<?php
/**
 * JSON renderer.
 *
 * @package FeedWeaver
 */

namespace FeedWeaver\Render;

use FeedWeaver\Mapping\Mapping_Engine;
use FeedWeaver\Mapping\Path_Validator;
use FeedWeaver\Mapping\Term_List;

defined( 'ABSPATH' ) || exit;

/**
 * Produces {"<root>": [ {item}, ... ]} using native JSON encoding.
 */
class Json_Renderer implements Renderer {

	/** @var string */
	private $root;

	/** @var bool */
	private $pretty;

	/**
	 * @param string $root   Collection key.
	 * @param bool   $pretty Pretty print.
	 * @throws \InvalidArgumentException For an invalid collection name.
	 */
	public function __construct( string $root, bool $pretty = false ) {
		if ( ! Path_Validator::is_valid_name( $root, true ) ) {
			throw new \InvalidArgumentException( 'Invalid JSON collection name.' );
		}
		$this->root   = $root;
		$this->pretty = $pretty;
	}

	/**
	 * {@inheritdoc}
	 */
	public function content_type(): string {
		return 'application/json; charset=UTF-8';
	}

	/**
	 * Renders items as JSON.
	 *
	 * @param array<int,array<string,mixed>> $items Mapped items.
	 * @return string
	 * @throws \JsonException When encoding fails.
	 * @throws \InvalidArgumentException For invalid keys.
	 */
	public function render( array $items ): string {
		$prepared = array();
		foreach ( $items as $item ) {
			$prepared[] = $this->prepare( $item );
		}
		// Readable output ("Q&A", "é", "a/b") but "<" and ">" stay escaped so the body can never be read as markup.
		$flags = JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES | JSON_HEX_TAG | JSON_THROW_ON_ERROR;
		if ( $this->pretty ) {
			$flags |= JSON_PRETTY_PRINT;
		}
		return json_encode( (object) array( $this->root => $prepared ), $flags ); // phpcs:ignore WordPress.WP.AlternativeFunctions.json_encode_json_encode -- wp_json_encode would add a non-throwing fallback; we need strict errors and no WordPress dependency.
	}

	/**
	 * Cleans strings and turns groups into objects so empty groups encode as {}.
	 *
	 * @param mixed $node Node.
	 * @return mixed
	 * @throws \InvalidArgumentException For invalid keys.
	 */
	private function prepare( $node ) {
		if ( $node instanceof Term_List ) {
			return array_map( array( Text_Cleaner::class, 'clean' ), $node->names );
		}
		if ( is_array( $node ) ) {
			// XML attributes do not exist in JSON: drop them, keep the text.
			if ( array_key_exists( Mapping_Engine::VALUE, $node ) ) {
				return $this->prepare( $node[ Mapping_Engine::VALUE ] );
			}
			unset( $node[ Mapping_Engine::ATTRIBUTES ] );
			if ( Text_Cleaner::is_list( $node ) && array() !== $node ) {
				return array_map( array( $this, 'prepare' ), $node );
			}
			$object = new \stdClass();
			foreach ( $node as $name => $value ) {
				$name = (string) $name;
				if ( ! Path_Validator::is_valid_name( $name, true ) ) {
					throw new \InvalidArgumentException( 'Invalid JSON key.' );
				}
				$object->$name = $this->prepare( $value );
			}
			return $object;
		}
		if ( is_int( $node ) ) {
			return $node;
		}
		return null === $node ? null : Text_Cleaner::clean( (string) $node );
	}
}