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# frozen_string_literal: true
module Responders
# Set HTTP Last-Modified headers based on the given resource. It's used only
# on API behavior (to_format) and is useful for a client to check in the server
# if a resource changed after a specific date or not.
#
# This is not usually not used in html requests because pages contains a lot
# information besides the resource information, as current_user, flash messages,
# widgets... that are better handled with other strategies, as fragment caches and
# the digest of the body.
#
module HttpCacheResponder
def initialize(controller, resources, options = {})
super
@http_cache = options.delete(:http_cache)
end
def to_format
return if do_http_cache? && do_http_cache!
super
end
protected
def do_http_cache!
timestamp = resources.map do |resource|
resource.updated_at.try(:utc) if resource.respond_to?(:updated_at)
end.compact.max
controller.response.last_modified ||= timestamp if timestamp
head :not_modified if fresh = request.fresh?(controller.response)
fresh
end
def do_http_cache?
get? && @http_cache != false && ActionController::Base.perform_caching &&
persisted? && resource.respond_to?(:updated_at)
end
def persisted?
resource.respond_to?(:persisted?) ? resource.persisted? : true
end
end
end
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