RedisBackend.coffee

exports.Backend: class RedisBackend extends Backend
  CONTENT:  'content'
  DEPS:     'dependencies'
  DATE:     'date'
  
  constructor: (config) ->
    @host: config.host || '127.0.0.1'
    @port: config.port || 6379
    @db: config.db || 0
    @client: new redis.Client(@port, @host)
    @connect()
  
  connect: (callback) ->
    defer @client.connect
    @client.select @db, callback
  
  key: (res, key) ->
    "$res.group::$res.path::$key"
  
  set: (res, callback) ->
    deps: ("\"$dep\"" for dep in res.deps)
    defer @client.set @key(res, @DATE), String(new Date())
    @client.mset @key(res, @CONTENT),  res.content, 
      @key(res, @DEPS), "[${deps.join(',')}]", callback
  
  get: (res) ->
    [err, values]: defer @client.mget @key(res, @CONTENT), @key(res, @DEPS)
    res.content: values[0]
    res.deps: eval(values[1])
    yield err
  
  getDate: (res) ->
    [err, date]: defer @client.get @key(res, @DEPS)
    yield date
  
  close: ->
    @client.close()