<?php
/**
 * Streaming CSV export.
 *
 * @package Recast\WCS
 */

namespace Recast\WCS\Export;

use Recast\WCS\Admin\Settings;
use Recast\WCS\Cohort\CohortQuery;
use Recast\WCS\Cohort\CohortSpec;

defined( 'ABSPATH' ) || exit;

/**
 * Writes a cohort as CSV to a stream, page by page.
 */
final class StreamExporter {

	/**
	 * Writes CSV rows to a resource.
	 *
	 * @param resource   $handle   Open stream.
	 * @param CohortSpec $spec     Cohort.
	 * @param bool       $header   Whether to write the header (and BOM if enabled).
	 * @param array      $cursor   Resume cursor (by reference).
	 * @param float      $budget   Seconds; PHP_INT_MAX for unlimited.
	 * @param bool       $stream   True when writing to the HTTP response: output is flushed every 200 rows.
	 *                             Background jobs pass false. Their request has no listener, and flushing
	 *                             to a closed connection makes PHP end the script without an error.
	 * @return array{rows: int, done: bool}
	 */
	public static function write( $handle, CohortSpec $spec, $header, array &$cursor, $budget = PHP_INT_MAX, $stream = false ) {
		if ( $header ) {
			if ( Settings::get( 'recast_csv_bom' ) ) {
				fwrite( $handle, "\xEF\xBB\xBF" ); // phpcs:ignore WordPress.WP.AlternativeFunctions
			}
			fputcsv( $handle, Columns::header(), ',', '"', '' );
		}
		$deadline = microtime( true ) + $budget;
		$rows     = 0;
		$stopped  = false;
		$query    = new CohortQuery( $spec );
		$query->iterate(
			static function ( \WC_Subscription $subscription ) use ( $handle, &$rows, &$stopped, $deadline, $stream ) {
				// No escape character: quotes are only doubled, as RFC 4180 and spreadsheets expect. A
				// backslash escape would let a value such as \",=1+1 end its cell early and open a new one.
				fputcsv( $handle, Columns::row( $subscription ), ',', '"', '' );
				$rows++;
				if ( 0 === $rows % 200 ) {
					if ( function_exists( 'wp_cache_flush_runtime' ) ) {
						wp_cache_flush_runtime();
					}
					if ( $stream ) {
						if ( ob_get_level() ) {
							ob_flush();
						}
						flush();
					}
				}
				if ( microtime( true ) > $deadline ) {
					$stopped = true;
					return false;
				}
				return true;
			},
			$cursor
		);
		return array(
			'rows' => $rows,
			'done' => ! $stopped && ! empty( $cursor['done'] ),
		);
	}

	/**
	 * Streams a whole cohort to the HTTP response and exits.
	 *
	 * @param CohortSpec $spec      Cohort.
	 * @param string     $file_name Download name.
	 * @return void
	 */
	public static function send( CohortSpec $spec, $file_name ) {
		if ( function_exists( 'wc_set_time_limit' ) ) {
			wc_set_time_limit( 0 );
		}
		nocache_headers();
		header( 'Content-Type: text/csv; charset=utf-8' );
		header( 'Content-Disposition: attachment; filename="' . sanitize_file_name( $file_name ) . '"' );
		header( 'X-Content-Type-Options: nosniff' );
		$handle = fopen( 'php://output', 'w' ); // phpcs:ignore WordPress.WP.AlternativeFunctions
		$cursor = array();
		self::write( $handle, $spec, true, $cursor, PHP_INT_MAX, true );
		fclose( $handle ); // phpcs:ignore WordPress.WP.AlternativeFunctions
	}
}