<?php

declare(strict_types=1);

/**
 * @copyright 2020 Christoph Wurst <christoph@winzerhof-wurst.at>
 *
 * @author 2020 Christoph Wurst <christoph@winzerhof-wurst.at>
 *
 * @license GNU AGPL version 3 or any later version
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

namespace OCA\Mail\IMAP\Threading;

use RuntimeException;
use function array_key_exists;
use function spl_object_id;

class Container {
	/** @var Message|null */
	private $message;

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

	/** @var Container|null */
	private $parent;

	/** @var Container[] */
	private $children = [];

	private function __construct(?Message $message,
								 bool $root = false) {
		$this->message = $message;
		$this->root = $root;
	}

	public static function root(): self {
		return new self(
			null,
			true
		);
	}

	public static function empty(): self {
		return new self(
			null
		);
	}

	public static function with(Message $message): self {
		return new self(
			$message
		);
	}

	public function fill(Message $message): void {
		$this->message = $message;
	}

	public function hasMessage(): bool {
		return $this->message !== null;
	}

	public function getMessage(): ?Message {
		return $this->message;
	}

	public function isRoot(): bool {
		return $this->root;
	}

	public function hasParent(): bool {
		return $this->parent !== null;
	}

	public function getParent(): Container {
		if ($this->isRoot() || $this->parent === null) {
			throw new RuntimeException('Container root has no parent');
		}
		return $this->parent;
	}

	public function setParent(?Container $parent): void {
		$this->unlink();
		$this->parent = $parent;
		if ($parent !== null) {
			$parent->children[spl_object_id($this)] = $this;
		}
	}

	public function hasAncestor(Container $container): bool {
		if ($this->parent === $container) {
			return true;
		}
		if ($this->parent !== null) {
			return $this->parent->hasAncestor($container);
		}
		return false;
	}

	public function unlink(): void {
		if ($this->parent !== null) {
			$this->parent->removeChild($this);
		}
		$this->parent = null;
	}

	private function removeChild(Container $child): void {
		$objId = spl_object_id($child);
		if (array_key_exists($objId, $this->children)) {
			unset($this->children[$objId]);
		}
	}

	public function hasChildren(): bool {
		return !empty($this->children);
	}

	/**
	 * @return Container[]
	 */
	public function getChildren(): array {
		return $this->children;
	}
}
