<?php
/**
 * How much of this request's execution time an export may still spend.
 *
 * @package Shiftora\Support
 */

declare(strict_types=1);

namespace Shiftora\Support;

// Prevent direct file access.
if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * A page of rows is cut short before PHP would kill the request: a half-built
 * page the caller can resume beats a 500 it has to guess at.
 */
final class RequestBudget {

	/** Share of max_execution_time an export may use; the rest is boot, output and the importer's slack. */
	private const SHARE = 0.5;

	/** Seconds granted when PHP sets no limit, so a shared host's proxy timeout still has margin. */
	private const UNLIMITED_SECONDS = 20.0;

	private const MIN_SECONDS = 2.0;

	private static ?float $started = null;

	/** Seconds the request has run. */
	public static function elapsed(): float {
		return microtime( true ) - self::started();
	}

	/** Seconds an export may run in total within this request. */
	public static function seconds(): float {
		$limit = (int) ini_get( 'max_execution_time' );
		if ( $limit <= 0 ) {
			return self::UNLIMITED_SECONDS;
		}

		return max( self::MIN_SECONDS, $limit * self::SHARE );
	}

	public static function exhausted(): bool {
		return self::elapsed() >= self::seconds();
	}

	/**
	 * Counts from the given moment (default now) instead of the request start; long
	 * CLI runs reset it, and a test backdates it to play a request that ran long.
	 */
	public static function restart( ?float $started = null ): void {
		self::$started = $started ?? microtime( true );
	}

	private static function started(): float {
		if ( null === self::$started ) {
			// phpcs:ignore WordPress.Security.ValidatedSanitizedInput.InputNotSanitized -- a float PHP itself sets at request start, not a client value; cast to float below.
			$request       = isset( $_SERVER['REQUEST_TIME_FLOAT'] ) ? (float) $_SERVER['REQUEST_TIME_FLOAT'] : 0.0;
			self::$started = $request > 0 ? $request : microtime( true );
		}

		return self::$started;
	}
}