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ConfigurablePerLinkFilter
#########################

This interface allows a :ref:`Filter <extensions-filters>` to have multiple configurations applied to it on a given Link that are independent of any particular :doc:`/classes/mapping`. If you need configurations that are different for a given Mapping, look at :doc:`/filter-interfaces/configurable-per-mapping-filter`.

Users can set up multiple configurations for your Filter on a single Link, so you'll notice that ``setFilterConfigurations()`` accepts a collection of serialized configurations and you should be prepared to apply each one to records.

Each actual String **configuration** value is whatever you need it to be. Most commonly it is a serialized JSON object of key-value pairs, but you are not locked into using that pattern.

.. note::

    For a deeper look at configurable extensions in Valence, read our guide on :doc:`/extension-concepts/configurability`.

**********
Definition
**********

.. code-block:: java

	/**
	 * Implementing this interface means your Filter is capable of being configured.
	 */
	global interface ConfigurablePerLinkFilter extends TransformationFilter {

		/**
		 * You can use your own Lightning component to let Users build and edit your configuration. If you want to do this, return the fully qualified
		 * name of your component, which looks like this:
		 *
		 * valence:MyAwesomeAdapterConfigurator
		 *
		 * Make sure your component is set to global so that Valence can instantiate it.
		 *
		 * @return The name of your Lightning component that will handle configuration, or null if you don't need your own component
		 */
		String getFilterConfigurationLightningComponent();

		/**
		 * If you don't need or don't want to use your own Lightning Component, you can simply describe your configuration shape and we will present
		 * the user with some basic input fields to populate values in your configuration.
		 *
		 * @return A serialized JSON object describing your configuration data structure, or null if you use your own component
		 */
		String getFilterConfigurationStructure();

		/**
		 * Given configuration data, return a user-friendly paragraph that explains how this specific configuration
		 * is going to be used by your Filter and what effect that will have on the Record.
		 *
		 * We show this in the user interface to help Users understand the impact of their configurations.
		 *
		 * @param configurationData The raw configuration for your Filter
		 *
		 * @return A human-readable and friendly explanation that specifically reflects and explains the configuration passed.
		 */
		String explainFilterConfiguration(String configurationData);

		/**
		 * Sets configuration data for your Filter. This is the first method called on your Filter during Link execution. User might configure your Filter multiple
		 * times (for example, setting two different constants for a Filter that sets constants), so you are passed a list of configurations.
		 *
		 * @param context Information about this Link and the current execution of it.
		 * @param configurationData List of configuration data in JSON format, or in whatever format your custom configuration component gave us
		 */
		void setFilterConfigurations(LinkContext context, List<String> configurationData);
	}

*******************************
Example - Access Configurations
*******************************

.. code-block:: java

	private List<FilterConfiguration> configs = new List<FilterConfiguration>();

	public void setFilterConfigurations(valence.LinkContext context, List<String> configurationData) {
		configs.clear();
		for(String configData : configurationData) {
			configs.add(interpretConfigData(configData));
		}
	}

	public void process(valence.LinkContext context, List<valence.RecordInFlight> records) {

		// do work on the records using our configurations
		for(valence.RecordInFlight record : records) {
			for(FilterConfiguration config : configs) {
				record.setOriginalPropertyValue(config.fieldName, config.value);
			}
		}
	}

	private static FilterConfiguration interpretConfigData(String data) {
		return String.isBlank(data) ? new FilterConfiguration() : (FilterConfiguration)JSON.deserialize(data, FilterConfiguration.class);
	}

	private class FilterConfiguration {
		String fieldName;
		String value;
	}