require 'rest-core/middleware'
require 'rest-core/util/json'

class RestCore::JsonResponse
  def self.members; [:json_response]; end
  include RestCore::Middleware

  class ParseError < Json.const_get(:ParseError)
    attr_reader :cause, :body
    def initialize cause, body
      msg = cause.message.force_encoding('utf-8')
      super("#{msg}\nOriginal text: #{body}")
      @cause, @body = cause, body
    end
  end

  JSON_RESPONSE_HEADER = {'Accept' => 'application/json'}.freeze

  def call env, &k
    return app.call(env, &k) if env[DRY]
    return app.call(env, &k) unless json_response(env)

    app.call(env.merge(REQUEST_HEADERS =>
      JSON_RESPONSE_HEADER.merge(env[REQUEST_HEADERS]||{}))){ |response|
        yield(process(response))
      }
  end

  def process response
    body = response[RESPONSE_BODY].to_s.sub(/\A\xEF\xBB\xBF/, '')
    if response[HIJACK] && Json.respond_to?(:decode_from_io)
      response.merge(
        RESPONSE_SOCKET => Json.decode_from_io(response[RESPONSE_SOCKET]))
    else
      # StackExchange returns the problematic BOM! in UTF-8, so we need to
      # strip it or it would break JSON parsers (i.e. yajl-ruby and json)
      response.merge(RESPONSE_BODY => Json.decode("[#{body}]").first)
      # [this].first is not needed for yajl-ruby
    end
  rescue Json.const_get(:ParseError) => error
    fail(response, ParseError.new(error, body))
  end
end