class Temple::Generator

def buffer
  options[:buffer]
end

def call(exp)
  [preamble, compile(exp), postamble].flatten.compact.join('; ')
end

def capture_generator
  @capture_generator ||= Class === options[:capture_generator] ?
  options[:capture_generator] :
    Generators.const_get(options[:capture_generator])
end

def concat(str)
  "#{buffer} << (#{str})"
end

def create_buffer
end

def on(*exp)
  raise InvalidExpression, "Generator supports only core expressions - found #{exp.inspect}"
end

def on_capture(name, exp)
  capture_generator.new(**options, buffer: name).call(exp)
end

def on_code(code)
  code
end

def on_dynamic(code)
  concat(code)
end

def on_multi(*exp)
  exp.map {|e| compile(e) }.join('; '.freeze)
end

def on_newline
  "\n"
end

def on_static(text)
  concat(options[:freeze_static] ? "#{text.inspect}.freeze" : text.inspect)
end

def postamble
  [return_buffer, restore_buffer]
end

def preamble
  [save_buffer, create_buffer]
end

def restore_buffer
  "ensure; #{buffer} = #{@original_buffer}; end" if options[:save_buffer]
end

def return_buffer
  'nil'
end

def save_buffer
  "begin; #{@original_buffer = unique_name} = #{buffer} if defined?(#{buffer})" if options[:save_buffer]
end