<?php
  /**
   * Copyright (c) 2014 Robin Appelman <icewind@owncloud.com>
   * This file is licensed under the Affero General Public License version 3 or
   * later.
   * See the COPYING-README file.
   */
  
  namespace OC\DB;
  
  use \Doctrine\DBAL\DBALException;
  use \Doctrine\DBAL\Schema\Index;
  use \Doctrine\DBAL\Schema\Table;
  use \Doctrine\DBAL\Schema\Schema;
  use \Doctrine\DBAL\Schema\SchemaConfig;
  use \Doctrine\DBAL\Schema\Comparator;
  
  class Migrator {
  	/**
  	 * @var \Doctrine\DBAL\Connection $connection
  	 */
  	protected $connection;
  
  	/**
  	 * @param \Doctrine\DBAL\Connection $connection
  	 */
  	public function __construct(\Doctrine\DBAL\Connection $connection) {
  		$this->connection = $connection;
  	}
  
  	/**
  	 * @param \Doctrine\DBAL\Schema\Schema $targetSchema
  	 */
  	public function migrate(Schema $targetSchema) {
  		$this->applySchema($targetSchema);
  	}
  
  	/**
  	 * @param \Doctrine\DBAL\Schema\Schema $targetSchema
  	 * @return string
  	 */
  	public function generateChangeScript(Schema $targetSchema) {
  		$schemaDiff = $this->getDiff($targetSchema, $this->connection);
  
  		$script = '';
  		$sqls = $schemaDiff->toSql($this->connection->getDatabasePlatform());
  		foreach ($sqls as $sql) {
  			$script .= $sql . ';';
  			$script .= PHP_EOL;
  		}
  
  		return $script;
  	}
  
  	/**
  	 * @param Schema $targetSchema
  	 * @throws \OC\DB\MigrationException
  	 */
  	public function checkMigrate(Schema $targetSchema) {
  		/**
  		 * @var \Doctrine\DBAL\Schema\Table[] $tables
  		 */
  		$tables = $targetSchema->getTables();
  
  		$existingTables = $this->connection->getSchemaManager()->listTableNames();
  
  		foreach ($tables as $table) {
  			if (strpos($table->getName(), '.')) {
  				list(, $tableName) = explode('.', $table->getName());
  			} else {
  				$tableName = $table->getName();
  			}
  			// don't need to check for new tables
  			if (array_search($tableName, $existingTables) !== false) {
  				$this->checkTableMigrate($table);
  			}
  		}
  	}
  
  	/**
  	 * Create a unique name for the temporary table
  	 *
  	 * @param string $name
  	 * @return string
  	 */
  	protected function generateTemporaryTableName($name) {
  		return 'oc_' . $name . '_' . \OCP\Util::generateRandomBytes(13);
  	}
  
  	/**
  	 * Check the migration of a table on a copy so we can detect errors before messing with the real table
  	 *
  	 * @param \Doctrine\DBAL\Schema\Table $table
  	 * @throws \OC\DB\MigrationException
  	 */
  	protected function checkTableMigrate(Table $table) {
  		$name = $table->getName();
  		$tmpName = $this->generateTemporaryTableName($name);
  
  		$this->copyTable($name, $tmpName);
  
  		//create the migration schema for the temporary table
  		$tmpTable = $this->renameTableSchema($table, $tmpName);
  		$schemaConfig = new SchemaConfig();
  		$schemaConfig->setName($this->connection->getDatabase());
  		$schema = new Schema(array($tmpTable), array(), $schemaConfig);
  
  		try {
  			$this->applySchema($schema);
  			$this->dropTable($tmpName);
  		} catch (DBALException $e) {
  			// pgsql needs to commit it's failed transaction before doing anything else
  			if ($this->connection->isTransactionActive()) {
  				$this->connection->commit();
  			}
  			$this->dropTable($tmpName);
  			throw new MigrationException($table->getName(), $e->getMessage());
  		}
  	}
  
  	/**
  	 * @param \Doctrine\DBAL\Schema\Table $table
  	 * @param string $newName
  	 * @return \Doctrine\DBAL\Schema\Table
  	 */
  	protected function renameTableSchema(Table $table, $newName) {
  		/**
  		 * @var \Doctrine\DBAL\Schema\Index[] $indexes
  		 */
  		$indexes = $table->getIndexes();
  		$newIndexes = array();
  		foreach ($indexes as $index) {
  			if ($index->isPrimary()) {
  				// do not rename primary key
  				$indexName = $index->getName();
  			} else {
  				// avoid conflicts in index names
  				$indexName = 'oc_' . \OCP\Util::generateRandomBytes(13);
  			}
  			$newIndexes[] = new Index($indexName, $index->getColumns(), $index->isUnique(), $index->isPrimary());
  		}
  
  		// foreign keys are not supported so we just set it to an empty array
  		return new Table($newName, $table->getColumns(), $newIndexes, array(), 0, $table->getOptions());
  	}
  
  	protected function getDiff(Schema $targetSchema, \Doctrine\DBAL\Connection $connection) {
  		$sourceSchema = $connection->getSchemaManager()->createSchema();
  
  		// remove tables we don't know about
  		/** @var $table \Doctrine\DBAL\Schema\Table */
  		foreach ($sourceSchema->getTables() as $table) {
  			if (!$targetSchema->hasTable($table->getName())) {
  				$sourceSchema->dropTable($table->getName());
  			}
  		}
  		// remove sequences we don't know about
  		foreach ($sourceSchema->getSequences() as $table) {
  			if (!$targetSchema->hasSequence($table->getName())) {
  				$sourceSchema->dropSequence($table->getName());
  			}
  		}
  
  		$comparator = new Comparator();
  		return $comparator->compare($sourceSchema, $targetSchema);
  	}
  
  	/**
  	 * @param \Doctrine\DBAL\Schema\Schema $targetSchema
  	 * @param \Doctrine\DBAL\Connection $connection
  	 */
  	protected function applySchema(Schema $targetSchema, \Doctrine\DBAL\Connection $connection = null) {
  		if (is_null($connection)) {
  			$connection = $this->connection;
  		}
  
  		$schemaDiff = $this->getDiff($targetSchema, $connection);
  
  		$connection->beginTransaction();
  		foreach ($schemaDiff->toSql($connection->getDatabasePlatform()) as $sql) {
  			$connection->query($sql);
  		}
  		$connection->commit();
  	}
  
  	/**
  	 * @param string $sourceName
  	 * @param string $targetName
  	 */
  	protected function copyTable($sourceName, $targetName) {
  		$quotedSource = $this->connection->quoteIdentifier($sourceName);
  		$quotedTarget = $this->connection->quoteIdentifier($targetName);
  
  		$this->connection->exec('CREATE TABLE ' . $quotedTarget . ' (LIKE ' . $quotedSource . ')');
  		$this->connection->exec('INSERT INTO ' . $quotedTarget . ' SELECT * FROM ' . $quotedSource);
  	}
  
  	/**
  	 * @param string $name
  	 */
  	protected function dropTable($name) {
  		$this->connection->exec('DROP TABLE ' . $this->connection->quoteIdentifier($name));
  	}
  }