<?php

/*
 * This file is part of the Predis package.
 *
 * (c) Daniele Alessandri <suppakilla@gmail.com>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Predis\Connection;

use Predis\Command\CommandInterface;
use Predis\Replication\ReplicationStrategy;

/**
 * Aggregated connection class used by to handle replication with a
 * group of servers in a master/slave configuration.
 *
 * @author Daniele Alessandri <suppakilla@gmail.com>
 */
class MasterSlaveReplication implements ReplicationConnectionInterface
{
    protected $strategy;
    protected $master;
    protected $slaves;
    protected $current;

    /**
     *
     */
    public function __construct(ReplicationStrategy $strategy = null)
    {
        $this->slaves = array();
        $this->strategy = $strategy ?: new ReplicationStrategy();
    }

    /**
     * Checks if one master and at least one slave have been defined.
     */
    protected function check()
    {
        if (!isset($this->master) || !$this->slaves) {
            throw new \RuntimeException('Replication needs a master and at least one slave.');
        }
    }

    /**
     * Resets the connection state.
     */
    protected function reset()
    {
        $this->current = null;
    }

    /**
     * {@inheritdoc}
     */
    public function add(SingleConnectionInterface $connection)
    {
        $alias = $connection->getParameters()->alias;

        if ($alias === 'master') {
            $this->master = $connection;
        } else {
            $this->slaves[$alias ?: count($this->slaves)] = $connection;
        }

        $this->reset();
    }

    /**
     * {@inheritdoc}
     */
    public function remove(SingleConnectionInterface $connection)
    {
        if ($connection->getParameters()->alias === 'master') {
            $this->master = null;
            $this->reset();

            return true;
        } else {
            if (($id = array_search($connection, $this->slaves, true)) !== false) {
                unset($this->slaves[$id]);
                $this->reset();

                return true;
            }
        }

        return false;
    }

    /**
     * {@inheritdoc}
     */
    public function getConnection(CommandInterface $command)
    {
        if ($this->current === null) {
            $this->check();
            $this->current = $this->strategy->isReadOperation($command) ? $this->pickSlave() : $this->master;

            return $this->current;
        }

        if ($this->current === $this->master) {
            return $this->current;
        }

        if (!$this->strategy->isReadOperation($command)) {
            $this->current = $this->master;
        }

        return $this->current;
    }

    /**
     * {@inheritdoc}
     */
    public function getConnectionById($connectionId)
    {
        if ($connectionId === 'master') {
            return $this->master;
        }

        if (isset($this->slaves[$connectionId])) {
            return $this->slaves[$connectionId];
        }

        return null;
    }

    /**
     * {@inheritdoc}
     */
    public function switchTo($connection)
    {
        $this->check();

        if (!$connection instanceof SingleConnectionInterface) {
            $connection = $this->getConnectionById($connection);
        }
        if ($connection !== $this->master && !in_array($connection, $this->slaves, true)) {
            throw new \InvalidArgumentException('The specified connection is not valid.');
        }

        $this->current = $connection;
    }

    /**
     * {@inheritdoc}
     */
    public function getCurrent()
    {
        return $this->current;
    }

    /**
     * {@inheritdoc}
     */
    public function getMaster()
    {
        return $this->master;
    }

    /**
     * {@inheritdoc}
     */
    public function getSlaves()
    {
        return array_values($this->slaves);
    }

    /**
     * Returns the underlying replication strategy.
     *
     * @return ReplicationStrategy
     */
    public function getReplicationStrategy()
    {
        return $this->strategy;
    }

    /**
     * Returns a random slave.
     *
     * @return SingleConnectionInterface
     */
    protected function pickSlave()
    {
        return $this->slaves[array_rand($this->slaves)];
    }

    /**
     * {@inheritdoc}
     */
    public function isConnected()
    {
        return $this->current ? $this->current->isConnected() : false;
    }

    /**
     * {@inheritdoc}
     */
    public function connect()
    {
        if ($this->current === null) {
            $this->check();
            $this->current = $this->pickSlave();
        }

        $this->current->connect();
    }

    /**
     * {@inheritdoc}
     */
    public function disconnect()
    {
        if ($this->master) {
            $this->master->disconnect();
        }

        foreach ($this->slaves as $connection) {
            $connection->disconnect();
        }
    }

    /**
     * {@inheritdoc}
     */
    public function writeCommand(CommandInterface $command)
    {
        $this->getConnection($command)->writeCommand($command);
    }

    /**
     * {@inheritdoc}
     */
    public function readResponse(CommandInterface $command)
    {
        return $this->getConnection($command)->readResponse($command);
    }

    /**
     * {@inheritdoc}
     */
    public function executeCommand(CommandInterface $command)
    {
        return $this->getConnection($command)->executeCommand($command);
    }

    /**
     * {@inheritdoc}
     */
    public function __sleep()
    {
        return array('master', 'slaves', 'strategy');
    }
}