require 'avm/creator'
require 'avm/xmp'
require 'avm/image_type'
require 'avm/image_quality'
require 'avm/spatial_quality'
require 'avm/coordinate_system_projection'
require 'avm/coordinate_frame'
require 'avm/observation'

module AVM
  # A single image, which has Observations, Contacts, and other metadata
  class Image
    DUBLIN_CORE_FIELDS = [ :title, :description ]

    PHOTOSHOP_SINGLE_FIELDS = [
      'Headline',
      'DateCreated',
      'Credit'
    ]

    PHOTOSHOP_SINGLE_METHODS = [
      :headline,
      :date,
      :credit
    ]

    PHOTOSHOP_SINGLES_MESSAGES = [
      :headline,
      :string_date,
      :credit
    ]

    PHOTOSHOP_SINGLES_FOR_METHODS = PHOTOSHOP_SINGLE_FIELDS.zip(PHOTOSHOP_SINGLE_METHODS)
    PHOTOSHOP_SINGLES_FOR_MESSAGES = PHOTOSHOP_SINGLE_FIELDS.zip(PHOTOSHOP_SINGLES_MESSAGES)

    AVM_SINGLE_FIELDS = [ 
      'Distance.Notes',
      'Spectral.Notes',
      'ReferenceURL',
      'ID',
      'Type',
      'Image.ProductQuality',
      'Spatial.Equinox',
      'Spatial.Rotation',
      'Spatial.Notes',
      'Spatial.FITSheader',
      'Spatial.Quality',
      'Spatial.CoordsystemProjection',
      'Spatial.CDMatrix',
      'Spatial.Scale',
      'Spatial.ReferencePixel',
      'Spatial.ReferenceDimension',
      'Spatial.ReferenceValue',
      'Spatial.Equinox',
      'Spatial.CoordinateFrame',
      'Publisher',
      'PublisherID',
      'ResourceID',
      'ResourceURL',
      'RelatedResources',
      'MetadataDate',
      'MetadataVersion',
      'Subject.Category',
    ]

    AVM_SINGLE_METHODS = [ 
      :distance_notes,
      :spectral_notes,
      :reference_url,
      :id,
      :type,
      :quality,
      :spatial_equinox,
      :spatial_rotation,
      :spatial_notes,
      :fits_header,
      :spatial_quality,
      :coordinate_system_projection,
      :spatial_cd_matrix,
      :spatial_scale,
      :reference_pixel,
      :reference_dimension,
      :reference_value,
      :equinox,
      :coordinate_frame,
      :publisher,
      :publisher_id,
      :resource_id,
      :resource_url,
      :related_resources,
      :metadata_date,
      :metadata_version,
      :categories
    ]

    AVM_SINGLE_MESSAGES = [
      :distance_notes, 
      :spectral_notes, 
      :reference_url, 
      :id, 
      :image_type, 
      :image_quality,
      :spatial_equinox,
      :spatial_rotation,
      :spatial_notes,
      :fits_header,
      :spatial_quality,
      :coordinate_system_projection,
      :spatial_cd_matrix,
      :spatial_scale,
      :reference_pixel,
      :reference_dimension,
      :reference_value,
      :equinox,
      :coordinate_frame,
      :publisher,
      :publisher_id,
      :resource_id,
      :resource_url,
      :related_resources,
      :string_metadata_date,
      :metadata_version,
      :categories
    ]

    AVM_SINGLES = AVM_SINGLE_FIELDS.zip(AVM_SINGLE_METHODS)
    AVM_SINGLES_FOR_MESSAGES = AVM_SINGLE_FIELDS.zip(AVM_SINGLE_MESSAGES)

    AVM_TO_FLOAT = [ 
      :spatial_rotation,
      :spatial_cd_matrix,
      :spatial_scale,
      :reference_pixel,
      :reference_dimension,
      :reference_value
    ]

    HASH_FIELDS = [ :title, :headline, :description, :distance_notes,
      :spectral_notes, :reference_url, :credit, :date,
      :id, :image_type, :image_quality, :coordinate_frame,
      :equinox, :reference_value, :reference_dimension, :reference_pixel,
      :spatial_scale, :spatial_rotation, :coordinate_system_projection, :spatial_quality,
      :spatial_notes, :fits_header, :spatial_cd_matrix, :distance,
      :publisher, :publisher_id, :resource_id, :resource_url,
      :related_resources, :metadata_date, :metadata_version, :subject_names, :categories
    ]

    attr_reader :creator, :observations

    def initialize(options = {})
      @creator = AVM::Creator.new(self)
      @options = options

      AVM_TO_FLOAT.each do |field| 
        @options[field] = case (value = @options[field])
                          when Array
                            value.collect(&:to_f)
                          else
                            value ? value.to_f : nil
                          end
      end


      @observations = []
    end

    def valid?
      self.title && self.credit
    end

    def create_observation(options)
      observation = Observation.new(self, options)
      @observations << observation
      observation
    end

    def to_xml
      document = AVM::XMP.new

      creator.add_to_document(document)
      Observation.add_to_document(document, observations)

      document.get_refs do |refs|
        DUBLIN_CORE_FIELDS.each do |field|
          refs[:dublin_core].add_child(%{<dc:#{field}>#{alt_li_tag(send(field))}</dc:#{field}>})
        end

        PHOTOSHOP_SINGLES_FOR_MESSAGES.each do |tag, message|
          refs[:photoshop].add_child(%{<photoshop:#{tag}>#{send(message)}</photoshop:#{tag}>})
        end

        AVM_SINGLES_FOR_MESSAGES.each do |tag, message|
          if value = send(message)
            case value
            when Array
              container_tag = (message == :related_resources) ? 'Bag' : 'Seq'
              value = "<rdf:#{container_tag}>" + value.collect { |v| "<rdf:li>#{v.to_s}</rdf:li>" }.join + "</rdf:#{container_tag}>"
            else
              value = value.to_s
            end

            refs[:avm].add_child(%{<avm:#{tag}>#{value}</avm:#{tag}>})
          end
        end

        distance_nodes = []
        distance_nodes << rdf_li(light_years) if light_years
        if redshift
          distance_nodes << rdf_li('-') if distance_nodes.empty?
          distance_nodes << rdf_li(redshift)
        end

        if !distance_nodes.empty?
          refs[:avm].add_child(%{<avm:Distance><rdf:Seq>#{distance_nodes.join}</rdf:Seq></avm:Distance>})
        end
      end

      document.doc
    end

    def id
      @options[:id]
    end
    
    def image_type
      cv_class_instance_for(AVM::ImageType, :type)
    end

    def image_quality
      cv_class_instance_for(AVM::ImageQuality, :quality)
    end

    def spatial_quality
      cv_class_instance_for(AVM::SpatialQuality, :spatial_quality)
    end

    def coordinate_frame
      cv_class_instance_for(AVM::CoordinateFrame, :coordinate_frame)
    end

    def coordinate_system_projection
      cv_class_instance_for(AVM::CoordinateSystemProjection, :coordinate_system_projection)
    end

    def date
      date_or_nil(:date)
    end

    def metadata_date
      date_or_nil(:metadata_date)
    end

    def string_date
      string_date_or_nil(:date)
    end

    def string_metadata_date
      string_date_or_nil(:metadata_date)
    end

    def distance
      [ light_years, redshift ]
    end

    def self.from_xml(string)
      document = AVM::XMP.from_string(string)

      options = {}

      document.get_refs do |refs|
        DUBLIN_CORE_FIELDS.each do |field|
          if node = refs[:dublin_core].at_xpath(".//dc:#{field}//rdf:li[1]")
            options[field] = node.text
          end
        end

        if node = refs[:dublin_core].at_xpath(".//dc:subject/rdf:Bag")
          options[:subject_names] = node.search('./rdf:li').collect(&:text)
        end

        AVM_SINGLES.each do |tag, field|
          if node = refs[:avm].at_xpath("./avm:#{tag}")
            if field == :categories
              options[field] = node.text.split(";").collect(&:strip)
            else
              if !(list_items = node.search('.//rdf:li')).empty?
                options[field] = list_items.collect(&:text)
              else
                options[field] = node.text
              end
            end
          end
        end

        PHOTOSHOP_SINGLES_FOR_METHODS.each do |tag, field|
          if node = refs[:photoshop].at_xpath("./photoshop:#{tag}")
            options[field] = node.text
          end
        end

        if node = refs[:avm].at_xpath('./avm:Distance')
          list_values = node.search('.//rdf:li').collect { |li| li.text }

          case list_values.length
          when 0
            options[:light_years] = node.text
          when 1
            options[:light_years] = list_values.first
          when 2
            options[:light_years] = (list_values.first == '-') ? nil : list_values.first
            options[:redshift] = list_values.last
          end
        end
      end

      image = new(options)
      image.creator.from_xml(self, document)
      Observation.from_xml(image, document)
      image
    end

    def to_h
      hash = Hash[HASH_FIELDS.collect { |key| [ key, send(key) ] }]
      hash[:creator] = creator.to_a
      hash[:observations] = observations.collect(&:to_h)
      hash
    end

    def method_missing(method)
      @options[method]
    end

    private
      def date_or_nil(field)
        (Time.parse(@options[field]) rescue nil)
      end

      def string_date_or_nil(field)
        (value = send(field)) ? value.strftime('%Y-%m-%d') : nil
      end

      def alt_li_tag(text)
        %{<rdf:Alt><rdf:li xml:lang="x-default">#{text}</rdf:li></rdf:Alt>}
      end

      def rdf_li(text)
        %{<rdf:li>#{text}</rdf:li>}
      end

      def cv_class_instance_for(mod, field)
        (mod.const_get(@options[field].to_sym).new rescue nil)
      end
  end
end