module Scrivito
# @api public
#
# This class represents a collection of meta data attributes.
#
# == Available meta data attributes
# All binaries have the meta attributes +content_length+ and +content_type+, in addition, PDFs
# and images have attributes specfic to their type.
#
# If not specified otherwise, the attributes contain +string+ values.
#
# [+content_length (Number)+]         Size in bytes of the given file.
# [+content_type+]                    MIME-type of the given file.
#
# == Available meta data attributes for PDFs
#
# [+text+]                            Text content of the PDF document.
#
# == Available meta data attributes for Images
#
# The meta data attributes starting with +iptc_+ or +exif_+ are extracted from the image itself
# and therefore may not be available for every image. +Iptc+ and +exif+ are both standardized
# formats supported by a wide array of software and hardware, like cameras and phones.
#
# [+width (Number)+]                  Width in pixels.
# [+height (Number)+]                 Height in pixels.
# [+exif_copyright+]                  Copyright of the image.
# [+exif_date_time+]                  The date at which the image was produced.
#
# [+iptc_keywords (Array<String>)+ ]  A list of keywords associated with the image.
# [+iptc_headline+]                   The headline of the image.
# [+iptc_copyright+]                  Copyright of the image.
# [+iptc_byline+]                     The name of the image creator.
# [+iptc_credit+]                     Contains the persons or companies that should be credited.
# [+iptc_source+]                     The original copyright holder.
# [+iptc_profile+]                    The color profile of the image.
# [+iptc_city+]                       The city in which the image was produced.
# [+iptc_state+]                      The state in which the image was produced.
# [+iptc_country_name+]               The country in which the image was produced.
# [+iptc_country_code+]               The code of the country in which the image was produced.
#
# == Searching for meta data
#
# Meta data is taken into account when searching. See the
# {Scrivito::ObjSearchEnumerator ObjSearchEnumerator} for details.
#
# @example Search for all JPEGs
#   Image.where('blob:content_type', :equals, 'image/jpeg')
#
# @example Search for wide images
#   Image.where('blob:width', :is_greater_than, 1024)
class MetaDataCollection
  def initialize(attributes)
    @attributes = ActiveSupport::HashWithIndifferentAccess.new(attributes)
  end

  # @api public
  #
  # Find value of a meta data attribute.
  #
  # @param name [Symbol, String] the name of the meta data attribute.
  # @return [String, Array, Fixnum, Date, nil] meta data attribute value if found or +nil+ otherwise.
  def [](name)
    @attributes[name]
  end
end
end