module Sprockets::ProcessorUtils

def call_processor(processor, input)

Returns a Hash with :data and other processor metadata key/values.

input - Hash of input data to pass to processor
processor - Processor callables

Public: Invoke processor. 
def call_processor(processor, input)
  metadata = (input[:metadata] || {}).dup
  metadata[:data] = input[:data]
  case result = processor.call({data: "", metadata: {}}.merge(input))
  when NilClass
    metadata
  when Hash
    metadata.merge(result)
  when String
    metadata.merge(data: result)
  else
    raise TypeError, "invalid processor return type: #{result.class}"
  end
end