post.rb

class Post

  attr_accessor :data

  def initialize(data)
    @data = Hashie::Mash.new(data)
  end

  def method_missing(key, *args)
    data.send(key)
  end

  def self.all(options = {})
    Tumblr::Post.all(options).map { |post| Post.new(post) }
  end

  def self.first(options = {})
    Post.new(Tumblr::Post.first(options))
  end

  def self.find(id)
    Post.new(Tumblr::Post.find(id))
  end

  class << self
    alias_method :get, :find
  end

end

tumblr.rb

module Tumblr

  class InvalidAction < StandardError; end
  class InvalidAPIResponse < StandardError; end

  class Post

    DEFAULTS = {}

    # Options:
    #   start - The post offset to start from. The default is 0.
    #   num - The number of posts to return. The default is 20, and the maximum is 50.
    #   type - The type of posts to return. If unspecified or empty, all types of posts are returned. Must be one of text, quote, photo, link, chat, video, or audio.
    #   id - A specific post ID to return. Use instead of start, num, or type.
    #   filter - Alternate filter to run on the text content. Allowed values:
    #     text - Plain text only. No HTML.
    #     none - No post-processing. Output exactly what the author entered. (Note: Some authors write in Markdown, which will not be converted to HTML when this option is used.)
    #   tagged - Return posts with this tag in reverse-chronological order (newest first). Optionally specify chrono=1 to sort in chronological order (oldest first).
    #   search - Search for posts with this query.

    def self.all(options = {})
      Tumblr::Request.read(DEFAULTS.merge(options))["tumblr"]["posts"]["post"]
    end

    def self.first(options)
      self.all(options.merge({ :num => 1 }))
    end

    def self.find(id)
      self.all(:id => id)
    end

    class << self
      alias_method :get, :find
    end

  end

  class Request

    KNOWN_ACTIONS = ["read"]

    def self.method_missing(action, *args)
      begin
        # Try to execute it to tumblr
        options = args[0]
        self.do(action.to_s, options)
      rescue Tumblr::InvalidAction => e
        raise NoMethodError
      end
    end

    private

      def self.do(action, options = {})
        # Make sure we understand this action
        raise Tumblr::InvalidAction unless KNOWN_ACTIONS.include?(action)
        # Make the request
        response = HTTParty.get("http://#{TUMBLR}.tumblr.com/api/#{action}", :query => options)
        # The response should be a hash
        raise Tumblr::InvalidAPIResponse unless response.is_a? Hash
        # Return the response
        response
      end

  end

end