<?php
/**
 * @link http://www.yiiframework.com/
 * @copyright Copyright (c) 2008 Yii Software LLC
 * @license http://www.yiiframework.com/license/
 */

namespace yii\redis;

use yii\base\Component;
use yii\db\Exception;
use yii\helpers\Inflector;

/**
 * The redis connection class is used to establish a connection to a [redis](http://redis.io/) server.
 *
 * By default it assumes there is a redis server running on localhost at port 6379 and uses the database number 0.
 *
 * It is possible to connect to a redis server using [[hostname]] and [[port]] or using a [[unixSocket]].
 *
 * It also supports [the AUTH command](http://redis.io/commands/auth) of redis.
 * When the server needs authentication, you can set the [[password]] property to
 * authenticate with the server after connect.
 *
 * The execution of [redis commands](http://redis.io/commands) is possible with via [[executeCommand()]].
 *
 * @method mixed set($key, $value) Set the string value of a key
 * @method mixed get($key) Set the string value of a key
 * TODO document methods
 *
 * @property string $driverName Name of the DB driver. This property is read-only.
 * @property boolean $isActive Whether the DB connection is established. This property is read-only.
 * @property LuaScriptBuilder $luaScriptBuilder This property is read-only.
 *
 * @author Carsten Brandt <mail@cebe.cc>
 * @since 2.0
 */
class Connection extends Component
{
    /**
     * @event Event an event that is triggered after a DB connection is established
     */
    const EVENT_AFTER_OPEN = 'afterOpen';

    /**
     * @var string the hostname or ip address to use for connecting to the redis server. Defaults to 'localhost'.
     * If [[unixSocket]] is specified, hostname and port will be ignored.
     */
    public $hostname = 'localhost';
    /**
     * @var integer the port to use for connecting to the redis server. Default port is 6379.
     * If [[unixSocket]] is specified, hostname and port will be ignored.
     */
    public $port = 6379;
    /**
     * @var string the unix socket path (e.g. `/var/run/redis/redis.sock`) to use for connecting to the redis server.
     * Unix socket 的地址
     * This can be used instead of [[hostname]] and [[port]] to connect to the server using a unix socket.
     * If a unix socket path is specified, [[hostname]] and [[port]] will be ignored.
     * @since 2.0.1
     */
    public $unixSocket;
    /**
     * @var string the password for establishing DB connection. Defaults to null meaning no AUTH command is send.
     * See http://redis.io/commands/auth
     */
    public $password;
    /**
     * @var integer the redis database to use. This is an integer value starting from 0. Defaults to 0.
     */
    public $database = 0;
    /**
     * @var float timeout to use for connection to redis. If not set the timeout set in php.ini will be used: ini_get("default_socket_timeout")
     */
    public $connectionTimeout = null;
    /**
     * @var float timeout to use for redis socket when reading and writing data. If not set the php default value will be used.
     */
    public $dataTimeout = null;
    /**
     * @var array List of available redis commands http://redis.io/commands
     * Redis 的命令
     */
    public $redisCommands = [
        'BRPOP', // key [key ...] timeout Remove and get the last element in a list, or block until one is available
        'BRPOPLPUSH', // source destination timeout Pop a value from a list, push it to another list and return it; or block until one is available
        'CLIENT KILL', // ip:port Kill the connection of a client
        'CLIENT LIST', // Get the list of client connections
        'CLIENT GETNAME', // Get the current connection name
        'CLIENT SETNAME', // connection-name Set the current connection name
        'CONFIG GET', // parameter Get the value of a configuration parameter
        'CONFIG SET', // parameter value Set a configuration parameter to the given value
        'CONFIG RESETSTAT', // Reset the stats returned by INFO
        'DBSIZE', // Return the number of keys in the selected database
        'DEBUG OBJECT', // key Get debugging information about a key
        'DEBUG SEGFAULT', // Make the server crash
        'DECR', // key Decrement the integer value of a key by one
        'DECRBY', // key decrement Decrement the integer value of a key by the given number
        'DEL', // key [key ...] Delete a key
        'DISCARD', // Discard all commands issued after MULTI
        'DUMP', // key Return a serialized version of the value stored at the specified key.
        'ECHO', // message Echo the given string
        'EVAL', // script numkeys key [key ...] arg [arg ...] Execute a Lua script server side
        'EVALSHA', // sha1 numkeys key [key ...] arg [arg ...] Execute a Lua script server side
        'EXEC', // Execute all commands issued after MULTI
        'EXISTS', // key Determine if a key exists
        'EXPIRE', // key seconds Set a key's time to live in seconds
        'EXPIREAT', // key timestamp Set the expiration for a key as a UNIX timestamp
        'FLUSHALL', // Remove all keys from all databases
        'FLUSHDB', // Remove all keys from the current database
        'GET', // key Get the value of a key
        'GETBIT', // key offset Returns the bit value at offset in the string value stored at key
        'GETRANGE', // key start end Get a substring of the string stored at a key
        'GETSET', // key value Set the string value of a key and return its old value
        'HDEL', // key field [field ...] Delete one or more hash fields
        'HEXISTS', // key field Determine if a hash field exists
        'HGET', // key field Get the value of a hash field
        'HGETALL', // key Get all the fields and values in a hash
        'HINCRBY', // key field increment Increment the integer value of a hash field by the given number
        'HINCRBYFLOAT', // key field increment Increment the float value of a hash field by the given amount
        'HKEYS', // key Get all the fields in a hash
        'HLEN', // key Get the number of fields in a hash
        'HMGET', // key field [field ...] Get the values of all the given hash fields
        'HMSET', // key field value [field value ...] Set multiple hash fields to multiple values
        'HSET', // key field value Set the string value of a hash field
        'HSETNX', // key field value Set the value of a hash field, only if the field does not exist
        'HVALS', // key Get all the values in a hash
        'INCR', // key Increment the integer value of a key by one
        'INCRBY', // key increment Increment the integer value of a key by the given amount
        'INCRBYFLOAT', // key increment Increment the float value of a key by the given amount
        'INFO', // [section] Get information and statistics about the server
        'KEYS', // pattern Find all keys matching the given pattern
        'LASTSAVE', // Get the UNIX time stamp of the last successful save to disk
        'LINDEX', // key index Get an element from a list by its index
        'LINSERT', // key BEFORE|AFTER pivot value Insert an element before or after another element in a list
        'LLEN', // key Get the length of a list
        'LPOP', // key Remove and get the first element in a list
        'LPUSH', // key value [value ...] Prepend one or multiple values to a list
        'LPUSHX', // key value Prepend a value to a list, only if the list exists
        'LRANGE', // key start stop Get a range of elements from a list
        'LREM', // key count value Remove elements from a list
        'LSET', // key index value Set the value of an element in a list by its index
        'LTRIM', // key start stop Trim a list to the specified range
        'MGET', // key [key ...] Get the values of all the given keys
        'MIGRATE', // host port key destination-db timeout Atomically transfer a key from a Redis instance to another one.
        'MONITOR', // Listen for all requests received by the server in real time
        'MOVE', // key db Move a key to another database
        'MSET', // key value [key value ...] Set multiple keys to multiple values
        'MSETNX', // key value [key value ...] Set multiple keys to multiple values, only if none of the keys exist
        'MULTI', // Mark the start of a transaction block
        'OBJECT', // subcommand [arguments [arguments ...]] Inspect the internals of Redis objects
        'PERSIST', // key Remove the expiration from a key
        'PEXPIRE', // key milliseconds Set a key's time to live in milliseconds
        'PEXPIREAT', // key milliseconds-timestamp Set the expiration for a key as a UNIX timestamp specified in milliseconds
        'PING', // Ping the server
        'PSETEX', // key milliseconds value Set the value and expiration in milliseconds of a key
        'PSUBSCRIBE', // pattern [pattern ...] Listen for messages published to channels matching the given patterns
        'PTTL', // key Get the time to live for a key in milliseconds
        'PUBLISH', // channel message Post a message to a channel
        'PUNSUBSCRIBE', // [pattern [pattern ...]] Stop listening for messages posted to channels matching the given patterns
        'QUIT', // Close the connection
        'RANDOMKEY', // Return a random key from the keyspace
        'RENAME', // key newkey Rename a key
        'RENAMENX', // key newkey Rename a key, only if the new key does not exist
        'RESTORE', // key ttl serialized-value Create a key using the provided serialized value, previously obtained using DUMP.
        'RPOP', // key Remove and get the last element in a list
        'RPOPLPUSH', // source destination Remove the last element in a list, append it to another list and return it
        'RPUSH', // key value [value ...] Append one or multiple values to a list
        'RPUSHX', // key value Append a value to a list, only if the list exists
        'SADD', // key member [member ...] Add one or more members to a set
        'SAVE', // Synchronously save the dataset to disk
        'SCARD', // key Get the number of members in a set
        'SCRIPT EXISTS', // script [script ...] Check existence of scripts in the script cache.
        'SCRIPT FLUSH', // Remove all the scripts from the script cache.
        'SCRIPT KILL', // Kill the script currently in execution.
        'SCRIPT LOAD', // script Load the specified Lua script into the script cache.
        'SDIFF', // key [key ...] Subtract multiple sets
        'SDIFFSTORE', // destination key [key ...] Subtract multiple sets and store the resulting set in a key
        'SELECT', // index Change the selected database for the current connection
        'SET', // key value Set the string value of a key
        'SETBIT', // key offset value Sets or clears the bit at offset in the string value stored at key
        'SETEX', // key seconds value Set the value and expiration of a key
        'SETNX', // key value Set the value of a key, only if the key does not exist
        'SETRANGE', // key offset value Overwrite part of a string at key starting at the specified offset
        'SHUTDOWN', // [NOSAVE] [SAVE] Synchronously save the dataset to disk and then shut down the server
        'SINTER', // key [key ...] Intersect multiple sets
        'SINTERSTORE', // destination key [key ...] Intersect multiple sets and store the resulting set in a key
        'SISMEMBER', // key member Determine if a given value is a member of a set
        'SLAVEOF', // host port Make the server a slave of another instance, or promote it as master
        'SLOWLOG', // subcommand [argument] Manages the Redis slow queries log
        'SMEMBERS', // key Get all the members in a set
        'SMOVE', // source destination member Move a member from one set to another
        'SORT', // key [BY pattern] [LIMIT offset count] [GET pattern [GET pattern ...]] [ASC|DESC] [ALPHA] [STORE destination] Sort the elements in a list, set or sorted set
        'SPOP', // key Remove and return a random member from a set
        'SRANDMEMBER', // key [count] Get one or multiple random members from a set
        'SREM', // key member [member ...] Remove one or more members from a set
        'STRLEN', // key Get the length of the value stored in a key
        'SUBSCRIBE', // channel [channel ...] Listen for messages published to the given channels
        'SUNION', // key [key ...] Add multiple sets
        'SUNIONSTORE', // destination key [key ...] Add multiple sets and store the resulting set in a key
        'SYNC', // Internal command used for replication
        'TIME', // Return the current server time
        'TTL', // key Get the time to live for a key
        'TYPE', // key Determine the type stored at key
        'UNSUBSCRIBE', // [channel [channel ...]] Stop listening for messages posted to the given channels
        'UNWATCH', // Forget about all watched keys
        'WATCH', // key [key ...] Watch the given keys to determine execution of the MULTI/EXEC block
        'ZADD', // key score member [score member ...] Add one or more members to a sorted set, or update its score if it already exists
        'ZCARD', // key Get the number of members in a sorted set
        'ZCOUNT', // key min max Count the members in a sorted set with scores within the given values
        'ZINCRBY', // key increment member Increment the score of a member in a sorted set
        'ZINTERSTORE', // destination numkeys key [key ...] [WEIGHTS weight [weight ...]] [AGGREGATE SUM|MIN|MAX] Intersect multiple sorted sets and store the resulting sorted set in a new key
        'ZRANGE', // key start stop [WITHSCORES] Return a range of members in a sorted set, by index
        'ZRANGEBYSCORE', // key min max [WITHSCORES] [LIMIT offset count] Return a range of members in a sorted set, by score
        'ZRANK', // key member Determine the index of a member in a sorted set
        'ZREM', // key member [member ...] Remove one or more members from a sorted set
        'ZREMRANGEBYRANK', // key start stop Remove all members in a sorted set within the given indexes
        'ZREMRANGEBYSCORE', // key min max Remove all members in a sorted set within the given scores
        'ZREVRANGE', // key start stop [WITHSCORES] Return a range of members in a sorted set, by index, with scores ordered from high to low
        'ZREVRANGEBYSCORE', // key max min [WITHSCORES] [LIMIT offset count] Return a range of members in a sorted set, by score, with scores ordered from high to low
        'ZREVRANK', // key member Determine the index of a member in a sorted set, with scores ordered from high to low
        'ZSCORE', // key member Get the score associated with the given member in a sorted set
        'ZUNIONSTORE', // destination numkeys key [key ...] [WEIGHTS weight [weight ...]] [AGGREGATE SUM|MIN|MAX] Add multiple sorted sets and store the resulting sorted set in a new key
    ];

    /**
     * @var resource redis socket connection
     * Redis socket 的连接实例
     */
    private $_socket;


    /**
     * Closes the connection when this component is being serialized.
     * @return array
     */
    public function __sleep()
    {
        // 在 serialize 时，关闭连接
        $this->close();

        // get_object_vars — Gets the properties of the given object
        // get_object_vars获取了所有的属性，因为是在自身的方法里，所以 private 的属性也能拿到
        return array_keys(get_object_vars($this));
    }

    /**
     * Returns a value indicating whether the DB connection is established.
     * @return boolean whether the DB connection is established
     */
    public function getIsActive()
    {
        // $this->_socket 为 null 则表示未连接
        return $this->_socket !== null;
    }

    /**
     * Establishes a DB connection.
     * It does nothing if a DB connection has already been established.
     * @throws Exception if connection fails
     */
    public function open()
    {
        if ($this->_socket !== null) {
            return;
        }
        // 在 PHP 中，a?:b 等价于 a?a:b
        $connection = ($this->unixSocket ?: $this->hostname . ':' . $this->port) . ', database=' . $this->database;
        \Yii::trace('Opening redis DB connection: ' . $connection, __METHOD__);
        $this->_socket = @stream_socket_client(
            // stream_socket_client — Open Internet or Unix domain socket connection
            $this->unixSocket ? 'unix://' . $this->unixSocket : 'tcp://' . $this->hostname . ':' . $this->port,
            $errorNumber,
            $errorDescription,
            // ini_get — Gets the value of a configuration option
            $this->connectionTimeout ? $this->connectionTimeout : ini_get("default_socket_timeout")
        );
        if ($this->_socket) {
            if ($this->dataTimeout !== null) {
                // stream_set_timeout — Set timeout period on a stream
                stream_set_timeout($this->_socket, $timeout = (int) $this->dataTimeout, (int) (($this->dataTimeout - $timeout) * 1000000));
            }
            if ($this->password !== null) {
                $this->executeCommand('AUTH', [$this->password]);
            }
            $this->executeCommand('SELECT', [$this->database]);
            $this->initConnection();
        } else {
            \Yii::error("Failed to open redis DB connection ($connection): $errorNumber - $errorDescription", __CLASS__);
            $message = YII_DEBUG ? "Failed to open redis DB connection ($connection): $errorNumber - $errorDescription" : 'Failed to open DB connection.';
            throw new Exception($message, $errorDescription, (int) $errorNumber);
        }
    }

    /**
     * Closes the currently active DB connection.
     * It does nothing if the connection is already closed.
     */
    public function close()
    {
        if ($this->_socket !== null) {
            $connection = ($this->unixSocket ?: $this->hostname . ':' . $this->port) . ', database=' . $this->database;
            \Yii::trace('Closing DB connection: ' . $connection, __METHOD__);
            // 执行 quit 命令
            $this->executeCommand('QUIT');
            // stream_socket_shutdown — Shutdown a full-duplex connection
            // One of the following constants:
            // 1. STREAM_SHUT_RD (disable further receptions) 接收
            // 2. STREAM_SHUT_WR (disable further transmissions) 传输
            // 3. STREAM_SHUT_RDWR (disable further receptions and transmissions) 接收和传输
            stream_socket_shutdown($this->_socket, STREAM_SHUT_RDWR);
            $this->_socket = null;
        }
    }

    /**
     * Initializes the DB connection.
     * This method is invoked right after the DB connection is established.
     * The default implementation triggers an [[EVENT_AFTER_OPEN]] event.
     */
    protected function initConnection()
    {
        // 触发 afterOpen 事件
        $this->trigger(self::EVENT_AFTER_OPEN);
    }

    /**
     * Returns the name of the DB driver for the current [[dsn]].
     * @return string name of the DB driver
     */
    public function getDriverName()
    {
        return 'redis';
    }

    /**
     * Redis 支持执行 Lua 命令，这里是 Yii 对其的封装
     * @return LuaScriptBuilder
     */
    public function getLuaScriptBuilder()
    {
        return new LuaScriptBuilder();
    }

    /**
     *
     * @param string $name
     * @param array $params
     * @return mixed
     */
    public function __call($name, $params)
    {
        // Inflector::camel2words -- Converts a CamelCase name into space-separated words.  For example, 'PostTag' will be converted to 'post tag'.
        $redisCommand = strtoupper(Inflector::camel2words($name, false));
        if (in_array($redisCommand, $this->redisCommands)) {
            // 在 redis 的命令中，就执行
            return $this->executeCommand($name, $params);
        } else {
            return parent::__call($name, $params);
        }
    }

    /**
     * Executes a redis command.
     * For a list of available commands and their parameters see http://redis.io/commands.
     *
     * @param string $name the name of the command
     * @param array $params list of parameters for the command
     * @return array|bool|null|string Dependent on the executed command this method
     * will return different data types:
     *
     * - `true` for commands that return "status reply" with the message `'OK'` or `'PONG'`.
     * - `string` for commands that return "status reply" that does not have the message `OK` (since version 2.0.1).
     * - `string` for commands that return "integer reply"
     *   as the value is in the range of a signed 64 bit integer.
     * - `string` or `null` for commands that return "bulk reply".
     * - `array` for commands that return "Multi-bulk replies".
     *
     * See [redis protocol description](http://redis.io/topics/protocol)
     * 中文相关内容：http://www.redis.cn/topics/protocol.html
     * for details on the mentioned reply types.
     * @trows Exception for commands that return [error reply](http://redis.io/topics/protocol#error-reply).
     */
    public function executeCommand($name, $params = [])
    {
        $this->open();

        // 将命令 $name 放入 $params 数组中，方便之后使用循环处理
        array_unshift($params, $name);
        // 一个合法格式的例子如下：
        // "*3\r\n$3\r\nSET\r\n$5\r\nmykey\r\n$7\r\nmyvalue\r\n"
        // 等价于在 redis-cli 中的 set mykey myValue
        $command = '*' . count($params) . "\r\n";
        foreach ($params as $arg) {
            $command .= '$' . mb_strlen($arg, '8bit') . "\r\n" . $arg . "\r\n";
        }

        \Yii::trace("Executing Redis Command: {$name}", __METHOD__);
        // 写入到 scoket 中，即去执行命令
        fwrite($this->_socket, $command);

        // 处理返回值
        return $this->parseResponse(implode(' ', $params));
    }

    /**
     * 用单行回复，回复的第一个字节将是“+”
     * 错误消息，回复的第一个字节将是“-”
     * 整型数字，回复的第一个字节将是“:”
     * 批量回复，回复的第一个字节将是“$”
     * 多个批量回复，回复的第一个字节将是“*”
     * @param string $command
     * @return mixed
     * @throws Exception on error
     */
    private function parseResponse($command)
    {
        if (($line = fgets($this->_socket)) === false) {
            throw new Exception("Failed to read from socket.\nRedis command was: " . $command);
        }
        // 获取开头的字符
        $type = $line[0];
        // 去掉开头的字符和最后的\n\r
        $line = mb_substr($line, 1, -2, '8bit');
        switch ($type) {
            case '+': // Status reply
                if ($line === 'OK' || $line === 'PONG') {
                    return true;
                } else {
                    return $line;
                }
            case '-': // Error reply
                throw new Exception("Redis error: " . $line . "\nRedis command was: " . $command);
            case ':': // Integer reply
                // no cast to int as it is in the range of a signed 64 bit integer
                return $line;
            case '$': // Bulk replies
                if ($line == '-1') {
                    return null;
                }
                $length = $line + 2;
                $data = '';
                while ($length > 0) {
                    if (($block = fread($this->_socket, $length)) === false) {
                        throw new Exception("Failed to read from socket.\nRedis command was: " . $command);
                    }
                    $data .= $block;
                    $length -= mb_strlen($block, '8bit');
                }

                return mb_substr($data, 0, -2, '8bit');
            case '*': // Multi-bulk replies
                $count = (int) $line;
                $data = [];
                for ($i = 0; $i < $count; $i++) {
                    // 处理多个批量回复
                    $data[] = $this->parseResponse($command);
                }

                return $data;
            default:
                throw new Exception('Received illegal data from redis: ' . $line . "\nRedis command was: " . $command);
        }
    }
}
