<?php

/**
 * This file is part of the FOSElasticaBundle project.
 *
 * (c) Infinite Networks Pty Ltd <http://www.infinite.net.au>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace FOS\ElasticaBundle\Index;

use Elastica\Client;
use Elastica\Exception\ExceptionInterface;
use Elastica\Request;
use FOS\ElasticaBundle\Configuration\IndexConfig;
use FOS\ElasticaBundle\Elastica\Index;
use FOS\ElasticaBundle\Exception\AliasIsIndexException;

class AliasProcessor
{
    /**
     * Sets the randomised root name for an index.
     *
     * @param IndexConfig $indexConfig
     * @param Index       $index
     */
    public function setRootName(IndexConfig $indexConfig, Index $index)
    {
        $index->overrideName(
            sprintf('%s_%s',
                $indexConfig->getElasticSearchName(),
                date('Y-m-d-His')
            )
        );
    }

    /**
     * Switches an index to become the new target for an alias. Only applies for
     * indexes that are set to use aliases.
     *
     * $force will delete an index encountered where an alias is expected.
     *
     * @param IndexConfig $indexConfig
     * @param Index       $index
     * @param bool        $force
     *
     * @throws AliasIsIndexException
     * @throws \RuntimeException
     */
    public function switchIndexAlias(IndexConfig $indexConfig, Index $index, $force = false)
    {
        $client = $index->getClient();

        $aliasName = $indexConfig->getElasticSearchName();
        $oldIndexName = null;
        $newIndexName = $index->getName();

        try {
            $oldIndexName = $this->getAliasedIndex($client, $aliasName);
        } catch (AliasIsIndexException $e) {
            if (!$force) {
                throw $e;
            }

            $this->deleteIndex($client, $aliasName);
        }

        try {
            $aliasUpdateRequest = $this->buildAliasUpdateRequest($oldIndexName, $aliasName, $newIndexName);
            $client->request('_aliases', 'POST', $aliasUpdateRequest);
        } catch (ExceptionInterface $e) {
            $this->cleanupRenameFailure($client, $newIndexName, $e);
        }

        // Delete the old index after the alias has been switched
        if (null !== $oldIndexName) {
            $this->deleteIndex($client, $oldIndexName);
        }
    }

    /**
     * Builds an ElasticSearch request to rename or create an alias.
     *
     * @param string|null $aliasedIndex
     * @param string $aliasName
     * @param string $newIndexName
     * @return array
     */
    private function buildAliasUpdateRequest($aliasedIndex, $aliasName, $newIndexName)
    {
        $aliasUpdateRequest = array('actions' => array());
        if (null !== $aliasedIndex) {
            // if the alias is set - add an action to remove it
            $aliasUpdateRequest['actions'][] = array(
                'remove' => array('index' => $aliasedIndex, 'alias' => $aliasName),
            );
        }

        // add an action to point the alias to the new index
        $aliasUpdateRequest['actions'][] = array(
            'add' => array('index' => $newIndexName, 'alias' => $aliasName),
        );

        return $aliasUpdateRequest;
    }

    /**
     * Cleans up an index when we encounter a failure to rename the alias.
     *
     * @param Client $client
     * @param string $indexName
     * @param \Exception $renameAliasException
     */
    private function cleanupRenameFailure(Client $client, $indexName, \Exception $renameAliasException)
    {
        $additionalError = '';
        try {
            $this->deleteIndex($client, $indexName);
        } catch (ExceptionInterface $deleteNewIndexException) {
            $additionalError = sprintf(
                'Tried to delete newly built index %s, but also failed: %s',
                $indexName,
                $deleteNewIndexException->getMessage()
            );
        }

        throw new \RuntimeException(sprintf(
            'Failed to updated index alias: %s. %s',
            $renameAliasException->getMessage(),
            $additionalError ?: sprintf('Newly built index %s was deleted', $indexName)
        ), 0, $renameAliasException);
    }

    /**
     * Delete an index.
     *
     * @param Client $client
     * @param string $indexName Index name to delete
     */
    private function deleteIndex(Client $client, $indexName)
    {
        try {
            $path = sprintf("%s", $indexName);
            $client->request($path, Request::DELETE);
        } catch (ExceptionInterface $deleteOldIndexException) {
            throw new \RuntimeException(sprintf(
                'Failed to delete index %s with message: %s',
                $indexName,
                $deleteOldIndexException->getMessage()
            ), 0, $deleteOldIndexException);
        }
    }

    /**
     * Returns the name of a single index that an alias points to or throws
     * an exception if there is more than one.
     *
     * @param Client $client
     * @param string $aliasName Alias name
     *
     * @return string|null
     *
     * @throws AliasIsIndexException
     */
    private function getAliasedIndex(Client $client, $aliasName)
    {
        $aliasesInfo = $client->request('_aliases', 'GET')->getData();
        $aliasedIndexes = array();

        foreach ($aliasesInfo as $indexName => $indexInfo) {
            if ($indexName === $aliasName) {
                throw new AliasIsIndexException($indexName);
            }
            if (!isset($indexInfo['aliases'])) {
                continue;
            }

            $aliases = array_keys($indexInfo['aliases']);
            if (in_array($aliasName, $aliases)) {
                $aliasedIndexes[] = $indexName;
            }
        }

        if (count($aliasedIndexes) > 1) {
            throw new \RuntimeException(sprintf(
                'Alias %s is used for multiple indexes: [%s]. Make sure it\'s'.
                'either not used or is assigned to one index only',
                $aliasName,
                implode(', ', $aliasedIndexes)
            ));
        }

        return array_shift($aliasedIndexes);
    }
}