<?php
/**
 * CSV helpers for import and export.
 *
 * @package NovoVerify
 */

defined( 'ABSPATH' ) || exit;

/**
 * Pure CSV helpers (no WordPress calls), unit tested.
 */
final class NovoVerify_Csv {

	/**
	 * Columns recognized in an import file, in positional order.
	 */
	const COLUMNS = array( 'code', 'product_name', 'batch' );

	/**
	 * Header aliases mapped to column keys.
	 */
	const HEADER_ALIASES = array(
		'code'         => 'code',
		'codes'        => 'code',
		'serial'       => 'code',
		'product_name' => 'product_name',
		'product'      => 'product_name',
		'name'         => 'product_name',
		'batch'        => 'batch',
		'lot'          => 'batch',
	);

	/**
	 * Picks the delimiter used in the first line: comma, semicolon or tab.
	 *
	 * Spreadsheet apps in many European locales save CSV files with semicolons.
	 *
	 * @param string $line First line of the file.
	 * @return string Delimiter.
	 */
	public static function detect_delimiter( $line ) {
		$line   = (string) $line;
		$counts = array(
			','  => substr_count( $line, ',' ),
			';'  => substr_count( $line, ';' ),
			"\t" => substr_count( $line, "\t" ),
		);
		arsort( $counts );
		$best = (string) key( $counts );
		return $counts[ $best ] > 0 ? $best : ',';
	}

	/**
	 * Removes a UTF-8 byte order mark from the start of a string.
	 *
	 * @param string $value Value.
	 * @return string
	 */
	public static function strip_bom( $value ) {
		$value = (string) $value;
		return 0 === strpos( $value, "\xEF\xBB\xBF" ) ? substr( $value, 3 ) : $value;
	}

	/**
	 * Builds a column map from a header row, or returns null when the row is not a header.
	 *
	 * A row is a header when its first cell is a known column name (e.g. "code").
	 *
	 * @param array $row First row of the file.
	 * @return array<string, int>|null Column key => index.
	 */
	public static function header_map( array $row ) {
		if ( empty( $row ) ) {
			return null;
		}

		$first = self::header_key( (string) reset( $row ) );
		if ( ! isset( self::HEADER_ALIASES[ $first ] ) ) {
			return null;
		}

		$map = array();
		foreach ( array_values( $row ) as $index => $cell ) {
			$key = self::header_key( (string) $cell );
			if ( isset( self::HEADER_ALIASES[ $key ] ) && ! isset( $map[ self::HEADER_ALIASES[ $key ] ] ) ) {
				$map[ self::HEADER_ALIASES[ $key ] ] = $index;
			}
		}

		return isset( $map['code'] ) ? $map : null;
	}

	/**
	 * Default column map when the file has no header: code, product_name, batch.
	 *
	 * @return array<string, int>
	 */
	public static function default_map() {
		return array_flip( self::COLUMNS );
	}

	/**
	 * Turns a CSV row into a record using a column map.
	 *
	 * @param array              $row CSV row.
	 * @param array<string, int> $map Column map.
	 * @return array{code: string, product_name: string, batch: string}
	 */
	public static function row_to_record( array $row, array $map ) {
		$row    = array_values( $row );
		$record = array();
		foreach ( self::COLUMNS as $column ) {
			$value             = isset( $map[ $column ], $row[ $map[ $column ] ] ) ? (string) $row[ $map[ $column ] ] : '';
			$record[ $column ] = trim( $value );
		}
		return $record;
	}

	/**
	 * Tells whether a CSV row is empty (blank line).
	 *
	 * @param array $row CSV row.
	 * @return bool
	 */
	public static function is_blank_row( array $row ) {
		foreach ( $row as $cell ) {
			if ( null !== $cell && '' !== trim( (string) $cell ) ) {
				return false;
			}
		}
		return true;
	}

	/**
	 * Protects a free-text cell against formula injection in spreadsheet apps.
	 *
	 * @param mixed $value Cell value.
	 * @return string
	 */
	public static function escape_cell( $value ) {
		$value = (string) $value;
		if ( '' !== $value && false !== strpos( "=+-@\t\r", $value[0] ) ) {
			return "'" . $value;
		}
		return $value;
	}

	/**
	 * Normalizes a header cell for comparison.
	 *
	 * @param string $cell Header cell.
	 * @return string
	 */
	private static function header_key( $cell ) {
		$cell = strtolower( trim( self::strip_bom( $cell ) ) );
		return str_replace( array( ' ', '-' ), '_', $cell );
	}
}