--- tcp网关
--@script gg.service.gate.tcp
--@author sundream
--@release 2018/12/25 10:30:00
--@usage
--  -- sproto
--  local proto = {
--      type = "sproto",
--      c2s = "src/proto/sproto/all.spb",
--      s2c = "src/proto/sproto/all.spb",
--      binary = true,
--  }
--  -- protobuf
--  local proto = {
--      type = "protobuf",
--      pbfile = "src/proto/protobuf/all.pb",
--      idfile = "src/proto/protobuf/message_define.lua",
--  }
--  -- json
--  local proto = {
--      type = "json"
--  }
--  local gate_conf = {
--      watchdog = address,     -- 主服地址
--      proto = proto,          -- 使用的编码协议
--      encrypt_algorithm = encrypt_algorithm, -- 协议加解密算法,nil--不握手,"nil"--握手但告知客户端不加密,其他--握手协商加密密码
--      timeout = timeout,          -- 多长时间(1/100秒为单位),自动关闭不活跃的连接
--      msg_max_len = msg_max_len,  -- 最大消息长度
--      maxclient = maxclient,      -- 最大连接个数
--  }
--  local tcp_port = skynet.getenv("tcp_port")
--  gate_conf.port = tcp_port
--  -- 启动tcp_gate服务
--  local tcp_gate = skynet.uniqueservice("gg/service/gate/tcp")
--
--  通信
--  tcp_gate -> watchdog
--  1. 新建连接
--      skynet.send(watchdog,"lua","client","onconnect","tcp",linkid,addr)
--  2. 关闭连接
--      skynet.send(watchdog,"lua","client","onclose",linkid)
--  3. 收到消息时转发给watchdog
--      skynet.send(watchdog,"lua","client","onmessage",linkid,message)
--  4. 告知watchdog成为某个连接的辅助连接
--      skynet.send(watchdog,"lua","client","saveof",master_linkid,slave_linkid)
--  5. 握手完毕
--      skynet.send(watchdog,"lua","client","onhandshake","tcp",linkid,addr,result)

--
--  watchdog -> tcp_gate
----1. 监听端口
--      skynet.call(tcp_gate,"lua","open",gate_conf)
--  2. 向某连接发送数据
--      skynet.send(tcp_gate,"lua","write",linkid,message)
--  3. 关闭连接
--      skynet.send(tcp_gate,"lua","close",linkid)
--  4. 热更协议
--      skynet.send(tcp_gate,"lua","reload")
----5. 转发协议到其他服务(默认是发到watchdog)
--      skynet.send(tcp_gate,"lua","forward",proto,address)
--
--  备注: linkid: 连接ID,addr: 客户端地址,message: 消息
--  包格式: 2字节长度(大端)+消息体(消息体编码由配置决定,如protobuf/sproto等,
--  另外加密也只对消息体加密)
--  分包用到了skynet_package,see https://github.com/cloudwu/skynet_package

local skynet = require "skynet"
local socket = require "skynet.socket"
local socket_proxy = require "socket_proxy"
local crypt = require "skynet.crypt"
local codec = require "gg.codec.codec"
local chandshake = require "gg.service.gate.handshake"

local connection = {}
local client_number = 0
local maxclient
local msg_max_len
local watchdog
local timeout       -- 1/100s为单位
local encrypt_algorithm
local codecobj
local forward_protos = {}
local handler = {}

local socket_start = socket_proxy.subscribe
local socket_read = function (linkid)
    local ok,msg,sz = pcall(socket_proxy.read,linkid)
    if not ok then
        return false
    end
    return true,skynet.tostring(msg,sz)
end
local socket_write = socket_proxy.write
local socket_close = socket_proxy.close

function handler.onconnect(linkid,addr)
    if client_number >= maxclient then
        skynet.error(string.format("op=overlimit,linktype=tcp,linkid=%s,addr=%s,client_number=%s,maxclient=%s",
        linkid,addr,client_number,maxclient))
        socket_close(linkid)
        return
    end
    client_number = client_number + 1
    local agent = {
        addr = addr,
        linkid = linkid,
        handshake = chandshake.new(),
    }
    connection[linkid] = agent
    skynet.error(string.format("op=onconnect,linktype=tcp,linkid=%s,addr=%s",linkid,addr))
    skynet.send(watchdog,"lua","client","onconnect","tcp",linkid,addr)
    if encrypt_algorithm then
        socket_write(linkid,agent.handshake:pack_challenge(linkid,encrypt_algorithm))
    else
        agent.handshake.result = "OK"
        handler.onhandshake(linkid,agent.handshake.result)
    end
end

function handler.onhandshake(linkid,result)
    local agent = connection[linkid]
    skynet.send(watchdog,"lua","client","onhandshake","tcp",linkid,agent.addr,result)
end

function handler.onclose(linkid)
    if not connection[linkid] then
        return
    end
    client_number = client_number - 1
    connection[linkid] = nil
    skynet.error(string.format("op=onclose,linktype=tcp,linkid=%s",linkid))
    skynet.send(watchdog,"lua","client","onclose",linkid)
end

function handler.onmessage(linkid,msg)
    local agent = connection[linkid]
    if not agent then
        return
    end
    if not agent.handshake.result then
        local ok,errmsg = agent.handshake:do_handshake(msg)
        skynet.error(string.format("op=handshake,linktype=tcp,linkid=%s,addr=%s,ok=%s,errmsg=%s,result=%s,step=%s",linkid,agent.addr,ok,errmsg,agent.handshake.result,agent.handshake.step))
        if agent.handshake.result then
            socket_write(linkid,agent.handshake:pack_result())
            handler.onhandshake(linkid,agent.handshake.result)
            if agent.handshake.result == "OK" and agent.handshake.master_linkid then
                skynet.error(string.format("op=slaveof,linktype=tcp,master=%s,slave=%s",agent.handshake.master_linkid,agent.linkid))
                skynet.send(watchdog,"lua","client","slaveof",agent.handshake.master_linkid,agent.linkid)
            end
        end
        if not ok then
            socket_close(linkid)
        end
        return
    end
    msg = agent.handshake:decrypt(msg)
    local message = codecobj:unpack_message(msg)
    local address = forward_protos[message.cmd] or watchdog
    skynet.send(address,"lua","client","onmessage",linkid,message)
end

local CMD = {}

function CMD.open(conf)
    -- 多长时间(单位:1/100秒)未收到客户端协议,则主动断开该客户端连接
    timeout = conf.timeout or 0
    watchdog = assert(conf.watchdog)
    encrypt_algorithm = conf.encrypt_algorithm
    codecobj = codec.new(conf.proto)
    msg_max_len = assert(conf.msg_max_len)
    maxclient = assert(conf.maxclient)
    local port = assert(conf.port)
    local ip = conf.ip or "0.0.0.0"
    local id = assert(socket.listen(ip,port))
    skynet.error("Tcp listen on",ip,port)
    socket.start(id,function (linkid,addr)
        socket_start(linkid,timeout)
        handler.onconnect(linkid,addr)
        if not connection[linkid] then
            return
        end
        while true do
            local ok,msg = socket_read(linkid)
            if not ok then
                handler.onclose(linkid)
                break
            end
            xpcall(handler.onmessage,skynet.error,linkid,msg)
        end
    end)
    skynet.retpack()
end

function CMD.reload()
    codecobj:reload()
end

function CMD.forward(proto,address)
    forward_protos[proto] = address
end

function CMD.write(linkid,message)
    local agent = connection[linkid]
    if not agent then
        return
    end
    local msg = codecobj:pack_message(message)
    msg = agent.handshake:encrypt(msg)
    assert(#msg <= msg_max_len)
    socket_write(linkid,msg)
end

function CMD.close(linkid)
    if not connection[linkid] then
        return
    end
    socket_close(linkid)
end

skynet.start(function ()
    skynet.dispatch("lua",function (session,source,cmd,...)
        local func = CMD[cmd]
        func(...)
    end)
end)
