<?php
/**
 * Compare two session summaries.
 *
 * @package Bloatwright
 */

namespace Bloatwright\Services;

/**
 * Diff.
 */
class Diff {

	/**
	 * Compare.
	 *
	 * @param array $a Older summary.
	 * @param array $b Newer summary.
	 * @return array{owners: array<string,array>, totals: array, added: string[], removed: string[]}
	 */
	public static function compare( array $a, array $b ): array {
		$dims   = array( 'php_ms', 'queries', 'query_ms', 'assets_kb', 'autoload_kb', 'cron_per_day', 'weight' );
		$oa     = (array) ( $a['owners'] ?? array() );
		$ob     = (array) ( $b['owners'] ?? array() );
		$owners = array();
		foreach ( array_unique( array_merge( array_keys( $oa ), array_keys( $ob ) ) ) as $key ) {
			$row = array(
				'key'  => $key,
				'name' => (string) ( $ob[ $key ]['name'] ?? $oa[ $key ]['name'] ?? $key ),
			);
			foreach ( $dims as $d ) {
				$before    = (float) ( $oa[ $key ][ $d ] ?? 0 );
				$after     = (float) ( $ob[ $key ][ $d ] ?? 0 );
				$row[ $d ] = array(
					'before' => $before,
					'after'  => $after,
					'delta'  => round( $after - $before, 2 ),
					'pct'    => $before > 0 ? round( ( $after - $before ) / $before * 100, 1 ) : ( $after > 0 ? 100.0 : 0.0 ),
				);
			}
			$owners[ $key ] = $row;
		}
		uasort(
			$owners,
			static function ( $x, $y ) {
				return abs( $y['php_ms']['delta'] ) <=> abs( $x['php_ms']['delta'] );
			}
		);
		$totals = array();
		foreach ( array( 'frontend_ms', 'admin_ms', 'queries' ) as $t ) {
			$before       = (float) ( $a['totals'][ $t ] ?? 0 );
			$after        = (float) ( $b['totals'][ $t ] ?? 0 );
			$totals[ $t ] = array(
				'before' => $before,
				'after'  => $after,
				'delta'  => round( $after - $before, 2 ),
				'pct'    => $before > 0 ? round( ( $after - $before ) / $before * 100, 1 ) : 0.0,
			);
		}
		return array(
			'owners'  => $owners,
			'totals'  => $totals,
			'added'   => array_values( array_diff( array_keys( $ob ), array_keys( $oa ) ) ),
			'removed' => array_values( array_diff( array_keys( $oa ), array_keys( $ob ) ) ),
		);
	}
}