<?php
if ( ! defined( 'ABSPATH' ) ) {
	die( 'You are not allowed to call this page directly.' );
}

class FrmCSVExportHelper {

	/**
	 * @var string
	 */
	protected static $separator = ', ';

	/**
	 * @var string
	 */
	protected static $column_separator = ',';

	/**
	 * @var string
	 */
	protected static $line_break = 'return';

	/**
	 * @var string
	 */
	protected static $charset = 'UTF-8';

	/**
	 * @var string
	 */
	protected static $to_encoding = 'UTF-8';

	/**
	 * @var string
	 */
	protected static $wp_date_format = 'Y-m-d H:i:s';

	/**
	 * @var int
	 */
	protected static $comment_count = 0;

	/**
	 * @var int
	 */
	protected static $form_id = 0;

	/**
	 * @var array
	 */
	protected static $headings = array();

	/**
	 * @var array
	 */
	protected static $fields = array();

	/**
	 * @var stdClass|null
	 */
	protected static $entry;

	/**
	 * @var bool|null
	 */
	protected static $has_parent_id;

	/**
	 * @var array|null
	 */
	protected static $fields_by_repeater_id;

	/**
	 * @var string either 'echo' or 'file' are supported.
	 */
	protected static $mode = 'echo';

	/**
	 * @var resource|null used to write a CSV file in file mode.
	 */
	protected static $fp;

	/**
	 * @var string the context of the CSV being generated. Possible values include 'email' when used as an email attachment, or 'default'.
	 */
	protected static $context = 'default';

	/**
	 * @var array
	 */
	protected static $meta = array();

	/**
	 * Whether to include the BOM (Byte Order Mark) in the CSV file.
	 * Only applicable for UTF-8 exports.
	 *
	 * @since 6.17
	 *
	 * @var bool
	 */
	private static $include_bom = false;

	/**
	 * Get all options for the CSV export format dropdown.
	 *
	 * @since 6.17 The UTF-8 with BOM option was added.
	 *
	 * @return array
	 */
	public static function csv_format_options() {
		$formats = array( 'UTF-8', 'ISO-8859-1', 'windows-1256', 'windows-1251', 'macintosh' );

		// Do not add the UTF-8 with BOM option if this function is called on Global Settings.
		// This is to improve compatibility with the Export View as CSV add-on (v1.10).
		// Otherwise, the option will appear twice since it is added in the add-on as well.
		$on_global_settings_page = 'formidable-settings' === FrmAppHelper::get_param( 'page' );

		if ( ! $on_global_settings_page ) {
			array_splice( $formats, 1, 0, 'UTF-8 with BOM' );
		}

		$formats = apply_filters( 'frm_csv_format_options', $formats );

		return $formats;
	}

	/**
	 * @param array $atts
	 *
	 * @return false|string|null returns a string file path or false if $atts['mode'] is set to 'file'.
	 */
	public static function generate_csv( $atts ) {
		global $frm_vars;
		$frm_vars['prevent_caching'] = true;

		self::$fields  = $atts['form_cols'];
		self::$form_id = $atts['form']->id;
		self::$mode    = ! empty( $atts['mode'] ) && 'file' === $atts['mode'] ? 'file' : 'echo';
		self::$context = ! empty( $atts['context'] ) ? $atts['context'] : 'default';
		self::$meta    = ! empty( $atts['meta'] ) ? $atts['meta'] : array();

		self::set_class_parameters();
		self::set_has_parent_id( $atts['form'] );

		$filename = self::generate_csv_filename( $atts['form'] );

		if ( 'file' === self::$mode ) {
			$filepath = get_temp_dir() . $filename;
			self::$fp = @fopen( $filepath, 'w' );

			if ( ! self::$fp ) {
				return false;
			}
		} elseif ( 'echo' === self::$mode ) {
			self::print_file_headers( $filename );
		}

		unset( $filename );

		$comment_count       = FrmDb::get_count(
			'frm_item_metas',
			array(
				'item_id'         => $atts['entry_ids'],
				'field_id'        => 0,
				'meta_value like' => 's:7:"comment";',
			),
			array(
				'group_by' => 'item_id',
				'order_by' => 'count(*) DESC',
				'limit'    => 1,
			)
		);
		self::$comment_count = $comment_count;

		self::prepare_csv_headings();

		/**
		 * For a target form with 50k entries (Locations List, with 7 fields), batch sizes of 100
		 * were significantly faster and used less memory, so a filter was added.
		 *
		 * @since 6.17
		 *
		 * @param int $batch_size
		 * @param int $form_id
		 */
		$csv_export_batch_size = (int) apply_filters( 'frm_csv_export_batch_size', 20, self::$form_id );

		// Fetch posts in batches rather than loading the entire table into memory.
		while ( $next_set = array_splice( $atts['entry_ids'], 0, $csv_export_batch_size ) ) {
			self::prepare_next_csv_rows( $next_set );
		}

		self::after_generate_csv( $atts );

		unset( $atts['form'], $atts['form_cols'] );

		if ( 'file' === self::$mode ) {
			fclose( self::$fp );
			return $filepath;
		}

		return null;
	}

	/**
	 * @since 6.8.4
	 *
	 * @param array $atts
	 *
	 * @return void
	 */
	private static function after_generate_csv( $atts ) {
		/**
		 * @since 6.8.4
		 *
		 * @param array $atts {
		 *
		 *   @type object $form
		 *   @type array  $entry_ids
		 *   @type array  $form_cols
		 * }
		 */
		do_action( 'frm_after_generate_csv', $atts );
	}

	/**
	 * @since 5.0.16
	 *
	 * @param stdClass $form
	 *
	 * @return string
	 */
	private static function generate_csv_filename( $form ) {
		$filename = gmdate( 'ymdHis', time() ) . '_' . sanitize_title_with_dashes( $form->name ) . '_formidable_entries.csv';
		return apply_filters( 'frm_csv_filename', $filename, $form, self::get_standard_filter_args() );
	}

	/**
	 * @since 5.0.16
	 *
	 * @return array
	 */
	private static function get_standard_filter_args() {
		return array(
			'context' => self::$context,
			'meta'    => self::$meta,
		);
	}

	/**
	 * @return void
	 */
	private static function set_class_parameters() {
		$args                 = self::get_standard_filter_args();
		self::$separator      = apply_filters( 'frm_csv_sep', self::$separator, $args );
		self::$line_break     = apply_filters( 'frm_csv_line_break', self::$line_break, $args );
		self::$wp_date_format = apply_filters( 'frm_csv_date_format', self::$wp_date_format, $args );
		self::get_csv_format();
		self::$charset = get_option( 'blog_charset' );

		$col_sep = ! empty( $_POST['csv_col_sep'] ) ? sanitize_text_field( wp_unslash( $_POST['csv_col_sep'] ) ) : self::$column_separator; // phpcs:ignore WordPress.Security.NonceVerification.Missing

		self::$column_separator = apply_filters( 'frm_csv_column_sep', $col_sep, $args );
	}

	/**
	 * @param object $form
	 *
	 * @return void
	 */
	private static function set_has_parent_id( $form ) {
		self::$has_parent_id = $form->parent_form_id > 0;
	}

	/**
	 * @param string $filename
	 *
	 * @return void
	 */
	private static function print_file_headers( $filename ) {
		header( 'Content-Description: File Transfer' );
		header( 'Content-Disposition: attachment; filename="' . esc_attr( $filename ) . '"' );
		header( 'Content-Type: text/csv; charset=' . self::$charset, true );
		header( 'Expires: ' . gmdate( 'D, d M Y H:i:s', mktime( gmdate( 'H' ) + 2, gmdate( 'i' ), gmdate( 's' ), gmdate( 'm' ), gmdate( 'd' ), gmdate( 'Y' ) ) ) . ' GMT' );
		header( 'Last-Modified: ' . gmdate( 'D, d M Y H:i:s' ) . ' GMT' );
		header( 'Cache-Control: no-cache, must-revalidate' );
		header( 'Pragma: no-cache' );

		if ( self::$include_bom ) {
			echo esc_html( chr( 239 ) . chr( 187 ) . chr( 191 ) );
		}

		do_action(
			'frm_csv_headers',
			array(
				'form_id' => self::$form_id,
				'fields'  => self::$fields,
			)
		);
	}

	/**
	 * Check the POST request data for the CSV format to use.
	 *
	 * @return void
	 */
	public static function get_csv_format() {
		$csv_format = FrmAppHelper::get_post_param( 'csv_format', 'UTF-8', 'sanitize_text_field' );

		if ( 'UTF-8 with BOM' === $csv_format ) {
			self::$include_bom = true;
			$csv_format        = 'UTF-8';
		}

		$csv_format        = apply_filters( 'frm_csv_format', $csv_format, self::get_standard_filter_args() );
		self::$to_encoding = $csv_format;
	}

	/**
	 * @return void
	 */
	private static function prepare_csv_headings() {
		$headings = array();
		self::csv_headings( $headings );
		$headings       = apply_filters(
			'frm_csv_columns',
			$headings,
			self::$form_id,
			array_merge(
				self::get_standard_filter_args(),
				array( 'fields' => self::$fields )
			)
		);
		self::$headings = $headings;

		self::print_csv_row( $headings );
	}

	/**
	 * @param object $col
	 *
	 * @return array
	 */
	private static function field_headings( $col ) {
		$field_type_obj = FrmFieldFactory::get_field_factory( $col );

		if ( ! empty( $field_type_obj->is_combo_field ) ) {
			// This is combo field.
			return $field_type_obj->get_export_headings();
		}

		$field_headings  = array();
		$separate_values = array( 'user_id', 'file', 'data', 'date' );

		if ( ! empty( $col->field_options['separate_value'] ) && ! in_array( $col->type, $separate_values, true ) ) {
			$field_headings[ $col->id . '_label' ] = strip_tags( $col->name . ' ' . __( '(label)', 'formidable' ) );
		}

		if ( ! empty( $field_headings[ $col->id . '_label' ] ) ) {
			$field_headings[ $col->id ] = strip_tags( $col->name . ' ' . __( '(value)', 'formidable' ) );
		} else {
			$field_headings[ $col->id ] = strip_tags( $col->name );
		}

		$field_headings             = apply_filters(
			'frm_csv_field_columns',
			$field_headings,
			array_merge(
				self::get_standard_filter_args(),
				array( 'field' => $col )
			)
		);

		return $field_headings;
	}

	/**
	 * @param array $headings
	 *
	 * @return void
	 */
	private static function csv_headings( &$headings ) {
		$fields_by_repeater_id = array();
		$repeater_ids          = array();

		foreach ( self::$fields as $col ) {
			if ( self::is_the_child_of_a_repeater( $col ) ) {
				$repeater_id = $col->field_options['in_section'];
				// Set a placeholder to maintain order for repeater fields.
				$headings[ 'repeater' . $repeater_id ] = array();

				if ( ! isset( $fields_by_repeater_id[ $repeater_id ] ) ) {
					$fields_by_repeater_id[ $repeater_id ] = array();
					$repeater_ids[]                        = $repeater_id;
				}

				$fields_by_repeater_id[ $repeater_id ][] = $col;

				continue;
			}

			$headings += self::field_headings( $col );
		}
		unset( $repeater_id, $col );

		if ( $repeater_ids ) {
			$where         = array( 'field_id' => $repeater_ids );
			$repeater_meta = FrmDb::get_results( 'frm_item_metas', $where, 'field_id, meta_value' );
			$max           = array_fill_keys( $repeater_ids, 0 );

			foreach ( $repeater_meta as $row ) {
				$start  = strpos( $row->meta_value, 'a:' ) + 2;
				$end    = strpos( $row->meta_value, ':{' );
				$length = substr( $row->meta_value, $start, $end - $start );

				if ( $length > $max[ $row->field_id ] ) {
					$max[ $row->field_id ] = $length;
				}
			}
			unset( $start, $end, $length, $row, $repeater_meta, $where );

			$flat = array();

			foreach ( $headings as $key => $heading ) {
				if ( is_array( $heading ) ) {
					$repeater_id = str_replace( 'repeater', '', $key );

					$repeater_headings = array();

					foreach ( $fields_by_repeater_id[ $repeater_id ] as $col ) {
						$repeater_headings += self::field_headings( $col );
					}

					for ( $i = 0; $i < $max[ $repeater_id ]; $i++ ) {
						foreach ( $repeater_headings as $repeater_key => $repeater_name ) {
							$flat[ $repeater_key . '[' . $i . ']' ] = $repeater_name;
						}
					}
				} else {
					$flat[ $key ] = $heading;
				}
			}

			self::$fields_by_repeater_id = $fields_by_repeater_id;

			unset( $key, $heading, $max, $repeater_headings, $repeater_id, $fields_by_repeater_id );

			$headings = $flat;
			unset( $flat );
		}//end if

		if ( self::$comment_count ) {
			for ( $i = 0; $i < self::$comment_count; $i++ ) {
				$headings[ 'comment' . $i ]            = __( 'Comment', 'formidable' );
				$headings[ 'comment_user_id' . $i ]    = __( 'Comment User', 'formidable' );
				$headings[ 'comment_created_at' . $i ] = __( 'Comment Date', 'formidable' );
			}
			unset( $i );
		}

		$headings['created_at'] = __( 'Timestamp', 'formidable' );
		$headings['updated_at'] = __( 'Last Updated', 'formidable' );
		$headings['user_id']    = __( 'Created By', 'formidable' );
		$headings['updated_by'] = __( 'Updated By', 'formidable' );
		$headings['is_draft']   = __( 'Entry Status', 'formidable' );
		$headings['ip']         = __( 'IP', 'formidable' );
		$headings['id']         = __( 'ID', 'formidable' );
		$headings['item_key']   = __( 'Key', 'formidable' );

		if ( self::has_parent_id() ) {
			$headings['parent_id'] = __( 'Parent ID', 'formidable' );
		}

		$headings = apply_filters( 'frm_export_csv_headings', $headings );
	}

	/**
	 * @param object $field
	 *
	 * @return bool
	 */
	private static function is_the_child_of_a_repeater( $field ) {
		if ( $field->form_id === self::$form_id || empty( $field->field_options['in_section'] ) ) {
			return false;
		}

		$section_id = $field->field_options['in_section'];
		$section    = FrmField::getOne( $section_id );

		if ( ! $section ) {
			return false;
		}

		return FrmField::is_repeating_field( $section );
	}

	/**
	 * @return bool
	 */
	private static function has_parent_id() {
		return self::$has_parent_id;
	}

	/**
	 * @param array $next_set
	 *
	 * @return void
	 */
	private static function prepare_next_csv_rows( $next_set ) {
		if ( FrmAppHelper::pro_is_installed() ) {
			$where    = array(
				'or'             => 1,
				'id'             => $next_set,
				'parent_item_id' => $next_set,
			);
			// Order by parent_item_id so children will be first.
			$order_by = ' ORDER BY parent_item_id DESC';
		} else {
			// When Pro is not installed, only query for direct ID matches only as we do not expect parent item id
			// matches and the more simplified query is faster.
			$where    = array(
				'id' => $next_set,
			);
			$order_by = '';
		}

		$entries = FrmEntry::getAll( $where, $order_by, '', true, false );

		foreach ( $entries as $entry ) {
			self::$entry = $entry;
			unset( $entry );

			if ( self::$entry->form_id !== self::$form_id ) {
				self::add_repeat_field_values_to_csv( $entries );
			} else {
				self::prepare_csv_row();
			}
		}
	}

	/**
	 * @return void
	 */
	private static function prepare_csv_row() {
		$row = array();
		self::add_field_values_to_csv( $row );
		self::add_entry_data_to_csv( $row );
		$row = apply_filters(
			'frm_csv_row',
			$row,
			array(
				'entry'         => self::$entry,
				'date_format'   => self::$wp_date_format,
				'comment_count' => self::$comment_count,
				'context'       => self::$context,
			)
		);
		self::print_csv_row( $row );
	}

	/**
	 * @param array $entries
	 *
	 * @return void
	 */
	private static function add_repeat_field_values_to_csv( &$entries ) {
		if ( isset( self::$entry->metas ) ) {
			// add child entries to the parent
			foreach ( self::$entry->metas as $meta_id => $meta_value ) {
				if ( ! is_numeric( $meta_id ) || '' === $meta_value ) {
					// if the hook is being used to include field keys in the metas array,
					// we need to skip the keys and only process field ids
					continue;
				}

				if ( ! isset( $entries[ self::$entry->parent_item_id ] ) ) {
					$entries[ self::$entry->parent_item_id ]        = new stdClass();
					$entries[ self::$entry->parent_item_id ]->metas = array();
				}

				if ( ! isset( $entries[ self::$entry->parent_item_id ]->metas[ $meta_id ] ) ) {
					$entries[ self::$entry->parent_item_id ]->metas[ $meta_id ] = array();
				} elseif ( ! is_array( $entries[ self::$entry->parent_item_id ]->metas[ $meta_id ] ) ) {
					// if the data is here, it should be an array but if this field has collected data
					// both while inside and outside of the repeating section, it's possible this is a string.
					$entries[ self::$entry->parent_item_id ]->metas[ $meta_id ] = (array) $entries[ self::$entry->parent_item_id ]->metas[ $meta_id ];
				}

				// Add the repeated values.
				$entries[ self::$entry->parent_item_id ]->metas[ $meta_id ][] = $meta_value;
			}//end foreach

			self::$entry->metas                              = self::fill_missing_repeater_metas( self::$entry->metas, $entries );
			$entries[ self::$entry->parent_item_id ]->metas += self::$entry->metas;
		}//end if

		// add the embedded form id
		if ( ! isset( $entries[ self::$entry->parent_item_id ]->embedded_fields ) ) {
			$entries[ self::$entry->parent_item_id ]->embedded_fields = array();
		}
		$entries[ self::$entry->parent_item_id ]->embedded_fields[ self::$entry->id ] = self::$entry->form_id;
	}

	/**
	 * When an empty field is saved, it isn't saved as a meta value
	 * The export needs all of the meta to be filled in, so we put blank strings for every missing repeater child
	 *
	 * @param array $metas
	 * @param array $entries
	 *
	 * @return array
	 */
	private static function fill_missing_repeater_metas( $metas, &$entries ) {
		$field_ids = array_keys( $metas );
		$field_id  = end( $field_ids );
		$field     = self::get_field( $field_id );

		if ( ! $field || empty( $field->field_options['in_section'] ) ) {
			return $metas;
		}

		$repeater_id = $field->field_options['in_section'];

		if ( ! isset( self::$fields_by_repeater_id[ $repeater_id ] ) ) {
			return $metas;
		}

		foreach ( self::$fields_by_repeater_id[ $repeater_id ] as $repeater_child ) {
			if ( ! isset( $metas[ $repeater_child->id ] ) ) {
				$metas[ $repeater_child->id ] = '';

				if ( ! isset( $entries[ self::$entry->parent_item_id ]->metas[ $repeater_child->id ] ) || ! is_array( $entries[ self::$entry->parent_item_id ]->metas[ $repeater_child->id ] ) ) {
					$entries[ self::$entry->parent_item_id ]->metas[ $repeater_child->id ] = array();
				}

				$entries[ self::$entry->parent_item_id ]->metas[ $repeater_child->id ][] = '';
			}
		}

		return $metas;
	}

	/**
	 * @param int|string $field_id
	 *
	 * @return false|object
	 */
	private static function get_field( $field_id ) {
		$field_id = (int) $field_id;

		foreach ( self::$fields as $field ) {
			if ( $field_id === (int) $field->id ) {
				return $field;
			}
		}
		return false;
	}

	/**
	 * @param array $row
	 *
	 * @return void
	 */
	private static function add_field_values_to_csv( &$row ) {
		foreach ( self::$fields as $col ) {
			$field_value = self::$entry->metas[ $col->id ] ?? false;

			FrmFieldsHelper::prepare_field_value( $field_value, $col->type );
			self::add_array_values_to_columns( $row, compact( 'col', 'field_value' ) );

			$field_value = apply_filters(
				'frm_csv_value',
				$field_value,
				array(
					'field'     => $col,
					'entry'     => self::$entry,
					'separator' => self::$separator,
					'context'   => self::$context,
				)
			);

			if ( ! empty( $col->field_options['separate_value'] ) ) {
				$label_key = $col->id . '_label';

				if ( self::is_the_child_of_a_repeater( $col ) ) {
					$row[ $label_key ] = array();

					if ( is_array( $field_value ) ) {
						foreach ( $field_value as $value ) {
							$row[ $label_key ][] = self::get_separate_value_label( $value, $col );
						}
					}
				} else {
					$row[ $label_key ] = self::get_separate_value_label( $field_value, $col );
				}
				unset( $label_key );
			}

			$row[ $col->id ] = $field_value;

			unset( $col, $field_value );
		}//end foreach
	}

	/**
	 * @since 5.0.06
	 *
	 * @param mixed    $field_value
	 * @param stdClass $field
	 *
	 * @return string
	 */
	private static function get_separate_value_label( $field_value, $field ) {
		return FrmEntriesHelper::display_value(
			$field_value,
			$field,
			array(
				'type'              => $field->type,
				'post_id'           => self::$entry->post_id,
				'show_icon'         => false,
				'entry_id'          => self::$entry->id,
				'sep'               => self::$separator,
				'embedded_field_id' => isset( self::$entry->embedded_fields ) && isset( self::$entry->embedded_fields[ self::$entry->id ] ) ? 'form' . self::$entry->embedded_fields[ self::$entry->id ] : 0,
			)
		);
	}

	/**
	 * @since 2.0.23
	 *
	 * @param array $row
	 * @param array $atts
	 *
	 * @return void
	 */
	private static function add_array_values_to_columns( &$row, $atts ) {
		if ( is_array( $atts['field_value'] ) ) {
			foreach ( $atts['field_value'] as $key => $sub_value ) {
				if ( is_array( $sub_value ) ) {
					// This is combo field inside repeater. The heading key has this format: [86_first[0]].
					foreach ( $sub_value as $sub_key => $sub_sub_value ) {
						$column_key = $atts['col']->id . '_' . $sub_key . '[' . $key . ']';

						if ( ! is_numeric( $sub_key ) && isset( self::$headings[ $column_key ] ) ) {
							$row[ $column_key ] = $sub_sub_value;
						}
					}

					continue;
				}

				$column_key = $atts['col']->id . '_' . $key;

				if ( ! is_numeric( $key ) && isset( self::$headings[ $column_key ] ) ) {
					$row[ $column_key ] = $sub_value;
				}
			}
		}//end if
	}

	/**
	 * @param array $row
	 *
	 * @return void
	 */
	private static function add_entry_data_to_csv( &$row ) {
		$row['created_at'] = FrmAppHelper::get_formatted_time( self::$entry->created_at, self::$wp_date_format, ' ' );
		$row['updated_at'] = FrmAppHelper::get_formatted_time( self::$entry->updated_at, self::$wp_date_format, ' ' );
		$row['user_id']    = self::$entry->user_id;
		$row['updated_by'] = self::$entry->updated_by;
		$row['is_draft']   = self::$entry->is_draft;
		$row['ip']         = self::$entry->ip;
		$row['id']         = self::$entry->id;
		$row['item_key']   = self::$entry->item_key;

		if ( self::has_parent_id() ) {
			$row['parent_id'] = self::$entry->parent_item_id;
		}
	}

	/**
	 * @param array $rows
	 *
	 * @return void
	 */
	private static function print_csv_row( $rows ) {
		$sep  = '';
		$echo = 'echo' === self::$mode;

		foreach ( self::$headings as $k => $heading ) {
			if ( isset( $rows[ $k ] ) ) {
				$row = $rows[ $k ];
			} else {
				$row = '';

				// array indexed data is not at $rows[ $k ]
				if ( $k[ strlen( $k ) - 1 ] === ']' ) {
					$start = strrpos( $k, '[' );
					$key   = substr( $k, 0, $start++ );
					$index = substr( $k, $start, strlen( $k ) - 1 - $start );

					if ( isset( $rows[ $key ] ) && isset( $rows[ $key ][ $index ] ) ) {
						$row = $rows[ $key ][ $index ];
					}

					unset( $start, $key, $index );
				}
			}

			if ( is_array( $row ) ) {
				// implode the repeated field values
				$row = implode( self::$separator, FrmAppHelper::array_flatten( $row, 'reset' ) );
			}

			$val = self::encode_value( $row );

			if ( 'return' !== self::$line_break ) {
				$val = str_replace( array( "\r\n", "\r", "\n" ), self::$line_break, $val );
			}

			if ( $echo ) {
				echo $sep . '"' . $val . '"'; // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped
			} else {
				fwrite( self::$fp, $sep . '"' . $val . '"' );
			}

			$sep = self::$column_separator;

			unset( $k, $row );
		}//end foreach

		if ( $echo ) {
			echo "\n";
		} else {
			fwrite( self::$fp, "\n" );
		}
	}

	/**
	 * @param string $line
	 *
	 * @return string
	 */
	public static function encode_value( $line ) {
		if ( '' === $line ) {
			return $line;
		}

		$convmap = false;

		switch ( self::$to_encoding ) {
			case 'macintosh':
				// this map was derived from the differences between the MacRoman and UTF-8 Charsets
				// Reference:
				// http://www.alanwood.net/demos/macroman.html.
				$convmap = array( 256, 304, 0, 0xffff, 306, 337, 0, 0xffff, 340, 375, 0, 0xffff, 377, 401, 0, 0xffff, 403, 709, 0, 0xffff, 712, 727, 0, 0xffff, 734, 936, 0, 0xffff, 938, 959, 0, 0xffff, 961, 8210, 0, 0xffff, 8213, 8215, 0, 0xffff, 8219, 8219, 0, 0xffff, 8227, 8229, 0, 0xffff, 8231, 8239, 0, 0xffff, 8241, 8248, 0, 0xffff, 8251, 8259, 0, 0xffff, 8261, 8363, 0, 0xffff, 8365, 8481, 0, 0xffff, 8483, 8705, 0, 0xffff, 8707, 8709, 0, 0xffff, 8711, 8718, 0, 0xffff, 8720, 8720, 0, 0xffff, 8722, 8729, 0, 0xffff, 8731, 8733, 0, 0xffff, 8735, 8746, 0, 0xffff, 8748, 8775, 0, 0xffff, 8777, 8799, 0, 0xffff, 8801, 8803, 0, 0xffff, 8806, 9673, 0, 0xffff, 9675, 63742, 0, 0xffff, 63744, 64256, 0, 0xffff );
				break;
			case 'ISO-8859-1':
				$convmap = array( 256, 10000, 0, 0xffff );
		}

		if ( is_array( $convmap ) ) {
			$line = mb_encode_numericentity( $line, $convmap, self::$charset );
		}

		if ( self::$to_encoding !== self::$charset ) {
			$line = iconv( self::$charset, self::$to_encoding . '//IGNORE', $line );
		}

		return self::escape_csv( $line );
	}

	/**
	 * Escape a " in a csv with another "
	 *
	 * @since 2.0
	 *
	 * @param mixed $value
	 *
	 * @return mixed
	 */
	public static function escape_csv( $value ) {
		if ( ! is_string( $value ) ) {
			return $value;
		}

		if ( '=' === $value[0] ) {
			// escape the = to prevent vulnerability
			$value = "'" . $value;
		}

		$value = str_replace( '"', '""', $value );

		return $value;
	}
}
