commands.js

"use strict";

var Class = require('./class');

var Commands = Class.extend({
  command_list: null,
  exec_stack: [],
  initialize: function (socket, type, ID, sequence) {
    var self = this;
    this.exec_stack = [];
    this.client = socket;
    this.command_list = require('./commands/' + type);
    //map commands for better use
    for (var cmd in this.command_list) {
      (function (command) {
        self[command] = function () {
          var args = Array.prototype.slice.call(arguments);
          args.unshift(command);
          return self.stack.apply(self, args);
        };
      }(cmd));
    }
    this.ID = ID || 0;
    this.sequence = this.sequenceNumber = sequence || 0x80;
  },
  getSequence: function () {
    return this.ID | (this.sequence = (this.sequence === this.sequenceNumber ? 0x00 : this.sequenceNumber));
  },
  CRC16: function (command) {
    var length = command.length,
      seed = 0xFFFF,
      poly = 0x8005,
      crc = seed;


    for (var i = 0; i < length; i++) {
      crc ^= (command[i] << 8);

      for (var j = 0; j < 8; j++) {

        if (crc & 0x8000) {
          crc = ((crc << 1) & 0xffff) ^ poly;
        } else {
          crc <<= 1;
        }

      }
    }
    return [(crc & 0xFF), ((crc >> 8) & 0xFF)];
  },
  stack: function (commandName) {
    var command,
      commandLine,
      args = Array.prototype.slice.call(arguments, 1);
    if (!this.command_list.hasOwnProperty(commandName)) {
      throw new Error("Unknown command '" + commandName + "'");
    }
    if (commandName instanceof Array) {
      for (var i in commandName) {
        this.stack(commandName[i]);
      }
    } else {
      commandName = commandName.toLowerCase();
      if ("function" === typeof this.command_list[commandName]) {
        command = this.command_list[commandName].call(this);
      } else {
        command = this.command_list[commandName];
      }
      commandLine = [this.getSequence(), args.length + 1, command].concat(args);
      commandLine = [0x7F].concat(commandLine, this.CRC16(commandLine));
      this.exec_stack.push(commandLine);
    }
    return this;
  },
  exec: function (command, cb) {
    var typeCmd = typeof command;
    if("function" === typeCmd) {
      cb = command;
      command = null;
    } else if("string" === typeCmd) {
      this.stack(command);
    } else if(command instanceof Array) {
      this.exec_stack.push(command);
    }
    if (this.exec_stack.length === 0) {
      cb && cb();
    } else {
      var buf = new Buffer(this.exec_stack.shift()), self = this;
      this.client.write(buf, function () {
        self.client.drain(function () {
          setTimeout(function() {
            self.exec(cb);
          }, 100);
        });
      });
    }
  }
});

module.exports = Commands;