module RCAP
  module Base
    class Resource
      include Validation

      # @return [String] Resource Description
      attr_accessor( :resource_desc )
      # @return [String]
      attr_accessor( :mime_type )
      # @return [Integer] Expressed in bytes
      attr_accessor( :size )
      # @return [String] Resource location
      attr_accessor( :uri )
      # @return [String] SHA-1 hash of contents of resource
      attr_accessor( :digest )

      validates_presence_of( :resource_desc )

      XML_ELEMENT_NAME           = 'resource'
      MIME_TYPE_ELEMENT_NAME     = 'mimeType'
      SIZE_ELEMENT_NAME          = 'size'
      URI_ELEMENT_NAME           = 'uri'
      DIGEST_ELEMENT_NAME        = 'digest'
      RESOURCE_DESC_ELEMENT_NAME = 'resourceDesc'

      XPATH               = "cap:#{ XML_ELEMENT_NAME }"
      MIME_TYPE_XPATH     = "cap:#{ MIME_TYPE_ELEMENT_NAME }"
      SIZE_XPATH          = "cap:#{ SIZE_ELEMENT_NAME }"
      URI_XPATH           = "cap:#{ URI_ELEMENT_NAME }"
      DIGEST_XPATH        = "cap:#{ DIGEST_ELEMENT_NAME }"
      RESOURCE_DESC_XPATH = "cap:#{ RESOURCE_DESC_ELEMENT_NAME }"

      # @param [Hash{Symbol => Object}] attributes
      # @option attributes [String] :mime_type
      # @option attributes [Numeric] :size Size in bytes
      # @option attributes [String] :uri
      # @option attributes [String] :digest
      # @option attributes [String] :resource_desc
      def initialize
        yield( self ) if block_given?
      end

      # @return [REXML::Element]
      def to_xml_element
        xml_element = REXML::Element.new( XML_ELEMENT_NAME )
        xml_element.add_element( RESOURCE_DESC_ELEMENT_NAME ).add_text( @resource_desc )
        xml_element.add_element( MIME_TYPE_ELEMENT_NAME ).add_text( @mime_type ) if @mime_type
        xml_element.add_element( SIZE_ELEMENT_NAME ).add_text( @size.to_s )      if @size
        xml_element.add_element( URI_ELEMENT_NAME ).add_text( @uri )             if @uri
        xml_element.add_element( DIGEST_ELEMENT_NAME ).add_text( @digest )       if @digest
        xml_element
      end

      # @param [REXML::Element] resource_xml_element
      # @return [Resource]
      def self.from_xml_element( resource_xml_element )
        resource = self.new do |resource|
          resource.resource_desc = RCAP.xpath_text( resource_xml_element, RESOURCE_DESC_XPATH, resource.xmlns )
          resource.uri           = RCAP.xpath_text( resource_xml_element, URI_XPATH, resource.xmlns )
          resource.mime_type     = RCAP.xpath_text( resource_xml_element, MIME_TYPE_XPATH, resource.xmlns )
          resource.size          = RCAP.xpath_text( resource_xml_element, SIZE_XPATH, resource.xmlns ).to_i
          resource.digest        = RCAP.xpath_text( resource_xml_element, DIGEST_XPATH, resource.xmlns )
        end
      end

      # Calculates the SHA-1 hash and size of the contents of {#deref_uri}.
      # Returns an array containing the size (in bytes) and SHA-1 hash if
      # {#deref_uri} is present otherwise returns nil.
      #
      # @return [nil,Array(Integer,String)]
      def calculate_hash_and_size
        if @deref_uri
          @digest = Digest::SHA1.hexdigest( @deref_uri )
          @size = @deref_uri.bytesize
          [ @size, @digest ]
        end
      end

      # The decoded contents of {#deref_uri} if present otherwise nil.
      #
      # @return [nil,String]
      def decoded_deref_uri
        Base64.decode64( @deref_uri ) if @deref_uri
      end

      # If size is defined returns the size in kilobytes
      # @return [Float]
      def size_in_kb
        if @size
          @size.to_f/1024
        end
      end

      # @return [String]
      def to_xml
        self.to_xml_element.to_s
      end

      # @return [String]
      def inspect
        [ @resource_desc, @uri, @mime_type, @size ? format( "%.1fKB", @size_in_kb ) : nil ].compact.join(' - ')
      end

      # Returns a string representation of the resource of the form
      #  resource_desc
      #
      # @return [String]
      def to_s
        @resource_desc
      end

      RESOURCE_DESC_YAML = "Resource Description"
      URI_YAML           = "URI"
      MIME_TYPE_YAML     = "Mime Type"
      SIZE_YAML          = "Size"
      DIGEST_YAML        = "Digest"

      # @param [Hash] options
      # @return [String]
      def to_yaml( options = {} )
        RCAP.attribute_values_to_hash( [ RESOURCE_DESC_YAML, @resource_desc ],
                                       [ URI_YAML,           @uri ],
                                       [ MIME_TYPE_YAML,     @mime_type ],
                                       [ SIZE_YAML,          @size ],
                                       [ DIGEST_YAML,        @digest ]).to_yaml( options )
      end

      # @param [Hash] resource_yaml_data
      # @return [Resource]
      def self.from_yaml_data( resource_yaml_data )
        self.new do |resource|
          resource.resource_desc = resource_yaml_data[ RESOURCE_DESC_YAML ]
          resource.uri           = resource_yaml_data[ URI_YAML ]
          resource.mime_type     = resource_yaml_data[ MIME_TYPE_YAML ]
          resource.size          = resource_yaml_data[ SIZE_YAML ]
          resource.digest        = resource_yaml_data[ DIGEST_YAML ]
        end
      end

      RESOURCE_DESC_KEY = 'resource_desc'
      URI_KEY           = 'uri'
      MIME_TYPE_KEY     = 'mime_type'
      SIZE_KEY          = 'size'
      DIGEST_KEY        = 'digest'

      # @return [Hash]
      def to_h
        RCAP.attribute_values_to_hash( [ RESOURCE_DESC_KEY, @resource_desc ],
                                       [ URI_KEY,           @uri],
                                       [ MIME_TYPE_KEY,     @mime_type],
                                       [ SIZE_KEY,          @size ],
                                       [ DIGEST_KEY,        @digest ])
      end

      # @param [Hash] resource_hash
      # @return [Resource]
      def self.from_h( resource_hash )
        self.new do |resource|
          resource.resource_desc = resource_hash[ RESOURCE_DESC_KEY ]
          resource.uri           = resource_hash[ URI_KEY ]
          resource.mime_type     = resource_hash[ MIME_TYPE_KEY ]
          resource.size          = resource_hash[ SIZE_KEY ]
          resource.digest        = resource_hash[ DIGEST_KEY ]
        end
      end
    end
  end
end