require 'tempfile'
require 'stringio'
require 'mime/types'

module RestClient
  module Payload
    extend self

    def generate(params)
      if params.is_a?(String)
        Base.new(params)
      elsif params
        if params.delete(:multipart) == true || has_file?(params)
          Multipart.new(params)
        else
          UrlEncoded.new(params)
        end
      else
        nil
      end
    end

    def has_file?(params)
      params.any? do |_, v|
        case v
          when Hash
            has_file?(v)
          else
            v.respond_to?(:path) && v.respond_to?(:read)
        end
      end
    end

    class Base
      def initialize(params)
        build_stream(params)
      end

      def build_stream(params)
        @stream = StringIO.new(params)
        @stream.seek(0)
      end

      def read(bytes=nil)
        @stream.read(bytes)
      end

      alias :to_s :read

      def escape(v)
        URI.escape(v.to_s, Regexp.new("[^#{URI::PATTERN::UNRESERVED}]"))
      end

      # Flatten parameters by converting hashes of hashes to flat hashes
      # {keys1 => {keys2 => value}} will be transformed into [keys1[key2], value]
      def flatten_params(params, parent_key = nil)
        result = []
        params.each do |key, value|
          calculated_key = parent_key ? "#{parent_key}[#{escape key}]" : escape(key)
          if value.is_a? Hash
            result += flatten_params(value, calculated_key)
          elsif value.is_a? Array
            result += flatten_params_array(value, calculated_key)
          else
            result << [calculated_key, value]
          end
        end
        result
      end

      def flatten_params_array value, calculated_key
        result = []
        value.each do |elem|
          if elem.is_a? Hash
            result +=  flatten_params(elem, calculated_key)
          elsif elem.is_a? Array
            result += flatten_params_array(elem, calculated_key)
          else
            result << ["#{calculated_key}[]", elem]
          end
        end
        result
      end

      def headers
        { 'Content-Length' => size.to_s }
      end

      def size
        @stream.size
      end

      alias :length :size

      def close
        @stream.close
      end

      def inspect
        result = to_s.inspect
        @stream.seek(0)
        result
      end

      def short_inspect
        (size > 500 ? "#{size} byte(s) length" : inspect)
      end

    end

    class UrlEncoded < Base
      def build_stream(params = nil)
        @stream = StringIO.new(flatten_params(params).collect do |entry|
          "#{entry[0]}=#{escape(entry[1])}"
        end.join("&"))
        @stream.seek(0)
      end

      def headers
        super.merge({ 'Content-Type' => 'application/x-www-form-urlencoded' })
      end
    end

    class Multipart < Base
      EOL = "\r\n"

      def build_stream(params)
        b = "--#{boundary}"

        @stream = Tempfile.new("RESTClient.Stream.#{rand(1000)}")
        @stream.binmode
        @stream.write(b + EOL)

        if params.is_a? Hash
          x = flatten_params(params)
        else
          x = params
        end

        last_index = x.length - 1
        x.each_with_index do |a, index|
          k, v = *a
          if v.respond_to?(:read) && v.respond_to?(:path)
            create_file_field(@stream, k, v)
          else
            create_regular_field(@stream, k, v)
          end
          @stream.write(EOL + b)
          @stream.write(EOL) unless last_index == index
        end
        @stream.write('--')
        @stream.write(EOL)
        @stream.seek(0)
      end

      def create_regular_field(s, k, v)
        s.write("Content-Disposition: form-data; name=\"#{k}\"")
        s.write(EOL)
        s.write(EOL)
        s.write(v)
      end

      def create_file_field(s, k, v)
        begin
          s.write("Content-Disposition: form-data;")
          s.write(" name=\"#{k}\";") unless (k.nil? || k=='')
          s.write(" filename=\"#{v.respond_to?(:original_filename) ? v.original_filename : File.basename(v.path)}\"#{EOL}")
          s.write("Content-Type: #{v.respond_to?(:content_type) ? v.content_type : mime_for(v.path)}#{EOL}")
          s.write(EOL)
          while data = v.read(8124)
            s.write(data)
          end
        ensure
          v.close
        end
      end

      def mime_for(path)
        mime = MIME::Types.type_for path
        mime.empty? ? 'text/plain' : mime[0].content_type
      end

      def boundary
        @boundary ||= rand(1_000_000).to_s
      end

      def headers
        super.merge({'Content-Type' => %Q{multipart/form-data; boundary=#{boundary}}})
      end

      def close
        @stream.close
      end
    end
  end
end