redis receiver

local serpent = require'serpent'
local socket = require'socket'

local connection = {}
connection.__index = connection

connection.default = {timeout = 5, ip = '127.0.0.1', port = 6379}
connection.protocol = socket.tcp4 or socket.tcp

function connection:new(ip, port, timeout)
    local o = {}
    o.ip = ip or self.default.ip
    o.port = port or self.default.port
    o.timeout = timeout or self.default.timeout

    return setmetatable(o, self)
end

function connection:connect()
    if self.tcp then return true end
    self.tcp = self.protocol()
    self.tcp:connect(self.ip, self.port)
    self.tcp:settimeout(self.timeout)
    self.tcp:send'PING\n'
    if self.tcp:receive'*l' == '+PONG' then return true end

    self:disconnect()
    return false, 'redis not responded'
end

function connection:disconnect()
    if not self.tcp then return end
    self.tcp:close()
    self.tcp = nil
end

local cr = {}
connection.receiver = cr

-- simple strings
cr['+'] = function(self, data) return data end

-- errors
cr['-'] = function(self, data) return false, data end

-- bulk strings
cr['$'] = function(self, data)
    local bytes = tonumber(data)
    if not bytes or bytes < 1 then return bytes end
    local res, err = self.tcp:receive(bytes + 2) -- data + \r\n
    return err and false or res:sub(1, -3), err  -- cut \r\n
end

-- integers
cr[':'] = function(self, data)
    return tonumber(data)
end

-- arrays
cr['*'] = function(self, data)
    local count = tonumber(data)
    if not count then return false, 'I can\'t help ((' end
    local list = {}
    for i = 1, count do
        list[i] = self:receive()
    end
    return list
end

function connection:receive()
    local res, err = self.tcp:receive'*l'
    if not res then return self.disconnect(), err end
    local head, tail = res:sub(1, 1), res:sub(2)
    return self.receiver[head](self, tail)
end

function connection:request(command, close)
    if not self:connect() then return end

    self.tcp:send(command..'\r\n')
    return self:receive()
end

if not ... then
    c = connection:new()

    local test_case = {
        'keys home*',
        'type home:1',
        'hgetall home:id1',
        'get home:1'
    }

    for i, v in ipairs(test_case) do
        local res, err = c:request(v)
        local tp = type(res)
        if not res then res = '--ERROR '..tostring(err) end
        res = type(res) == 'table' and serpent.block(res) or tostring(res)
        print('REQUEST ['..v..'] : ('..tp..') '..res)
    end
end