<?php
/**
 * Deterministic canonical-to-JSON-Schema compiler.
 *
 * @package ModelGainWebmcpForms
 */

namespace ModelGain\WordPress\WebmcpForms;

/**
 * Compiles only the canonical allowlisted model.
 */
final class SchemaCompiler {
	/**
	 * Perform the documented operation.
	 *
	 * @param FormModel $form Canonical form.
	 * @return array<string,mixed>
	 */
	public function compile( FormModel $form ) {
		$properties = array();
		$required   = array();

		foreach ( $form->fields() as $field ) {
			$json_type = $this->json_type( $field->type() );
			$property  = array(
				'type'        => $json_type,
				'description' => $field->label(),
			);

			if ( 'date' === $field->type() ) {
				$property['format'] = 'date';
			}
			if ( 'email' === $field->type() ) {
				$property['format'] = 'email';
			}
			if ( 'url' === $field->type() ) {
				$property['format'] = 'uri';
			}

			if ( 'number' === $field->type() ) {
				$property['description'] .= ' Enter a number.';
			}

			if ( in_array( $field->type(), array( 'select', 'radio' ), true ) ) {
				$property['enum'] = $field->options();
			}
			if ( $field->required() && 'string' === $json_type && ! isset( $property['enum'] ) ) {
				$property['minLength'] = 1;
			}

			$properties[ $field->name() ] = $property;
			if ( $field->required() ) {
				$required[] = $field->name();
			}
		}

		ksort( $properties, SORT_STRING );
		sort( $required, SORT_STRING );

		$schema = array(
			'$schema'              => 'https://json-schema.org/draft/2020-12/schema',
			'type'                 => 'object',
			'properties'           => $properties,
			'additionalProperties' => false,
		);

		if ( ! empty( $required ) ) {
			$schema['required'] = $required;
		}

		return $schema;
	}

	/**
	 * Perform the documented operation.
	 *
	 * @param string $type Canonical type.
	 * @return string
	 */
	private function json_type( $type ) {
		return 'number' === $type ? 'number' : 'string';
	}
}