Redis passthrough cache for node

redis-cache-example.coffee

# Example usage
AvatarCache = new RedisCache
  keyPrefix: "userAvatar:"
  expiry: 3600
  generator: (key, callback) ->
    request "https://api.github.com/users/#{key}", (error, response, body) ->
      if !error and response.statusCode == 200
        user = JSON.parse(body)
        generate user.avatar_url

AvatarCache.get "loopj", (response) ->
  console.log response

redis-cache.coffee

class RedisCache
  constructor: (opts) ->
    @keyPrefix = opts.keyPrefix if opts.keyPrefix?
    @generator = opts.generator
    @redisClient = opts.redisClient if opts.redisClient?
    @expiry = opts.expiry if opts.expiry?

  get: (key, callback, expiry=null) ->
    @redisClient.get prefixedKey(key), (err, response) ->
      if response?
        callback response
      else
        @generator key, (response) ->
          @set key, response
          callback response

  set: (key, value, expiry=null) ->
    @redisClient.set prefixedKey(key), value
    @redisClient.expire prefixedKey(key), (expiry or @expiry if expiry or @expiry)

  prefixedKey = (key) ->
    "#{@keyPrefix}#{key}"