<?php
/**
 * Form metadata lookup.
 *
 * @package FormPilot
 * @since   1.0.0
 */

declare( strict_types = 1 );

namespace FormPilot\Services;

use FormPilot\Database\Repositories\FieldRepository;
use FormPilot\Database\Repositories\FormRepository;
use FormPilot\Fields\FieldTypes;
use FormPilot\Models\Form;

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

/**
 * Answers the small questions screens keep asking about a form.
 *
 * The entries list, the entry detail screen and the export manager each need a
 * form title and a map of field keys to labels while walking rows. Each used to
 * carry its own copy of that lookup and its own cache; this service holds one
 * of each, so a page render or an export resolves a given form once.
 *
 * @since 1.0.0
 */
final class FormMetadata {

	/**
	 * Resolved titles, keyed by form ID.
	 *
	 * @var array<int, string>
	 */
	private array $titles = array();

	/**
	 * Resolved label maps, keyed by form ID.
	 *
	 * @var array<int, array<string, string>>
	 */
	private array $labels = array();

	/**
	 * Constructor.
	 *
	 * @param FormRepository  $forms  Repository reading forms.
	 * @param FieldRepository $fields Repository reading fields.
	 */
	public function __construct( private FormRepository $forms, private FieldRepository $fields ) {}

	/**
	 * Returns the title of a form.
	 *
	 * @param int $form_id Form ID.
	 *
	 * @return string The title, or an empty string when the form is gone.
	 */
	public function title( int $form_id ): string {
		if ( ! isset( $this->titles[ $form_id ] ) ) {
			$form = $this->forms->find( $form_id );

			$this->titles[ $form_id ] = $form instanceof Form ? $form->title() : '';
		}

		return $this->titles[ $form_id ];
	}

	/**
	 * Returns the field labels of a form, keyed by field key.
	 *
	 * A field with no label falls back to its key, so a column never renders
	 * blank.
	 *
	 * @param int $form_id Form ID.
	 *
	 * @return array<string, string> Labels keyed by field key.
	 */
	public function field_labels( int $form_id ): array {
		if ( isset( $this->labels[ $form_id ] ) ) {
			return $this->labels[ $form_id ];
		}

		$labels = array();

		foreach ( $this->fields->for_form( $form_id ) as $field ) {
			// A page break is a marker in the field list, never an answer, so it
			// must not become a column in the entry list or the export.
			if ( FieldTypes::STEP === $field->type() ) {
				continue;
			}

			$labels[ $field->field_key() ] = '' !== $field->label() ? $field->label() : $field->field_key();
		}

		$this->labels[ $form_id ] = $labels;

		return $labels;
	}

	/**
	 * Forgets everything resolved so far.
	 */
	public function flush(): void {
		$this->titles = array();
		$this->labels = array();
	}
}