<?php

namespace Nest\Database\Transactions;

use Nest\Database\Database;
use Nest\Database\Exceptions\NotCurrentTransactionException;
use Symfony\Component\Uid\Uuid;

/**
 * Instance of a database transaction.
 */
class Transaction
{
	/**
	 * UUID of the transaction.
	 * @var string
	 */
	private string $uuid;

	/**
	 * Determine if the transaction is active (started and not committed nor rolled back).
	 * @var bool
	 */
	private bool $active = false;

	/**
	 * Subtransaction of the current transaction.
	 * @var Transaction|null
	 */
	protected ?Transaction $childTransaction = null;

	/**
	 * Create a new transaction for the given database.
	 * @param Database $database The database.
	 * @param Transaction|null $parentTransaction The parent transaction, if there is one.
	 */
	public function __construct(protected Database $database, protected ?Transaction $parentTransaction = null)
	{
		$this->uuid = Uuid::v4()->toString();
	}

	/**
	 * Get UUID of the transaction.
	 * @return string
	 */
	public function getUuid(): string
	{
		return $this->uuid;
	}

	/**
	 * Get the parent transaction.
	 * @return Transaction|null
	 */
	public function getParent(): ?Transaction
	{
		return $this->parentTransaction;
	}

	/**
	 * Set the current child transaction of this transaction.
	 * @param Transaction|null $transaction The child transaction. NULL if there is no child transaction.
	 * @return void
	 */
	public function setChild(?Transaction $transaction): void
	{
		$this->childTransaction = $transaction;
	}

	/**
	 * Start the transaction.
	 * @return void
	 * @throws NotCurrentTransactionException
	 */
	public function start(): void
	{
		// Transaction activation state changed.
		$this->active = true;
		$this->database->onTransactionStateChanged($this);

		// Start the transaction.
		$this->database->getQueriesAdapter()->newTransaction();
	}

	/**
	 * Commit the transaction.
	 * @return void
	 * @throws NotCurrentTransactionException
	 */
	public function commit(): void
	{
		if (!$this->isActive())
			// Do not commit a non-active transaction.
			return;

		if (!empty($this->childTransaction))
			// First commit the child transaction, if there is one.
			$this->childTransaction->commit();

		// Transaction activation state changed.
		$this->active = false;
		$this->database->onTransactionStateChanged($this);

		// Commit the current transaction.
		$this->database->getQueriesAdapter()->commitTransaction();
	}

	/**
	 * Rollback the transaction.
	 * @return void
	 * @throws NotCurrentTransactionException
	 */
	public function rollback(): void
	{
		if (!$this->isActive())
			// Do not rollback a non-active transaction.
			return;

		if (!empty($this->childTransaction))
			// First rollback the child transaction, if there is one.
			$this->childTransaction->rollback();

		// Transaction activation state changed.
		$this->active = false;
		$this->database->onTransactionStateChanged($this);

		// Rollback the current transaction.
		$this->database->getQueriesAdapter()->rollbackTransaction();
	}

	/**
	 * Determine if the transaction is still active (not committed nor rolled back).
	 * @return bool
	 */
	public function isActive(): bool
	{
		return $this->active;
	}
}