<?php

class WP_Export_Split_Files_Writer extends WP_Export_Base_Writer {
    private $max_file_size;
    private $destination_directory;
    private $filename_template;
    private $before_posts_xml;
    private $after_posts_xml;

    private $f;
    private $next_file_number    = 0;
    private $current_file_size   = 0;
    private $available_sections  = array(
        'header',
        'site_metadata',
        'authors',
        'categories',
        'tags',
        'nav_menu_terms',
        'custom_taxonomies_terms',
        'rss2_head_action',
    );
    private $subsequent_sections = array();

    public function __construct( $formatter, $writer_args = [] ) {
        parent::__construct( $formatter );

        if ( ! defined( 'MB_IN_BYTES' ) ) {
            // phpcs:ignore WordPress.NamingConventions.PrefixAllGlobals.NonPrefixedConstantFound -- WordPress native constants.
            define( 'MB_IN_BYTES', 1024 * 1024 );
        }

        //TODO: check if args are not missing
        if ( is_null( $writer_args['max_file_size'] ) ) {
            $this->max_file_size = 15 * MB_IN_BYTES;
        } elseif ( WP_CLI_EXPORT_COMMAND_NO_SPLIT === (string) $writer_args['max_file_size'] ) {
            $this->max_file_size = WP_CLI_EXPORT_COMMAND_NO_SPLIT;
        } else {
            $this->max_file_size = $writer_args['max_file_size'] * MB_IN_BYTES;
        }

        // Filter and handle condition where subsequent export files should not contain
        // all of the export sections
        if ( is_array( $writer_args['include_once'] ) && ! empty( $writer_args['include_once'] ) ) {
            $this->subsequent_sections = array_diff( $this->available_sections, $writer_args['include_once'] );
        }

        $this->destination_directory = $writer_args['destination_directory'];
        $this->filename_template     = $writer_args['filename_template'];
        $this->before_posts_xml      = $this->formatter->before_posts();
        $this->after_posts_xml       = $this->formatter->after_posts();
    }

    public function export() {
        $this->start_new_file();
        foreach ( $this->formatter->posts() as $post_xml ) {
            if ( WP_CLI_EXPORT_COMMAND_NO_SPLIT !== $this->max_file_size && $this->current_file_size + strlen( $post_xml ) > $this->max_file_size ) {
                $this->start_new_file();
            }
            $this->write( $post_xml );
        }
        $this->close_current_file();
    }

    protected function write( $xml ) {
        $res = fwrite( $this->f, $xml );
        if ( false === $res ) {
            throw new WP_Export_Exception( 'WP Export: error writing to export file.' );
        }
        $this->current_file_size += strlen( $xml );
    }

    private function start_new_file() {
        if ( $this->f ) {
            $this->close_current_file();
        }
        $file_path = $this->next_file_path();
        $this->f   = fopen( $file_path, 'w' );
        if ( ! $this->f ) {
            throw new WP_Export_Exception( "WP Export: error opening {$file_path} for writing." );
        }
        // phpcs:ignore WordPress.NamingConventions.PrefixAllGlobals.NonPrefixedHooknameFound -- Possibly used by third party extension.
        do_action( 'wp_export_new_file', $file_path );
        $this->current_file_size = 0;

        $this->write( $this->before_posts_xml );
        if ( 1 === $this->next_file_number && ! empty( $this->subsequent_sections ) ) {
            $this->before_posts_xml = $this->formatter->before_posts( $this->subsequent_sections );
        }
    }

    private function close_current_file() {
        if ( ! $this->f ) {
            return;
        }
        $this->write( $this->after_posts_xml );
        fclose( $this->f );
    }

    private function next_file_name() {
        $next_file_name = sprintf( $this->filename_template, $this->next_file_number );
        ++$this->next_file_number;
        return $next_file_name;
    }

    private function next_file_path() {
        return untrailingslashit( $this->destination_directory ) . DIRECTORY_SEPARATOR . $this->next_file_name();
    }
}