require 'grape/middleware/base'

module Grape
  module Middleware
    class Formatter < Base
      def default_options
        {
          default_format: :txt,
          formatters: {},
          parsers: {}
        }
      end

      def headers
        env.dup.inject({}) do |h, (k, v)|
          h[k.to_s.downcase[5..-1]] = v if k.to_s.downcase.start_with?('http_')
          h
        end
      end

      def before
        negotiate_content_type
        read_body_input
      end

      def after
        status, headers, bodies = *@app_response
        # allow content-type to be explicitly overwritten
        api_format = mime_types[headers["Content-Type"]] || env['api.format']
        formatter = Grape::Formatter::Base.formatter_for api_format, options
        begin
          bodymap = bodies.collect do |body|
            formatter.call body, env
          end
        rescue Grape::Exceptions::InvalidFormatter => e
          throw :error, status: 500, message: e.message
        end
        headers['Content-Type'] = content_type_for(env['api.format']) unless headers['Content-Type']
        Rack::Response.new(bodymap, status, headers).to_a
      end

      private

      def request
        @request ||= Rack::Request.new(env)
      end

      # store read input in env['api.request.input']
      def read_body_input
        if (request.post? || request.put? || request.patch? || request.delete?) &&
          (!request.form_data? || !request.media_type) &&
          (!request.parseable_data?) &&
          (request.content_length.to_i > 0 || request.env['HTTP_TRANSFER_ENCODING'] == 'chunked')

          if (input = env['rack.input'])
            input.rewind
            body = env['api.request.input'] = input.read
            begin
              read_rack_input(body) if body && body.length > 0
            ensure
              input.rewind
            end
          end
        end
      end

      # store parsed input in env['api.request.body']
      def read_rack_input(body)
        fmt = mime_types[request.media_type] if request.media_type
        fmt ||= options[:default_format]
        if content_type_for(fmt)
          parser = Grape::Parser::Base.parser_for fmt, options
          if parser
            begin
              body = (env['api.request.body'] = parser.call(body, env))
              if body.is_a?(Hash)
                if env['rack.request.form_hash']
                  env['rack.request.form_hash'] = env['rack.request.form_hash'].merge(body)
                else
                  env['rack.request.form_hash'] = body
                end
                env['rack.request.form_input'] = env['rack.input']
              end
            rescue StandardError => e
              throw :error, status: 400, message: e.message
            end
          else
            env['api.request.body'] = body
          end
        else
          throw :error, status: 406, message: "The requested content-type '#{request.media_type}' is not supported."
        end
      end

      def negotiate_content_type
        fmt = format_from_extension || format_from_params || options[:format] || format_from_header || options[:default_format]
        if content_type_for(fmt)
          env['api.format'] = fmt
        else
          throw :error, status: 406, message: "The requested format '#{fmt}' is not supported."
        end
      end

      def format_from_extension
        parts = request.path.split('.')

        if parts.size > 1
          extension = parts.last
          # avoid symbol memory leak on an unknown format
          return extension.to_sym if content_type_for(extension)
        end
        nil
      end

      def format_from_params
        fmt = Rack::Utils.parse_nested_query(env['QUERY_STRING'])["format"]
        # avoid symbol memory leak on an unknown format
        return fmt.to_sym if content_type_for(fmt)
        fmt
      end

      def format_from_header
        mime_array.each do |t|
          return mime_types[t] if mime_types.key?(t)
        end
        nil
      end

      def mime_array
        accept = headers['accept']
        return [] unless accept

        accept_into_mime_and_quality = %r{
          (
            \w+/[\w+.-]+)     # eg application/vnd.example.myformat+xml
          (?:
           (?:;[^,]*?)?       # optionally multiple formats in a row
           ;\s*q=([\d.]+)     # optional "quality" preference (eg q=0.5)
          )?
        }x

        vendor_prefix_pattern = /vnd\.[^+]+\+/

        accept.scan(accept_into_mime_and_quality)
          .sort_by { |_, quality_preference| -quality_preference.to_f }
          .map { |mime, _| mime.sub(vendor_prefix_pattern, '') }
      end
    end
  end
end