Q-Sys Redis Client

redis.lua

--[[
  Q-Sys Redis Client
  Author: Michael Goodyear
  Email: michael@locimation.com
  Version: 1.1
  
  Copyright 2020 Locimation Pty Ltd
  Permission is hereby granted, free of charge,
  to any person obtaining a copy of this software
  and associated documentation files (the "Software"),
  to deal in the Software without restriction, including
  without limitation the rights to use, copy, modify,
  merge, publish, distribute, sublicense, and/or sell
  copies of the Software, and to permit persons to whom
  the Software is furnished to do so, subject to the
  following conditions:
  The above copyright notice and this permission
  notice shall be included in all copies or substantial
  portions of the Software.
  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY
  OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT
  LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
  FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO
  EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
  FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
  AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
  OTHER DEALINGS IN THE SOFTWARE.
]]

Redis = (function(host, port)

  local R = { _ = {} };
  
  -- Socket management
  R._.Host = host;
  R._.Port = port;
  R._.Socket = TcpSocket.New();
  R._.Socket.ReconnectTimeout = 0.1;
  R._.Socket.EventHandler = function(sock, evt)
    print(evt);
  end;
  R.Reconnect = function()
    if(R._.Socket.IsConnected) then R._.Socket:Disconnect(); end;
    R._.Socket:Connect(host, port);
  end
  
  -- Command queue & timeout timer
  R.Timeout = 1000; -- one second
  R._.TimeoutTimer = Timer.New();
  R._.CmdQueue = {};
  function enqueue(msg)
    table.insert(R._.CmdQueue, msg);          -- add the command to the queue
    if(not R._.Waiting) then dequeue(); end;  -- send immediately if we can
  end;
  function dequeue()
    local msg = table.remove(R._.CmdQueue, 1);
    if(not msg) then return; end;             -- bail out if the queue is empty
    R._.Waiting = msg;                        -- store command details for data handler
    R._.Socket:Write(msg.s);                  -- send command out to the socket
    R._.TimeoutTimer:Start(R.Timeout / 1000); -- start timeout timer in milliseconds
  end;
  R._.TimeoutTimer.EventHandler = function()
    R._.TimeoutTimer:Stop();
    R.Reconnect();
    error('redis - timeout waiting for response to ' .. (R._.Waiting.cmd) .. ' (' .. R.Timeout .. 'ms)');
  end
  
  -- Multi-mode response tokenizer
  function s_read(sock, amt)
    return (sock.BufferLength > amt) and sock:Read(amt) or nil;
  end
  R._.Deserializer = { read = 'crlf' };
  R._.Socket.Data = function(sock)
    local d = R._.Deserializer;
    -- modes: linemode & binary mode.
    while(d.read ~= 'crlf' and sock.BufferLength > d.read+2 or sock:Search('\r\n')) do
      if(d.read == 'crlf') then
        handleToken(sock:ReadLine(TcpSocket.EOL.CrLf), 'line');
      else
        handleToken(sock:Read(d.read), 'bin');
        sock:Read(2);; -- discard a CrLf
        d.read = 'crlf'; -- go back to line mode
      end;
    end
  end;
  
  -- Result inflater
  R._.ObjectConstructor = { tree = {}, obj = {} };
  function handleToken(val, typ)
    local d = R._.ObjectConstructor;
    local el, more, err = (function()
      if(typ == 'line') then
        return deserialize(val)
      else
        return val, 0
      end
    end)();
    
    -- Track the depth into the resultant object, and the number of items at that level
    local target = d.tree[#d.tree] or { obj = d.obj, len = 1 };
    local new_leaf = {obj = el or target.obj, len = more};
    
    -- Construct the result object
    table.insert(target.obj, el);
    target.len = target.len - 1;
    
    -- Walk back up the tree as far as we can
    table.insert(d.tree, new_leaf);
    while(#d.tree > 0 and d.tree[#d.tree].len == 0) do
      table.remove(d.tree);
    end;
    
    -- If we're back at level 0, we've parsed all the objects and can return.
    if(#d.tree == 0) then
      R._.TimeoutTimer:Stop();
      R._.Waiting.cb(d.obj[1], err);
      R._.Waiting = nil;
      d.obj = {};
      dequeue();
    end;
    
  end;
  
  -- Serialization
  function serializeCommand(parts)
    local serialized = '*'         -- commands are sent as an array
            .. (#parts) .. '\r\n'; -- number of parts = array length
    for _,p in ipairs(parts) do        -- serialize each part
      serialized = serialized  .. '$'  -- as a bulk string type
                    .. (#p) ..'\r\n'   -- with a given length
                    .. p .. '\r\n'     -- the string itself
    end
    return serialized;
  end
  
  function deserialize(line)
    local resp_type, data = line:match('(.)(.+)');
    if(resp_type == '+') then     -- it's a string
      return data, 0;
    elseif(resp_type == '$') then -- it's a bulk string
      if(data == '-1') then
        return nil, 0;
      else
        R._.Deserializer.read = tonumber(data);
        return nil,1;
      end;
    elseif(resp_type == '-') then -- it's an error
      return nil, 0, data;
    elseif(resp_type == ':') then -- it's an integer
      return tonumber(data), 0;
    elseif(resp_type == '*') then -- it's an array!
      if(data == '-1') then
        return nil, 0;
      else
        return {}, tonumber(data);
      end;
    else
      error('redis: unrecognized type ' .. resp_type);
    end;
  end;
  
  
  function sendCommand(cmd, args, cb)
  
    -- Serialize command
    cmd = cmd:upper();
    local parts = {cmd};
    for i=1,#args do table.insert(parts, tostring(args[i])); end;
    local s = serializeCommand(parts);
    
    -- Enqueue for sending
    enqueue({s=s, cb=cb, cmd=cmd});
    
  end;
  
  -- Lazy creation of methods for the Redis API
  setmetatable(R, {
    __index = function(o,k)
      k = k:gsub('_',' '):upper();
      local method = function(...)
        local args = {...};
        local cb = table.remove(args);
        sendCommand(k:upper(), args, cb);
      end;
      R[k] = method; -- cache the function
      return method;
    end
  });
  
  R.Reconnect();
  return R;

end);

--[[
EXAMPLE USAGE:

  local redis = Redis('localhost', 6379);

  redis.auth('mypassword', function(result, err)
    if(result ~= 'OK') then error(err); end;
  end)

  redis.get('foo', function(result, err) 
    if(err) then error(err); end;
    print('RESULT: ', result);
  end);

]]