<?php

namespace SilverStripe\Forms\Schema;

use SilverStripe\Control\Session;
use SilverStripe\Forms\CompositeField;
use SilverStripe\Forms\Form;
use SilverStripe\Forms\FormField;

/**
 * Represents a {@link Form} as structured data which allows a frontend library to render it.
 * Includes information about the form as well as its fields.
 * Can create a "schema" (structure only) as well as "state" (data only).
 */
class FormSchema
{

    /**
     * Gets the schema for this form as a nested array.
     *
     * @param Form $form
     * @return array
     */
    public function getSchema(Form $form)
    {
        $schema = [
            'name' => $form->getName(),
            'id' => $form->FormName(),
            'action' => $form->FormAction(),
            'method' => $form->FormMethod(),
            'attributes' => $form->getAttributes(),
            'data' => [],
            'fields' => [],
            'actions' => []
        ];

        /** @var FormField $action */
        foreach ($form->Actions() as $action) {
            $schema['actions'][] = $action->getSchemaData();
        }

        /** @var FormField $field */
        foreach ($form->Fields() as $field) {
            $schema['fields'][] = $field->getSchemaData();
        }

        return $schema;
    }

    /**
     * Gets the current state of this form as a nested array.
     *
     * @param Form $form
     * @return array
     */
    public function getState(Form $form)
    {
        // Ensure that session errors are populated within form field messages
        $form->setupFormErrors();

        // @todo - Replace with ValidationResult handling
        // Currently tri-state; null (unsubmitted), true (submitted-valid), false (submitted-invalid)
        $errors = Session::get("FormInfo.{$form->FormName()}.errors");
        $valid = isset($errors) ? empty($errors) : null;

        $state = [
            'id' => $form->FormName(),
            'fields' => [],
            'valid' => $valid,
            'messages' => [],
        ];

        // flattened nested fields are returned, rather than only top level fields.
        $state['fields'] = array_merge(
            $this->getFieldStates($form->Fields()),
            $this->getFieldStates($form->Actions())
        );

        if ($message = $form->Message()) {
            $state['messages'][] = [
                // TODO Make form / field messages not always stored as html
                'value' => ['html' => $message],
                'type' => $form->MessageType(),
            ];
        }

        return $state;
    }

    protected function getFieldStates($fields)
    {
        $states = [];
        /** @var FormField $field */
        foreach ($fields as $field) {
            $states[] = $field->getSchemaState();

            if ($field instanceof CompositeField) {
                $subFields = $field->FieldList();
                $states = array_merge($states, $this->getFieldStates($subFields));
            }
        }
        return $states;
    }
}