<?php

namespace ChargeForms\Includes;

use ChargeForms\Admin\Entries_Page;

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * CSV/JSON entry export, extracted out of Admin\Entries_Page (roadmap
 * issue #31: "Admin Tables Mix Concerns in Large PHP Page Classes" —
 * that one file mixed rendering, filtering, import/export, mutation
 * handlers, and CSV/JSON serialization together). Entries_Page's
 * handle_export() still owns the actual HTTP request (nonce, capability,
 * $_FILES/$_GET validation) — that's an admin-post concern, not an
 * export concern — and calls into this class only once it's confirmed
 * the request is legitimate and knows which form/format to export.
 *
 * Reuses Entries_Page::column_label()/display_value() (made `public`
 * for exactly this) rather than a second copy of the same display
 * rules — the CSV/JSON export should show a value exactly the way the
 * entries table/detail view does, not a third, silently-diverging
 * formatting path.
 */
class Entry_Exporter {

	/** Batch size (roadmap issue #18 — see the original doc comment on this constant before it moved here): fetches this many rows from the DB at a time via Entry::query_for_form() instead of loading every entry into one array up front, bounding peak memory regardless of how many entries a form has. */
	const BATCH_SIZE = 500;

	/** Non-layout, non-decorative field types — the exact same filter used to decide which columns appear in the entries table, so an export's columns always match what's actually on screen. */
	public static function data_fields_for( array $form ) {
		return array_values( array_filter( $form['fields'], function ( $field ) {
			return ! in_array( $field['type'], Entries_Page::NON_DATA_FIELD_TYPES, true );
		} ) );
	}

	public static function stream_csv( array $form, $form_id, array $csv_fields ) {
		nocache_headers();
		header( 'Content-Type: text/csv; charset=utf-8' );
		header( 'Content-Disposition: attachment; filename="' . sanitize_file_name( $form['title'] ) . '-entries.csv"' );

		$out = fopen( 'php://output', 'w' ); // phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_fopen

		$headers = [ 'Date' ];
		foreach ( $csv_fields as $field ) {
			$headers[] = Entries_Page::column_label( $field );
		}
		fputcsv( $out, array_map( [ __CLASS__, 'csv_safe_cell' ], $headers ) );

		$page = 1;
		do {
			$result = Entry::query_for_form( $form_id, [ 'page' => $page, 'per_page' => self::BATCH_SIZE ] );
			foreach ( $result['items'] as $entry ) {
				$row = [ $entry['created_at'] ];
				foreach ( $csv_fields as $field ) {
					$row[] = Entries_Page::display_value( $entry['values'][ $field['id'] ] ?? '' );
				}
				fputcsv( $out, array_map( [ __CLASS__, 'csv_safe_cell' ], $row ) );
			}
			$page++;
		} while ( count( $result['items'] ) === self::BATCH_SIZE );

		fclose( $out ); // phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_fclose
		exit;
	}

	/** One object per entry with column-labeled keys (not the field-id-keyed raw shape used internally), so the file reads the same way the CSV columns do. Fetched in batches like stream_csv() above, though (unlike CSV) the transformed rows still accumulate in memory until wp_json_encode() runs at the end — a real JSON array needs its full contents before it can be encoded. */
	public static function stream_json( array $form, $form_id, array $csv_fields ) {
		$rows = [];
		$page = 1;
		do {
			$result = Entry::query_for_form( $form_id, [ 'page' => $page, 'per_page' => self::BATCH_SIZE ] );
			foreach ( $result['items'] as $entry ) {
				$row = [ 'date' => $entry['created_at'], 'status' => $entry['status'] ];
				foreach ( $csv_fields as $field ) {
					$row[ Entries_Page::column_label( $field ) ] = $entry['values'][ $field['id'] ] ?? '';
				}
				$rows[] = $row;
			}
			$page++;
		} while ( count( $result['items'] ) === self::BATCH_SIZE );

		nocache_headers();
		header( 'Content-Type: application/json; charset=utf-8' );
		header( 'Content-Disposition: attachment; filename="' . sanitize_file_name( $form['title'] ) . '-entries.json"' );
		echo wp_json_encode( $rows, JSON_PRETTY_PRINT );
		exit;
	}

	/**
	 * Neutralizes CSV/formula injection: a submitted value starting with
	 * =, +, -, or @ (or a leading tab/CR) is interpreted as a formula by
	 * Excel/Sheets when the exported file is opened, which is a well-known
	 * attack vector for form plugins — a visitor's own submission shouldn't
	 * be able to run a formula on the admin's machine later. Prefixing a
	 * single quote is the standard OWASP-recommended mitigation; it forces
	 * spreadsheet apps to treat the cell as plain text.
	 */
	public static function csv_safe_cell( $value ) {
		$value = (string) $value;
		return preg_match( '/^[=+\-@\t\r]/', $value ) ? "'" . $value : $value;
	}
}