyed by context name.
     *   - context_values: An array of context values, keyed by context name.
     *   - context_processors: An array of data processor config, keyed by context
     *     name and process plugin id.
     *   - provides_mapping: An array of context names to use for provided
     *     context, keyed by provided context name.
     *   - Any other other config keys that have been set.
     */
    public function toArray() {
        return $this->config;
    }
    
    /**
     * Checks the config for the given plugin.
     *
     * @param \Drupal\Core\Plugin\ContextAwarePluginInterface $plugin
     *   An instance of the plugin for which the config has been created.
     *
     * @todo Implement.
     */
    public function checkConfig(CoreContextAwarePluginInterface $plugin) {
        // @todo Implement.
    }

}