<?php
/**
 * Abstract condition base.
 *
 * @package BlockSieve
 */

namespace BlockSieve\Conditions;

use BlockSieve\Conditions\Contracts\ConditionInterface;
use BlockSieve\Conditions\Context\Context;

/**
 * Base class for condition types, providing sensible defaults.
 *
 * Concrete conditions implement id(), label(), operators() and evaluate(); the
 * remaining methods have working defaults.
 */
abstract class AbstractCondition implements ConditionInterface {

	/**
	 * Gets the unique condition identifier.
	 *
	 * @return string
	 */
	abstract public function id(): string;

	/**
	 * Gets the translated human label.
	 *
	 * @return string
	 */
	abstract public function label(): string;

	/**
	 * Gets the list of supported operator identifiers.
	 *
	 * @return string[]
	 */
	abstract public function operators(): array;

	/**
	 * Evaluates the condition against the given context.
	 *
	 * @param Context $context  Request context value object.
	 * @param string  $operator Operator identifier.
	 * @param mixed   $value    Configured value.
	 * @return bool
	 */
	abstract public function evaluate( Context $context, string $operator, $value ): bool;

	/**
	 * Gets the translated description shown in the UI.
	 *
	 * @return string
	 */
	public function description(): string {
		return '';
	}

	/**
	 * Gets the category used to group this condition in the UI.
	 *
	 * @return string
	 */
	public function category(): string {
		return 'general';
	}

	/**
	 * Gets the default operator identifier.
	 *
	 * @return string
	 */
	public function default_operator(): string {
		$operators = $this->operators();

		return isset( $operators[0] ) ? (string) $operators[0] : '';
	}

	/**
	 * Gets the JSON-schema-like description of the value field for the UI.
	 *
	 * @return array
	 */
	public function value_schema(): array {
		return array();
	}

	/**
	 * Gets the default value for a newly created condition of this type.
	 *
	 * @return mixed
	 */
	public function default_value() {
		return null;
	}

	/**
	 * Validates a value against this condition's schema.
	 *
	 * @param mixed $value Value to validate.
	 * @return bool
	 */
	public function is_valid_value( $value ): bool {
		return true;
	}

	/**
	 * Normalises a stored list value (or a lone scalar) to a list of strings.
	 *
	 * Non-scalar entries (e.g. a nested array in hand-edited markup) are
	 * dropped rather than cast, so a malformed value never raises an
	 * "Array to string conversion" warning or becomes the literal "Array".
	 *
	 * @param mixed $value Stored value.
	 * @return string[]
	 */
	protected function string_list( $value ): array {
		$items = is_array( $value ) ? $value : array( $value );

		return array_values( array_map( 'strval', array_filter( $items, 'is_scalar' ) ) );
	}
}