<?php
/**
 * Turns segments into Google API filters.
 *
 * @package TurtleReport
 */

namespace TurtleReport\Reports;

use TurtleReport\Auth\ApiException;
use TurtleReport\Policy\Segments;
use TurtleReport\Profiles\Profile;

defined( 'ABSPATH' ) || exit;

/**
 * Finds a report's requested segment and turns it into Google API filters.
 *
 * Query segments filter Search Console only, because GA4 has no search
 * queries. Page segments filter Search Console pages and GA4 landing pages.
 */
final class SegmentFilter {

	/**
	 * Finds the segment named by a request parameter ("gabc12" or "!gabc12").
	 *
	 * @param Profile  $site    Site.
	 * @param string   $param   Parameter value; empty for no segment.
	 * @param string[] $allowed Segment types the report supports.
	 * @return array|null ['segment' => array, 'negate' => bool], or null for no segment.
	 * @throws ApiException When the segment doesn't exist or doesn't apply to the report.
	 */
	public static function resolve( Profile $site, $param, array $allowed ) {
		$param = (string) $param;
		if ( '' === $param ) {
			return null;
		}
		$negate = '!' === $param[0];
		$id     = ltrim( $param, '!' );
		foreach ( $site->segments as $segment ) {
			if ( $segment['id'] === $id ) {
				if ( ! in_array( $segment['type'], $allowed, true ) ) {
					throw new ApiException( __( 'That segment doesn\'t apply to this part of the report.', 'turtlereport' ), ApiException::INVALID ); // phpcs:ignore WordPress.Security.EscapeOutput.ExceptionNotEscaped -- Caught by the plugin; escaped where the message is shown.
				}
				return array(
					'segment' => $segment,
					'negate'  => $negate,
				);
			}
		}
		throw new ApiException( __( 'That segment no longer exists. Reload the page.', 'turtlereport' ), ApiException::INVALID ); // phpcs:ignore WordPress.Security.EscapeOutput.ExceptionNotEscaped -- Caught by the plugin; escaped where the message is shown.
	}

	/**
	 * Search Console dimensionFilterGroups for a resolved segment.
	 *
	 * @param array $resolved Result of resolve().
	 * @return array
	 */
	public static function gsc( array $resolved ) {
		return array(
			array(
				'filters' => array(
					array(
						'dimension'  => $resolved['segment']['type'],
						'operator'   => $resolved['negate'] ? 'excludingRegex' : 'includingRegex',
						'expression' => '(?i)' . Segments::pattern( $resolved['segment'] ),
					),
				),
			),
		);
	}

	/**
	 * GA4 filter on landing page for a resolved page segment.
	 *
	 * @param array $resolved Result of resolve().
	 * @return array
	 */
	public static function ga( array $resolved ) {
		$filter = Filters::regex( 'landingPage', Segments::pattern( $resolved['segment'] ) );
		return $resolved['negate'] ? array( 'notExpression' => $filter ) : $filter;
	}
}