<?php

declare(strict_types=1);

namespace App\Serialize;

use Symfony\Component\Yaml\Yaml as SymfonyYaml;
use Symfony\Component\Yaml\Tag\TaggedValue;
use App\Dom\Document;
use App\Dom\Node;
use App\Dom\NodeValue;
use App\Dom\NodeFunction;
use App\Dom\NodeFunctionValue;

/**
 * Handles serializing and unserializing between documents and Yaml.
 *
 * @author Adam Pippin <hello@adampippin.ca>
 */
class Yaml implements ISerialize, IUnserialize
{
	/**
	 * Convert a YAML string into a Dom\Document.
	 *
	 * @param  string   $document
	 * @return Document
	 */
	public function unserialize(string $document): Document
	{
		$data = SymfonyYaml::parse($document, SymfonyYaml::PARSE_CUSTOM_TAGS);
		$document = new Document();
		$this->arrayToDom($document, $data);
		return $document;
	}

	/**
	 * Convert a Dom\Document into a YAML string.
	 *
	 * @param  Document $document
	 * @return string
	 */
	public function serialize(Document $document): string
	{
		$data = $this->domToArray($document);
		return SymfonyYaml::dump($data, 6);
	}

	/**
	 * Take a DOM node and return it turned into an array appropriate
	 * for serializing with the Symfony Yaml component.
	 *
	 * @param  Node  $node dom node to convert to array
	 * @return mixed
	 */
	protected function domToArray(Node $node)
	{
		$result = null;
		foreach ($node as $child)
		{
			$child_ser = $this->serializeNode($child);
			if (is_array($child_ser))
			{
				if (isset($result) && !is_array($result))
				{
					throw new \Exception('Invalid DOM: tagged value adjacent to property map');
				}
				$result = $result ?? [];
				$result = array_merge($result, $child_ser);
			}
			else
			{
				$result = $child_ser;
			}
		}
		return $result;
	}

	/**
	 * Serialize a single node, only meant to be used as part of/by domToArray.
	 *
	 * @param  Node  $node
	 * @return mixed
	 */
	private function serializeNode(Node $node)
	{
		switch (true)
		{
			case $node instanceof NodeFunctionValue:
				return new TaggedValue($node->getName(), $node->getValue());
			case $node instanceof NodeFunction:
				return new TaggedValue($node->getName(), $this->domToArray($node));
			case $node instanceof NodeValue:
				return $node->hasName() ? [$node->getName() => $node->getValue()] : [$node->getValue()];
			default:
				return $node->hasName() ? [$node->getName() => $this->domToArray($node)] : [$this->domToArray($node)];
		}
	}

	/**
	 * Convert an array returned from Symfony's Yaml component when parsing a
	 * yaml document and convert it into a Dom\Document.
	 *
	 * Children are pushed directly onto the passed $parent node
	 *
	 * @param  Node               $parent node that the data is to be unserialized under
	 * @param  array<mixed,mixed> $data   the data to unserialize
	 * @return void
	 */
	protected function arrayToDom(Node $parent, array $data)
	{
		foreach ($data as $k => $v)
		{
			if ($v instanceof TaggedValue)
			{
				$node = new Node($parent, is_string($k) ? $k : null);
				$fun_node = null;
				$fun_name = $v->getTag();
				$fun_value = $v->getValue();
				if (is_array($fun_value))
				{
					$fun_node = new NodeFunction($node, $fun_name);
					$this->arrayToDom($fun_node, $fun_value);
				}
				elseif (is_scalar($fun_value))
				{
					$fun_node = new NodeFunctionValue($node, $fun_name, $fun_value);
				}
				else
				{
					throw new \Exception('Cannot unserialize value from function node--is not array or scalar');
				}
				$node->addChild($fun_node);
			}
			else
			{
				if (is_array($v))
				{
					$node = new Node($parent, is_string($k) ? $k : null);
					$this->arrayToDom($node, $v);
				}
				elseif (is_scalar($v))
				{
					$node = new NodeValue($parent, is_string($k) ? $k : null, $v);
				}
				else
				{
					throw new \Exception('Cannot unserialize value from YAML--value is not TaggedValue, array or scalar');
				}
			}
			$parent->addChild($node);
		}
	}
}