module Faraday
  # Used to setup urls, params, headers, and the request body in a sane manner.
  #
  #   @connection.post do |req|
  #     req.url 'http://localhost', 'a' => '1' # 'http://localhost?a=1'
  #     req.headers['b'] = '2' # header
  #     req['b']         = '2' # header
  #     req.body = 'abc'
  #   end
  #
  class Request < Struct.new(:path, :params, :headers, :body)
    extend AutoloadHelper
    autoload_all 'faraday/request',
      :Yajl              => 'yajl',
      :ActiveSupportJson => 'active_support_json'

    register_lookup_modules \
      :yajl                => :Yajl,
      :activesupport_json  => :ActiveSupportJson,
      :rails_json          => :ActiveSupportJson,
      :active_support_json => :ActiveSupportJson

    def self.run(connection, request_method)
      req = create
      yield req if block_given?
      req.run(connection, request_method)
    end

    def self.create
      req = new(nil, {}, {}, nil)
      yield req if block_given?
      req
    end

    def url(path, params = {})
      self.path   = path
      self.params = params
    end

    def [](key)
      headers[key]
    end

    def []=(key, value)
      headers[key] = value
    end

    # ENV Keys
    # :method - a symbolized request method (:get, :post)
    # :body   - the request body that will eventually be converted to a string.
    # :url    - Addressable::URI instance of the URI for the current request.
    # :status           - HTTP response status code
    # :request_headers  - hash of HTTP Headers to be sent to the server
    # :response_headers - Hash of HTTP headers from the server
    # :parallel_manager - sent if the connection is in parallel mode
    # :response         - the actual response object that stores the rack response
    def to_env_hash(connection, request_method)
      env_headers = connection.headers.dup
      env_params  = connection.params.dup
      connection.merge_headers env_headers, headers
      connection.merge_params  env_params,  params

      { :method           => request_method, 
        :body             => body, 
        :url              => connection.build_url(path, env_params),
        :request_headers  => env_headers.update(headers),
        :parallel_manager => connection.parallel_manager,
        :response         => Response.new}
    end

    def run(connection, request_method)
      app = connection.to_app
      env = to_env_hash(connection, request_method)
      app.call(env)
    end
  end
end